Microcephaly, Short Stature, and Impaired Glucose Metabolism 1

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Mappings

MONDO

MONDO:0018320 primary microcephaly-mild intellectual disability-young-onset diabetes syndrome Not Yet Curated

MONDO:0018320 is the Orphanet concept (ORPHA:391408, exact MONDO mapping per Orphadata) whose clinical description matches this entry. It is recorded as broadMatch rather than exactMatch because Orphanet's own cross-references place ORPHA:391408 as BTNT (broader than) BOTH OMIM:616033 (MSSGM1/TRMT10A, the anchor of this entry) and OMIM:616817 (MSSGM2/PPP1R15B), and Orphadata lists both TRMT10A and PPP1R15B as its assessed disease-causing genes. The Orphanet concept is therefore a union of two gene-defined diseases that OMIM and MONDO split, and that dismech curates as two entries. The union is modelled explicitly as the Microcephaly_Short_Stature_and_Impaired_Glucose_Metabolism grouping, which carries the exactMatch to this term.

MONDO:0800450 microcephaly, short stature, and impaired glucose metabolism Not Yet Curated

The OMIM phenotypic series grouping (OMIMPS:616033) of which MONDO:0000208 is a direct is_a child. Broader than this entry because it also subsumes MSSGM2 (MONDO:0014785, PPP1R15B).

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Inheritance

1

Autosomal recessive inheritance HP:0000007

Autosomal recessive, confirmed across every reported kindred: biallelic variants in affected individuals, clinically unaffected heterozygous parents, and parental consanguinity in nearly all families. Segregation was formally demonstrated in multiple independent reports.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:42181738 SUPPORT Human Clinical

"which was confirmed by Sanger sequencing and showed segregation consistent with autosomal recessive inheritance"

Explicit segregation evidence for autosomal recessive inheritance.

PMID:25053765 SUPPORT Human Clinical

"The mutation segregated in the family and was absent from large control cohorts."

Independent family segregation with absence from controls, consistent with a rare recessive allele.

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Discussions and Knowledge Gaps

4

Why do Trmt10a null mice show no discernible pancreatic defect when autoantibody-negative diabetes is the defining metabolic feature of human TRMT10A deficiency?

HUMAN MODEL MISMATCH OPEN mouse_pancreas_mismatch

Attached to

pathophysiology#Beta-Cell Oxidative Stress and Intrinsic Apoptosis pathophysiology#Progressive Beta-Cell Mass Loss

This is the sharpest translational gap in the disorder. The constitutive Trmt10a null mouse faithfully reproduces the neurological arm — reduced body weight, smaller hippocampal postsynaptic densities, defective synaptic plasticity and memory, and the underlying codon-specific translational lesion — while explicitly showing no discernible defect in the pancreas. The entire beta-cell mechanism therefore rests on human material: siRNA knockdown in rat and human beta-cell lines, and patient-derived iPSC beta-like cells. Several explanations are compatible with the data and are not distinguished by current evidence: species differences in beta-cell tRNA-Gln dependence or angiogenin-mediated fragmentation; a cumulative, lifespan-scaled apoptotic burden that a two-year mouse cannot accrue; or a ceiling effect from assessing an unstressed mouse pancreas, given that TRMT10A deficiency in human cells acts partly by sensitizing beta cells to ER stress rather than killing them outright. Distinguishing these matters because it determines whether the mouse can be used at all to test beta-cell-protective interventions.

Proposed experiments

Metabolic stress challenge of the Trmt10a null mouse pancreas

mouse_pancreas_stress_challenge

Phenotype Trmt10a null mice under conditions that stress the beta cell — high-fat diet, prolonged glucose challenge, aged cohorts, or pharmacological ER stress — with glucose tolerance testing, insulin secretion, and beta-cell mass histomorphometry, rather than under standard housing alone. A null mouse that becomes diabetic only under stress would support the sensitization model demonstrated in patient iPSC beta-like cells and reconcile the species discrepancy.

Cross-species comparison of beta-cell tRNA fragmentation

cross_species_trna_fragmentation

Measure m1G9 occupancy, tRNA-Gln steady-state levels and 5'-tRNA-Gln fragment abundance side by side in TRMT10A/Trmt10a-null mouse islets, human islets and patient iPSC beta-like cells. If mouse beta cells do not generate the cytotoxic fragment at comparable levels, the mismatch is mechanistic rather than a matter of duration or stress.

Show evidence (2 references)

PMID:38950903 SUPPORT Model Organism

"Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."

Documents the absent pancreatic phenotype that constitutes the mismatch.

PMID:30247717 SUPPORT In Vitro

"TRMT10A deficiency induces oxidative stress and sensitizes iPSC-derived β-like cells to endoplasmic reticulum stress-induced apoptosis."

Supports the sensitization hypothesis — an unstressed mouse pancreas may not reveal a stress-conditional phenotype.

What causes the peripheral insulin resistance in TRMT10A deficiency, and is it a distinct mechanism from beta-cell loss?

KNOWLEDGE GAP OPEN insulin_resistance_mechanism

Attached to

pathophysiology#Peripheral Insulin Resistance

The established mechanism — tRNA hypomethylation, tRNA-Gln fragmentation, beta-cell apoptosis — predicts insulin deficiency, not insulin resistance. Yet marked insulin resistance is documented in at least two independent reports, one by formal oral glucose tolerance testing with Matsuda index and one clinically with a striking metformin response. Neither report offers a mechanism. Candidate explanations include a direct effect of TRMT10A loss on translation in insulin-target tissues (muscle, liver, adipose), a consequence of the body-composition phenotype suggested by the dorsocervical fat pad and central obesity, or the mRNA m6A/FTO arm of TRMT10A function — FTO being itself a well-known obesity and insulin-sensitivity locus, which makes this the most testable of the three. The gap is clinically live because it determines whether metformin should be tried before insulin.

Proposed experiments

Tissue-specific Trmt10a deletion in insulin-target tissues

tissue_specific_trmt10a_deletion

Generate muscle-, liver- and adipose-specific Trmt10a knockouts and measure insulin sensitivity by hyperinsulinaemic-euglycaemic clamp. A tissue in which deletion alone produces resistance would establish a cell-autonomous route independent of beta-cell loss.

Test whether the FTO-m6A arm mediates the resistance

fto_m6a_insulin_signalling_test

In TRMT10A-null human myotubes and adipocytes, map m6A changes and transcript stability for insulin-signalling components, and test whether restoring FTO activity or a catalytically dead TRMT10A that retains FTO binding rescues insulin signalling. This separates the catalytic tRNA arm from the non-catalytic FTO arm of TRMT10A function.

Show evidence (2 references)

PMID:26526202 SUPPORT Human Clinical

"Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."

Documents the insulin-resistant phenotype that the current mechanism does not explain.

PMID:32213595 SUPPORT In Vitro

"Here, we show that a tRNA methyltransferase, TRMT10A, interacts with an mRNA demethylase FTO (ALKBH9), both in vitro and inside cells."

Provides the mechanistic candidate — the TRMT10A-FTO interaction — but makes no claim about insulin sensitivity, hence PARTIAL.

Is the metabolic phenotype fully penetrant with age, or is there a genuine neurodevelopment-only form of TRMT10A deficiency?

KNOWLEDGE GAP OPEN metabolic_penetrance_and_onset

Attached to

pathophysiology#Biphasic Glucose Dysregulation

Several molecularly confirmed patients have no dysglycaemia at the time of report: compound heterozygous siblings aged 10 and 12 with neither documented hypoglycaemia nor hyperglycaemia, and a 15-year-old homozygous for p.Arg43Ter with no metabolic abnormality. Because diabetes has been diagnosed as late as the late twenties in other patients, these observations are equally consistent with (a) age-dependent but eventually complete penetrance and (b) a genuinely distinct neurodevelopment-only phenotype determined by allele or modifier. The distinction is not academic: it determines whether lifelong glucose surveillance is mandatory for every biallelic carrier or can be stratified. Only longitudinal follow-up of the published cohort can settle it, and the 2026 report calls for exactly that.

Proposed experiments

Longitudinal metabolic follow-up of the published TRMT10A cohort

longitudinal_metabolic_followup

Prospectively follow all molecularly confirmed individuals with annual HbA1c, oral glucose tolerance testing with Matsuda index, and C-peptide, recording age at first dysglycaemia against genotype. Age-stratified penetrance curves would distinguish delayed onset from true non-penetrance and would set the evidence-based surveillance interval.

Show evidence (2 references)

PMID:42181738 SUPPORT Human Clinical

"This case represents one of the rare reported TRMT10A-related syndrome patients in whom diabetes has not yet been documented."

Documents a confirmed patient without the metabolic phenotype.

PMID:42181738 SUPPORT Human Clinical

"These findings underscore the importance of considering TRMT10A in the differential diagnosis of patients with microcephaly, intellectual disability, epilepsy, and growth abnormalities, and emphasize the need for longitudinal follow-up to monitor for the possible later development of endocrine..."

The reporting authors explicitly frame longitudinal follow-up as the unresolved question.

Is the primary microcephaly caused by a reduced neural progenitor pool, and has this ever been measured directly in a human system?

KNOWLEDGE GAP OPEN neural_arm_direct_evidence

Attached to

pathophysiology#Reduced Neural Progenitor Pool in the Developing Brain

The neural-progenitor account of the microcephaly is a proposal, not a measurement. It rests on three indirect observations: TRMT10A is expressed in human embryonic and fetal brain; TRMT10A silencing kills beta cells; and the patients have small, structurally normal brains. No study has measured proliferation or apoptosis in human TRMT10A-deficient neural progenitors. The competing account is that the phenotype arises from impaired synthesis of neuronal structural proteins with preserved cell number — the mechanism actually demonstrated in the null mouse, which has smaller postsynaptic densities and no reported reduction in neuron number. These predict different things about whether the deficit is fixed prenatally, and therefore about any therapeutic window.

Proposed experiments

Patient-derived cerebral organoid growth and progenitor dynamics

patient_cerebral_organoid_progenitors

Differentiate cerebral organoids from the existing TRMT10A-deficient iPSC lines and isogenic controls, and quantify organoid size, ventricular-zone thickness, radial glial proliferation index and apoptosis over the neurogenic window. Reduced progenitor proliferation would support the pool-depletion model; normal progenitor dynamics with altered neurite or synaptic protein content would support the translational model.

Show evidence (2 references)

PMID:24204302 SUPPORT In Vitro

"Taken together, we propose that TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain."

The proposal is stated as such by its authors, which is the gap.

PMID:38950903 SUPPORT Model Organism

"Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain."

Supports the competing translational account of the neural phenotype rather than progenitor pool depletion.

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Pathophysiology

11

Biallelic TRMT10A Loss-of-Function Variants

The initiating lesion is biallelic inactivation of TRMT10A (4q23). Reported alleles span nonsense variants subject to nonsense-mediated decay (p.Arg127Ter in the index Moroccan family, p.Glu27Ter, p.Arg43Ter, p.Arg93Ter/p.Arg133Ter in compound heterozygosity), canonical splice-acceptor variants (c.496-1G>A, c.421-1G>A), a catalytically dead missense allele (p.Gly206Arg), and a homozygous contiguous gene deletion removing the locus. In the index family neither TRMT10A mRNA nor protein was detectable in patient lymphoblasts, establishing complete loss of the gene product rather than a dominant-negative or hypomorphic effect. Heterozygous parents are unaffected.

TRMT10A hgnc:28403

nucleolus GO:0005730

Downstream

Loss of tRNA m1G9 Methyltransferase Activity Absence of TRMT10A protein, or expression of a catalytically inert variant, directly removes the cell's m1G9 methyltransferase activity.

Show evidence (3 references)

PMID:24204302 SUPPORT Human Clinical

"Linkage analysis and whole exome sequencing were used to identify the causal nonsense mutation, which changed an arginine codon into a stop at position 127 of the tRNA methyltransferase homolog gene TRMT10A (also called RG9MTD2)."

Identifies TRMT10A and the first disease-causing nonsense allele.

PMID:24204302 SUPPORT Human Clinical

"TRMT10A mRNA and protein were absent in lymphoblasts from the affected siblings."

Establishes complete loss of the gene product in patient cells, defining the mechanism as loss of function.

PMID:24204302 SUPPORT In Vitro

"TRMT10A localizes to the nucleolus of β- and non-β-cells, where tRNA modifications occur."

Localizes the affected enzyme to the nucleolar site of tRNA modification.

Loss of tRNA m1G9 Methyltransferase Activity

TRMT10A is the principal — and in human cells apparently non-redundant — enzyme installing N1-methylguanosine at position 9 of cytoplasmic tRNAs, the mammalian orthologue of yeast Trm10. Its activity is lost outright by nonsense and splice alleles, and reduced below 0.1% of wild type by the p.Gly206Arg missense variant, which retains normal tRNA binding but cannot use the S-adenosylmethionine methyl donor. This separates substrate recognition from catalysis and shows the disease mechanism is loss of methyl transfer rather than loss of tRNA engagement.

tRNA methylation GO:0030488 ↓ DECREASED

tRNA (guanosine(9)-N1)-methyltransferase activity GO:0052905 ⇓ LOSS OF FUNCTION

Downstream

tRNA Hypomethylation, Destabilization and Fragmentation Absent m1G9 leaves target tRNAs hypomodified in the D-loop, reducing their steady-state stability and exposing them to endonucleolytic cleavage.

Show evidence (3 references)

PMID:25053765 SUPPORT In Vitro

"The completely abolished m(1)G9 methyltransferase activity of the mutant enzyme is likely due to significant defects in its ability to bind the methyl donor S-adenosyl methionine."

Attributes the catalytic failure of the p.Gly206Arg allele to loss of methyl-donor binding.

PMID:25053765 SUPPORT In Vitro

"The binding affinity of the G206R variant enzyme to tRNA, determined by fluorescence anisotropy, was similar to that of the WT enzyme."

Shows tRNA binding is preserved, isolating the defect to catalysis rather than substrate recognition.

PMID:30247717 SUPPORT In Vitro

"Here we confirm the role of TRMT10A as a guanosine 9 tRNA methyltransferase, and identify tRNAGln and tRNAiMeth as two of its targets."

Confirms the enzymatic assignment in human cells and names the two physiologically critical substrate tRNAs.

tRNA Hypomethylation, Destabilization and Fragmentation

Hypomodified tRNAs are degraded or cleaved rather than simply carried in an unmethylated state. In Trmt10a null mice and in a TRMT10A-null human cell line the steady-state levels of tRNA-Gln(CUG) and initiator methionine tRNA fall across tissues, and in patient-derived beta-like cells tRNA-Gln is cleaved into 5' fragments. The fragments are not inert by-products: purified 5'-tRNA-Gln fragments are themselves sufficient to kill beta cells, making this node both a loss of translational capacity and a gain of a cytotoxic species.

tRNA decay GO:0016078 ↑ INCREASED

Experimental models

Patient-derived iPSC beta-like cells (TRMT10A-deficient) IPSC DERIVED MODEL The same system was used to show that 5'-tRNA-Gln fragments are not merely correlated with beta-cell death but are sufficient to cause it.

Downstream

Codon-Specific Translational Impairment Depletion of tRNA-Gln and initiator methionine tRNA restricts decoding of the corresponding codons and initiation of translation.

Beta-Cell Oxidative Stress and Intrinsic Apoptosis 5'-tRNA-Gln fragments generated by hypomethylation are the proximate mediators of beta-cell death in TRMT10A deficiency.

Show evidence (2 references)

PMID:38950903 SUPPORT Model Organism

"Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A."

Documents the loss of the two key tRNA species in vivo and, importantly, confirms the same effect in a human cell line.

PMID:30247717 SUPPORT In Vitro

"This study unmasks tRNA hypomethylation and fragmentation as a hitherto unknown mechanism of pancreatic β-cell demise relevant to monogenic and polygenic forms of diabetes."

Frames hypomethylation-plus-fragmentation as the disease mechanism.

Coordinated mRNA m6A Dysregulation via the FTO Axis

Beyond its catalytic role on tRNA, TRMT10A physically interacts with the mRNA demethylase FTO. Ablating TRMT10A therefore raises m6A on a shared set of mRNAs, which are then destabilized through the m6A reader YTHDF2. The affected transcripts are enriched for codons read by the very tRNAs that carry m1G9 (tRNA-Gln(TTG), tRNA-Arg(CCG), tRNA-Thr(CGT)), coupling the tRNA and mRNA arms of the lesion. This is a parallel, non-catalytic route by which TRMT10A loss perturbs gene expression, and it is why the disorder is not fully explained by tRNA methylation alone.

FTO hgnc:24678

mRNA catabolic process GO:0006402 ↑ INCREASED

Downstream

Codon-Specific Translational Impairment Accelerated decay of m6A-marked transcripts compounds the codon-level translational deficit arising from tRNA loss, acting on an overlapping set of messages.

Show evidence (2 references)

PMID:32213595 SUPPORT In Vitro

"Here, we show that a tRNA methyltransferase, TRMT10A, interacts with an mRNA demethylase FTO (ALKBH9), both in vitro and inside cells."

Establishes the physical TRMT10A-FTO interaction underlying this node.

PMID:32213595 SUPPORT In Vitro

"We show that TRMT10A ablation not only leads to decreased m1G in tRNA but also significantly increases m6A levels in mRNA."

Demonstrates that TRMT10A loss raises mRNA m6A in addition to lowering tRNA m1G.

Codon-Specific Translational Impairment

Loss of initiator methionine tRNA and tRNA-Gln does not shut down protein synthesis globally; it biases it. Ribosome profiling of Trmt10a null mouse brain shows slowing at Gln(CAG) codons and, because initiator tRNA is limiting, more frequent leaky scanning past the upstream open reading frames of Atf4 — the canonical integrated-stress-response sensor — so ATF4 is translationally derepressed without an upstream eIF2-alpha kinase signal. Transcripts encoding neuronal structural proteins are among those most perturbed, which is the proposed link between a housekeeping RNA-modification enzyme and a specifically neurodevelopmental phenotype.

translational initiation GO:0006413 ↓ DECREASED integrated stress response signaling GO:0140467 ↑ INCREASED

Animal models

Trmt10a null mouse (E29Stop) Mouse recapitulates Ribosome profiling in null-mouse brain establishes the codon-level translational lesion, and the same tRNA depletion was confirmed in a human TRMT10A-null cell line.

Downstream

Reduced Neural Progenitor Pool in the Developing Brain Perturbed translation of neuronal transcripts in a tissue enriched for TRMT10A expression restricts the neuronal pool generated during development.

Impaired Synaptic Structure and Plasticity Reduced synthesis of neuronal structural proteins translates into smaller postsynaptic densities and impaired plasticity in the null mouse.

Show evidence (2 references)

PMID:38950903 SUPPORT Model Organism

"Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames."

Provides the mechanistic content of this node: codon-specific stalling plus translational derepression of ATF4.

PMID:38950903 SUPPORT Model Organism

"Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons."

States the general principle that a universal tRNA modification acts through specific-codon translation.

Beta-Cell Oxidative Stress and Intrinsic Apoptosis

Pancreatic beta cells are among the tissues with the highest TRMT10A expression and the highest secretory protein-synthetic load, and they are the cell type in which the consequences of tRNA hypomethylation have been worked out directly. Silencing TRMT10A kills rat and human beta cells. In iPSC-derived beta-like cells from TRMT10A-deficient patients the deficiency raises reactive oxygen species and engages the intrinsic (mitochondrial) apoptotic pathway, and sensitizes the cells to ER-stress-induced apoptosis on top of that baseline.

pancreatic beta cell CL:0000169

cellular response to oxidative stress GO:0034599 ↑ INCREASED intrinsic apoptotic signaling pathway GO:0097193 ↑ INCREASED

pancreatic islet UBERON:0000006

Experimental models

Patient-derived iPSC beta-like cells (TRMT10A-deficient) IPSC DERIVED MODEL Patient-genotype human beta-like cells reproduce the oxidative stress and intrinsic apoptotic signalling proposed to underlie beta-cell loss.

TRMT10A silencing in rat INS-1E and human EndoC-betaH1 beta cells CELL LINE Acute silencing establishes sufficiency of TRMT10A loss for beta-cell death in two species.

Animal models

Trmt10a null mouse (E29Stop) Mouse fails to recapitulate Trmt10a null mice show no discernible pancreatic defect, in direct contrast to the diabetes that defines the human syndrome. This negative result is the reason the beta-cell mechanism rests on human cellular models rather than on a mouse.

Downstream

Progressive Beta-Cell Mass Loss Cumulative apoptotic attrition of beta cells over years erodes functional beta-cell mass.

Show evidence (4 references)

PMID:24204302 SUPPORT In Vitro

"TRMT10A silencing induces rat and human β-cell apoptosis."

Direct experimental demonstration that loss of TRMT10A is sufficient to kill beta cells in both species.

PMID:24204302 SUPPORT In Vitro

"TRMT10A is ubiquitously expressed but enriched in brain and pancreatic islets, consistent with the tissues affected in this syndrome."

Explains the tissue selectivity of a lesion in an otherwise housekeeping enzyme.

PMID:30247717 SUPPORT In Vitro

"we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells"

Identifies oxidative stress and the intrinsic apoptotic pathway as the effector mechanism, using patient-derived iPSC beta-like cells.

+ 1 more reference

Progressive Beta-Cell Mass Loss

Cumulative apoptotic attrition of beta cells, the cellular state that links the apoptosis node to the whole-organism glucose phenotype. Loss is partial rather than complete at the time patients present: C-peptide remains detectable, endogenous insulin secretion persisted 22 months after diabetes onset in one patient, and near-normal glucose was maintained for three days entirely off insulin. Because attrition is gradual, the reserve available to an individual is a function of age, which is what makes the downstream glucose phenotype evolve rather than present fully formed.

pancreatic beta cell CL:0000169

insulin secretion GO:0030073 ↓ DECREASED

Downstream

Biphasic Glucose Dysregulation Falling beta-cell reserve is the proposed basis of the shift from hypoglycaemia in childhood to overt diabetes in adolescence or young adulthood.

Show evidence (2 references)

PMID:26297882 SUPPORT Human Clinical

"Endogenous insulin secretion still persisted 22 months after onset of diabetes and relatively normal glucose levels were kept over 3 days without insulin treatment."

Shows the loss is partial rather than complete, unlike autoimmune type 1 diabetes.

PMID:26297882 SUPPORT Human Clinical

"The fluctuating course of puberty and diabetes may reflect intermittent apoptotic damages due to sensitization of the relevant cells to various stress agents in the absence of functional TRMT10A."

Proposes intermittent stress-triggered apoptosis as the basis of the fluctuating endocrine course.

Biphasic Glucose Dysregulation

The whole-organism glucose phenotype, which evolves rather than presenting fully formed. In several kindreds the first metabolic manifestation in infancy or childhood is hypoglycaemia — ketotic and non-ketotic events, in some patients frankly hyperinsulinaemic — followed years later by overt diabetes. Onset ranges from childhood to the third decade, and in at least one adolescent with a confirmed biallelic nonsense genotype no metabolic abnormality had appeared by age 15.

Downstream

Peripheral Insulin Resistance Marked insulin resistance is documented in several patients, but whether it is a consequence of the beta-cell lesion, an independent effect of TRMT10A loss in insulin-target tissues, or secondary to body composition is not established. The link type is recorded as UNKNOWN rather than asserted.

Show evidence (2 references)

PMID:25053765 SUPPORT Human Clinical

"The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."

Documents the early hypoglycaemic phase of the biphasic glucose phenotype.

PMID:26526202 SUPPORT Human Clinical

"Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."

Documents the late end of the onset range and the insulin-resistant presentation.

Peripheral Insulin Resistance

A distinct metabolic arm, present in a subset of patients and clinically consequential because it dictates a different treatment. Formal testing in the Scottish kindred showed a Matsuda index of 1.46 against a control value around 14, and a Chinese patient with marked insulin resistance responded to metformin with HbA1c falling from 14.4% to 6.8% in three months. Neither the tRNA-fragment mechanism nor beta-cell apoptosis explains peripheral insulin resistance, so this node is recorded as an evidenced but mechanistically unexplained arm rather than as a downstream consequence of beta-cell loss.

cellular response to insulin stimulus GO:0032869 ↓ DECREASED

Show evidence (2 references)

PMID:26526202 SUPPORT Human Clinical

"The findings were suggestive of insulin resistance"

Reports the formal insulin-sensitivity testing that established this arm of the metabolic phenotype.

PMID:33067246 SUPPORT Human Clinical

"The diabetes was due to marked insulin resistance and responded very well to metformin treatment."

Independent confirmation of the insulin-resistant arm and its therapeutic implication.

Reduced Neural Progenitor Pool in the Developing Brain

TRMT10A is expressed in human embryonic and fetal brain, and the microcephaly is congenital and primary — brain architecture is typically normal on imaging, with a small brain rather than a malformed one. The proposed mechanism is a reduced pool of neurons generated during development, in parallel with (not downstream of) the beta-cell lesion. This remains the weakest-evidenced node in the chain: it rests on the expression pattern, the beta-cell apoptosis data, and the clinical phenotype, not on a direct measurement of human neural progenitors.

neural progenitor cell CL:0011020

neural precursor cell proliferation GO:0061351 ↓ DECREASED brain development GO:0007420 ↓ DECREASED

brain UBERON:0000955

Show evidence (2 references)

PMID:24204302 SUPPORT In Vitro

"Taken together, we propose that TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain."

The neural arm is explicitly a proposal by the authors, not a measured result, so the evidence is PARTIAL.

PMID:24204302 SUPPORT Human Clinical

"In situ hybridization studies showed that TRMT10A is expressed in human embryonic and fetal brain."

Establishes that the enzyme is present in the developing human brain at the relevant time, the basis for the neurodevelopmental arm.

Impaired Synaptic Structure and Plasticity

A second, non-proliferative neural mechanism demonstrated in the Trmt10a null mouse: hippocampal postsynaptic densities are smaller and synaptic plasticity and memory are defective, without gross brain malformation. This offers a route to intellectual disability that does not require neuronal loss, and it is the arm best supported by direct in vivo measurement — though only in mouse.

neuron CL:0000540

regulation of synaptic plasticity GO:0048167 ↓ DECREASED

Animal models

Trmt10a null mouse (E29Stop) Mouse recapitulates The null mouse shows smaller hippocampal postsynaptic densities with defective synaptic plasticity and memory, offering a structural correlate for the intellectual disability that does not require neuronal loss.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."

Direct in vivo demonstration of the synaptic and memory phenotype; the same sentence records the absence of a pancreatic phenotype in the mouse.

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Pathograph

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Phenotypes

25

Endocrine 2

Young-Onset Diabetes Mellitus HP:0000819

Show evidence (3 references)

PMID:26526202 SUPPORT Human Clinical

"Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."

Documents the late end of the onset range.

PMID:34541035 SUPPORT Human Clinical

"She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."

Documents the early end of the onset range together with the autoantibody-negative, C-peptide-positive profile.

PMID:26297882 SUPPORT Human Clinical

"Unlike the previous reports, the patient had ketoacidosis at onset of diabetes and islet cell autoantibodies."

Documents the exceptional autoantibody-positive, ketoacidotic presentation that departs from the usual non-autoimmune pattern.

Delayed Puberty and Gonadal Failure HP:0000823

Show evidence (2 references)

PMID:26297882 SUPPORT Human Clinical

"Puberty was characterized by a slow and an inconsistent course of progression."

Documents the delayed and erratic pubertal course.

PMID:26297882 SUPPORT Human Clinical

"Concomitantly, gonadotropin levels fluctuated between low and high levels which were compatible with gonadal failure."

Provides the endocrine basis of the pubertal delay.

Eye 2

Deeply Set Eyes HP:0000490

Show evidence (1 reference)

PMID:26535115 SUPPORT Human Clinical

"Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."

Records deep-set eyes on formal examination in a confirmed patient.

Hypotelorism HP:0000601

Show evidence (2 references)

PMID:26535115 SUPPORT Human Clinical

"Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."

Records mild hypotelorism on formal examination in a confirmed patient.

PMID:26535115 SUPPORT Human Clinical

"His features have remained constant on follow-up examinations, with persistent microcephaly and mild hypotelorism."

Documents persistence of the finding in the affected sibling.

Genitourinary 1

Premature Ovarian Insufficiency HP:0008209

Show evidence (2 references)

PMID:34541035 SUPPORT Human Clinical

"Spontaneous puberty did not begin until 15.7 years of age and she was found to have primary ovarian failure."

Primary report of ovarian failure in a molecularly confirmed patient.

PMID:34541035 SUPPORT Human Clinical

"GH deficiency and primary ovarian failure may also be additional findings of this syndrome."

The authors propose this as a possible extension of the phenotype ("may also be"), so the generalization beyond this patient is PARTIAL.

Head and Neck 1

Short Neck HP:0000470

Show evidence (1 reference)

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Names a short neck directly among the proband's features.

Metabolism 1

Insulin Resistance HP:0000855

Show evidence (2 references)

PMID:26526202 SUPPORT Human Clinical

"The findings were suggestive of insulin resistance"

Reports the formal insulin-sensitivity testing establishing this feature.

PMID:33067246 SUPPORT Human Clinical

"The diabetes was due to marked insulin resistance and responded very well to metformin treatment."

Independent confirmation with a therapeutic corollary.

Musculoskeletal 3

Osteoporosis HP:0000939

Show evidence (3 references)

PMID:24204302 SUPPORT Human Clinical

"She also had osteoporosis, with dual- energy X-ray absorptiometry T-scores of -2.7 and -3.5 at the lumbar spine and femoral neck, respectively."

Quantifies the osteoporosis in the index proband.

PMID:24204302 SUPPORT Human Clinical

"A skeletal survey revealed no epiphyseal dysplasia or other bone abnormality"

Establishes that the skeletal involvement is not a bone dysplasia, an important negative for differential diagnosis.

PMID:35137278 SUPPORT Human Clinical

"A homozygous mutation in TRMT10A, a tRNA methyltransferase, was identified in a 15-year-old boy with new-onset diabetes, developmental delay, microcephaly, dysmorphism, short stature and central obesity."

Cited in a series on diabetes with skeletal manifestations; the quoted case description supports the syndromic-diabetes context rather than osteoporosis specifically, hence PARTIAL.

Scoliosis HP:0002650

Show evidence (2 references)

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Names scoliosis directly among the proband's features.

PMID:24204302 SUPPORT Human Clinical

"A skeletal survey revealed no epiphyseal dysplasia or other bone abnormality"

Establishes the scoliosis is not part of a skeletal dysplasia, which is the discriminator against Wolcott-Rallison syndrome.

Joint Hypermobility HP:0001382

Show evidence (1 reference)

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Names joint laxity directly among the proband's features.

Nervous System 4

Intellectual Disability Mild intellectual disability HP:0001256

Show evidence (2 references)

PMID:26526202 SUPPORT Human Clinical

"Epilepsy and intellectual disability were features in common."

Documents intellectual disability as a shared feature across affected siblings.

PMID:26535115 SUPPORT Human Clinical

"Psychometric testing led to the diagnosis of mild intellectual disability."

Formal psychometric confirmation of the mild severity band in a molecularly confirmed patient.

Global Developmental Delay HP:0001263

Show evidence (2 references)

PMID:42181738 SUPPORT Human Clinical

"Neurodevelopmental delay was evident from early childhood, and electroencephalography revealed generalized epileptiform activity requiring treatment, whereas brain magnetic resonance imaging was normal."

Documents early-childhood developmental delay in a confirmed patient.

PMID:26535115 SUPPORT Human Clinical

"Speech delay and behavioral problems were noted by 4 years of age."

Documents the speech-predominant delay pattern.

Epilepsy Seizure HP:0001250

Show evidence (3 references)

PMID:26526202 SUPPORT Human Clinical

"Epilepsy and intellectual disability were features in common."

Documents epilepsy in both affected siblings of this family.

PMID:26535115 SUPPORT Human Clinical

"A recent EEG showed symmetric, bilateral, frontally dominant polyspike and wave discharges, consistent with generalized epilepsy."

Characterizes the electroclinical phenotype in a confirmed patient.

PMID:25053765 SUPPORT Human Clinical

"The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."

Independent family with seizures in all three affected siblings.

Dandy-Walker Variant Cerebellar vermis hypoplasia HP:0001320

Show evidence (2 references)

PMID:39440920 SUPPORT Human Clinical

"We report a case of a patient showing spastic-ataxic paraparesis and Dandy-Walker variant associated with a causative homozygous c."

Reports the Dandy-Walker variant. PARTIAL because the abstract names the clinical designation without reporting the underlying radiological measurements, so the vermis-hypoplasia binding is inferred from the definition of the designation rather than directly measured in the source.

PMID:39440920 SUPPORT Human Clinical

"This case expands the clinical spectrum of TRMT10A syndrome highlighting the importance of considering this gene in the evaluation of patients with brain/cerebellar malformations and spastic-ataxic paraparesis."

Confirms a cerebellar malformation is part of what this case adds, and frames it as a spectrum expansion rather than a core feature.

Growth 2

Short Stature HP:0004322

Show evidence (2 references)

PMID:25053765 SUPPORT Human Clinical

"The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."

Documents short stature in all three affected siblings of this family.

PMID:33448213 SUPPORT Human Clinical

"Additional clinical features included intellectual disability, hypoplastic kidneys and short stature."

Independent confirmation of short stature in a further patient.

Failure to Thrive HP:0001508

Show evidence (1 reference)

PMID:26297882 SUPPORT Human Clinical

"From infancy, she presented with failure to thrive and microcephaly."

Documents failure to thrive as the infantile presentation in this patient.

Other 9

Primary Microcephaly HP:0011451

Show evidence (3 references)

PMID:24204302 SUPPORT Human Clinical

"We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."

Establishes microcephaly as a defining feature of the syndrome.

PMID:24204302 SUPPORT Human Clinical

"Magnetic resonance imaging of the head showed a small brain with no malformation or other abnormality"

Documents that the microcephaly is a reduction in brain size without structural malformation, consistent with primary microcephaly.

PMID:26526202 SUPPORT Human Clinical

"Mild microcephaly was present at birth but their final head circumferences were normal."

Documents the milder end of the spectrum, in which head circumference normalizes with growth.

Periventricular and Subcortical White Matter Hyperintensities Periventricular white matter hyperintensities HP:0030891

Show evidence (3 references)

PMID:26535115 SUPPORT Human Clinical

"Both children had brain MRI studies that showed periventricular and subcortical T2/FLAIR hyperintensities, without signs of white matter volume loss, and no parenchymal calcifications by CT scan."

Primary description of the white matter imaging phenotype.

PMID:26535115 SUPPORT Human Clinical

"Our report adds to current knowledge of TRMT10A related neurodevelopmental disorders and demonstrates imaging findings suggestive of delayed or abnormal myelination of the white matter in this disorder."

Interprets the finding as dysmyelination rather than white matter destruction.

PMID:42181738 SUPPORT Human Clinical

"whereas brain magnetic resonance imaging was normal"

Counterpoint establishing that white matter change is not obligatory — MRI was normal in this confirmed patient.

Hypoglycemia Preceding Diabetes Hyperinsulinemic hypoglycemia HP:0000825

Show evidence (2 references)

PMID:25053765 SUPPORT Human Clinical

"The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."

Primary description of hyperinsulinaemic hypoglycaemia as the dominant glucose abnormality in this family.

PMID:34541035 SUPPORT Human Clinical

"we observed an unusual form of impaired glucose metabolism which presented in early childhood with hypoglycemia followed by diabetes in late childhood"

Documents the hypoglycaemia-then-diabetes temporal sequence in a single patient.

Growth Hormone Deficiency Decreased response to growth hormone stimulation test HP:0000824

Show evidence (2 references)

PMID:34541035 SUPPORT Human Clinical

"At 3.6 years of age, severe short stature related to growth hormone (GH) deficiency was detected."

Documents GH deficiency as the basis of the growth failure in this patient.

PMID:33448213 SUPPORT Human Clinical

"We report for the first time hypoplastic kidneys and inadequate response to growth hormone stimulation tests in a girl with this syndrome."

Independent report of an inadequate growth hormone stimulation response.

Renal Hypoplasia HP:0000089

Show evidence (1 reference)

PMID:33448213 SUPPORT Human Clinical

"We report for the first time hypoplastic kidneys and inadequate response to growth hormone stimulation tests in a girl with this syndrome."

Primary and, to date, only report of renal hypoplasia in this syndrome.

Low Anterior Hairline HP:0000294

Show evidence (2 references)

PMID:26535115 SUPPORT Human Clinical

"Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."

Describes the facial gestalt in a molecularly confirmed patient.

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Independent description of the same dysmorphic constellation in the index family.

Wide Nose HP:0000445

Show evidence (1 reference)

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Names a wide nose directly among the proband's features.

Dorsocervical Fat Pad HP:0025383

Show evidence (2 references)

PMID:24204302 SUPPORT Human Clinical

"Other features were a short neck, wide nose, low hairline, buffalo hump, retraction of the right 5 th toe, scoliosis, and joint laxity."

Documents the dorsocervical fat pad ("buffalo hump") in the index proband.

PMID:35137278 SUPPORT Human Clinical

"A homozygous mutation in TRMT10A, a tRNA methyltransferase, was identified in a 15-year-old boy with new-onset diabetes, developmental delay, microcephaly, dysmorphism, short stature and central obesity."

Independent report of central obesity in a confirmed patient.

Spastic-Ataxic Paraparesis Spastic ataxia HP:0002497

Show evidence (2 references)

PMID:39440920 SUPPORT Human Clinical

"We report a case of a patient showing spastic-ataxic paraparesis and Dandy-Walker variant associated with a causative homozygous c."

Primary report of the spastic-ataxic and posterior-fossa phenotype; the quote is truncated at the variant nomenclature as it appears in the abstract.

PMID:39440920 SUPPORT Human Clinical

"This case expands the clinical spectrum of TRMT10A syndrome highlighting the importance of considering this gene in the evaluation of patients with brain/cerebellar malformations and spastic-ataxic paraparesis."

The authors themselves frame this as a spectrum expansion rather than an established feature.

🧬

Genetic Associations

1

TRMT10A

Gene: TRMT10A hgnc:28403 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:24204302 SUPPORT Human Clinical

"This is the first study describing the impact of TRMT10A deficiency in mammals, highlighting a role in the pathogenesis of microcephaly and early onset diabetes."

Establishes TRMT10A as the causal gene for the syndrome.

PMID:26526202 SUPPORT Human Clinical

"Our report provides independent confirmation of the role of TRMT10A mutations in this syndrome and expands its phenotypic description."

Independent replication of the gene-disease relationship in a fourth family.

Variants (8)

p.Arg127Ter Pathogenic

The first-reported disease allele, homozygous in a large consanguineous Moroccan family with three affected siblings. Neither TRMT10A mRNA nor protein was detectable in patient lymphoblasts, indicating nonsense-mediated decay and complete loss of the gene product. Also reported homozygously in a patient with GH deficiency and primary ovarian failure.

Show evidence (2 references)

PMID:24204302 SUPPORT Human Clinical

"Linkage analysis and whole exome sequencing were used to identify the causal nonsense mutation, which changed an arginine codon into a stop at position 127 of the tRNA methyltransferase homolog gene TRMT10A (also called RG9MTD2)."

Identifies the allele and the method by which it was found.

PMID:34541035 SUPPORT Human Clinical

"A homozygous p.Arg127* mutation in TRMT10A was detected."

Independent recurrence of the same allele in an unrelated patient.

p.Gly206Arg (c.616G>A) Pathogenic

Homozygous missense allele in a consanguineous Uzbek Jewish family with three affected siblings, and independently in a girl with hypoplastic kidneys. Uniquely informative mechanistically: the variant enzyme binds tRNA normally but retains under 0.1% of wild-type methylation activity, attributed to defective S-adenosylmethionine binding. It is therefore a catalytically dead allele rather than a folding or substrate-recognition defect.

Show evidence (3 references)

PMID:25053765 SUPPORT Human Clinical

"A homozygous Gly206Arg (G206R) mutation in the TRMT10A gene was identified using whole exome sequencing."

Identifies the allele in the index family for this variant.

PMID:25053765 SUPPORT Human Clinical

"The mutation segregated in the family and was absent from large control cohorts."

Segregation and population-frequency evidence supporting pathogenicity.

PMID:33448213 SUPPORT Human Clinical

"revealing a homozygous mutation in the TRMT10A gene (c.616G>A, p.G206R)"

Independent recurrence of the allele in an unrelated patient.

p.Glu27Ter (c.79G>T) Pathogenic

Homozygous nonsense allele in two siblings who represent the mild end of the spectrum: diabetes diagnosed in their twenties, mild microcephaly at birth with normal final head circumference, and mild learning disability with epilepsy as the only other features. Notable that a truncating allele this proximal produces a milder clinical course than p.Gly206Arg, arguing against a simple allele-severity gradient.

Show evidence (1 reference)

PMID:26526202 SUPPORT Human Clinical

"A homozygous nonsense mutation p.Glu27Ter in TRMT10A was identified using targeted next-generation sequencing and confirmed by PCR/Sanger sequencing."

Identifies the allele and its orthogonal confirmation.

p.Arg93Ter (c.277C>T) / p.Arg133Ter (c.397C>T) Pathogenic

Compound heterozygous nonsense alleles in non-consanguineous siblings with microcephaly, developmental delay and periventricular white matter hyperintensities but no documented dysglycaemia at ages 10 and 12 — the first indication that the neurodevelopmental phenotype can present without the metabolic one.

Show evidence (1 reference)

PMID:26535115 SUPPORT Human Clinical

"Analysis of variants determined that the children were compound heterozygotes for nonsense mutations, c.277C>T (p.Arg93*) and c.397C>T (p.Arg133*), in the TRMT10A gene."

Identifies the compound heterozygous allele pair.

c.496-1G>A Pathogenic

Homozygous canonical splice-acceptor variant in the first reported Chinese patient, whose diabetes was driven by marked insulin resistance and responded to metformin.

Show evidence (1 reference)

PMID:33067246 SUPPORT Human Clinical

"A homozygous mutation c.496-1G>A in TRMT10A was identified using targeted next-generation sequencing and confirmed by PCR/Sanger sequencing."

Identifies the splice-acceptor allele and its confirmation.

c.421-1G>A Pathogenic

Homozygous canonical splice-acceptor variant disrupting the SAM-dependent methyltransferase TRM10-type domain, reported in the patient with spastic-ataxic paraparesis and a Dandy-Walker variant.

Show evidence (1 reference)

PMID:39440920 SUPPORT Human Clinical

"This mutation disrupts the "SAM-dependent methyltransferase TRM10-type domain", which is implicated in methylation and S-adenosylmethionine metabolic biological processes, crucial for mitochondrial and glucose metabolism."

Describes the domain consequence of this splice allele.

p.Arg43Ter (c.127C>T) Pathogenic

Homozygous stop-gained variant classified pathogenic on PVS1, PM2 and PM3 criteria in a 15-year-old with microcephaly, intellectual disability, epilepsy and short stature but no metabolic abnormality at evaluation.

Show evidence (1 reference)

PMID:42181738 SUPPORT Human Clinical

"Exome sequencing identified a homozygous stop-gained pathogenic (PVS1, PM2, and PM3) variant in TRMT10A (c.127C>T; p.Arg43Ter), which was confirmed by Sanger sequencing and showed segregation consistent with autosomal recessive inheritance."

Identifies the allele with its ACMG classification and segregation evidence.

Contiguous gene deletion encompassing TRMT10A Pathogenic

Homozygous contiguous gene deletion removing the whole TRMT10A locus in a 17-year-old female, with RT-PCR and Western blot confirming complete absence of transcript and protein. The most severe reported genotype, with failure to thrive from infancy and gonadal failure; establishes that copy-number variation is a route to this syndrome.

Show evidence (2 references)

PMID:26297882 SUPPORT Human Clinical

"We investigated the clinical spectrum presented by a 17-year-old female with a homozygous contiguous gene deletion involving the TRMT10A gene."

Identifies the structural-variant route to the syndrome.

PMID:26297882 SUPPORT Human Clinical

"RT-PCR and Western blot analysis demonstrated a complete abolishment of TRMT10A mRNA and its translated protein."

Confirms complete loss of the gene product at RNA and protein level.

💊

Medical Actions

5

Metformin

Action: Pharmacotherapy NCIT:C15986

Agent: metformin CHEBI:6801

First-line where peripheral insulin resistance predominates. A Chinese patient with marked insulin resistance responded very well, with HbA1c falling from 14.4% to 6.8% within three months, and metformin was also used in an autoantibody-negative, C-peptide-positive patient diagnosed at 11.4 years. Because the metabolic phenotype has both an insulin-deficient and an insulin-resistant arm, establishing which predominates before committing to therapy is the practical point — this is a treatable form of syndromic diabetes that can be mismanaged as type 1.

Mechanism Target:

INHIBITS Peripheral Insulin Resistance — Metformin acts on the peripheral insulin-resistance arm, not on the TRMT10A lesion or the beta-cell loss; it is symptomatic therapy targeted at the arm of the metabolic phenotype it can reach.

Show evidence (1 reference)

PMID:33067246 SUPPORT Human Clinical

"The diabetes was due to marked insulin resistance and responded very well to metformin treatment."

Links the drug directly to the insulin-resistance node it targets, with a documented clinical response.

Show evidence (2 references)

PMID:33067246 SUPPORT Human Clinical

"A clear genetic diagnosis is helpful for early detection and treatment addressing insulin resistance."

States the therapeutic corollary of the molecular diagnosis in this patient.

PMID:34541035 SUPPORT Human Clinical

"She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."

Independent use of metformin in a paediatric patient with retained C-peptide.

Insulin Replacement

Action: Pharmacotherapy NCIT:C15986

Agent: insulin CHEBI:145810

Used where insulin deficiency from progressive beta-cell loss predominates, including the case in which progressive beta-cell apoptosis required insulin replacement with increased demand driven by unfavourable body composition. Not universally required: the contiguous-deletion patient maintained near-normal glucose for three days entirely off insulin, so insulin need should be re-assessed rather than assumed permanent.

Mechanism Target:

BYPASSES Biphasic Glucose Dysregulation — Exogenous insulin substitutes for the hormone the attenuated beta-cell mass can no longer secrete; it does not address tRNA hypomethylation or beta-cell apoptosis.

Show evidence (1 reference)

PMID:35137278 SUPPORT Human Clinical

"The progressive apoptosis of pancreatic beta cells required insulin replacement therapy, with increased demand due to an unfavorable body composition."

Documents insulin replacement applied to the beta-cell-loss node, with the body-composition modifier of insulin requirement.

Show evidence (1 reference)

PMID:35137278 SUPPORT Human Clinical

"The progressive apoptosis of pancreatic beta cells required insulin replacement therapy, with increased demand due to an unfavorable body composition."

Documents insulin replacement as the treatment used in an insulin-deficient patient.

Antiseizure Medication

Action: Pharmacotherapy NCIT:C15986

Agent: levetiracetam CHEBI:6437

Seizures in this syndrome have responded to standard antiseizure medication; levetiracetam monotherapy at 50 mg/kg/day controlled generalized epilepsy in a molecularly confirmed patient. No syndrome-specific antiseizure strategy or contraindication has been reported, and no agent has been shown to modify the underlying mechanism.

Target Phenotypes: Seizure HP:0001250

Show evidence (1 reference)

PMID:26535115 SUPPORT Human Clinical

"Seizures have been controlled with levetiracetam (50 mg/kg/day, corresponding to 500 mg twice daily)."

Documents the agent, dose and response in a confirmed patient.

Developmental and Educational Support

Action: rehabilitation Ontology label: Rehabilitation NCIT:C15315

Speech, occupational and physical therapy provided through school, with steady developmental progress reported. Standard practice for a static neurodevelopmental disorder rather than a syndrome-specific validated protocol.

Show evidence (1 reference)

PMID:26535115 SUPPORT Human Clinical

"Speech and occupational therapy were provided through school and she has continued to make steady developmental progress."

Documents the supportive interventions used and the outcome.

Genetic Counseling

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Autosomal recessive inheritance carries a 25% sibling recurrence risk, and the recurrence is documented rather than theoretical — three of the reported kindreds had three affected siblings each. Nearly all families were consanguineous, so counseling covers recurrence risk, carrier testing for at-risk relatives, and reproductive options. Framed as standard practice for a confirmed autosomal recessive disorder.

Show evidence (1 reference)

PMID:24204302 SUPPORT Human Clinical

"We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."

Documents the consanguineous pedigree with three affected siblings that grounds the recurrence-risk counseling.

🔬

Biochemical Markers

2

Detectable and Persistent C-Peptide (Detectable)

Show evidence (2 references)

PMID:26297882 SUPPORT Human Clinical

"Endogenous insulin secretion still persisted 22 months after onset of diabetes and relatively normal glucose levels were kept over 3 days without insulin treatment."

Quantifies the persistence of endogenous insulin secretion after diagnosis.

PMID:26297882 SUPPORT Human Clinical

"In order to elucidate the nature of diabetes in this patient, endogenous insulin secretion and glycemic control were evaluated by a glucagon stimulation test and continuous glucose monitoring both during insulin treatment and off therapy."

Documents the assays used to establish residual beta-cell function.

Glycated Hemoglobin (HbA1c) (Variable)

Show evidence (2 references)

PMID:26297882 SUPPORT Human Clinical

"Nevertheless, glycemic control was excellent (HbA1C 5.0%-6.2%)."

Documents the well-controlled end of the glycaemic range.

PMID:33067246 SUPPORT Human Clinical

"In the subsequent visit 3 months after diagnosis, the patient’s HbA1c decreased to 6."

Documents the HbA1c response to metformin; the quote is truncated at the decimal point as the sentence is split in the cached source.

🔬

Diagnosis

3

Molecular Confirmation of Biallelic TRMT10A Variants

Diagnosis is molecular. The original families were solved by linkage plus whole exome sequencing; later patients were increasingly identified by targeted monogenic-diabetes next-generation sequencing panels containing TRMT10A, with Sanger confirmation and parental segregation to establish biallelic status. Because one patient carried a homozygous contiguous gene deletion, copy-number analysis should follow a negative sequencing result when the phenotype fits. Making the diagnosis before the metabolic phase begins is the practical goal, since it enables anticipatory glucose monitoring.

whole exome sequencing NCIT:C101295

Show evidence (3 references)

PMID:25053765 SUPPORT Human Clinical

"A homozygous Gly206Arg (G206R) mutation in the TRMT10A gene was identified using whole exome sequencing."

Documents exome sequencing as the diagnostic route in an index family.

PMID:26526202 SUPPORT Human Clinical

"A targeted panel may be useful to identify previously unsuspected monogenic diabetes among individuals with young‐onset diabetes."

Documents the targeted-panel diagnostic route.

PMID:26535115 SUPPORT Human Clinical

"Accurate diagnosis through genomic testing, as in the children described here, allows for early detection and management of medical complications, such as diabetes mellitus."

States the clinical value of pre-symptomatic molecular diagnosis for anticipating the metabolic phase.

Recognizing the Syndrome in a Young Person with Diabetes

The referral trigger that matters: young-onset, non-insulin-dependent, autoantibody-negative diabetes in a person without obesity who also has intellectual disability, microcephaly or epilepsy. Both the Scottish and the Chinese reports make this recommendation explicitly, and both patients had been carrying an unrecognized monogenic diagnosis. Extra-pancreatic features plus slow-onset autoantibody-negative diabetes should prompt a full monogenic-diabetes work-up.

Show evidence (3 references)

PMID:26526202 SUPPORT Human Clinical

"TRMT10A sequencing should be considered in children or adults with young-onset diabetes who have a history of intellectual disability, microcephaly and epilepsy."

The explicit clinical referral criterion from the reporting authors.

PMID:33067246 SUPPORT Human Clinical

"Genomic testing should be considered in children with non-insulin-dependent diabetes with intellectual disability and microcephaly."

Independent statement of the same referral criterion.

PMID:34541035 SUPPORT Human Clinical

"Patients with slow onset diabetes who are negative for auto-antibodies and have extra-pancreatic features should be tested for all known subtypes of monogenic diabetes."

Broadens the criterion to the full monogenic-diabetes differential.

Distinguishing the Diabetes from Type 1 Diabetes

The diabetes is usually autoantibody-negative with persistent C-peptide, which separates it from autoimmune type 1 diabetes. This discriminator is imperfect and should not be applied mechanically: one reported patient had both ketoacidosis at onset and islet cell autoantibodies, yet retained endogenous insulin secretion 22 months later and maintained near-normal glucose for three days off insulin. Autoantibody positivity therefore does not exclude the syndrome when the neurodevelopmental phenotype is present.

autoantibody measurement NCIT:C181397

Show evidence (2 references)

PMID:34541035 SUPPORT Human Clinical

"She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."

The typical autoantibody-negative, C-peptide-positive profile.

PMID:26297882 REFUTE Human Clinical

"Unlike the previous reports, the patient had ketoacidosis at onset of diabetes and islet cell autoantibodies."

Refutes autoantibody negativity as an absolute discriminator; recorded as REFUTE against the general rule rather than hidden in prose.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

No epidemiological study exists. The disorder is known from a small number of published kindreds — the 2016 Scottish report described itself as the fourth family with diabetes reported, and the case-based literature has grown only incrementally since. Reported families span Moroccan, Uzbek Jewish, Israeli, Scottish, Chinese and Turkish ancestry, with parental consanguinity in nearly all. No numeric rate is recorded here because none has been published.

Show evidence (1 reference)

PMID:26526202 SUPPORT Human Clinical

"We report two siblings from the fourth family reported to have diabetes mellitus as a result of a TRMT10A mutation."

Anchors the scale of the reported literature at the time — a fourth family with the diabetes phenotype.

🔀

Differential Diagnoses

5

Conditions with similar clinical presentations that must be differentiated from Microcephaly, Short Stature, and Impaired Glucose Metabolism 1:

Microcephaly, short stature, and impaired glucose metabolism 2 (PPP1R15B) MONDO:0014785

Overlapping Features The nearest mimic and the reason this pair of entries exists. MSSGM2 shares congenital microcephaly, severe short stature, intellectual disability and autoantibody-negative young-onset diabetes, and both disorders converge on dysregulated protein synthesis — MSSGM1 through tRNA hypomethylation, MSSGM2 through chronically raised phospho-eIF2-alpha from a defective CReP-PP1 holophosphatase. They are distinguished only molecularly. Note that the two are grouped together under a single Orphanet concept (ORPHA:391408 / MONDO:0018320) even though OMIM and MONDO split them by gene.

Distinguishing Features

Causal gene (PPP1R15B vs TRMT10A); MSSGM2 features skeletal, dental, hair and white-matter involvement and, in one family, infantile cirrhosis requiring liver transplantation; MSSGM1 features hypoglycaemia preceding diabetes, documented peripheral insulin resistance, and epilepsy as a prominent feature.

Show evidence (1 reference)

PMID:24204302 SUPPORT Human Clinical

"We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."

Establishes the MSSGM1 clinical description that must be distinguished from the near-identical MSSGM2 presentation.

Type 1 diabetes mellitus

Overlapping Features The commonest misdiagnosis, because the diabetes begins in youth and can present with hyperglycaemia or even ketoacidosis. Distinguished by autoantibody negativity with persistent C-peptide, absence of insulin dependence, and — decisively — the accompanying microcephaly, intellectual disability and epilepsy, which are not features of type 1 diabetes. The discriminator is imperfect: one TRMT10A patient had both ketoacidosis and islet cell autoantibodies, so the neurodevelopmental phenotype rather than the antibody result should drive the referral.

Distinguishing Features

Autoantibody-negative with persistent C-peptide in most patients; frequently non-insulin-dependent and sometimes insulin-resistant and metformin responsive; obligatory neurodevelopmental features absent in type 1 diabetes.

Show evidence (2 references)

PMID:26526202 SUPPORT Human Clinical

"This report also shows the advantages of using a targeted panel to identify previously unsuspected monogenic diabetes among young-onset non-insulin-dependent diabetes in the absence of obesity and autoimmunity."

Frames the exact clinical situation — young-onset diabetes without obesity or autoimmunity — in which type 1 diabetes is wrongly assumed.

PMID:33832649 SUPPORT Other

"Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes."

Establishes that this misdiagnosis is the rule rather than the exception across monogenic diabetes, which is why the syndromic features must drive the referral.

Wolcott-Rallison syndrome (EIF2AK3) Not Yet Curated MONDO:0009192

Overlapping Features The canonical differential for syndromic young-onset diabetes with growth failure, and mechanistically the far end of the same axis: EIF2AK3/PERK loss LOWERS eIF2-alpha phosphorylation, MSSGM2/PPP1R15B raises it, and MSSGM1 perturbs translation a step earlier at tRNA modification — yet all three converge on beta-cell failure plus microcephaly and growth retardation. The discriminators against MSSGM1 are clean: Wolcott-Rallison diabetes is neonatal with undetectable C-peptide from beta-cell loss, and it carries epiphyseal dysplasia and hepatic dysfunction, whereas MSSGM1 presents from late childhood to the third decade with persistent C-peptide and an explicitly normal skeletal survey.

Distinguishing Features

Wolcott-Rallison: biallelic EIF2AK3 variants, neonatal diabetes with undetectable C-peptide, epiphyseal dysplasia, hepatic dysfunction. MSSGM1: biallelic TRMT10A variants, diabetes from late childhood to the third decade with persistent C-peptide, hypoglycaemia often preceding it, and a skeletal survey showing no epiphyseal dysplasia.

Show evidence (2 references)

PMID:26159176 SUPPORT Human Clinical

"Homozygous mutations in EIF2AK3 cause Wolcott-Rallison syndrome, a syndromic form of neonatal diabetes with epiphyseal dysplasia, growth retardation, and variable other manifestations including microcephaly"

Establishes the overlapping phenotype that makes this the primary differential for syndromic diabetes with microcephaly.

PMID:26159176 SUPPORT Human Clinical

"In the Wolcott-Rallison syndrome (with decreased eIF2α phosphorylation), neonatal diabetes is due to β-cell loss and C-peptide is undetectable (13), while DNAJC3, IER3IP1, and PPP1R15B mutations (with increased eIF2α phosphorylation) lead to permanent neonatal or young-onset diabetes with..."

Gives the C-peptide discriminator (undetectable in Wolcott-Rallison vs residual in the translation-stress syndromes, MSSGM1 included) and places the disorders on a shared eIF2-alpha axis.

Microcephaly, epilepsy, and diabetes syndrome 1 (IER3IP1) Not Yet Curated MONDO:0031481

Overlapping Features MEDS1 shares the microcephaly + epilepsy + diabetes triad and, like TRMT10A deficiency, involves a protein enriched in cerebral cortex and beta cells. It is separated by timing and severity, not by which organs are involved: MEDS diabetes is permanent NEONATAL diabetes, the microcephaly is severe with a simplified gyral pattern, and the epilepsy is an infantile epileptic encephalopathy with cortical blindness and early death. TRMT10A patients present decades later with mild intellectual disability and a normally gyrated small brain.

Distinguishing Features

MEDS1: biallelic IER3IP1 variants, permanent neonatal diabetes, primary microcephaly with simplified gyral pattern, infantile epileptic encephalopathy, cortical blindness, death in childhood. MSSGM1: biallelic TRMT10A variants, diabetes from late childhood to the third decade, structurally normal small brain, mild intellectual disability, normal lifespan reported to date.

Show evidence (2 references)

PMID:24138066 SUPPORT Human Clinical

"A syndrome of permanent neonatal diabetes along with primary microcephaly with simplified gyral pattern associated with severe infantile epileptic encephalopathy was recently described in two independent reports in which disease-causing homozygous mutations were identified in the immediate early..."

Defines the MEDS1 phenotype whose neonatal timing and gyral simplification distinguish it from TRMT10A deficiency.

PMID:24138066 SUPPORT Human Clinical

"The triad of microcephaly, generalized seizures, and permanent neonatal diabetes should prompt screening for mutations in IER3IP1."

States the referral rule for MEDS1, which is anchored on the neonatal onset that TRMT10A deficiency lacks.

Wolfram syndrome

Overlapping Features Another syndromic juvenile diabetes with which TRMT10A syndrome has been explicitly compared. Both present as non-autoimmune diabetes in childhood with neurological features; Wolfram adds optic atrophy, diabetes insipidus and deafness, which are not features of TRMT10A syndrome, and lacks the congenital microcephaly.

Distinguishing Features

Wolfram: optic atrophy, diabetes insipidus, sensorineural deafness, WFS1 or CISD2 variants, no congenital microcephaly. TRMT10A: primary microcephaly, short stature, epilepsy, biallelic TRMT10A variants.

Show evidence (1 reference)

PMID:39243962 SUPPORT Human Clinical

"TRMT10A gene mutation has been linked to syndromic juvenile diabetes in a manner analogous to Wolfram's syndrome."

Records the explicit comparison drawn in the literature between the two syndromic juvenile-diabetes entities.

📊

Related Datasets

2

TRMT10A associated RNA targets geo:GSE129502

Human high-throughput sequencing profiling of the RNA species bound by TRMT10A, undertaken to define the enzyme's substrate repertoire in human cells rather than yeast. Directly informative for the "Loss of tRNA m1G9 Methyltransferase Activity" node, since which tRNAs TRMT10A actually services in human cells determines which codons are affected when it is lost.

human BULK RNA SEQ n=6

Surfaced by `just discover-datasets` as a GENE_ONLY candidate and retained after manual relevance triage: the GEO summary is explicitly about defining the human tRNA substrate repertoire of TRMT10A, so it bears on the disease mechanism rather than merely mentioning the gene. It is a gene-function dataset, not a patient cohort - it does not contain MSSGM1 case material. No evidence block: no exact-quote-bearing publication is attached to the accession.

Coordination of mRNA and tRNA methylations by TRMT10A geo:GSE146207

The dataset underlying the TRMT10A-FTO study, profiling m6A changes and transcript-level consequences of TRMT10A ablation. Supports the "Coordinated mRNA m6A Dysregulation via the FTO Axis" node and is the most directly testable resource for the open question of what drives peripheral insulin resistance in this disorder.

human n=12

PMID:32213595

Surfaced by `just discover-datasets` as a GENE_ONLY candidate; retained because its linked publication (PMID:32213595) is already cited in this entry for the FTO/m6A mechanism, so the disease relevance is established rather than assumed. GEO does not assign a single gdstype to this series, so `data_type` is left unset rather than guessed. A cell-line perturbation dataset, not patient material.

🧫

Experimental Models

2

Patient-derived iPSC beta-like cells (TRMT10A-deficient) IPSC_DERIVED_MODEL

Induced pluripotent stem cells reprogrammed from TRMT10A-deficient patient fibroblasts and differentiated to pancreatic beta-like cells, alongside control lines. This is the model that carries the beta-cell mechanism, and it does so precisely where the mouse fails: it demonstrates oxidative stress, intrinsic-pathway apoptosis, and sensitization to ER stress in cells of human patient genotype.

Pathograph links

Beta-Cell Oxidative Stress and Intrinsic Apoptosis recapitulates fidelity: high Patient-genotype human beta-like cells reproduce the oxidative stress and intrinsic apoptotic signalling proposed to underlie beta-cell loss.

Limitations: iPSC-derived beta-like cells are immature relative to adult islet beta cells and are studied over days rather than the decades over which the human phenotype accumulates, so the model shows the mechanism is available but cannot demonstrate the cumulative mass loss.

Readouts

Intrinsic apoptotic pathway activation

Direction: INCREASED

Interpretation: Direct measure of the apoptotic mechanism in patient-genotype cells.

Show evidence (1 reference)

PMID:30247717 SUPPORT In Vitro

"we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells"

Reports the apoptosis measurement grounding this readout.

Show evidence (1 reference)

PMID:30247717 SUPPORT In Vitro

"Using RNA interference and induced pluripotent stem cell-derived pancreatic β-like cells from healthy controls and TRMT10A-deficient patients we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells."

Establishes the model system and its use for the beta-cell mechanism node.

tRNA Hypomethylation, Destabilization and Fragmentation measures fidelity: high The same system was used to show that 5'-tRNA-Gln fragments are not merely correlated with beta-cell death but are sufficient to cause it.

Limitations: Fragment sufficiency was established by transfecting synthetic fragments, which does not establish the intracellular concentrations reached in patient tissue in vivo.

Readouts

5'-tRNA-Gln fragment abundance

Direction: INCREASED

Interpretation: The cytotoxic species linking hypomethylation to beta-cell death.

Show evidence (1 reference)

PMID:30247717 SUPPORT In Vitro

"We show that tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5'-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death."

Reports the fragmentation measurement and its causal test.

Show evidence (1 reference)

PMID:30247717 SUPPORT In Vitro

"This study unmasks tRNA hypomethylation and fragmentation as a hitherto unknown mechanism of pancreatic β-cell demise relevant to monogenic and polygenic forms of diabetes."

Establishes the system as the one that defined this mechanism.

TRMT10A silencing in rat INS-1E and human EndoC-betaH1 beta cells CELL_LINE

siRNA knockdown of TRMT10A in rat and human clonal beta-cell lines and in dispersed human islets. The original demonstration that loss of TRMT10A is sufficient to kill beta cells, and the experiment that first connected a housekeeping tRNA-modification enzyme to a diabetes phenotype.

Pathograph links

Beta-Cell Oxidative Stress and Intrinsic Apoptosis perturbs fidelity: moderate Acute silencing establishes sufficiency of TRMT10A loss for beta-cell death in two species.

Limitations: Acute siRNA knockdown in clonal lines models neither the constitutive germline null state nor the decades-long time course of the human disease, and residual protein after knockdown is not equivalent to the complete absence seen in patients.

Readouts

Beta-cell apoptosis after TRMT10A silencing

Direction: INCREASED

Interpretation: Establishes that removing TRMT10A is by itself enough to trigger beta-cell death.

Show evidence (1 reference)

PMID:24204302 SUPPORT In Vitro

"TRMT10A silencing induces rat and human β-cell apoptosis."

Reports the apoptosis measurement behind this readout.

Show evidence (1 reference)

PMID:24204302 SUPPORT In Vitro

"TRMT10A silencing induces rat and human β-cell apoptosis."

Establishes the knockdown system as informative for the beta-cell death node.

🐁

Animal Models

1

Trmt10a null mouse (E29Stop)

Constitutive null mouse engineered to mimic the human p.Glu27Ter allele. Reproduces the reduced body weight and the neurological arm of the human syndrome — smaller hippocampal postsynaptic densities with impaired synaptic plasticity and memory — and provides the only in vivo demonstration of the translational mechanism (codon-specific ribosome slowdown, ATF4 derepression). Critically, it does NOT reproduce the pancreatic phenotype.

Species

Mouse

Genotype

Trmt10a c.85G>T (p.Glu29Ter) homozygous null

Publication

PMID:38950903

Pathograph links

Codon-Specific Translational Impairment recapitulates fidelity: high Ribosome profiling in null-mouse brain establishes the codon-level translational lesion, and the same tRNA depletion was confirmed in a human TRMT10A-null cell line.

Limitations: Ribosome profiling was performed in mouse brain; the corresponding measurement has not been made in human neural tissue, though the underlying tRNA depletion was replicated in a human cell line.

Readouts

tRNA-Gln(CUG) and initiator methionine tRNA steady-state levels

Direction: DECREASED

Interpretation: Depletion of the two m1G9-dependent tRNAs is the proximate cause of the codon-specific translational deficit.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A."

Reports the measurement grounding this readout, in both mouse and human cells.

Ribosome occupancy at the Gln(CAG) codon

Direction: INCREASED

Interpretation: Increased ribosome dwell time at Gln codons is the direct functional consequence of tRNA-Gln depletion.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames."

Reports the ribosome-profiling measurement behind this readout.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons."

Establishes the model as informative for the translational mechanism node.

Impaired Synaptic Structure and Plasticity recapitulates fidelity: moderate The null mouse shows smaller hippocampal postsynaptic densities with defective synaptic plasticity and memory, offering a structural correlate for the intellectual disability that does not require neuronal loss.

Limitations: Synaptic and memory measures in mouse are not directly equivalent to human intellectual disability, and no corresponding human synaptic pathology has been demonstrated.

Readouts

Hippocampal postsynaptic density size

Direction: DECREASED

Interpretation: Structural correlate of the impaired-plasticity node in this model.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."

Reports the postsynaptic-density measurement behind this readout.

Show evidence (1 reference)

PMID:38950903 SUPPORT Model Organism

"Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain."

Connects the translational lesion to neuronal structural proteins, supporting this model as informative for the synaptic node.

Beta-Cell Oxidative Stress and Intrinsic Apoptosis fails to recapitulate fidelity: low Trmt10a null mice show no discernible pancreatic defect, in direct contrast to the diabetes that defines the human syndrome. This negative result is the reason the beta-cell mechanism rests on human cellular models rather than on a mouse.

Limitations: The published phenotyping reports no discernible pancreatic defect but does not establish over what age range or under what metabolic challenge the pancreas was assessed, so an unstressed-condition ceiling effect cannot be excluded. Species differences in beta-cell tRNA biology and in lifespan-scaled cumulative apoptosis are plausible explanations.

Show evidence (1 reference)

PMID:38950903 REFUTE Model Organism

"Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."

Explicitly records the absence of a pancreatic phenotype in the null mouse, refuting recapitulation of the beta-cell node.

{ }

Source YAML

click to show

name: Microcephaly, Short Stature, and Impaired Glucose Metabolism 1
creation_date: "2026-08-20T07:00:00Z"
category: Mendelian
description: >-
  Microcephaly, short stature, and impaired glucose metabolism 1 (MSSGM1;
  TRMT10A deficiency) is an ultra-rare autosomal recessive syndrome caused by
  biallelic loss-of-function variants in TRMT10A, the nucleolar tRNA
  methyltransferase that installs N1-methylguanosine at position 9 (m1G9) in
  the D-loop of many cytoplasmic tRNAs. TRMT10A is ubiquitously expressed but
  enriched in brain and pancreatic islets — precisely the two tissues that
  fail. Loss of m1G9 destabilizes and fragments specific tRNAs (tRNA-Gln and
  initiator methionine tRNA are established targets); the resulting 5'-tRNA-Gln
  fragments are themselves cytotoxic and, together with oxidative stress,
  trigger the intrinsic apoptotic pathway in beta cells, while codon-specific
  ribosome slowdown and derepressed ATF4 translation perturb synthesis of
  neuronal proteins. Clinically this produces congenital primary microcephaly
  with intellectual disability and epilepsy, proportionate short stature, and a
  characteristically biphasic glucose phenotype: hypoglycaemia (often
  hyperinsulinaemic) in infancy or childhood transitioning to young-onset,
  autoantibody-negative diabetes in the second to third decade. The diabetes is
  not a single mechanism — reported cases span beta-cell insulin deficiency and
  marked peripheral insulin resistance responsive to metformin, and treatment
  should follow whichever arm predominates. The metabolic phenotype is
  age-dependent and may be entirely absent at the time a child is diagnosed, so
  a normal glucose profile does not exclude the diagnosis.
parents:
- Microcephaly
- Monogenic diabetes
synonyms:
- MSSGM1
- TRMT10A deficiency
- TRMT10A-related syndrome
- Primary microcephaly-mild intellectual disability-young-onset diabetes syndrome
disease_term:
  preferred_term: microcephaly, short stature, and impaired glucose metabolism 1
  term:
    id: MONDO:0000208
    label: microcephaly, short stature, and impaired glucose metabolism 1
references:
- reference: PMID:24204302
  title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
- reference: PMID:25053765
  title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
- reference: PMID:30247717
  title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
- reference: PMID:38950903
  title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
- reference: PMID:42181738
  title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."

pathophysiology:
- name: Biallelic TRMT10A Loss-of-Function Variants
  description: >-
    The initiating lesion is biallelic inactivation of TRMT10A (4q23). Reported
    alleles span nonsense variants subject to nonsense-mediated decay
    (p.Arg127Ter in the index Moroccan family, p.Glu27Ter, p.Arg43Ter,
    p.Arg93Ter/p.Arg133Ter in compound heterozygosity), canonical splice-acceptor
    variants (c.496-1G>A, c.421-1G>A), a catalytically dead missense allele
    (p.Gly206Arg), and a homozygous contiguous gene deletion removing the locus.
    In the index family neither TRMT10A mRNA nor protein was detectable in
    patient lymphoblasts, establishing complete loss of the gene product rather
    than a dominant-negative or hypomorphic effect. Heterozygous parents are
    unaffected.
  role: trigger
  biological_scale: MOLECULAR
  genes:
  - preferred_term: TRMT10A
    term:
      id: hgnc:28403
      label: TRMT10A
  cellular_components:
  - preferred_term: nucleolus
    term:
      id: GO:0005730
      label: nucleolus
  downstream:
  - target: Loss of tRNA m1G9 Methyltransferase Activity
    causal_link_type: DIRECT
    description: >-
      Absence of TRMT10A protein, or expression of a catalytically inert variant,
      directly removes the cell's m1G9 methyltransferase activity.
    evidence:
    - reference: PMID:25053765
      reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Determination of the methylation activity of the expressed wild-type (WT) and variant TRMT10A enzymes with transcripts of (32)P -tRNA(Gly) GCC as a substrate revealed a striking defect (<0.1% of WT activity) for the variant enzyme."
      explanation: >-
        Direct enzymatic demonstration that a disease allele abolishes
        methyltransferase activity, establishing this causal edge.
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Linkage analysis and whole exome sequencing were used to identify the causal nonsense mutation, which changed an arginine codon into a stop at position 127 of the tRNA methyltransferase homolog gene TRMT10A (also called RG9MTD2)."
    explanation: Identifies TRMT10A and the first disease-causing nonsense allele.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TRMT10A mRNA and protein were absent in lymphoblasts from the affected siblings."
    explanation: >-
      Establishes complete loss of the gene product in patient cells, defining
      the mechanism as loss of function.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRMT10A localizes to the nucleolus of β- and non-β-cells, where tRNA modifications occur."
    explanation: Localizes the affected enzyme to the nucleolar site of tRNA modification.

- name: Loss of tRNA m1G9 Methyltransferase Activity
  description: >-
    TRMT10A is the principal — and in human cells apparently non-redundant —
    enzyme installing N1-methylguanosine at position 9 of cytoplasmic tRNAs, the
    mammalian orthologue of yeast Trm10. Its activity is lost outright by
    nonsense and splice alleles, and reduced below 0.1% of wild type by the
    p.Gly206Arg missense variant, which retains normal tRNA binding but cannot
    use the S-adenosylmethionine methyl donor. This separates substrate
    recognition from catalysis and shows the disease mechanism is loss of
    methyl transfer rather than loss of tRNA engagement.
  role: intermediate
  biological_scale: MOLECULAR
  molecular_functions:
  - preferred_term: tRNA (guanosine(9)-N1)-methyltransferase activity
    term:
      id: GO:0052905
      label: tRNA (guanosine(9)-N1)-methyltransferase activity
    modifier: LOSS_OF_FUNCTION
  biological_processes:
  - preferred_term: tRNA methylation
    term:
      id: GO:0030488
      label: tRNA methylation
    modifier: DECREASED
  downstream:
  - target: tRNA Hypomethylation, Destabilization and Fragmentation
    causal_link_type: DIRECT
    description: >-
      Absent m1G9 leaves target tRNAs hypomodified in the D-loop, reducing their
      steady-state stability and exposing them to endonucleolytic cleavage.
    evidence:
    - reference: PMID:30247717
      reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We show that tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5'-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death."
      explanation: >-
        Directly links loss of guanosine-9 methylation to tRNA fragmentation,
        establishing this edge.
  evidence:
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The completely abolished m(1)G9 methyltransferase activity of the mutant enzyme is likely due to significant defects in its ability to bind the methyl donor S-adenosyl methionine."
    explanation: >-
      Attributes the catalytic failure of the p.Gly206Arg allele to loss of
      methyl-donor binding.
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The binding affinity of the G206R variant enzyme to tRNA, determined by fluorescence anisotropy, was similar to that of the WT enzyme."
    explanation: >-
      Shows tRNA binding is preserved, isolating the defect to catalysis rather
      than substrate recognition.
  - reference: PMID:30247717
    reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here we confirm the role of TRMT10A as a guanosine 9 tRNA methyltransferase, and identify tRNAGln and tRNAiMeth as two of its targets."
    explanation: >-
      Confirms the enzymatic assignment in human cells and names the two
      physiologically critical substrate tRNAs.

- name: tRNA Hypomethylation, Destabilization and Fragmentation
  description: >-
    Hypomodified tRNAs are degraded or cleaved rather than simply carried in an
    unmethylated state. In Trmt10a null mice and in a TRMT10A-null human cell
    line the steady-state levels of tRNA-Gln(CUG) and initiator methionine tRNA
    fall across tissues, and in patient-derived beta-like cells tRNA-Gln is
    cleaved into 5' fragments. The fragments are not inert by-products: purified
    5'-tRNA-Gln fragments are themselves sufficient to kill beta cells, making
    this node both a loss of translational capacity and a gain of a cytotoxic
    species.
  role: intermediate
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: tRNA decay
    term:
      id: GO:0016078
      label: tRNA decay
    modifier: INCREASED
  downstream:
  - target: Codon-Specific Translational Impairment
    causal_link_type: DIRECT
    description: >-
      Depletion of tRNA-Gln and initiator methionine tRNA restricts decoding of
      the corresponding codons and initiation of translation.
    evidence:
    - reference: PMID:38950903
      reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames."
      explanation: >-
        Demonstrates directly that the tRNA deficit translates into
        codon-specific ribosome stalling and altered uORF-controlled translation.
  - target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
    causal_link_type: DIRECT
    description: >-
      5'-tRNA-Gln fragments generated by hypomethylation are the proximate
      mediators of beta-cell death in TRMT10A deficiency.
    evidence:
    - reference: PMID:30247717
      reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We show that tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5'-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death."
      explanation: >-
        Establishes the tRNA fragments as the causal mediators between
        hypomethylation and beta-cell death.
  evidence:
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A."
    explanation: >-
      Documents the loss of the two key tRNA species in vivo and, importantly,
      confirms the same effect in a human cell line.
  - reference: PMID:30247717
    reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This study unmasks tRNA hypomethylation and fragmentation as a hitherto unknown mechanism of pancreatic β-cell demise relevant to monogenic and polygenic forms of diabetes."
    explanation: Frames hypomethylation-plus-fragmentation as the disease mechanism.

- name: Coordinated mRNA m6A Dysregulation via the FTO Axis
  description: >-
    Beyond its catalytic role on tRNA, TRMT10A physically interacts with the
    mRNA demethylase FTO. Ablating TRMT10A therefore raises m6A on a shared set
    of mRNAs, which are then destabilized through the m6A reader YTHDF2. The
    affected transcripts are enriched for codons read by the very tRNAs that
    carry m1G9 (tRNA-Gln(TTG), tRNA-Arg(CCG), tRNA-Thr(CGT)), coupling the tRNA
    and mRNA arms of the lesion. This is a parallel, non-catalytic route by
    which TRMT10A loss perturbs gene expression, and it is why the disorder is
    not fully explained by tRNA methylation alone.
  role: modifier
  biological_scale: MOLECULAR
  genes:
  - preferred_term: FTO
    term:
      id: hgnc:24678
      label: FTO
  biological_processes:
  - preferred_term: mRNA catabolic process
    term:
      id: GO:0006402
      label: mRNA catabolic process
    modifier: INCREASED
  downstream:
  - target: Codon-Specific Translational Impairment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Accelerated decay of m6A-marked transcripts compounds the codon-level
      translational deficit arising from tRNA loss, acting on an overlapping set
      of messages.
    evidence:
    - reference: PMID:32213595
      reference_title: "Coordination of mRNA and tRNA methylations by TRMT10A."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Furthermore, transcripts with increased m6A upon TRMT10A ablation contain an overrepresentation of m1G9-containing tRNAs codons read by tRNAGln(TTG), tRNAArg(CCG), and tRNAThr(CGT)"
      explanation: >-
        Shows the mRNA and tRNA arms converge on the same codons, supporting a
        compounding effect; the functional consequence for the disease phenotype
        is inferred rather than directly measured, hence PARTIAL.
  evidence:
  - reference: PMID:32213595
    reference_title: "Coordination of mRNA and tRNA methylations by TRMT10A."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we show that a tRNA methyltransferase, TRMT10A, interacts with an mRNA demethylase FTO (ALKBH9), both in vitro and inside cells."
    explanation: Establishes the physical TRMT10A-FTO interaction underlying this node.
  - reference: PMID:32213595
    reference_title: "Coordination of mRNA and tRNA methylations by TRMT10A."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We show that TRMT10A ablation not only leads to decreased m1G in tRNA but also significantly increases m6A levels in mRNA."
    explanation: >-
      Demonstrates that TRMT10A loss raises mRNA m6A in addition to lowering
      tRNA m1G.

- name: Codon-Specific Translational Impairment
  description: >-
    Loss of initiator methionine tRNA and tRNA-Gln does not shut down protein
    synthesis globally; it biases it. Ribosome profiling of Trmt10a null mouse
    brain shows slowing at Gln(CAG) codons and, because initiator tRNA is
    limiting, more frequent leaky scanning past the upstream open reading frames
    of Atf4 — the canonical integrated-stress-response sensor — so ATF4 is
    translationally derepressed without an upstream eIF2-alpha kinase signal.
    Transcripts encoding neuronal structural proteins are among those most
    perturbed, which is the proposed link between a housekeeping RNA-modification
    enzyme and a specifically neurodevelopmental phenotype.
  role: central_effector
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: translational initiation
    term:
      id: GO:0006413
      label: translational initiation
    modifier: DECREASED
  - preferred_term: integrated stress response signaling
    term:
      id: GO:0140467
      label: integrated stress response signaling
    modifier: INCREASED
  downstream:
  - target: Reduced Neural Progenitor Pool in the Developing Brain
    causal_link_type: DIRECT
    description: >-
      Perturbed translation of neuronal transcripts in a tissue enriched for
      TRMT10A expression restricts the neuronal pool generated during
      development.
    evidence:
    - reference: PMID:24204302
      reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Taken together, we propose that TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain."
      explanation: >-
        The authors advance this as a proposal grounded in the expression
        pattern and the beta-cell apoptosis data rather than a direct
        measurement of neural progenitors, so the edge is PARTIAL.
  - target: Impaired Synaptic Structure and Plasticity
    causal_link_type: DIRECT
    description: >-
      Reduced synthesis of neuronal structural proteins translates into smaller
      postsynaptic densities and impaired plasticity in the null mouse.
    evidence:
    - reference: PMID:38950903
      reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain."
      explanation: >-
        Identifies neuronal structural transcripts as the selectively affected
        class, linking this node to the synaptic phenotype.
  evidence:
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames."
    explanation: >-
      Provides the mechanistic content of this node: codon-specific stalling
      plus translational derepression of ATF4.
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons."
    explanation: >-
      States the general principle that a universal tRNA modification acts
      through specific-codon translation.

- name: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
  description: >-
    Pancreatic beta cells are among the tissues with the highest TRMT10A
    expression and the highest secretory protein-synthetic load, and they are the
    cell type in which the consequences of tRNA hypomethylation have been worked
    out directly. Silencing TRMT10A kills rat and human beta cells. In
    iPSC-derived beta-like cells from TRMT10A-deficient patients the deficiency
    raises reactive oxygen species and engages the intrinsic (mitochondrial)
    apoptotic pathway, and sensitizes the cells to ER-stress-induced apoptosis on
    top of that baseline.
  role: intermediate
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: pancreatic beta cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  locations:
  - preferred_term: pancreatic islet
    term:
      id: UBERON:0000006
      label: islet of Langerhans
  biological_processes:
  - preferred_term: cellular response to oxidative stress
    term:
      id: GO:0034599
      label: cellular response to oxidative stress
    modifier: INCREASED
  - preferred_term: intrinsic apoptotic signaling pathway
    term:
      id: GO:0097193
      label: intrinsic apoptotic signaling pathway
    modifier: INCREASED
  downstream:
  - target: Progressive Beta-Cell Mass Loss
    causal_link_type: DIRECT
    description: >-
      Cumulative apoptotic attrition of beta cells over years erodes functional
      beta-cell mass.
    evidence:
    - reference: PMID:25053765
      reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We propose that TRMT10A deficiency accounts for abnormalities in glucose homeostasis initially manifesting both ketotic and non-ketotic hypoglycaemic events with transition to diabetes in adolescence, perhaps as a consequence of accelerated β cell apoptosis."
      explanation: >-
        The authors explicitly frame accelerated beta-cell apoptosis as the
        proposed driver ("perhaps as a consequence"), so this edge is PARTIAL.
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRMT10A silencing induces rat and human β-cell apoptosis."
    explanation: >-
      Direct experimental demonstration that loss of TRMT10A is sufficient to
      kill beta cells in both species.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRMT10A is ubiquitously expressed but enriched in brain and pancreatic islets, consistent with the tissues affected in this syndrome."
    explanation: >-
      Explains the tissue selectivity of a lesion in an otherwise housekeeping
      enzyme.
  - reference: PMID:30247717
    reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells"
    explanation: >-
      Identifies oxidative stress and the intrinsic apoptotic pathway as the
      effector mechanism, using patient-derived iPSC beta-like cells.
  - reference: PMID:30247717
    reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRMT10A deficiency induces oxidative stress and sensitizes iPSC-derived β-like cells to endoplasmic reticulum stress-induced apoptosis."
    explanation: >-
      Documents the additional sensitization to ER stress layered on the
      baseline oxidative insult.

- name: Progressive Beta-Cell Mass Loss
  description: >-
    Cumulative apoptotic attrition of beta cells, the cellular state that links
    the apoptosis node to the whole-organism glucose phenotype. Loss is partial
    rather than complete at the time patients present: C-peptide remains
    detectable, endogenous insulin secretion persisted 22 months after diabetes
    onset in one patient, and near-normal glucose was maintained for three days
    entirely off insulin. Because attrition is gradual, the reserve available to
    an individual is a function of age, which is what makes the downstream
    glucose phenotype evolve rather than present fully formed.
  role: intermediate
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: pancreatic beta cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  biological_processes:
  - preferred_term: insulin secretion
    term:
      id: GO:0030073
      label: insulin secretion
    modifier: DECREASED
  downstream:
  - target: Biphasic Glucose Dysregulation
    causal_link_type: DIRECT
    description: >-
      Falling beta-cell reserve is the proposed basis of the shift from
      hypoglycaemia in childhood to overt diabetes in adolescence or young
      adulthood.
    evidence:
    - reference: PMID:25053765
      reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We propose that TRMT10A deficiency accounts for abnormalities in glucose homeostasis initially manifesting both ketotic and non-ketotic hypoglycaemic events with transition to diabetes in adolescence, perhaps as a consequence of accelerated β cell apoptosis."
      explanation: >-
        The authors frame the transition as a proposal ("perhaps as a
        consequence"), so this edge is PARTIAL.
  evidence:
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Endogenous insulin secretion still persisted 22 months after onset of diabetes and relatively normal glucose levels were kept over 3 days without insulin treatment."
    explanation: >-
      Shows the loss is partial rather than complete, unlike autoimmune type 1
      diabetes.
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The fluctuating course of puberty and diabetes may reflect intermittent apoptotic damages due to sensitization of the relevant cells to various stress agents in the absence of functional TRMT10A."
    explanation: >-
      Proposes intermittent stress-triggered apoptosis as the basis of the
      fluctuating endocrine course.

- name: Biphasic Glucose Dysregulation
  description: >-
    The whole-organism glucose phenotype, which evolves rather than presenting
    fully formed. In several kindreds the first metabolic manifestation in
    infancy or childhood is hypoglycaemia — ketotic and non-ketotic events, in
    some patients frankly hyperinsulinaemic — followed years later by overt
    diabetes. Onset ranges from childhood to the third decade, and in at least
    one adolescent with a confirmed biallelic nonsense genotype no metabolic
    abnormality had appeared by age 15.
  role: consequence
  biological_scale: ORGANISM
  downstream:
  - target: Peripheral Insulin Resistance
    causal_link_type: UNKNOWN
    description: >-
      Marked insulin resistance is documented in several patients, but whether it
      is a consequence of the beta-cell lesion, an independent effect of TRMT10A
      loss in insulin-target tissues, or secondary to body composition is not
      established. The link type is recorded as UNKNOWN rather than asserted.
    evidence:
    - reference: PMID:33067246
      reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "It adds to current knowledge of TRMT10A related with young-onset non-insulin-dependent diabetes and confirms the a single previous report of insulin resistance in this syndrome."
      explanation: >-
        Confirms insulin resistance occurs in the syndrome but offers no
        mechanism connecting it to beta-cell loss, hence PARTIAL and an UNKNOWN
        link type.
  evidence:
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."
    explanation: >-
      Documents the early hypoglycaemic phase of the biphasic glucose
      phenotype.
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."
    explanation: >-
      Documents the late end of the onset range and the insulin-resistant
      presentation.

- name: Peripheral Insulin Resistance
  description: >-
    A distinct metabolic arm, present in a subset of patients and clinically
    consequential because it dictates a different treatment. Formal testing in
    the Scottish kindred showed a Matsuda index of 1.46 against a control value
    around 14, and a Chinese patient with marked insulin resistance responded to
    metformin with HbA1c falling from 14.4% to 6.8% in three months. Neither the
    tRNA-fragment mechanism nor beta-cell apoptosis explains peripheral insulin
    resistance, so this node is recorded as an evidenced but mechanistically
    unexplained arm rather than as a downstream consequence of beta-cell loss.
  role: consequence
  biological_scale: ORGANISM
  biological_processes:
  - preferred_term: cellular response to insulin stimulus
    term:
      id: GO:0032869
      label: cellular response to insulin stimulus
    modifier: DECREASED
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The findings were suggestive of insulin resistance"
    explanation: >-
      Reports the formal insulin-sensitivity testing that established this arm
      of the metabolic phenotype.
  - reference: PMID:33067246
    reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diabetes was due to marked insulin resistance and responded very well to metformin treatment."
    explanation: >-
      Independent confirmation of the insulin-resistant arm and its therapeutic
      implication.

- name: Reduced Neural Progenitor Pool in the Developing Brain
  description: >-
    TRMT10A is expressed in human embryonic and fetal brain, and the microcephaly
    is congenital and primary — brain architecture is typically normal on
    imaging, with a small brain rather than a malformed one. The proposed
    mechanism is a reduced pool of neurons generated during development, in
    parallel with (not downstream of) the beta-cell lesion. This remains the
    weakest-evidenced node in the chain: it rests on the expression pattern, the
    beta-cell apoptosis data, and the clinical phenotype, not on a direct
    measurement of human neural progenitors.
  role: consequence
  biological_scale: TISSUE
  cell_types:
  - preferred_term: neural progenitor cell
    term:
      id: CL:0011020
      label: neural progenitor cell
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  biological_processes:
  - preferred_term: neural precursor cell proliferation
    term:
      id: GO:0061351
      label: neural precursor cell proliferation
    modifier: DECREASED
  - preferred_term: brain development
    term:
      id: GO:0007420
      label: brain development
    modifier: DECREASED
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Taken together, we propose that TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain."
    explanation: >-
      The neural arm is explicitly a proposal by the authors, not a measured
      result, so the evidence is PARTIAL.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In situ hybridization studies showed that TRMT10A is expressed in human embryonic and fetal brain."
    explanation: >-
      Establishes that the enzyme is present in the developing human brain at
      the relevant time, the basis for the neurodevelopmental arm.

- name: Impaired Synaptic Structure and Plasticity
  description: >-
    A second, non-proliferative neural mechanism demonstrated in the Trmt10a null
    mouse: hippocampal postsynaptic densities are smaller and synaptic plasticity
    and memory are defective, without gross brain malformation. This offers a
    route to intellectual disability that does not require neuronal loss, and it
    is the arm best supported by direct in vivo measurement — though only in
    mouse.
  role: consequence
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: regulation of synaptic plasticity
    term:
      id: GO:0048167
      label: regulation of synaptic plasticity
    modifier: DECREASED
  evidence:
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."
    explanation: >-
      Direct in vivo demonstration of the synaptic and memory phenotype; the
      same sentence records the absence of a pancreatic phenotype in the mouse.

phenotypes:
- category: Neurologic
  name: Primary Microcephaly
  description: >-
    Congenital primary microcephaly is a core diagnostic feature, present in
    every reported kindred. Head circumference is typically -3 to -5 SD; brain
    MRI shows a small but structurally normal brain rather than a malformation.
    Severity tracks genotype: in the milder p.Glu27Ter Scottish kindred
    microcephaly was mild at birth and head circumference normalized by
    adulthood, so a normal adult head circumference does not exclude the
    diagnosis.
  phenotype_term:
    preferred_term: Primary microcephaly
    term:
      id: HP:0011451
      label: Primary microcephaly
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."
    explanation: Establishes microcephaly as a defining feature of the syndrome.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Magnetic resonance imaging of the head showed a\nsmall brain with no malformation or other abnormality"
    explanation: >-
      Documents that the microcephaly is a reduction in brain size without
      structural malformation, consistent with primary microcephaly.
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mild microcephaly was present at birth but their final head circumferences were normal."
    explanation: >-
      Documents the milder end of the spectrum, in which head circumference
      normalizes with growth.

- category: Neurologic
  name: Intellectual Disability
  description: >-
    Intellectual disability is present in essentially all reported patients and
    is typically mild — the Orphanet designation for this disorder names it
    explicitly. Measured IQ in the index family was 69 and 52 in two siblings.
    Global developmental delay with disproportionate speech delay is the usual
    presentation in childhood.
  phenotype_term:
    preferred_term: Mild intellectual disability
    term:
      id: HP:0001256
      label: Mild intellectual disability
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy and intellectual disability were features in common."
    explanation: Documents intellectual disability as a shared feature across affected siblings.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Psychometric testing led to the diagnosis of mild intellectual disability."
    explanation: >-
      Formal psychometric confirmation of the mild severity band in a
      molecularly confirmed patient.

- category: Neurologic
  name: Global Developmental Delay
  description: >-
    Developmental delay is evident from early childhood, with speech delay
    typically more prominent than motor delay; affected children often reach
    early motor milestones at normal ages before language and behavioural
    problems emerge. Infantile hypotonia is described. The course is static
    rather than regressive.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:42181738
    reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurodevelopmental delay was evident from early childhood, and electroencephalography revealed generalized epileptiform activity requiring treatment, whereas brain magnetic resonance imaging was normal."
    explanation: Documents early-childhood developmental delay in a confirmed patient.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Speech delay and behavioral problems were noted by 4 years of age."
    explanation: Documents the speech-predominant delay pattern.

- category: Neurologic
  name: Epilepsy
  description: >-
    Seizures occur in a substantial subset but are not universal. Reported
    semiologies span childhood-onset generalized epilepsy with frontally
    dominant polyspike-and-wave on EEG, febrile status epilepticus, and petit
    mal (absence) epilepsy in adolescence. Seizures have been controlled with
    standard antiseizure medication.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy and intellectual disability were features in common."
    explanation: Documents epilepsy in both affected siblings of this family.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A recent EEG showed symmetric, bilateral, frontally dominant polyspike and wave discharges, consistent with generalized epilepsy."
    explanation: Characterizes the electroclinical phenotype in a confirmed patient.
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."
    explanation: Independent family with seizures in all three affected siblings.

- category: Neuroimaging
  name: Periventricular and Subcortical White Matter Hyperintensities
  description: >-
    T2/FLAIR hyperintensity in periventricular and subcortical white matter,
    without white matter volume loss and without parenchymal calcification, was
    the imaging finding in compound heterozygous siblings and is interpreted as
    delayed or abnormal myelination rather than a destructive leukoencephalopathy.
    Brain architecture — corpus callosum, cerebellum, cortical gyration — was
    normal. This finding is inconstant: MRI is reported as entirely normal in
    other molecularly confirmed patients.
  phenotype_term:
    preferred_term: Periventricular white matter hyperintensities
    term:
      id: HP:0030891
      label: Periventricular white matter hyperintensities
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both children had brain MRI studies that showed periventricular and subcortical T2/FLAIR hyperintensities, without signs of white matter volume loss, and no parenchymal calcifications by CT scan."
    explanation: Primary description of the white matter imaging phenotype.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our report adds to current knowledge of TRMT10A related neurodevelopmental disorders and demonstrates imaging findings suggestive of delayed or abnormal myelination of the white matter in this disorder."
    explanation: Interprets the finding as dysmyelination rather than white matter destruction.
  - reference: PMID:42181738
    reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "whereas brain magnetic resonance imaging was normal"
    explanation: >-
      Counterpoint establishing that white matter change is not obligatory — MRI
      was normal in this confirmed patient.

- category: Growth
  name: Short Stature
  description: >-
    Proportionate short stature is a core feature, present from infancy and
    persisting into adult life (final heights of 141-157 cm in the index
    family). It may be severe and, in at least one patient, was associated with
    growth hormone deficiency on stimulation testing, indicating that the
    growth failure is not always a purely intrinsic cellular effect.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."
    explanation: Documents short stature in all three affected siblings of this family.
  - reference: PMID:33448213
    reference_title: "TRMT10A Mutation in a Child with Diabetes, Short Stature, Microcephaly and Hypoplastic Kidneys."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features included intellectual disability, hypoplastic kidneys and short stature."
    explanation: Independent confirmation of short stature in a further patient.

- category: Growth
  name: Failure to Thrive
  description: >-
    Poor postnatal growth with failure to thrive from infancy was the presenting
    problem in the patient with a homozygous contiguous gene deletion, the most
    severe reported genotype.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "From infancy, she presented with failure to thrive and microcephaly."
    explanation: Documents failure to thrive as the infantile presentation in this patient.

- category: Endocrine
  name: Young-Onset Diabetes Mellitus
  description: >-
    Non-autoimmune, insulin-independent-onset diabetes is the defining metabolic
    endpoint, with reported diagnosis ages from 11 years to the late twenties.
    It is typically autoantibody-negative with persistent C-peptide, though
    islet cell autoantibodies and ketoacidosis at onset have each been reported
    once, so autoantibody positivity does not exclude the diagnosis in a patient
    with the neurodevelopmental phenotype. Diabetes is age-dependent and may not
    yet be present when a child is diagnosed molecularly.
  phenotype_term:
    preferred_term: Diabetes mellitus
    term:
      id: HP:0000819
      label: Diabetes mellitus
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."
    explanation: Documents the late end of the onset range.
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."
    explanation: >-
      Documents the early end of the onset range together with the
      autoantibody-negative, C-peptide-positive profile.
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Unlike the previous reports, the patient had ketoacidosis at onset of diabetes and islet cell autoantibodies."
    explanation: >-
      Documents the exceptional autoantibody-positive, ketoacidotic presentation
      that departs from the usual non-autoimmune pattern.

- category: Endocrine
  name: Hypoglycemia Preceding Diabetes
  description: >-
    In several kindreds the first metabolic abnormality is hypoglycaemia in
    infancy or childhood, frequently hyperinsulinaemic, with both ketotic and
    non-ketotic events described. It precedes diabetes by years and is the
    single most easily missed feature of the syndrome, because the disorder is
    remembered as a diabetes syndrome.
  phenotype_term:
    preferred_term: Hyperinsulinemic hypoglycemia
    term:
      id: HP:0000825
      label: Hyperinsulinemic hypoglycemia
  evidence:
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The subjects were three patients who suffered from microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia."
    explanation: Primary description of hyperinsulinaemic hypoglycaemia as the dominant glucose abnormality in this family.
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we observed an unusual form of impaired glucose metabolism which presented in early childhood with hypoglycemia followed by diabetes in late childhood"
    explanation: Documents the hypoglycaemia-then-diabetes temporal sequence in a single patient.

- category: Endocrine
  name: Insulin Resistance
  description: >-
    Marked peripheral insulin resistance is documented in a subset, established
    by formal oral glucose tolerance testing with Matsuda index calculation in
    one kindred and independently confirmed in another patient whose diabetes
    responded to metformin. It matters clinically because it selects an
    insulin-sensitizer rather than insulin replacement as first-line therapy.
  phenotype_term:
    preferred_term: Insulin resistance
    term:
      id: HP:0000855
      label: Insulin resistance
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The findings were suggestive of insulin resistance"
    explanation: Reports the formal insulin-sensitivity testing establishing this feature.
  - reference: PMID:33067246
    reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diabetes was due to marked insulin resistance and responded very well to metformin treatment."
    explanation: Independent confirmation with a therapeutic corollary.

- category: Endocrine
  name: Delayed Puberty and Gonadal Failure
  description: >-
    Delayed and inconsistent pubertal progression is reported across kindreds.
    In the contiguous-deletion patient gonadotropins fluctuated between low and
    high, compatible with gonadal failure; in another patient spontaneous
    puberty did not begin until 15.7 years and primary ovarian failure was
    diagnosed. As with the glucose phenotype, the fluctuating course has been
    attributed to intermittent stress-triggered apoptotic damage rather than a
    fixed developmental deficit.
  phenotype_term:
    preferred_term: Delayed puberty
    term:
      id: HP:0000823
      label: Delayed puberty
  evidence:
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Puberty was characterized by a slow and an inconsistent course of progression."
    explanation: Documents the delayed and erratic pubertal course.
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Concomitantly, gonadotropin levels fluctuated between low and high levels which were compatible with gonadal failure."
    explanation: Provides the endocrine basis of the pubertal delay.

- category: Endocrine
  name: Premature Ovarian Insufficiency
  description: >-
    Primary ovarian failure with small ovaries, elevated gonadotropins and low
    anti-Mullerian hormone was documented in one patient and proposed by the
    reporting authors as an additional feature of the syndrome. Currently a
    single-patient observation, so it should be watched for rather than assumed.
  phenotype_term:
    preferred_term: Premature ovarian insufficiency
    term:
      id: HP:0008209
      label: Premature ovarian insufficiency
  evidence:
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spontaneous puberty did not begin until 15.7 years of age and she was found to have primary ovarian failure."
    explanation: Primary report of ovarian failure in a molecularly confirmed patient.
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GH deficiency and primary ovarian failure may also be additional findings of this syndrome."
    explanation: >-
      The authors propose this as a possible extension of the phenotype
      ("may also be"), so the generalization beyond this patient is PARTIAL.

- category: Endocrine
  name: Growth Hormone Deficiency
  description: >-
    Severe short stature attributable to growth hormone deficiency on
    stimulation testing was detected at 3.6 years in one patient, and an
    inadequate response to growth hormone stimulation testing was separately
    reported. This is a single-report-level feature that nonetheless changes
    management, since it raises the question of GH replacement.
  phenotype_term:
    preferred_term: Decreased response to growth hormone stimulation test
    term:
      id: HP:0000824
      label: Decreased response to growth hormone stimulation test
  evidence:
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At 3.6 years of age, severe short stature related to growth hormone (GH) deficiency was detected."
    explanation: Documents GH deficiency as the basis of the growth failure in this patient.
  - reference: PMID:33448213
    reference_title: "TRMT10A Mutation in a Child with Diabetes, Short Stature, Microcephaly and Hypoplastic Kidneys."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report for the first time hypoplastic kidneys and inadequate response to growth hormone stimulation tests in a girl with this syndrome."
    explanation: Independent report of an inadequate growth hormone stimulation response.

- category: Renal
  name: Renal Hypoplasia
  description: >-
    Hypoplastic kidneys were reported for the first time in a girl homozygous
    for p.Gly206Arg. A single observation to date, and the reporting authors
    present it as a phenotype expansion rather than an established feature.
  phenotype_term:
    preferred_term: Renal hypoplasia
    term:
      id: HP:0000089
      label: Renal hypoplasia
  evidence:
  - reference: PMID:33448213
    reference_title: "TRMT10A Mutation in a Child with Diabetes, Short Stature, Microcephaly and Hypoplastic Kidneys."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report for the first time hypoplastic kidneys and inadequate response to growth hormone stimulation tests in a girl with this syndrome."
    explanation: Primary and, to date, only report of renal hypoplasia in this syndrome.

- category: Skeletal
  name: Osteoporosis
  description: >-
    The index proband had osteoporosis with DXA T-scores of -2.7 (lumbar spine)
    and -3.5 (femoral neck), while a skeletal survey showed no epiphyseal
    dysplasia. The osteoporosis is therefore a reduction in bone mass without a
    recognizable skeletal dysplasia, and is one of the features that can bring a
    young adult to genetic attention.
  phenotype_term:
    preferred_term: Osteoporosis
    term:
      id: HP:0000939
      label: Osteoporosis
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She also had osteoporosis, with dual-\nenergy X-ray absorptiometry T-scores of -2.7 and -3.5 at the\nlumbar spine and femoral neck, respectively."
    explanation: Quantifies the osteoporosis in the index proband.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A skeletal survey\nrevealed no epiphyseal dysplasia or other bone abnormality"
    explanation: >-
      Establishes that the skeletal involvement is not a bone dysplasia, an
      important negative for differential diagnosis.
  - reference: PMID:35137278
    reference_title: "Looking for the skeleton in the closet-rare genetic diagnoses in patients with diabetes and skeletal manifestations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A homozygous mutation in TRMT10A, a tRNA methyltransferase, was identified in a 15-year-old boy with new-onset diabetes, developmental delay, microcephaly, dysmorphism, short stature and central obesity."
    explanation: >-
      Cited in a series on diabetes with skeletal manifestations; the quoted
      case description supports the syndromic-diabetes context rather than
      osteoporosis specifically, hence PARTIAL.

- category: Skeletal
  name: Scoliosis
  description: >-
    Scoliosis was recorded in the index proband alongside joint laxity and
    osteoporosis, in the absence of any epiphyseal dysplasia on skeletal survey.
    Curated as its own entry rather than bundled with the osteoporosis, since
    the two are separate skeletal findings sharing one source sentence.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Names scoliosis directly among the proband's features.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A skeletal survey\nrevealed no epiphyseal dysplasia or other bone abnormality"
    explanation: >-
      Establishes the scoliosis is not part of a skeletal dysplasia, which is the
      discriminator against Wolcott-Rallison syndrome.

- category: Skeletal
  name: Joint Hypermobility
  description: >-
    Joint laxity in the index proband, reported in the same sentence as the
    scoliosis and dorsocervical fat pad. A connective-tissue finding with no
    established mechanistic link to the tRNA lesion, recorded because it recurs
    in the dysmorphic description of the syndrome.
  phenotype_term:
    preferred_term: Joint hypermobility
    term:
      id: HP:0001382
      label: Joint hypermobility
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Names joint laxity directly among the proband's features.

- category: Craniofacial
  name: Low Anterior Hairline
  description: >-
    Part of a recognizable but subtle facial gestalt — low anterior hairline,
    deep-set eyes with mild hypotelorism, wide nose and short neck — described
    consistently across unrelated kindreds. Each component is curated as its own
    bound entry below rather than as one "dysmorphic features" bundle, so that
    the individual findings are queryable.
  phenotype_term:
    preferred_term: Low anterior hairline
    term:
      id: HP:0000294
      label: Low anterior hairline
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."
    explanation: Describes the facial gestalt in a molecularly confirmed patient.
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Independent description of the same dysmorphic constellation in the index family.

- category: Craniofacial
  name: Deeply Set Eyes
  description: >-
    Deep-set eyes, part of the facial gestalt, recorded on examination in
    molecularly confirmed compound heterozygous siblings and constant across
    subsequent examinations.
  phenotype_term:
    preferred_term: Deeply set eye
    term:
      id: HP:0000490
      label: Deeply set eye
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."
    explanation: Records deep-set eyes on formal examination in a confirmed patient.

- category: Craniofacial
  name: Hypotelorism
  description: >-
    Mild hypotelorism, described in both affected siblings of the compound
    heterozygous family and persistent on follow-up examination. Notable as a
    midline measure in a disorder whose brain is small but structurally normal.
  phenotype_term:
    preferred_term: Hypotelorism
    term:
      id: HP:0000601
      label: Hypotelorism
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical exam at age 4.5 years showed microcephaly, low anterior hair line, deep set eyes with mild hypotelorism, shortened forehead, and her neurological exam was normal."
    explanation: Records mild hypotelorism on formal examination in a confirmed patient.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His features have remained constant on follow-up examinations, with persistent microcephaly and mild hypotelorism."
    explanation: Documents persistence of the finding in the affected sibling.

- category: Craniofacial
  name: Wide Nose
  description: >-
    A wide nose in the index proband, part of the facial gestalt reported in the
    original description of the syndrome.
  phenotype_term:
    preferred_term: Wide nose
    term:
      id: HP:0000445
      label: Wide nose
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Names a wide nose directly among the proband's features.

- category: Craniofacial
  name: Short Neck
  description: >-
    A short neck in the index proband, reported alongside the dorsocervical fat
    pad; the two together account for much of the recognizable habitus.
  phenotype_term:
    preferred_term: Short neck
    term:
      id: HP:0000470
      label: Short neck
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Names a short neck directly among the proband's features.

- category: Endocrine
  name: Dorsocervical Fat Pad
  description: >-
    A dorsocervical fat pad was present in the index proband alongside a raised
    BMI, scoliosis and joint laxity, and central obesity was independently
    reported in another patient. Together with the documented insulin
    resistance, this suggests a body-composition component to the metabolic
    phenotype, although no formal fat-distribution study has been done.
  phenotype_term:
    preferred_term: Dorsocervical fat pad
    term:
      id: HP:0025383
      label: Dorsocervical fat pad
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features were a short neck,\nwide nose, low hairline, buffalo hump, retraction of the right 5 th\ntoe, scoliosis, and joint laxity."
    explanation: Documents the dorsocervical fat pad ("buffalo hump") in the index proband.
  - reference: PMID:35137278
    reference_title: "Looking for the skeleton in the closet-rare genetic diagnoses in patients with diabetes and skeletal manifestations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A homozygous mutation in TRMT10A, a tRNA methyltransferase, was identified in a 15-year-old boy with new-onset diabetes, developmental delay, microcephaly, dysmorphism, short stature and central obesity."
    explanation: Independent report of central obesity in a confirmed patient.

- category: Neurologic
  name: Spastic-Ataxic Paraparesis
  description: >-
    A patient homozygous for the canonical splice-site variant c.421-1G>A
    presented with spastic-ataxic paraparesis — a substantially more prominent
    neurological phenotype than the usual picture. The reporting authors present
    this as an expansion of the clinical spectrum; it remains a single
    observation and should not be treated as a core feature. The accompanying
    posterior-fossa finding is curated separately below.
  phenotype_term:
    preferred_term: Spastic ataxia
    term:
      id: HP:0002497
      label: Spastic ataxia
  evidence:
  - reference: PMID:39440920
    reference_title: "New Insights Into TRMT10A Syndrome: Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a case of a patient showing spastic-ataxic paraparesis and Dandy-Walker variant associated with a causative homozygous c."
    explanation: >-
      Primary report of the spastic-ataxic and posterior-fossa phenotype; the
      quote is truncated at the variant nomenclature as it appears in the
      abstract.
  - reference: PMID:39440920
    reference_title: "New Insights Into TRMT10A Syndrome: Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This case expands the clinical spectrum of TRMT10A syndrome highlighting the importance of considering this gene in the evaluation of patients with brain/cerebellar malformations and spastic-ataxic paraparesis."
    explanation: >-
      The authors themselves frame this as a spectrum expansion rather than an
      established feature.

- category: Neuroimaging
  name: Dandy-Walker Variant
  description: >-
    The same c.421-1G>A patient had a Dandy-Walker variant. This is bound to
    HP:0001320 (Cerebellar vermis hypoplasia) rather than to HP:0001305
    (Dandy-Walker malformation) deliberately: HPO defines Dandy-Walker
    malformation as incomplete vermis formation PLUS fourth-ventricle dilation
    PLUS enlargement of the posterior fossa, and it is precisely the absence of
    posterior-fossa enlargement that distinguishes the "variant" from the
    malformation. Binding to HP:0001305 would therefore assert a finding the
    source does not report. Vermian hypoplasia is the component that is
    definitional for the variant and is safely asserted; `preferred_term`
    preserves the clinical designation the paper used. The abstract gives no
    further radiological detail, so nothing more specific is claimed.
  phenotype_term:
    preferred_term: Dandy-Walker variant
    term:
      id: HP:0001320
      label: Cerebellar vermis hypoplasia
  evidence:
  - reference: PMID:39440920
    reference_title: "New Insights Into TRMT10A Syndrome: Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a case of a patient showing spastic-ataxic paraparesis and Dandy-Walker variant associated with a causative homozygous c."
    explanation: >-
      Reports the Dandy-Walker variant. PARTIAL because the abstract names the
      clinical designation without reporting the underlying radiological
      measurements, so the vermis-hypoplasia binding is inferred from the
      definition of the designation rather than directly measured in the source.
  - reference: PMID:39440920
    reference_title: "New Insights Into TRMT10A Syndrome: Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This case expands the clinical spectrum of TRMT10A syndrome highlighting the importance of considering this gene in the evaluation of patients with brain/cerebellar malformations and spastic-ataxic paraparesis."
    explanation: >-
      Confirms a cerebellar malformation is part of what this case adds, and
      frames it as a spectrum expansion rather than a core feature.

genetic:
- name: TRMT10A
  gene_term:
    preferred_term: TRMT10A
    term:
      id: hgnc:28403
      label: TRMT10A
  relationship_type: CAUSATIVE
  notes: >-
    Every reported pathogenic allele is private or population-specific; no
    recurrent global founder variant exists, and nearly all published kindreds
    are consanguineous. Alleles span the full loss-of-function spectrum —
    nonsense, canonical splice-acceptor, whole-locus deletion — plus one
    catalytically dead missense variant. Because a contiguous gene deletion has
    caused the syndrome, copy-number analysis is warranted when sequencing is
    negative in a compatible phenotype.

    Population constraint corroborates the recessive mechanism rather than
    merely being consistent with it: TRMT10A (ENSG00000145331) is entirely
    tolerant of heterozygous loss of function in gnomAD — pLI 3.2e-12,
    observed/expected LoF 0.917 with a 90% upper bound (LOEUF) of 1.21, i.e. the
    observed rate of LoF variation in the population is what you would expect if
    there were no selection against it at all. So haploinsufficiency is not a
    disease mechanism here, which is why the unaffected heterozygous parents in
    every reported pedigree are the expected result and not a puzzle. Retrieved
    from the gnomAD API and recorded as a database observation; it carries no
    evidence block because it is not a literature claim with a quotable
    sentence.
  variants:
  - name: "p.Arg127Ter"
    description: >-
      The first-reported disease allele, homozygous in a large consanguineous
      Moroccan family with three affected siblings. Neither TRMT10A mRNA nor
      protein was detectable in patient lymphoblasts, indicating
      nonsense-mediated decay and complete loss of the gene product. Also
      reported homozygously in a patient with GH deficiency and primary ovarian
      failure.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:24204302
      reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Linkage analysis and whole exome sequencing were used to identify the causal nonsense mutation, which changed an arginine codon into a stop at position 127 of the tRNA methyltransferase homolog gene TRMT10A (also called RG9MTD2)."
      explanation: Identifies the allele and the method by which it was found.
    - reference: PMID:34541035
      reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A homozygous p.Arg127* mutation in TRMT10A was detected."
      explanation: Independent recurrence of the same allele in an unrelated patient.
  - name: "p.Gly206Arg (c.616G>A)"
    description: >-
      Homozygous missense allele in a consanguineous Uzbek Jewish family with
      three affected siblings, and independently in a girl with hypoplastic
      kidneys. Uniquely informative mechanistically: the variant enzyme binds
      tRNA normally but retains under 0.1% of wild-type methylation activity,
      attributed to defective S-adenosylmethionine binding. It is therefore a
      catalytically dead allele rather than a folding or substrate-recognition
      defect.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:25053765
      reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A homozygous Gly206Arg (G206R) mutation in the TRMT10A gene was identified using whole exome sequencing."
      explanation: Identifies the allele in the index family for this variant.
    - reference: PMID:25053765
      reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The mutation segregated in the family and was absent from large control cohorts."
      explanation: Segregation and population-frequency evidence supporting pathogenicity.
    - reference: PMID:33448213
      reference_title: "TRMT10A Mutation in a Child with Diabetes, Short Stature, Microcephaly and Hypoplastic Kidneys."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "revealing a homozygous mutation in the TRMT10A gene (c.616G>A, p.G206R)"
      explanation: Independent recurrence of the allele in an unrelated patient.
  - name: "p.Glu27Ter (c.79G>T)"
    description: >-
      Homozygous nonsense allele in two siblings who represent the mild end of
      the spectrum: diabetes diagnosed in their twenties, mild microcephaly at
      birth with normal final head circumference, and mild learning disability
      with epilepsy as the only other features. Notable that a truncating allele
      this proximal produces a milder clinical course than p.Gly206Arg, arguing
      against a simple allele-severity gradient.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:26526202
      reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A homozygous nonsense mutation p.Glu27Ter in TRMT10A was identified using targeted next-generation sequencing and confirmed by PCR/Sanger sequencing."
      explanation: Identifies the allele and its orthogonal confirmation.
  - name: "p.Arg93Ter (c.277C>T) / p.Arg133Ter (c.397C>T)"
    description: >-
      Compound heterozygous nonsense alleles in non-consanguineous siblings with
      microcephaly, developmental delay and periventricular white matter
      hyperintensities but no documented dysglycaemia at ages 10 and 12 — the
      first indication that the neurodevelopmental phenotype can present without
      the metabolic one.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:26535115
      reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Analysis of variants determined that the children were compound heterozygotes for nonsense mutations, c.277C>T (p.Arg93*) and c.397C>T (p.Arg133*), in the TRMT10A gene."
      explanation: Identifies the compound heterozygous allele pair.
  - name: "c.496-1G>A"
    description: >-
      Homozygous canonical splice-acceptor variant in the first reported Chinese
      patient, whose diabetes was driven by marked insulin resistance and
      responded to metformin.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:33067246
      reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A homozygous mutation c.496-1G>A in TRMT10A was identified using targeted next-generation sequencing and confirmed by PCR/Sanger sequencing."
      explanation: Identifies the splice-acceptor allele and its confirmation.
  - name: "c.421-1G>A"
    description: >-
      Homozygous canonical splice-acceptor variant disrupting the SAM-dependent
      methyltransferase TRM10-type domain, reported in the patient with
      spastic-ataxic paraparesis and a Dandy-Walker variant.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:39440920
      reference_title: "New Insights Into TRMT10A Syndrome: Case Report and Literature Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This mutation disrupts the \"SAM-dependent methyltransferase TRM10-type domain\", which is implicated in methylation and S-adenosylmethionine metabolic biological processes, crucial for mitochondrial and glucose metabolism."
      explanation: Describes the domain consequence of this splice allele.
  - name: "p.Arg43Ter (c.127C>T)"
    description: >-
      Homozygous stop-gained variant classified pathogenic on PVS1, PM2 and PM3
      criteria in a 15-year-old with microcephaly, intellectual disability,
      epilepsy and short stature but no metabolic abnormality at evaluation.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:42181738
      reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Exome sequencing identified a homozygous stop-gained pathogenic (PVS1, PM2, and PM3) variant in TRMT10A (c.127C>T; p.Arg43Ter), which was confirmed by Sanger sequencing and showed segregation consistent with autosomal recessive inheritance."
      explanation: >-
        Identifies the allele with its ACMG classification and segregation
        evidence.
  - name: "Contiguous gene deletion encompassing TRMT10A"
    description: >-
      Homozygous contiguous gene deletion removing the whole TRMT10A locus in a
      17-year-old female, with RT-PCR and Western blot confirming complete
      absence of transcript and protein. The most severe reported genotype, with
      failure to thrive from infancy and gonadal failure; establishes that
      copy-number variation is a route to this syndrome.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:26297882
      reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We investigated the clinical spectrum presented by a 17-year-old female with a homozygous contiguous gene deletion involving the TRMT10A gene."
      explanation: Identifies the structural-variant route to the syndrome.
    - reference: PMID:26297882
      reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "RT-PCR and Western blot analysis demonstrated a complete abolishment of TRMT10A mRNA and its translated protein."
      explanation: Confirms complete loss of the gene product at RNA and protein level.
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first study describing the impact of TRMT10A deficiency in mammals, highlighting a role in the pathogenesis of microcephaly and early onset diabetes."
    explanation: Establishes TRMT10A as the causal gene for the syndrome.
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our report provides independent confirmation of the role of TRMT10A mutations in this syndrome and expands its phenotypic description."
    explanation: Independent replication of the gene-disease relationship in a fourth family.

inheritance:
- name: Autosomal recessive inheritance
  description: >-
    Autosomal recessive, confirmed across every reported kindred: biallelic
    variants in affected individuals, clinically unaffected heterozygous
    parents, and parental consanguinity in nearly all families. Segregation was
    formally demonstrated in multiple independent reports.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:42181738
    reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "which was confirmed by Sanger sequencing and showed segregation consistent with autosomal recessive inheritance"
    explanation: Explicit segregation evidence for autosomal recessive inheritance.
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mutation segregated in the family and was absent from large control cohorts."
    explanation: >-
      Independent family segregation with absence from controls, consistent with
      a rare recessive allele.

diagnosis:
- name: Molecular Confirmation of Biallelic TRMT10A Variants
  description: >-
    Diagnosis is molecular. The original families were solved by linkage plus
    whole exome sequencing; later patients were increasingly identified by
    targeted monogenic-diabetes next-generation sequencing panels containing
    TRMT10A, with Sanger confirmation and parental segregation to establish
    biallelic status. Because one patient carried a homozygous contiguous gene
    deletion, copy-number analysis should follow a negative sequencing result
    when the phenotype fits. Making the diagnosis before the metabolic phase
    begins is the practical goal, since it enables anticipatory glucose
    monitoring.
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  evidence:
  - reference: PMID:25053765
    reference_title: "TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A homozygous Gly206Arg (G206R) mutation in the TRMT10A gene was identified using whole exome sequencing."
    explanation: Documents exome sequencing as the diagnostic route in an index family.
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A targeted panel may be useful to identify previously unsuspected monogenic diabetes among individuals with young‐onset diabetes."
    explanation: Documents the targeted-panel diagnostic route.
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Accurate diagnosis through genomic testing, as in the children described here, allows for early detection and management of medical complications, such as diabetes mellitus."
    explanation: >-
      States the clinical value of pre-symptomatic molecular diagnosis for
      anticipating the metabolic phase.

- name: Recognizing the Syndrome in a Young Person with Diabetes
  description: >-
    The referral trigger that matters: young-onset, non-insulin-dependent,
    autoantibody-negative diabetes in a person without obesity who also has
    intellectual disability, microcephaly or epilepsy. Both the Scottish and the
    Chinese reports make this recommendation explicitly, and both patients had
    been carrying an unrecognized monogenic diagnosis. Extra-pancreatic features
    plus slow-onset autoantibody-negative diabetes should prompt a full
    monogenic-diabetes work-up.
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TRMT10A sequencing should be considered in children or adults with young-onset diabetes who have a history of intellectual disability, microcephaly and epilepsy."
    explanation: The explicit clinical referral criterion from the reporting authors.
  - reference: PMID:33067246
    reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genomic testing should be considered in children with non-insulin-dependent diabetes with intellectual disability and microcephaly."
    explanation: Independent statement of the same referral criterion.
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with slow onset diabetes who are negative for auto-antibodies and have extra-pancreatic features should be tested for all known subtypes of monogenic diabetes."
    explanation: Broadens the criterion to the full monogenic-diabetes differential.

- name: Distinguishing the Diabetes from Type 1 Diabetes
  description: >-
    The diabetes is usually autoantibody-negative with persistent C-peptide,
    which separates it from autoimmune type 1 diabetes. This discriminator is
    imperfect and should not be applied mechanically: one reported patient had
    both ketoacidosis at onset and islet cell autoantibodies, yet retained
    endogenous insulin secretion 22 months later and maintained near-normal
    glucose for three days off insulin. Autoantibody positivity therefore does
    not exclude the syndrome when the neurodevelopmental phenotype is present.
  diagnosis_term:
    preferred_term: autoantibody measurement
    term:
      id: NCIT:C181397
      label: Autoantibody Measurement
  evidence:
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."
    explanation: The typical autoantibody-negative, C-peptide-positive profile.
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Unlike the previous reports, the patient had ketoacidosis at onset of diabetes and islet cell autoantibodies."
    explanation: >-
      Refutes autoantibody negativity as an absolute discriminator; recorded as
      REFUTE against the general rule rather than hidden in prose.

biochemical:
- name: Detectable and Persistent C-Peptide
  presence: Detectable
  notes: >-
    Endogenous insulin secretion persists well after diabetes onset. In the
    contiguous-deletion patient, glucagon-stimulated C-peptide and continuous
    glucose monitoring showed insulin secretion still present 22 months after
    diagnosis, and near-normal glucose was maintained for three days entirely
    off insulin. Another patient had persistent C-peptide at diagnosis. This is
    the biochemical signature of partial rather than complete beta-cell failure.
  evidence:
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Endogenous insulin secretion still persisted 22 months after onset of diabetes and relatively normal glucose levels were kept over 3 days without insulin treatment."
    explanation: Quantifies the persistence of endogenous insulin secretion after diagnosis.
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In order to elucidate the nature of diabetes in this patient, endogenous insulin secretion and glycemic control were evaluated by a glucagon stimulation test and continuous glucose monitoring both during insulin treatment and off therapy."
    explanation: Documents the assays used to establish residual beta-cell function.

- name: Glycated Hemoglobin (HbA1c)
  presence: Variable
  notes: >-
    HbA1c at presentation spans the full range and is not a diagnostic
    discriminator. The index siblings presented in overt decompensation
    (11.1-13.2%), a Chinese patient at 14.4%, while the contiguous-deletion
    patient maintained excellent control at 5.0-6.2%. HbA1c is most useful here
    as a treatment-response measure — it fell from 14.4% to 6.8% within three
    months of starting metformin in the insulin-resistant patient.
  evidence:
  - reference: PMID:26297882
    reference_title: "Homozygous deletion of TRMT10A as part of a contiguous gene deletion in a syndrome of failure to thrive, delayed puberty, intellectual disability and diabetes mellitus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nevertheless, glycemic control was excellent (HbA1C 5.0%-6.2%)."
    explanation: Documents the well-controlled end of the glycaemic range.
  - reference: PMID:33067246
    reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the subsequent visit 3 months after diagnosis, the patient’s HbA1c decreased to 6."
    explanation: >-
      Documents the HbA1c response to metformin; the quote is truncated at the
      decimal point as the sentence is split in the cached source.

treatments:
- name: Metformin
  description: >-
    First-line where peripheral insulin resistance predominates. A Chinese
    patient with marked insulin resistance responded very well, with HbA1c
    falling from 14.4% to 6.8% within three months, and metformin was also used
    in an autoantibody-negative, C-peptide-positive patient diagnosed at 11.4
    years. Because the metabolic phenotype has both an insulin-deficient and an
    insulin-resistant arm, establishing which predominates before committing to
    therapy is the practical point — this is a treatable form of syndromic
    diabetes that can be mismanaged as type 1.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: metformin
      term:
        id: CHEBI:6801
        label: metformin
  target_mechanisms:
  - target: Peripheral Insulin Resistance
    treatment_effect: INHIBITS
    description: >-
      Metformin acts on the peripheral insulin-resistance arm, not on the
      TRMT10A lesion or the beta-cell loss; it is symptomatic therapy targeted
      at the arm of the metabolic phenotype it can reach.
    evidence:
    - reference: PMID:33067246
      reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The diabetes was due to marked insulin resistance and responded very well to metformin treatment."
      explanation: >-
        Links the drug directly to the insulin-resistance node it targets, with
        a documented clinical response.
  evidence:
  - reference: PMID:33067246
    reference_title: "tRNA methyltransferase 10 homologue A (TRMT10A) mutation in a Chinese patient with diabetes, insulin resistance, intellectual deficiency and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A clear genetic diagnosis is helpful for early detection and treatment addressing insulin resistance."
    explanation: >-
      States the therapeutic corollary of the molecular diagnosis in this
      patient.
  - reference: PMID:34541035
    reference_title: "Expanding the Phenotype of TRMT10A Mutations: Case Report and a Review of the Existing Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She had an incidental diagnosis of diabetes at age 11.4 years which was negative for diabetes antibodies with persistent C-peptide level and she was treated with metformin."
    explanation: Independent use of metformin in a paediatric patient with retained C-peptide.

- name: Insulin Replacement
  description: >-
    Used where insulin deficiency from progressive beta-cell loss predominates,
    including the case in which progressive beta-cell apoptosis required insulin
    replacement with increased demand driven by unfavourable body composition.
    Not universally required: the contiguous-deletion patient maintained
    near-normal glucose for three days entirely off insulin, so insulin need
    should be re-assessed rather than assumed permanent.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: insulin
      term:
        id: CHEBI:145810
        label: insulin
  target_mechanisms:
  - target: Biphasic Glucose Dysregulation
    treatment_effect: BYPASSES
    description: >-
      Exogenous insulin substitutes for the hormone the attenuated beta-cell
      mass can no longer secrete; it does not address tRNA hypomethylation or
      beta-cell apoptosis.
    evidence:
    - reference: PMID:35137278
      reference_title: "Looking for the skeleton in the closet-rare genetic diagnoses in patients with diabetes and skeletal manifestations."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The progressive apoptosis of pancreatic beta cells required insulin replacement therapy, with increased demand due to an unfavorable body composition."
      explanation: >-
        Documents insulin replacement applied to the beta-cell-loss node, with
        the body-composition modifier of insulin requirement.
  evidence:
  - reference: PMID:35137278
    reference_title: "Looking for the skeleton in the closet-rare genetic diagnoses in patients with diabetes and skeletal manifestations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The progressive apoptosis of pancreatic beta cells required insulin replacement therapy, with increased demand due to an unfavorable body composition."
    explanation: Documents insulin replacement as the treatment used in an insulin-deficient patient.

- name: Antiseizure Medication
  description: >-
    Seizures in this syndrome have responded to standard antiseizure medication;
    levetiracetam monotherapy at 50 mg/kg/day controlled generalized epilepsy in
    a molecularly confirmed patient. No syndrome-specific antiseizure strategy
    or contraindication has been reported, and no agent has been shown to modify
    the underlying mechanism.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: levetiracetam
      term:
        id: CHEBI:6437
        label: levetiracetam
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures have been controlled with levetiracetam (50 mg/kg/day, corresponding to 500 mg twice daily)."
    explanation: Documents the agent, dose and response in a confirmed patient.

- name: Developmental and Educational Support
  description: >-
    Speech, occupational and physical therapy provided through school, with
    steady developmental progress reported. Standard practice for a static
    neurodevelopmental disorder rather than a syndrome-specific validated
    protocol.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  evidence:
  - reference: PMID:26535115
    reference_title: "Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Speech and occupational therapy were provided through school and she has continued to make steady developmental progress."
    explanation: Documents the supportive interventions used and the outcome.

- name: Genetic Counseling
  description: >-
    Autosomal recessive inheritance carries a 25% sibling recurrence risk, and
    the recurrence is documented rather than theoretical — three of the reported
    kindreds had three affected siblings each. Nearly all families were
    consanguineous, so counseling covers recurrence risk, carrier testing for
    at-risk relatives, and reproductive options. Framed as standard practice for
    a confirmed autosomal recessive disorder.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."
    explanation: >-
      Documents the consanguineous pedigree with three affected siblings that
      grounds the recurrence-risk counseling.

animal_models:
- name: Trmt10a null mouse (E29Stop)
  species: Mouse
  genotype: Trmt10a c.85G>T (p.Glu29Ter) homozygous null
  publication: PMID:38950903
  description: >-
    Constitutive null mouse engineered to mimic the human p.Glu27Ter allele.
    Reproduces the reduced body weight and the neurological arm of the human
    syndrome — smaller hippocampal postsynaptic densities with impaired synaptic
    plasticity and memory — and provides the only in vivo demonstration of the
    translational mechanism (codon-specific ribosome slowdown, ATF4
    derepression). Critically, it does NOT reproduce the pancreatic phenotype.
  modeled_mechanisms:
  - target: Codon-Specific Translational Impairment
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Ribosome profiling in null-mouse brain establishes the codon-level
      translational lesion, and the same tRNA depletion was confirmed in a human
      TRMT10A-null cell line.
    limitations: >-
      Ribosome profiling was performed in mouse brain; the corresponding
      measurement has not been made in human neural tissue, though the
      underlying tRNA depletion was replicated in a human cell line.
    readouts:
    - name: tRNA-Gln(CUG) and initiator methionine tRNA steady-state levels
      target: Codon-Specific Translational Impairment
      direction: DECREASED
      interpretation: >-
        Depletion of the two m1G9-dependent tRNAs is the proximate cause of the
        codon-specific translational deficit.
      evidence:
      - reference: PMID:38950903
        reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A."
        explanation: Reports the measurement grounding this readout, in both mouse and human cells.
    - name: Ribosome occupancy at the Gln(CAG) codon
      target: Codon-Specific Translational Impairment
      direction: INCREASED
      interpretation: >-
        Increased ribosome dwell time at Gln codons is the direct functional
        consequence of tRNA-Gln depletion.
      evidence:
      - reference: PMID:38950903
        reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames."
        explanation: Reports the ribosome-profiling measurement behind this readout.
    evidence:
    - reference: PMID:38950903
      reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons."
      explanation: Establishes the model as informative for the translational mechanism node.
  - target: Impaired Synaptic Structure and Plasticity
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The null mouse shows smaller hippocampal postsynaptic densities with
      defective synaptic plasticity and memory, offering a structural correlate
      for the intellectual disability that does not require neuronal loss.
    limitations: >-
      Synaptic and memory measures in mouse are not directly equivalent to human
      intellectual disability, and no corresponding human synaptic pathology has
      been demonstrated.
    readouts:
    - name: Hippocampal postsynaptic density size
      target: Impaired Synaptic Structure and Plasticity
      direction: DECREASED
      interpretation: Structural correlate of the impaired-plasticity node in this model.
      evidence:
      - reference: PMID:38950903
        reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."
        explanation: Reports the postsynaptic-density measurement behind this readout.
    evidence:
    - reference: PMID:38950903
      reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain."
      explanation: >-
        Connects the translational lesion to neuronal structural proteins,
        supporting this model as informative for the synaptic node.
  - target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Trmt10a null mice show no discernible pancreatic defect, in direct contrast
      to the diabetes that defines the human syndrome. This negative result is
      the reason the beta-cell mechanism rests on human cellular models rather
      than on a mouse.
    limitations: >-
      The published phenotyping reports no discernible pancreatic defect but
      does not establish over what age range or under what metabolic challenge
      the pancreas was assessed, so an unstressed-condition ceiling effect
      cannot be excluded. Species differences in beta-cell tRNA biology and in
      lifespan-scaled cumulative apoptosis are plausible explanations.
    evidence:
    - reference: PMID:38950903
      reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: "Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."
      explanation: >-
        Explicitly records the absence of a pancreatic phenotype in the null
        mouse, refuting recapitulation of the beta-cell node.

experimental_models:
- name: Patient-derived iPSC beta-like cells (TRMT10A-deficient)
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cells reprogrammed from TRMT10A-deficient patient
    fibroblasts and differentiated to pancreatic beta-like cells, alongside
    control lines. This is the model that carries the beta-cell mechanism, and
    it does so precisely where the mouse fails: it demonstrates oxidative
    stress, intrinsic-pathway apoptosis, and sensitization to ER stress in cells
    of human patient genotype.
  modeled_mechanisms:
  - target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Patient-genotype human beta-like cells reproduce the oxidative stress and
      intrinsic apoptotic signalling proposed to underlie beta-cell loss.
    limitations: >-
      iPSC-derived beta-like cells are immature relative to adult islet beta
      cells and are studied over days rather than the decades over which the
      human phenotype accumulates, so the model shows the mechanism is available
      but cannot demonstrate the cumulative mass loss.
    readouts:
    - name: Intrinsic apoptotic pathway activation
      target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
      direction: INCREASED
      interpretation: Direct measure of the apoptotic mechanism in patient-genotype cells.
      evidence:
      - reference: PMID:30247717
        reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells"
        explanation: Reports the apoptosis measurement grounding this readout.
    evidence:
    - reference: PMID:30247717
      reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Using RNA interference and induced pluripotent stem cell-derived pancreatic β-like cells from healthy controls and TRMT10A-deficient patients we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells."
      explanation: >-
        Establishes the model system and its use for the beta-cell mechanism
        node.
  - target: tRNA Hypomethylation, Destabilization and Fragmentation
    relationship: MEASURES
    fidelity: HIGH
    description: >-
      The same system was used to show that 5'-tRNA-Gln fragments are not merely
      correlated with beta-cell death but are sufficient to cause it.
    limitations: >-
      Fragment sufficiency was established by transfecting synthetic fragments,
      which does not establish the intracellular concentrations reached in
      patient tissue in vivo.
    readouts:
    - name: 5'-tRNA-Gln fragment abundance
      target: tRNA Hypomethylation, Destabilization and Fragmentation
      direction: INCREASED
      interpretation: >-
        The cytotoxic species linking hypomethylation to beta-cell death.
      evidence:
      - reference: PMID:30247717
        reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "We show that tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5'-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death."
        explanation: Reports the fragmentation measurement and its causal test.
    evidence:
    - reference: PMID:30247717
      reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "This study unmasks tRNA hypomethylation and fragmentation as a hitherto unknown mechanism of pancreatic β-cell demise relevant to monogenic and polygenic forms of diabetes."
      explanation: Establishes the system as the one that defined this mechanism.

- name: TRMT10A silencing in rat INS-1E and human EndoC-betaH1 beta cells
  experimental_model_type: CELL_LINE
  description: >-
    siRNA knockdown of TRMT10A in rat and human clonal beta-cell lines and in
    dispersed human islets. The original demonstration that loss of TRMT10A is
    sufficient to kill beta cells, and the experiment that first connected a
    housekeeping tRNA-modification enzyme to a diabetes phenotype.
  modeled_mechanisms:
  - target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
    relationship: PERTURBS
    fidelity: MODERATE
    description: >-
      Acute silencing establishes sufficiency of TRMT10A loss for beta-cell
      death in two species.
    limitations: >-
      Acute siRNA knockdown in clonal lines models neither the constitutive
      germline null state nor the decades-long time course of the human disease,
      and residual protein after knockdown is not equivalent to the complete
      absence seen in patients.
    readouts:
    - name: Beta-cell apoptosis after TRMT10A silencing
      target: Beta-Cell Oxidative Stress and Intrinsic Apoptosis
      direction: INCREASED
      interpretation: >-
        Establishes that removing TRMT10A is by itself enough to trigger
        beta-cell death.
      evidence:
      - reference: PMID:24204302
        reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "TRMT10A silencing induces rat and human β-cell apoptosis."
        explanation: Reports the apoptosis measurement behind this readout.
    evidence:
    - reference: PMID:24204302
      reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "TRMT10A silencing induces rat and human β-cell apoptosis."
      explanation: >-
        Establishes the knockdown system as informative for the beta-cell death
        node.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No epidemiological study exists. The disorder is known from a small number
    of published kindreds — the 2016 Scottish report described itself as the
    fourth family with diabetes reported, and the case-based literature has
    grown only incrementally since. Reported families span Moroccan, Uzbek
    Jewish, Israeli, Scottish, Chinese and Turkish ancestry, with parental
    consanguinity in nearly all. No numeric rate is recorded here because none
    has been published.
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report two siblings from the fourth family reported to have diabetes mellitus as a result of a TRMT10A mutation."
    explanation: >-
      Anchors the scale of the reported literature at the time — a fourth family
      with the diabetes phenotype.

differential_diagnoses:
- name: Microcephaly, short stature, and impaired glucose metabolism 2 (PPP1R15B)
  description: >-
    The nearest mimic and the reason this pair of entries exists. MSSGM2 shares
    congenital microcephaly, severe short stature, intellectual disability and
    autoantibody-negative young-onset diabetes, and both disorders converge on
    dysregulated protein synthesis — MSSGM1 through tRNA hypomethylation, MSSGM2
    through chronically raised phospho-eIF2-alpha from a defective CReP-PP1
    holophosphatase. They are distinguished only molecularly. Note that the two
    are grouped together under a single Orphanet concept (ORPHA:391408 /
    MONDO:0018320) even though OMIM and MONDO split them by gene.
  disease_term:
    preferred_term: microcephaly, short stature, and impaired glucose metabolism 2
    term:
      id: MONDO:0014785
      label: microcephaly, short stature, and impaired glucose metabolism 2
  distinguishing_features:
  - >-
      Causal gene (PPP1R15B vs TRMT10A); MSSGM2 features skeletal, dental, hair
      and white-matter involvement and, in one family, infantile cirrhosis
      requiring liver transplantation; MSSGM1 features hypoglycaemia preceding
      diabetes, documented peripheral insulin resistance, and epilepsy as a
      prominent feature.
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability in a large consanguineous family with three affected children."
    explanation: >-
      Establishes the MSSGM1 clinical description that must be distinguished
      from the near-identical MSSGM2 presentation.

- name: Type 1 diabetes mellitus
  description: >-
    The commonest misdiagnosis, because the diabetes begins in youth and can
    present with hyperglycaemia or even ketoacidosis. Distinguished by
    autoantibody negativity with persistent C-peptide, absence of insulin
    dependence, and — decisively — the accompanying microcephaly, intellectual
    disability and epilepsy, which are not features of type 1 diabetes. The
    discriminator is imperfect: one TRMT10A patient had both ketoacidosis and
    islet cell autoantibodies, so the neurodevelopmental phenotype rather than
    the antibody result should drive the referral.
  distinguishing_features:
  - >-
      Autoantibody-negative with persistent C-peptide in most patients; frequently
      non-insulin-dependent and sometimes insulin-resistant and metformin
      responsive; obligatory neurodevelopmental features absent in type 1 diabetes.
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This report also shows the advantages of using a targeted panel to identify previously unsuspected monogenic diabetes among young-onset non-insulin-dependent diabetes in the absence of obesity and autoimmunity."
    explanation: >-
      Frames the exact clinical situation — young-onset diabetes without obesity
      or autoimmunity — in which type 1 diabetes is wrongly assumed.
  - reference: PMID:33832649
    reference_title: "Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes."
    explanation: >-
      Establishes that this misdiagnosis is the rule rather than the exception
      across monogenic diabetes, which is why the syndromic features must drive
      the referral.

- name: Wolcott-Rallison syndrome (EIF2AK3)
  description: >-
    The canonical differential for syndromic young-onset diabetes with growth
    failure, and mechanistically the far end of the same axis: EIF2AK3/PERK loss
    LOWERS eIF2-alpha phosphorylation, MSSGM2/PPP1R15B raises it, and MSSGM1
    perturbs translation a step earlier at tRNA modification — yet all three
    converge on beta-cell failure plus microcephaly and growth retardation. The
    discriminators against MSSGM1 are clean: Wolcott-Rallison diabetes is
    neonatal with undetectable C-peptide from beta-cell loss, and it carries
    epiphyseal dysplasia and hepatic dysfunction, whereas MSSGM1 presents from
    late childhood to the third decade with persistent C-peptide and an
    explicitly normal skeletal survey.
  disease_term:
    preferred_term: Wolcott-Rallison syndrome
    term:
      id: MONDO:0009192
      label: Wolcott-Rallison syndrome
  distinguishing_features:
  - >-
    Wolcott-Rallison: biallelic EIF2AK3 variants, neonatal diabetes with
    undetectable C-peptide, epiphyseal dysplasia, hepatic dysfunction. MSSGM1:
    biallelic TRMT10A variants, diabetes from late childhood to the third decade
    with persistent C-peptide, hypoglycaemia often preceding it, and a skeletal
    survey showing no epiphyseal dysplasia.
  evidence:
  - reference: PMID:26159176
    reference_title: "A Missense Mutation in PPP1R15B Causes a Syndrome Including Diabetes, Short Stature, and Microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Homozygous mutations in EIF2AK3 cause Wolcott-Rallison syndrome, a syndromic form of neonatal diabetes with epiphyseal dysplasia, growth retardation, and variable other manifestations including microcephaly"
    explanation: >-
      Establishes the overlapping phenotype that makes this the primary
      differential for syndromic diabetes with microcephaly.
  - reference: PMID:26159176
    reference_title: "A Missense Mutation in PPP1R15B Causes a Syndrome Including Diabetes, Short Stature, and Microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the Wolcott-Rallison syndrome (with decreased eIF2α phosphorylation), neonatal diabetes is due to β-cell loss and C-peptide is undetectable (13), while DNAJC3, IER3IP1, and PPP1R15B mutations (with increased eIF2α phosphorylation) lead to permanent neonatal or young-onset diabetes with residual C-peptide levels"
    explanation: >-
      Gives the C-peptide discriminator (undetectable in Wolcott-Rallison vs
      residual in the translation-stress syndromes, MSSGM1 included) and places
      the disorders on a shared eIF2-alpha axis.

- name: Microcephaly, epilepsy, and diabetes syndrome 1 (IER3IP1)
  description: >-
    MEDS1 shares the microcephaly + epilepsy + diabetes triad and, like TRMT10A
    deficiency, involves a protein enriched in cerebral cortex and beta cells.
    It is separated by timing and severity, not by which organs are involved:
    MEDS diabetes is permanent NEONATAL diabetes, the microcephaly is severe
    with a simplified gyral pattern, and the epilepsy is an infantile epileptic
    encephalopathy with cortical blindness and early death. TRMT10A patients
    present decades later with mild intellectual disability and a normally
    gyrated small brain.
  disease_term:
    preferred_term: microcephaly, epilepsy, and diabetes syndrome 1
    term:
      id: MONDO:0031481
      label: microcephaly, epilepsy, and diabetes syndrome 1
  distinguishing_features:
  - >-
    MEDS1: biallelic IER3IP1 variants, permanent neonatal diabetes, primary
    microcephaly with simplified gyral pattern, infantile epileptic
    encephalopathy, cortical blindness, death in childhood. MSSGM1: biallelic
    TRMT10A variants, diabetes from late childhood to the third decade,
    structurally normal small brain, mild intellectual disability, normal
    lifespan reported to date.
  evidence:
  - reference: PMID:24138066
    reference_title: "Microcephaly, epilepsy, and neonatal diabetes due to compound heterozygous mutations in IER3IP1: insights into the natural history of a rare disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A syndrome of permanent neonatal diabetes along with primary microcephaly with simplified gyral pattern associated with severe infantile epileptic encephalopathy was recently described in two independent reports in which disease-causing homozygous mutations were identified in the immediate early response-3 interacting protein-1 (IER3IP1) gene."
    explanation: >-
      Defines the MEDS1 phenotype whose neonatal timing and gyral simplification
      distinguish it from TRMT10A deficiency.
  - reference: PMID:24138066
    reference_title: "Microcephaly, epilepsy, and neonatal diabetes due to compound heterozygous mutations in IER3IP1: insights into the natural history of a rare disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The triad of microcephaly, generalized seizures, and permanent neonatal diabetes should prompt screening for mutations in IER3IP1."
    explanation: >-
      States the referral rule for MEDS1, which is anchored on the neonatal
      onset that TRMT10A deficiency lacks.

- name: Wolfram syndrome
  description: >-
    Another syndromic juvenile diabetes with which TRMT10A syndrome has been
    explicitly compared. Both present as non-autoimmune diabetes in childhood
    with neurological features; Wolfram adds optic atrophy, diabetes insipidus
    and deafness, which are not features of TRMT10A syndrome, and lacks the
    congenital microcephaly.
  distinguishing_features:
  - >-
      Wolfram: optic atrophy, diabetes insipidus, sensorineural deafness, WFS1 or
      CISD2 variants, no congenital microcephaly. TRMT10A: primary microcephaly,
      short stature, epilepsy, biallelic TRMT10A variants.
  evidence:
  - reference: PMID:39243962
    reference_title: "Discovery of a TRMT10A mutation in a case of atypical diabetes: Case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TRMT10A gene mutation has been linked to syndromic juvenile diabetes in a manner analogous to Wolfram's syndrome."
    explanation: >-
      Records the explicit comparison drawn in the literature between the two
      syndromic juvenile-diabetes entities.

discussions:
- discussion_id: mouse_pancreas_mismatch
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Why do Trmt10a null mice show no discernible pancreatic defect when
    autoantibody-negative diabetes is the defining metabolic feature of human
    TRMT10A deficiency?
  attaches_to:
  - "pathophysiology#Beta-Cell Oxidative Stress and Intrinsic Apoptosis"
  - "pathophysiology#Progressive Beta-Cell Mass Loss"
  rationale: >-
    This is the sharpest translational gap in the disorder. The constitutive
    Trmt10a null mouse faithfully reproduces the neurological arm — reduced body
    weight, smaller hippocampal postsynaptic densities, defective synaptic
    plasticity and memory, and the underlying codon-specific translational
    lesion — while explicitly showing no discernible defect in the pancreas.
    The entire beta-cell mechanism therefore rests on human material: siRNA
    knockdown in rat and human beta-cell lines, and patient-derived iPSC
    beta-like cells. Several explanations are compatible with the data and are
    not distinguished by current evidence: species differences in beta-cell
    tRNA-Gln dependence or angiogenin-mediated fragmentation; a cumulative,
    lifespan-scaled apoptotic burden that a two-year mouse cannot accrue; or a
    ceiling effect from assessing an unstressed mouse pancreas, given that
    TRMT10A deficiency in human cells acts partly by sensitizing beta cells to
    ER stress rather than killing them outright. Distinguishing these matters
    because it determines whether the mouse can be used at all to test
    beta-cell-protective interventions.
  proposed_experiments:
  - experiment_id: mouse_pancreas_stress_challenge
    name: Metabolic stress challenge of the Trmt10a null mouse pancreas
    description: >-
      Phenotype Trmt10a null mice under conditions that stress the beta cell —
      high-fat diet, prolonged glucose challenge, aged cohorts, or pharmacological
      ER stress — with glucose tolerance testing, insulin secretion, and
      beta-cell mass histomorphometry, rather than under standard housing alone.
      A null mouse that becomes diabetic only under stress would support the
      sensitization model demonstrated in patient iPSC beta-like cells and
      reconcile the species discrepancy.
  - experiment_id: cross_species_trna_fragmentation
    name: Cross-species comparison of beta-cell tRNA fragmentation
    description: >-
      Measure m1G9 occupancy, tRNA-Gln steady-state levels and 5'-tRNA-Gln
      fragment abundance side by side in TRMT10A/Trmt10a-null mouse islets,
      human islets and patient iPSC beta-like cells. If mouse beta cells do not
      generate the cytotoxic fragment at comparable levels, the mismatch is
      mechanistic rather than a matter of duration or stress.
  evidence:
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory."
    explanation: Documents the absent pancreatic phenotype that constitutes the mismatch.
  - reference: PMID:30247717
    reference_title: "Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRMT10A deficiency induces oxidative stress and sensitizes iPSC-derived β-like cells to endoplasmic reticulum stress-induced apoptosis."
    explanation: >-
      Supports the sensitization hypothesis — an unstressed mouse pancreas may
      not reveal a stress-conditional phenotype.

- discussion_id: insulin_resistance_mechanism
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What causes the peripheral insulin resistance in TRMT10A deficiency, and is
    it a distinct mechanism from beta-cell loss?
  attaches_to:
  - "pathophysiology#Peripheral Insulin Resistance"
  rationale: >-
    The established mechanism — tRNA hypomethylation, tRNA-Gln fragmentation,
    beta-cell apoptosis — predicts insulin deficiency, not insulin resistance.
    Yet marked insulin resistance is documented in at least two independent
    reports, one by formal oral glucose tolerance testing with Matsuda index and
    one clinically with a striking metformin response. Neither report offers a
    mechanism. Candidate explanations include a direct effect of TRMT10A loss on
    translation in insulin-target tissues (muscle, liver, adipose), a
    consequence of the body-composition phenotype suggested by the dorsocervical
    fat pad and central obesity, or the mRNA m6A/FTO arm of TRMT10A function —
    FTO being itself a well-known obesity and insulin-sensitivity locus, which
    makes this the most testable of the three. The gap is clinically live
    because it determines whether metformin should be tried before insulin.
  proposed_experiments:
  - experiment_id: tissue_specific_trmt10a_deletion
    name: Tissue-specific Trmt10a deletion in insulin-target tissues
    description: >-
      Generate muscle-, liver- and adipose-specific Trmt10a knockouts and measure
      insulin sensitivity by hyperinsulinaemic-euglycaemic clamp. A tissue in
      which deletion alone produces resistance would establish a cell-autonomous
      route independent of beta-cell loss.
  - experiment_id: fto_m6a_insulin_signalling_test
    name: Test whether the FTO-m6A arm mediates the resistance
    description: >-
      In TRMT10A-null human myotubes and adipocytes, map m6A changes and
      transcript stability for insulin-signalling components, and test whether
      restoring FTO activity or a catalytically dead TRMT10A that retains FTO
      binding rescues insulin signalling. This separates the catalytic tRNA arm
      from the non-catalytic FTO arm of TRMT10A function.
  evidence:
  - reference: PMID:26526202
    reference_title: "tRNA methyltransferase homologue gene TRMT10A mutation in young adult-onset diabetes with intellectual disability, microcephaly and epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diabetes was diagnosed while the subjects were in their 20s and was characterized by insulin resistance."
    explanation: Documents the insulin-resistant phenotype that the current mechanism does not explain.
  - reference: PMID:32213595
    reference_title: "Coordination of mRNA and tRNA methylations by TRMT10A."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we show that a tRNA methyltransferase, TRMT10A, interacts with an mRNA demethylase FTO (ALKBH9), both in vitro and inside cells."
    explanation: >-
      Provides the mechanistic candidate — the TRMT10A-FTO interaction — but
      makes no claim about insulin sensitivity, hence PARTIAL.

- discussion_id: metabolic_penetrance_and_onset
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Is the metabolic phenotype fully penetrant with age, or is there a genuine
    neurodevelopment-only form of TRMT10A deficiency?
  attaches_to:
  - "pathophysiology#Biphasic Glucose Dysregulation"
  rationale: >-
    Several molecularly confirmed patients have no dysglycaemia at the time of
    report: compound heterozygous siblings aged 10 and 12 with neither
    documented hypoglycaemia nor hyperglycaemia, and a 15-year-old homozygous
    for p.Arg43Ter with no metabolic abnormality. Because diabetes has been
    diagnosed as late as the late twenties in other patients, these observations
    are equally consistent with (a) age-dependent but eventually complete
    penetrance and (b) a genuinely distinct neurodevelopment-only phenotype
    determined by allele or modifier. The distinction is not academic: it
    determines whether lifelong glucose surveillance is mandatory for every
    biallelic carrier or can be stratified. Only longitudinal follow-up of the
    published cohort can settle it, and the 2026 report calls for exactly that.
  proposed_experiments:
  - experiment_id: longitudinal_metabolic_followup
    name: Longitudinal metabolic follow-up of the published TRMT10A cohort
    description: >-
      Prospectively follow all molecularly confirmed individuals with annual
      HbA1c, oral glucose tolerance testing with Matsuda index, and C-peptide,
      recording age at first dysglycaemia against genotype. Age-stratified
      penetrance curves would distinguish delayed onset from true
      non-penetrance and would set the evidence-based surveillance interval.
  evidence:
  - reference: PMID:42181738
    reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This case represents one of the rare reported TRMT10A-related syndrome patients in whom diabetes has not yet been documented."
    explanation: Documents a confirmed patient without the metabolic phenotype.
  - reference: PMID:42181738
    reference_title: "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These findings underscore the importance of considering TRMT10A in the differential diagnosis of patients with microcephaly, intellectual disability, epilepsy, and growth abnormalities, and emphasize the need for longitudinal follow-up to monitor for the possible later development of endocrine and metabolic manifestations."
    explanation: >-
      The reporting authors explicitly frame longitudinal follow-up as the
      unresolved question.

- discussion_id: neural_arm_direct_evidence
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Is the primary microcephaly caused by a reduced neural progenitor pool, and
    has this ever been measured directly in a human system?
  attaches_to:
  - "pathophysiology#Reduced Neural Progenitor Pool in the Developing Brain"
  rationale: >-
    The neural-progenitor account of the microcephaly is a proposal, not a
    measurement. It rests on three indirect observations: TRMT10A is expressed
    in human embryonic and fetal brain; TRMT10A silencing kills beta cells; and
    the patients have small, structurally normal brains. No study has measured
    proliferation or apoptosis in human TRMT10A-deficient neural progenitors.
    The competing account is that the phenotype arises from impaired synthesis
    of neuronal structural proteins with preserved cell number — the mechanism
    actually demonstrated in the null mouse, which has smaller postsynaptic
    densities and no reported reduction in neuron number. These predict
    different things about whether the deficit is fixed prenatally, and
    therefore about any therapeutic window.
  proposed_experiments:
  - experiment_id: patient_cerebral_organoid_progenitors
    name: Patient-derived cerebral organoid growth and progenitor dynamics
    description: >-
      Differentiate cerebral organoids from the existing TRMT10A-deficient iPSC
      lines and isogenic controls, and quantify organoid size, ventricular-zone
      thickness, radial glial proliferation index and apoptosis over the
      neurogenic window. Reduced progenitor proliferation would support the
      pool-depletion model; normal progenitor dynamics with altered neurite or
      synaptic protein content would support the translational model.
  evidence:
  - reference: PMID:24204302
    reference_title: "tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Taken together, we propose that TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain."
    explanation: The proposal is stated as such by its authors, which is the gap.
  - reference: PMID:38950903
    reference_title: "TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain."
    explanation: >-
      Supports the competing translational account of the neural phenotype
      rather than progenitor pool depletion.

mappings:
  mondo_mappings:
  - term:
      id: MONDO:0018320
      label: primary microcephaly-mild intellectual disability-young-onset diabetes syndrome
    mapping_predicate: skos:broadMatch
    mapping_source: Orphanet
    mapping_justification: >
      MONDO:0018320 is the Orphanet concept (ORPHA:391408, exact MONDO mapping
      per Orphadata) whose clinical description matches this entry. It is
      recorded as broadMatch rather than exactMatch because Orphanet's own
      cross-references place ORPHA:391408 as BTNT (broader than) BOTH
      OMIM:616033 (MSSGM1/TRMT10A, the anchor of this entry) and OMIM:616817
      (MSSGM2/PPP1R15B), and Orphadata lists both TRMT10A and PPP1R15B as its
      assessed disease-causing genes. The Orphanet concept is therefore a union
      of two gene-defined diseases that OMIM and MONDO split, and that dismech
      curates as two entries. The union is modelled explicitly as the
      Microcephaly_Short_Stature_and_Impaired_Glucose_Metabolism grouping, which
      carries the exactMatch to this term.
  - term:
      id: MONDO:0800450
      label: microcephaly, short stature, and impaired glucose metabolism
    mapping_predicate: skos:broadMatch
    mapping_source: MONDO
    mapping_justification: >
      The OMIM phenotypic series grouping (OMIMPS:616033) of which MONDO:0000208
      is a direct is_a child. Broader than this entry because it also subsumes
      MSSGM2 (MONDO:0014785, PPP1R15B).

datasets:
- accession: geo:GSE129502
  title: TRMT10A associated RNA targets
  description: >-
    Human high-throughput sequencing profiling of the RNA species bound by
    TRMT10A, undertaken to define the enzyme's substrate repertoire in human
    cells rather than yeast. Directly informative for the "Loss of tRNA m1G9
    Methyltransferase Activity" node, since which tRNAs TRMT10A actually
    services in human cells determines which codons are affected when it is
    lost.
  data_type: BULK_RNA_SEQ
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  sample_count: 6
  genes:
  - preferred_term: TRMT10A
    term:
      id: hgnc:28403
      label: TRMT10A
  notes: >-
    Surfaced by `just discover-datasets` as a GENE_ONLY candidate and retained
    after manual relevance triage: the GEO summary is explicitly about defining
    the human tRNA substrate repertoire of TRMT10A, so it bears on the disease
    mechanism rather than merely mentioning the gene. It is a gene-function
    dataset, not a patient cohort - it does not contain MSSGM1 case material.
    No evidence block: no exact-quote-bearing publication is attached to the
    accession.
- accession: geo:GSE146207
  title: Coordination of mRNA and tRNA methylations by TRMT10A
  description: >-
    The dataset underlying the TRMT10A-FTO study, profiling m6A changes and
    transcript-level consequences of TRMT10A ablation. Supports the
    "Coordinated mRNA m6A Dysregulation via the FTO Axis" node and is the most
    directly testable resource for the open question of what drives peripheral
    insulin resistance in this disorder.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  sample_count: 12
  genes:
  - preferred_term: TRMT10A
    term:
      id: hgnc:28403
      label: TRMT10A
  publication: PMID:32213595
  notes: >-
    Surfaced by `just discover-datasets` as a GENE_ONLY candidate; retained
    because its linked publication (PMID:32213595) is already cited in this
    entry for the FTO/m6A mechanism, so the disease relevance is established
    rather than assumed. GEO does not assign a single gdstype to this series,
    so `data_type` is left unset rather than guessed. A cell-line perturbation
    dataset, not patient material.

notes: >-
  Curation notes.

  (1) Entity identity. The curation request named this disorder by its Orphanet
  label, "primary microcephaly-mild intellectual disability-young-onset diabetes
  syndrome" (ORPHA:391408 / MONDO:0018320). That concept resolves to TWO
  gene-defined diseases, not one: Orphadata lists both TRMT10A and PPP1R15B as
  assessed disease-causing genes and cross-references ORPHA:391408 as broader
  than both OMIM:616033 and OMIM:616817. This entry curates the TRMT10A disease
  (MSSGM1, MONDO:0000208); the PPP1R15B disease (MSSGM2, MONDO:0014785) was
  already curated. The Orphanet-level union is modelled as a Grouping rather
  than being blended into either Disease entry.

  (2) Deep-research provenance and a caught error. Two providers returned:
  claude_code (10/10 references resolved, 0 unresolved, 0 off-topic;
  `just preflight-dr` PASS against MONDO:0000208, TRMT10A mentioned 62 times
  against 4 for the nearest rival gene) and openscientist (12/12 resolved,
  0 unresolved, 0 off-topic; preflight WARN because it discusses PPP1R15B
  alongside TRMT10A — the expected consequence of the lump/split situation in
  point 1, not a wrong-entity report). falcon was attempted first per the
  default and failed with HTTP 402 Payment Required; the Edison key carries no
  credit.

  The claude_code report asserted that MSSGM2 is caused by biallelic IGF2BP1
  variants. That is wrong — MSSGM2 (OMIM:616817, MONDO:0014785) is caused by
  PPP1R15B, verified against the MONDO record, against the existing dismech
  MSSGM2 entry, and independently against the openscientist report, which
  states the correct gene assignment and flags the conflation risk explicitly.
  The claim was discarded and is recorded here so it is not reintroduced. Two
  ontology suggestions from the same report were also rejected on verification:
  HP:0009806 for dorsocervical fat pad (the correct term is HP:0025383) and
  HP:0040270 for insulin resistance (HP:0000855). A report can pass every
  automated check and still be wrong about an adjacent entity.

  (3) Frequency qualifiers are deliberately omitted throughout. With on the
  order of twenty published probands and no cohort study, any FrequencyEnum
  value would be a manufactured justification for a band. The descriptions state
  what was observed in which report instead.

  (4) Review round 1 (PR #9162). Four phenotypes that were named in an entry
  title or description but carried no bound term were split out and bound:
  Scoliosis (HP:0002650), Joint hypermobility (HP:0001382), and the individual
  craniofacial features (deep-set eyes, hypotelorism, wide nose, short neck).
  The bundled "Progressive Beta-Cell Loss and Biphasic Glucose Dysregulation"
  node was split into a CELLULAR node (beta-cell mass loss) and an ORGANISM node
  (biphasic glucose dysregulation), per the single-value `biological_scale`
  discipline. Wolcott-Rallison syndrome was added as a differential.

  The Dandy-Walker finding is bound to HP:0001320 (Cerebellar vermis
  hypoplasia), NOT to HP:0001305 (Dandy-Walker malformation), and the reasoning
  is on that phenotype entry: HPO's definition of the malformation requires
  posterior-fossa enlargement, which is exactly what a Dandy-Walker *variant*
  lacks. Binding the variant to the malformation term would assert a finding the
  source does not report.

  Hypoglycaemia-phase management is deliberately absent from `treatments`: no
  cached abstract contains a quotable management sentence for the hypoglycaemic
  phase, and manufacturing one would be the failure mode the evidence SOP
  warns about.

  (5) Orphanet HPO annotations were not cited. `just refresh-orphadata` failed on
  a sha256 mismatch against the pinned manifest (the upstream bulk files have
  moved on), and updating the manifest would have required rebuilding all 8,823
  ORPHA cache files — an unrelated diff far larger than this curation. All
  phenotype evidence here therefore comes from primary literature.

📚

References & Deep Research

References

5

PMID:24204302

tRNA methyltransferase homolog gene TRMT10A mutation in young onset diabetes and primary microcephaly in humans.

No top-level findings curated for this source.

PMID:25053765

TRMT10A dysfunction is associated with abnormalities in glucose homeostasis, short stature and microcephaly.

No top-level findings curated for this source.

PMID:30247717

Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes.

No top-level findings curated for this source.

PMID:38950903

TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice.

No top-level findings curated for this source.

PMID:42181738

TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings.

No top-level findings curated for this source.

Deep Research

2

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-sonnet-5 14 citations 2026-08-20T07:23:15.708950

1. Disease Information

Overview. Microcephaly, short stature, and impaired glucose metabolism 1 (MSSGM1) is a rare, autosomal recessive multisystem Mendelian syndrome characterized by primary (congenital or early-postnatal) microcephaly with intellectual disability, proportionate short stature, and disturbed glucose homeostasis — typically hyperinsulinemic hypoglycemia in infancy/early childhood evolving into young-onset diabetes mellitus in adolescence or young adulthood (OMIM #616033; MedGen C4014997). It is caused by biallelic (homozygous or compound heterozygous) loss-of-function mutations in TRMT10A (tRNA methyltransferase 10 homolog A), located at chromosome 4q23 (OMIM *616013).

Key identifiers: - OMIM phenotype: #616033 (MSSGM1); gene locus OMIM 616013 (TRMT10A) - MONDO: MONDO:0000208 (per NCBI MedGen cross-reference) - MedGen: C4014997 / UID 863434 - Orphanet: ORPHA:391408 — "Primary microcephaly-mild intellectual disability-young-onset diabetes syndrome" - HGNC: HGNC:28403 (TRMT10A) - Gene location: 4q23; Ensembl: ENSG00000145331 - Note: A phenotypically overlapping but molecularly and nosologically distinct entity exists — MSSGM2 (OMIM #616817), caused by biallelic mutations in IGF2BP1* — and NSMCE2-related primordial dwarfism (OMIM #617253) also has overlapping features (short stature, microcephaly, insulin resistance) but is a separate gene/disorder. These should not be conflated with MSSGM1/TRMT10A.

Synonyms: MSSGM1; TRMT10A deficiency; TRMT10A-related syndrome; "microcephaly, intellectual disability, short stature, and diabetes"; young-onset diabetes with microcephaly.

Data provenance: Knowledge is derived almost entirely from aggregated case reports and small case series (individual patients and consanguineous families) rather than large population-level cohorts or EHR-based studies — consistent with an ultra-rare Mendelian disease with an estimated total of only ~15–20 published cases across the literature to date (multiple independent kindreds: Moroccan, Uzbek Jewish, Israeli/Bedouin, Scottish, Chinese, Turkish).

Sources: - OMIM #616033 - OMIM *616013 TRMT10A - MedGen C4014997 - Orphanet TRMT10A

2. Etiology

Disease-causal factor: MSSGM1 is a monogenic, autosomal recessive disorder caused exclusively by biallelic loss-of-function variants in TRMT10A. There is no known environmental, infectious, or polygenic contribution to the core syndrome — it is a purely genetic/mechanistic disease. TRMT10A encodes a nucleolar tRNA methyltransferase (the human ortholog of yeast Trm10) that catalyzes N1-methylation of guanosine 9 (m¹G9) in the D-loop of multiple cytoplasmic tRNAs.

Genetic risk factors (causal variants reported across kindreds): - c.379G>A (p.Arg127Ter/R127X) — homozygous nonsense mutation, first-described Moroccan consanguineous family (3 siblings) (Igoillo-Esteve et al. 2013, PMID: 24204302) - c.616G>A (p.Gly206Arg/G206R) — homozygous missense mutation at a highly conserved catalytic residue, consanguineous Uzbek Jewish family (3 siblings); in vitro methyltransferase activity assays showed the mutant enzyme had >10⁴-fold reduced methylation activity compared to wild type (Gillis et al. 2014, J Med Genet 51:581–586, DOI: 10.1136/jmedgenet-2014-102282) - p.Glu27Ter (c.79G>T) — homozygous nonsense mutation, Scottish siblings with milder, adult-onset phenotype (Yew et al. 2016, PMID: 26526202) - c.496-1G>A — homozygous canonical splice-acceptor mutation, first reported Chinese/Asian patient (Lin et al. 2020, BMJ Open Diabetes Res Care 8:e001601) - Homozygous contiguous gene deletion encompassing TRMT10A, causing a more severe multisystem phenotype including failure to thrive and delayed puberty (Zung et al. 2015, Am J Med Genet A, DOI: 10.1002/ajmg.a.37341) - Additional homozygous/compound heterozygous TRMT10A variants reported in subsequent case reports (e.g., a case with hypoplastic kidneys, PMID: 33448213; a 2024 case report of microcephaly/diabetes/epilepsy, PMID: 38302348)

All disease-causing variants are inherited in an autosomal recessive pattern, and virtually all reported cases arose in the setting of parental consanguinity, consistent with a rare recessive founder/private-mutation disease.

Environmental/lifestyle risk factors: None established — this is not modified by known environmental exposures; disease expression is driven by genotype (complete vs. partial loss of TRMT10A methyltransferase activity), which correlates with phenotypic severity (see below).

Protective factors: None specifically documented. No modifier genes or protective alleles have been reported. Heterozygous carriers (parents of affected probands) are clinically unaffected, consistent with fully recessive inheritance without a dominant-negative or haploinsufficiency mechanism.

Genotype-phenotype/severity correlation (an important "gene-environment"-adjacent theme): Emerging literature (including a 2026 study on "TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings," Ülker Üstebay et al., Human Mutation 2026) suggests residual enzymatic activity of the mutant allele modulates phenotype severity — some hypomorphic alleles produce a neurodevelopmental phenotype (intellectual disability, microcephaly) without the metabolic (diabetes/hypoglycemia) component, broadening the recognized phenotypic spectrum beyond the "full" MSSGM1 triad.

Sources: - Igoillo-Esteve et al. 2013, PLOS Genetics (PMC3814312) - Gillis et al. 2014, J Med Genet (DOI 10.1136/jmedgenet-2014-102282) - Yew et al. 2016, Diabetic Medicine (PMC4995728) - Lin et al. 2020, BMJ Open Diabetes Res Care (PMC7569974) - Zung et al. 2015, Am J Med Genet A - TRMT10A Mutation in a Child with Diabetes... Hypoplastic Kidneys, PMID 33448213 - A rare syndrome: Microcephaly, diabetes mellitus, and epilepsy, PMID 38302348 - TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings, Human Mutation 2026

3. Phenotypes

The MSSGM1 phenotype (compiled from MedGen's HPO-term listing and the primary case-series literature) spans neurodevelopmental, growth/skeletal, endocrine-metabolic, and immune domains.

Neurological/developmental

Phenotype	Suggested HPO term	Notes
Intellectual disability	HP:0001249	Present in nearly all reported cases; ranges mild–moderate
Global developmental delay	HP:0001263	Congenital-onset
Motor delay	HP:0001270
Seizures / epilepsy	HP:0001250	Reported in multiple kindreds (Gillis 2014; Yew 2016; 2024 case report)
Generalized non-motor (absence) seizure	HP:0011147
Primary microcephaly	HP:0011451	Congenital onset; core diagnostic feature
Microcephaly (postnatal/progressive in some)	HP:0000252	Some patients show normalization of head circumference with age (Yew 2016)

Growth/skeletal

Phenotype	Suggested HPO term	Notes
Short stature	HP:0004322	Proportionate; core diagnostic feature
Short neck	HP:0000470
Wide/broad nose	HP:0000445
Low anterior hairline	HP:0000294
Dorsocervical fat pad	HP:0009806	Reported in association with insulin resistance
Scoliosis	HP:0002650
Joint hypermobility	HP:0001382
Osteoporosis	HP:0000939
Hypoplastic kidneys	HP:0000089	Reported in one case (PMID 33448213), possibly expands phenotype

Endocrine/metabolic (the defining "impaired glucose metabolism" component)

Phenotype	Suggested HPO term	Notes
Hyperinsulinemic hypoglycemia	HP:0000825	Typical early-childhood presentation; ketotic and non-ketotic events described (Gillis 2014)
Diabetes mellitus (young/adolescent-onset)	HP:0000819	Onset ranges early adolescence (Igoillo-Esteve cohort, age 14–22) to young adulthood (Yew cohort, age 24–28)
Insulin resistance	HP:0040270	Documented directly via Matsuda index in Yew 2016 (Matsuda 1.46 vs. controls ~14.2) and in the Chinese case (Lin 2020)
Delayed puberty	HP:0000823
Delayed thelarche	HP:0025499
Primary amenorrhea	HP:0000786
Anti-GAD65 antibody	— (laboratory finding, not core autoimmunity)	Reported but disease is not classically autoimmune in mechanism

Age of onset / progression: Congenital microcephaly and short stature are apparent from birth/infancy. Glucose dysregulation frequently begins as hyperinsulinemic hypoglycemia in infancy or early childhood, transitioning over years to overt diabetes mellitus in the second or third decade — proposed to reflect progressive β-cell loss via apoptosis (see Mechanism section). Severity and the specific metabolic phenotype (hypoglycemia-predominant vs. insulin-resistant diabetes-predominant, vs. purely neurodevelopmental with no metabolic disease) vary by allele and possibly by residual enzymatic activity, per the 2026 phenotype-expansion report. Epilepsy/seizures appear to be a variably penetrant feature rather than universal.

Frequency across the literature: Because MSSGM1 is known from fewer than ~20 published probands, "frequency" data (e.g., % of patients with a given feature) should be treated as descriptive of the small reported case series rather than population-level statistics; frequency qualifiers in a knowledge base entry should be sourced to specific cohort counts (e.g., "3/3 siblings" in a given family report) rather than generalized percentages.

Quality of life impact: Not formally studied with standardized instruments (no EQ-5D/SF-36 data identified); qualitatively, affected individuals face lifelong intellectual disability, need for insulin/metabolic management, and growth-related morbidity, but no dedicated QOL study was found in the literature reviewed.

Sources: - MedGen C4014997 — clinical feature listing - Igoillo-Esteve et al. 2013 (PMC3814312) - Gillis et al. 2014, J Med Genet - Yew et al. 2016 (PMC4995728) - Lin et al. 2020 (PMC7569974)

4. Genetic/Molecular Information

Causal gene: TRMT10A (HGNC:28403), chromosome 4q23, Ensembl ENSG00000145331. Gene-level OMIM entry: *616013.

Protein: tRNA methyltransferase 10 homolog A — a nucleolar enzyme, mammalian ortholog of S. cerevisiae Trm10, that catalyzes formation of N1-methylguanosine at position 9 (m¹G9) in the D-loop of multiple cytoplasmic tRNAs. TRMT10A localizes to the nucleolus in both β-cells and non-β-cells, the site of tRNA processing/modification (Igoillo-Esteve et al. 2013). TRMT10A is ubiquitously expressed but enriched in brain and pancreatic islets, directly consistent with the two principal affected tissues in MSSGM1 (Igoillo-Esteve et al. 2013; OMIM *616013).

Reported pathogenic variants (all biallelic, loss-of-function or severely hypomorphic): - p.Arg127Ter (c.379G>A) — complete loss via nonsense-mediated decay (NMD); no detectable mRNA/protein (Igoillo-Esteve 2013) - p.Gly206Arg (c.616G>A) — missense at a conserved catalytic residue; methylation activity reduced >10⁴-fold in vitro (Gillis 2014) - p.Glu27Ter (c.79G>T) — nonsense, presumed NMD (Yew 2016) — associated with a milder phenotype (adult-onset diabetes, normalized head circumference, minimal dysmorphism), suggesting some genotype-severity correlation - c.496-1G>A — canonical splice acceptor variant (Lin et al. 2020) - Contiguous gene deletion encompassing TRMT10A (Zung et al. 2015) — more severe multisystem phenotype

Variant classification: Per ACMG/AMP framework, the nonsense and canonical splice-site variants are consistently classified pathogenic (complete loss of function); the G206R missense is functionally validated as pathogenic via direct enzymatic assay. Genes/variants are catalogued in ClinVar and GenCC (TRMT10A: GenCC HGNC:28403).

Functional consequence: Loss-of-function — all characterized variants abolish or nearly abolish tRNA m¹G9 methyltransferase activity, leading to hypomodified tRNAs.

Allele frequency: TRMT10A biallelic pathogenic variants are each private/family-specific (found in single consanguineous kindreds); no common population founder allele has been reported. Carrier frequency has not been systematically estimated in large population databases (e.g., gnomAD) for any specific pathogenic allele given the rarity and family-specific nature of variants identified to date.

Origin: Germline (constitutional), consistent with a classic autosomal recessive Mendelian disease — not a somatic/cancer-associated gene.

Modifier genes/epigenetics: None specifically identified for MSSGM1. No DNA methylation, histone modification, or chromatin-level disease mechanism has been reported for TRMT10A-related disease; the pathology is a direct enzymatic (RNA-modification) loss-of-function, not an epigenetic-regulatory mechanism.

Chromosomal abnormalities: One reported case involved a homozygous contiguous gene deletion spanning the TRMT10A locus (Zung et al. 2015), rather than a point mutation — illustrating that both intragenic pathogenic variants and larger structural deletions of the locus can cause the syndrome.

Suggested ontology terms: HGNC:28403 (TRMT10A); GO:0002939 (tRNA N1-guanine methylation) / GO:0160104 (tRNA (guanine-N1)-methyltransferase activity, if applicable term exists) for molecular function; GO:0005730 (nucleolus) for subcellular localization.

Sources: - OMIM *616013 TRMT10A - Igoillo-Esteve et al. 2013 (PMC3814312) - Gillis et al. 2014 - GenCC TRMT10A - GeneCards TRMT10A

5. Environmental Information

No environmental toxin, radiation, pollutant, occupational exposure, infectious agent, or lifestyle factor has been implicated as a cause or trigger of MSSGM1 in the literature reviewed. This is a purely monogenic disease. No infectious-agent association applies. Not applicable for this disorder beyond standard supportive-care/diet management of secondary diabetes (see Treatment).

6. Mechanism / Pathophysiology

Core molecular defect → cellular consequence → organ phenotype causal chain:

Molecular lesion: Biallelic TRMT10A loss-of-function → loss of nucleolar tRNA m¹G9 methyltransferase activity → accumulation of hypomodified cytoplasmic tRNAs.
Cellular consequence (pancreatic β-cells): Igoillo-Esteve et al. (2013) demonstrated directly that "TRMT10A silencing induces rat and human β-cell apoptosis" — i.e., loss of TRMT10A function triggers programmed cell death specifically in insulin-producing β-cells, likely via unresolved translational/proteostatic stress from hypomodified tRNAs impairing translational fidelity/efficiency.
Cellular consequence (neurons): The same mechanistic principle is proposed to operate in the developing brain — "TRMT10A deficiency negatively affects β-cell mass and the pool of neurons in the developing brain" (Igoillo-Esteve et al. 2013) — i.e., reduced neuronal progenitor pool/survival during neurodevelopment, producing primary microcephaly and the associated intellectual disability.
Organ/systemic consequence — glucose homeostasis: Progressive β-cell apoptosis initially manifests as hyperinsulinemic hypoglycemia (proposed to reflect dysregulated/excessive insulin release from stressed or dying β-cells in early life) and evolves over time, as β-cell mass is progressively lost, into insulin-deficient/insulin-resistant diabetes mellitus in adolescence/young adulthood (Gillis et al. 2014: "TRMT10A deficiency accounts for abnormalities in glucose homeostasis initially manifesting both ketotic and non-ketotic hypoglycaemic events with transition to diabetes in adolescence, perhaps as a consequence of accelerated β cell apoptosis"). A separate arm — peripheral insulin resistance — is also directly documented (low Matsuda index in Yew 2016; marked insulin resistance responsive to metformin in Lin et al. 2020), suggesting the metabolic phenotype has both a β-cell-apoptotic/insulin-secretory component and a peripheral insulin-sensitivity component.
Organ/systemic consequence — CNS: Impaired neuronal pool generation during development → primary microcephaly, global developmental delay, intellectual disability, and (in a subset) epilepsy.
Growth: Short stature is proportionate and likely reflects a combination of the systemic translational-stress mechanism (affecting growth-plate chondrocytes and other proliferating tissues generally) plus downstream endocrine dysfunction (delayed puberty), though a specific growth-hormone-axis lesion has not been demonstrated.

Upstream vs. downstream: The TRMT10A enzymatic defect is the single upstream initiating lesion; β-cell apoptosis/dysfunction and impaired neurodevelopmental neuron pool are parallel (not sequential) downstream consequences occurring in different tissues due to the same ubiquitous but tissue-enriched enzyme loss — i.e., a "single-gene, two-tissue convergent phenotype" pattern (analogous in structure to modules like metabolic_intoxication_decompensation but distinct in that here the same molecular lesion independently damages two enriched-expression tissues rather than one metabolic block causing a toxic cascade).

Cell types/tissues involved: - Pancreatic islet β-cells (insulin-secreting) - Neural progenitor cells / developing cortical neurons

Suggested ontology terms: - GO:0006915 apoptotic process (β-cell apoptosis) - GO:0002943 tRNA dihydrouridine synthesis / GO:0030488 tRNA methylation (general parent term; more specific m¹G9 term may need verification via OAK) - CL:0000169 type B pancreatic cell (β-cell) - CL:0011020 neural progenitor cell / CL:0000540 neuron - UBERON:0000006 islet of Langerhans - UBERON:0000955 brain / UBERON:0001851 cortex

Molecular profiling: No transcriptomic, proteomic, or single-cell datasets specific to human TRMT10A-deficient tissue were identified in this search; the primary functional evidence is (a) direct in vitro enzymatic methyltransferase assays on recombinant mutant protein (Gillis 2014) and (b) siRNA-knockdown apoptosis assays in rat/human β-cell lines (Igoillo-Esteve 2013). No CRISPR screen or multi-omics human-tissue dataset for this specific gene/disease was found.

Sources: - Igoillo-Esteve et al. 2013, PLOS Genetics (PMC3814312) — direct quotes above - Gillis et al. 2014, J Med Genet — direct quote above - Yew et al. 2016 (PMC4995728) — Matsuda index data

7. Anatomical Structures Affected

Organ level: - Primary: Brain (microcephaly, structural under-development), pancreas (endocrine islets — β-cell loss) - Secondary/complication-related: Kidney (hypoplastic kidneys reported in one case), skeletal system (short stature, scoliosis, osteoporosis), reproductive/endocrine axis (delayed puberty, primary amenorrhea) - Body systems: Nervous system, endocrine system, skeletal system, and (in one case) renal system

Tissue/cell level: - Pancreatic islet β-cells (CL:0000169) - Neural progenitor cells / cortical neurons during development - Bone (osteoporosis) — osteoblast/osteoclast balance not specifically studied

Subcellular level: - Nucleolus (GO:0005730) — the specific subcellular site where TRMT10A functions and where tRNA modification occurs, per Igoillo-Esteve et al. 2013 ("TRMT10A localizes to the nucleolus of β- and non-β-cells") - Cytoplasm — the ultimate site of action of the modified tRNAs during translation

Localization/laterality: No lateralization is described; microcephaly and short stature are symmetric/systemic findings; hypoplastic kidney was reported without specified laterality detail in the abstract reviewed.

Suggested UBERON terms: UBERON:0000955 (brain), UBERON:0001264 (pancreas), UBERON:0000006 (islet of Langerhans), UBERON:0002113 (kidney), UBERON:0001474 (bone element).

8. Temporal Development

Onset: Congenital/perinatal for microcephaly and short stature (present from birth); infancy/early childhood for hyperinsulinemic hypoglycemia; adolescence to young adulthood for overt diabetes mellitus (reported range: age 14–22 in the original Moroccan family vs. mid-20s in the milder Scottish family, per Yew 2016) — i.e., a chronic, congenital-onset, progressive disorder with a delayed/evolving metabolic phenotype.
Progression: The metabolic axis specifically shows a biphasic progression — early hypoglycemia (proposed β-cell dysregulation/early apoptosis phase) transitioning to diabetes (progressive β-cell loss) over years. Neurodevelopmental features (intellectual disability, microcephaly) are generally static/non-progressive once established, though in some patients head circumference "normalized" with growth (Yew 2016), suggesting variable postnatal catch-up in milder alleles.
Disease course pattern: Chronic, lifelong; not relapsing-remitting. No spontaneous remission of the metabolic or neurodevelopmental features has been described.
Critical periods: Neurodevelopment (prenatal through early childhood) appears to be the critical window during which loss of TRMT10A most directly determines the eventual degree of microcephaly/intellectual disability, given the mechanism operating on the developing neuronal progenitor pool.

Sources: as above (Igoillo-Esteve 2013; Gillis 2014; Yew 2016).

9. Inheritance and Population

Epidemiology: MSSGM1 is an ultra-rare disease. No formal prevalence or incidence estimate (per 100,000) has been published; the disease is known from approximately 15–20 reported probands worldwide across independent kindreds (Moroccan, Uzbek Jewish/Israeli, Scottish, Chinese, Turkish, and others), consistent with Orphanet-level "ultra-rare" classification. A knowledge-base entry should record prevalence_class: NOT_YET_DOCUMENTED or a qualitative ULTRA_RARE band rather than a specific numeric rate, given the absence of a published epidemiological study.
Inheritance pattern: Autosomal recessive (AR) — confirmed across every reported kindred (biallelic variants, unaffected heterozygous parents, consanguinity in essentially all reported families).
Penetrance: Appears complete for the core phenotype (microcephaly, short stature) among biallelic carriers reported to date, though the specific metabolic sub-phenotype (hypoglycemia vs. diabetes vs. isolated neurodevelopmental disease without metabolic findings, per the 2026 report) is variable/genotype-dependent.
Expressivity: Variable — e.g., the p.Glu27Ter Scottish family had a substantially milder, later-onset phenotype (adult-onset diabetes, normalized head circumference, minimal dysmorphism) compared with the original Moroccan R127X family and the Uzbek Jewish G206R family (severe congenital microcephaly, childhood-onset hyperinsulinemic hypoglycemia, seizures).
Genetic anticipation: Not reported/applicable (not a repeat-expansion disorder).
Germline mosaicism: Not specifically reported.
Founder effects: Each reported pathogenic variant appears to be family/population-specific (Moroccan founder R127X; Uzbek Jewish founder G206R), consistent with multiple independent founder mutations in geographically/ethnically distinct consanguineous populations rather than one recurring global founder allele.
Consanguinity: A major contributing factor — nearly every published kindred involved first-cousin or otherwise consanguineous unions, as expected for a fully recessive ultra-rare disease.
Carrier frequency: Not established in population reference databases for any specific allele (each variant is private/rare).
Population demographics: Reported cases span Moroccan, Israeli/Uzbek Jewish, Scottish/European, and Chinese/East Asian populations, indicating the disease is not restricted to a single ethnic group, though each specific pathogenic allele so far has been population/family-specific.
Sex ratio: No skewed sex ratio has been reported; both males and females affected across kindreds (though some phenotypes like delayed thelarche/primary amenorrhea are necessarily reported in affected females).
Age distribution: Presentation from birth (microcephaly, short stature) through childhood (hypoglycemia) to adolescence/young adulthood (diabetes diagnosis); no adult-onset-only presentation has been described absent the childhood neurodevelopmental features.

10. Diagnostics

Laboratory tests: - Fasting glucose, insulin, C-peptide (to characterize hyperinsulinemic hypoglycemia in early presentation) - HbA1c (for diabetes monitoring — e.g., decreased from 14.4% to 6.8% with metformin in the Lin et al. 2020 case) - Oral glucose tolerance testing with Matsuda index calculation for insulin sensitivity (used in Yew 2016) - Anti-GAD65 antibody (reported feature; may be used to help exclude autoimmune/type 1 diabetes in differential diagnosis) - Insulinogenic index / disposition index for β-cell function assessment

Genetic testing: - Targeted gene testing / gene panel for TRMT10A is the primary recommended approach once the clinical triad (microcephaly + short stature + glucose dysregulation) is recognized; several diagnoses were made via targeted next-generation sequencing panels for monogenic diabetes (Yew 2016; Lin 2020). - Whole-exome sequencing (WES) was the discovery method in the original families (Igoillo-Esteev 2013; Gillis 2014) and remains appropriate when the phenotype is not immediately recognized as monogenic-diabetes-related. - Chromosomal microarray (CMA) is relevant given at least one reported case involved a contiguous gene deletion encompassing TRMT10A (Zung et al. 2015) rather than a point mutation — CMA/deletion analysis should be considered when sequencing is negative but phenotype is compatible. - Standard monogenic-diabetes gene panels (e.g., MODY panels) may include TRMT10A in comprehensive versions; clinicians are advised (per Yew et al. 2016) that "TRMT10A sequencing should be considered in children or adults with young-onset diabetes who have a history of intellectual disability, microcephaly and epilepsy."

Imaging: Head circumference/growth charting for microcephaly; brain MRI to characterize any structural abnormality (specific MRI findings were not detailed in the sources reviewed here, and would need per-case verification before citing generically).

Clinical criteria: No formal consensus diagnostic criteria/society guideline was identified (consistent with the disease's rarity); diagnosis rests on the clinical triad (microcephaly + short stature + glucose dysregulation) plus confirmatory molecular genetic testing.

Differential diagnosis: Should include other monogenic diabetes/growth-microcephaly syndromes — notably MSSGM2 (IGF2BP1), NSMCE2-related primordial dwarfism, Wolcott-Rallison syndrome, and other syndromic causes of congenital hyperinsulinism/primordial dwarfism with microcephaly (e.g., MOPD II/PCNT). Molecular confirmation is essential to distinguish these overlapping phenotypes.

Screening: No population newborn-screening or carrier-screening program specifically targets TRMT10A (disease too rare); targeted carrier testing may be offered within consanguineous families with a known proband variant.

11. Outcome/Prognosis

Survival/mortality: No specific survival statistics or life-expectancy data were identified in the sources reviewed; the disease has not been characterized as immediately life-threatening in reported cases, though severe/prolonged hypoglycemic episodes in infancy carry inherent neurological risk if unrecognized/untreated, and uncontrolled diabetes carries the usual long-term complication risk.
Morbidity: Lifelong intellectual disability and short stature are essentially fixed; ongoing management burden from diabetes/insulin resistance, and skeletal complications (scoliosis, osteoporosis) may accrue over time.
Complications: Diabetes-related complications (standard long-term diabetic complications would be expected if poorly controlled, though not specifically documented in this small case literature); seizure disorder in a subset; renal hypoplasia in at least one reported case.
Recovery potential: The neurodevelopmental component (microcephaly, intellectual disability) is not reversible; the metabolic component is manageable with standard diabetes therapy, and in at least one case responded very well to metformin (HbA1c improved from 14.4% to 6.8% within 3 months; Lin et al. 2020), indicating meaningful treatment-responsive disease course for the insulin-resistant subtype.
Prognostic factors: Genotype severity appears to correlate with phenotype severity (complete loss-of-function alleles like R127X and G206R associated with more severe congenital phenotype vs. the milder p.Glu27Ter Scottish kindred) — this is the closest available "prognostic biomarker," i.e., genotype itself, though small numbers preclude a rigorous prognostic model.

12. Treatment

There is no disease-modifying or curative therapy for the underlying TRMT10A enzymatic defect; management is entirely symptomatic/supportive, targeted at the metabolic and neurodevelopmental manifestations.

Pharmacotherapy (metabolic management): - Insulin therapy — for hypoglycemia management in infancy (in the hyperinsulinemic-hypoglycemia phase) and/or for insulin-deficient diabetes later in disease course. NCIT term: NCIT:C15986 (Pharmacotherapy) generically, or a more specific insulin/glucose-management term if available. - Metformin — demonstrated highly effective for the insulin-resistance-predominant metabolic phenotype (HbA1c 14.4%→6.8% in 3 months in the Chinese case; Lin et al. 2020). therapeutic_agent: CHEBI:6801 (metformin); treatment_term: NCIT:C15986 Pharmacotherapy. - Standard diabetes monitoring and dietary management for glucose control (dietary intervention, NCIT:C15447).

Supportive/rehabilitative: - Physical therapy, occupational therapy, and special-education/developmental support for intellectual disability and motor delay (NCIT:C15302 Physical Therapy; general developmental/rehabilitation services NCIT:C15315). - Management of seizures with standard antiepileptic therapy where epilepsy is present (specific agent not detailed per-case in sources reviewed). - Endocrine management of delayed puberty (e.g., hormone replacement as clinically indicated). - Orthopedic monitoring/management for scoliosis and osteoporosis.

Genetic counseling: Recommended for affected families given the autosomal recessive inheritance and typically consanguineous presentation (NCIT:C15240 Genetic Counseling).

Experimental/advanced therapeutics: No gene therapy, RNA-based therapy, or targeted molecular therapy specific to TRMT10A deficiency has been reported or is in clinical trials, based on the sources reviewed. No NCT-registered trial specific to this disease was identified.

Treatment strategy: Because the metabolic phenotype has (at least) two distinct pathophysiological arms — β-cell apoptosis/insulin deficiency vs. peripheral insulin resistance — treatment should be individualized based on which pattern predominates (insulin therapy vs. insulin-sensitizing agents like metformin), as illustrated directly by the divergent management needs and metformin responsiveness reported across cases.

13. Prevention

Primary prevention: Not applicable in the traditional sense (monogenic recessive disease); the only "primary prevention" avenue is genetic counseling and reproductive risk communication in consanguineous families with a known TRMT10A pathogenic variant, including discussion of carrier testing, prenatal diagnosis, or preimplantation genetic diagnosis (PGD) where desired and available (NCIT:C15240 Genetic Counseling).
Secondary prevention: Early recognition of the clinical triad (microcephaly + short stature + hypoglycemia/diabetes) enables earlier initiation of metabolic management, potentially preventing acute hypoglycemic neurological injury in infancy.
Screening: No population-level newborn or carrier screening program exists for this ultra-rare gene; targeted familial cascade testing is the only applicable "screening" approach once a proband is identified.
Behavioral/public health interventions: Not applicable — no modifiable environmental risk factor has been identified.

14. Other Species / Natural Disease

No naturally occurring veterinary/companion-animal disease caused by TRMT10A mutation was identified in the sources searched (no OMIA entry surfaced). This appears to be a disease characterized essentially exclusively through human clinical genetics to date; a systematic OMIA search was not exhaustively completed in this pass and should be verified independently before asserting a negative finding in the knowledge base.

15. Model Organisms

Cellular/in vitro models: - siRNA knockdown of TRMT10A in rat and human β-cell lines — directly demonstrated increased β-cell apoptosis upon TRMT10A silencing, providing the primary functional/mechanistic evidence for the β-cell-loss arm of pathophysiology (Igoillo-Esteve et al. 2013). Evidence source classification: IN_VITRO. - Recombinant enzyme assays quantifying loss of m¹G9 methylation activity for the G206R mutant (>10⁴-fold reduction vs. wild type) (Gillis et al. 2014). Evidence source: IN_VITRO (biochemical/COMPUTATIONAL-adjacent enzymatic assay).

Animal models: - IMPC (International Mouse Phenotyping Consortium) Trmt10a knockout mouse (MGI:1920421) — systematic phenotyping identified significant abnormalities across multiple physiological systems, specifically including homeostasis/metabolism, growth/size/body region, skeleton, behavior/neurological, and vision/eye systems, with 11 significant phenotypes reported and 2 associated diseases linked to the gene in the IMPC database. This provides model-organism-level support (fidelity: likely MODERATE, given it is a systematic phenotyping-pipeline knockout rather than a disease-mechanism-focused study) for the growth, metabolic, and neurological dimensions of the human syndrome. Evidence source: MODEL_ORGANISM. - No detailed IMPC phenotype table (specific glucose-tolerance-test results, body-weight curves, etc.) was retrievable in this pass due to dynamically loaded content; a curator populating a knowledge-base animal_models block should fetch the full IMPC data table directly (https://www.mousephenotype.org/data/genes/MGI:1920421) before finalizing specific readout values, rather than relying on this summary alone.

Notable limitation: No zebrafish, Drosophila, or C. elegans model specific to TRMT10A/MSSGM1 was identified in the sources reviewed (contrast with NSMCE2, where a zebrafish knockdown model exists — but that is a different, non-orthologous disease gene, and should not be conflated with TRMT10A model-organism evidence in the knowledge base).

Applications: The β-cell siRNA-knockdown model directly supports research into the apoptotic mechanism underlying the hypoglycemia-to-diabetes transition; the IMPC mouse knockout supports broader phenotype-recapitulation (growth, metabolism, neurological) but has not yet been used, per the sources found here, for a dedicated mechanistic dissection of the neurodevelopmental (microcephaly) arm of the human disease.

Summary of Key Ontology Term Suggestions for Knowledge-Base Curation

Category	Term
Disease (MONDO)	MONDO:0000208
Disease (OMIM)	616033
Disease (Orphanet)	ORPHA:391408
Gene	HGNC:28403 (TRMT10A)
Phenotype (HP)	HP:0011451 (primary microcephaly), HP:0004322 (short stature), HP:0000825 (hyperinsulinemic hypoglycemia), HP:0000819 (diabetes mellitus), HP:0040270 (insulin resistance), HP:0001249 (intellectual disability), HP:0001250 (seizures), HP:0000823 (delayed puberty)
Biological process (GO)	GO:0006915 (apoptotic process), tRNA methylation-related GO term (verify exact m¹G9 term via OAK)
Cell type (CL)	CL:0000169 (type B pancreatic cell), CL:0000540 (neuron) / neural progenitor cell
Anatomy (UBERON)	UBERON:0000955 (brain), UBERON:0000006 (islet of Langerhans), UBERON:0002113 (kidney)
Chemical/drug (CHEBI)	CHEBI:6801 (metformin)
Treatment (NCIT)	NCIT:C15986 (Pharmacotherapy), NCIT:C15240 (Genetic Counseling), NCIT:C15302 (Physical Therapy)

Important curation note: Before final entry, all PMIDs above should be re-verified against just fetch-reference and cached abstracts per the dismech evidence SOP — in particular, this research pass was unable to independently confirm the exact PMID for Gillis et al. 2014 (J Med Genet 51:581–586; DOI: 10.1136/jmedgenet-2014-102282) through the tools available and it is cited here by DOI/journal citation rather than a verified PMID; a curator should resolve this PMID via PubMed/just fetch-reference before use, and must independently verify NEC risk against the two similarly-named but distinct entities (MSSGM2/IGF2BP1 and NSMCE2-related primordial dwarfism) given their overlapping phenotype and eponym-adjacent naming pattern.

Sources (consolidated): - OMIM #616033 — MSSGM1 - OMIM *616013 — TRMT10A - MedGen C4014997 - Orphanet — TRMT10A - Igoillo-Esteve et al. 2013, PLOS Genetics, PMID 24204302 (PMC3814312) - Gillis et al. 2014, J Med Genet 51:581–586 (DOI 10.1136/jmedgenet-2014-102282) - Yew et al. 2016, Diabetic Medicine, PMID 26526202 (PMC4995728) - Lin et al. 2020, BMJ Open Diabetes Res Care (PMC7569974) - Zung et al. 2015, Am J Med Genet A - TRMT10A Mutation... Hypoplastic Kidneys, PMID 33448213 - A rare syndrome: Microcephaly, diabetes mellitus, and epilepsy, PMID 38302348 - TRMT10A-Related Neurodevelopmental Disorder Without Metabolic Findings, Human Mutation 2026 - IMPC Trmt10a knockout mouse, MGI:1920421 - GenCC TRMT10A - GeneCards TRMT10A

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OpenScientist ▸

Key Findings

openscientist-autonomous 12 citations 2026-08-20T08:01:54.627282

Key Findings

Finding 1 — MSSGM1 is an autosomal-recessive TRMT10A disorder (gene–disease correction)

Authoritative gene–disease mapping (HPO/JAX gene-annotation network integrated with OMIM) assigns OMIM:616033 / MONDO:0000208 "Microcephaly, short stature, and impaired glucose metabolism 1" to the gene TRMT10A (NCBI Gene 93587). The phenotype was first delineated by Igoillo-Esteve et al. (2013) in a large consanguineous family with three affected children, who reported "a new syndrome of young onset diabetes, short stature and microcephaly with intellectual disability" (PMID: 24204302). A second family, reported by Gillis et al. (2014), independently identified TRMT10A and expanded the phenotype to include the hypoglycemic pole of the glucose disturbance (PMID: 25053765). These two papers are the OMIM/HPO source documents for the disease entity.

A key correction established in this investigation: the closely related gene PPP1R15B (NCBI Gene 84919) does not cause MSSGM1 — it causes MSSGM2 (OMIM:616817 / MONDO:0014785). Both disorders map to the same Orphanet umbrella term ORPHA:391408 "Primary microcephaly–mild intellectual disability–young-onset diabetes syndrome" (MONDO:0018320), which is why they are so easily conflated. The correct causal gene for MSSGM1 is TRMT10A.

Finding 2 — Molecular mechanism: loss of tRNA m1G9 methyltransferase activity → tRNA fragmentation → β-cell death

TRMT10A (Q8TBZ6; 339 aa; 4q23; gene MIM 616013; HGNC:28403) is the mammalian ortholog of yeast Trm10 and catalyzes 1-methylguanosine at tRNA position 9 (m1G9). It localizes to the nucleolus and is ubiquitously expressed but enriched in brain and pancreatic islets — precisely the tissues affected in the syndrome, providing a clean explanation of tissue tropism (microcephaly/intellectual disability from brain; diabetes from islet) (PMID: 24204302): "TRMT10A is ubiquitously expressed but enriched in brain and pancreatic islets, consistent with the tissues affected in this syndrome."

Cosentino et al. (2018) provided the definitive functional mechanism using patient iPSC-derived β-cells (PMID: 30247717). They "confirm the role of TRMT10A as a guanosine 9 tRNA methyltransferase, and identify tRNAGln and tRNAiMeth as two of its targets." They further "demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells," and showed that "tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5′-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death." This defines a complete causal chain from enzyme loss to cell death.

Gillis et al. (2014) localized pathogenicity to the catalytic step: the G206R missense variant "completely abolished m(1)G9 methyltransferase activity" (<0.1% of wild-type), and this was "likely due to significant defects in its ability to bind the methyl donor S-adenosyl methionine" while the mutant retained tRNA binding (PMID: 25053765). Loss of SAM-dependent catalysis, not loss of substrate recognition, is the pathogenic event.

Finding 3 — Core phenotype and biphasic glucose dysregulation

Authoritative HPO annotations for OMIM:616033 with observed frequencies across the reported families are summarized in the phenotype table below. The single most striking clinical feature is the biphasic glucose phenotype: the Gillis family presented with hyperinsulinemic hypoglycemia, while the Igoillo-Esteve family presented with young-onset diabetes — two poles of the same β-cell dysfunction. Gillis et al. described "microcephaly, intellectual disability, short stature, delayed puberty, seizures and disturbed glucose metabolism, mainly hyperinsulinaemic hypoglycaemia" (PMID: 25053765).

Finding 4 — Allelic spectrum and population genetics

Reported pathogenic TRMT10A variants are biallelic and predominantly loss-of-function: nonsense p.Arg127 (PMID: 24204302); missense p.Gly206Arg abolishing SAM binding (PMID: 25053765); splice-acceptor c.496-1G>A (PMID: 33067246); whole-gene/contiguous-gene deletion (PMID: 26297882); and compound-heterozygous nonsense variants (PMID: 26535115). gnomAD constraint metrics (pLI ≈ 3×10⁻¹², LOEUF ≈ 1.21, observed/expected LoF ≈ 0.92) indicate TRMT10A is tolerant of heterozygous loss of function*, fully consistent with a recessive mechanism requiring two damaged alleles. ClinVar lists ~196 TRMT10A variants, ~50 classified pathogenic/likely pathogenic.

Phenotype Table (HPO annotations, OMIM:616033)

Phenotype	HPO term	Frequency (reported families)	Notes
Intellectual disability	HP:0001249	6/6	Universal core feature
Microcephaly / Primary microcephaly	HP:0000252 / HP:0011451	3/3	Congenital, primary
Short stature	HP:0004322	3/3	Postnatal growth failure
Global developmental delay	HP:0001263	3/3	Congenital onset
Seizures	HP:0001250	3/3	Epilepsy-predominant in some
Diabetes mellitus (young-onset, insulin-deficient)	HP:0000819	3/3 (Igoillo-Esteve family)	Diabetic pole
Hyperinsulinemic hypoglycemia	HP:0000825	3/3 (Gillis family)	Hypoglycemic pole (early)
Delayed puberty	HP:0000823	Variable	Delayed thelarche, primary amenorrhea
Osteoporosis	HP:0000939	Variable	Skeletal fragility
Scoliosis	HP:0002650	Variable
Joint hypermobility	HP:0001382	Variable
Anti-GAD65 autoantibodies	—	0/3 (negative)	Distinguishes from type 1 diabetes
Hypoplastic kidneys	HP:0000089	Phenotype expansion	[PMID: 33448213]

Dysmorphic features reported: wide nose, short neck, low anterior hairline, dorsocervical fat pad. A neurodevelopmental-only presentation without metabolic findings has also been reported (phenotype expansion, [PMID: 42181738]), underscoring variable expressivity.

Mechanistic Model / Interpretation

MSSGM1 is fundamentally a tRNA-modification / translational-homeostasis disorder with tissue-selective consequences in high-secretory-demand and high-proliferation tissues (pancreatic β-cells and neural progenitors). The causal chain is:

  Biallelic LoF TRMT10A (4q23)
     │
     ▼
  Loss of nucleolar SAM-dependent m1G9 methyltransferase activity
     │  (G206R: SAM-binding defect; nonsense/splice/deletion: absent protein)
     ▼
  tRNA guanosine-9 HYPOMETHYLATION (targets: tRNA-Gln, tRNA-iMet)
     │
     ▼
  tRNA destabilization → tRNA-Gln FRAGMENTATION → 5′-tRNAGln fragments
     │
     ┌───────┴────────────────────────┐
     ▼                                 ▼
  PANCREATIC β-CELL                NEURAL PROGENITOR
  Oxidative stress →              proliferation/survival
  intrinsic (mitochondrial)       impairment
  apoptosis                            │
     │                                 ▼
     ▼                            PRIMARY MICROCEPHALY
  β-cell mass loss                Intellectual disability
     │                            Developmental delay, seizures
     ▼
  Biphasic glucose phenotype:
  early hyperinsulinemic hypoglycemia → young-onset insulin-deficient diabetes

Upstream vs downstream: The upstream, primary defect is loss of the enzymatic (m1G9) function of TRMT10A. Downstream events are hypomethylation → tRNA fragmentation → oxidative stress → apoptosis. The clinical manifestations (diabetes, microcephaly, short stature) are the most downstream nodes.

Cell types (CL) and processes (GO): β-cells (CL:0000169, type B pancreatic cell); neural progenitor/radial glial cells (CL:0000047 / CL:0000681). Relevant GO biological processes: tRNA methylation (GO:0030488), tRNA (guanine-N1-)-methyltransferase activity (GO:0009019), response to oxidative stress (GO:0006979), intrinsic apoptotic signaling pathway (GO:0097193), regulation of neuron apoptotic process / neural progenitor proliferation. Cellular component: nucleolus (GO:0005730). Chemical entities (CHEBI): S-adenosyl-L-methionine (CHEBI:15414), 1-methylguanosine (CHEBI:19702), guanosine.

Relationship to the integrated stress response and MSSGM2: Both MSSGM1 (TRMT10A) and MSSGM2 (PPP1R15B/CReP) converge on translational stress in β-cells and brain. In MSSGM2, biallelic PPP1R15B variants impair the constitutive eIF2α phosphatase, chronically elevating eIF2α-phosphorylation and dysregulating the ISR, causing β-cell apoptosis (PMID: 26159176: "the R658C mutation decreases PP1 binding and eIF2α dephosphorylation and results in β-cell apoptosis"). This shared biology — where perturbing global translational control (whether via tRNA modification or eIF2α phosphatase activity) selectively harms β-cells and neural progenitors — explains the near-identical clinical syndromes and their shared Orphanet umbrella term. The ISR literature further situates MSSGM1 within a family of eIF2α-pathway β-cell disorders alongside Wolcott-Rallison syndrome (EIF2AK3/PERK).

Section-by-Section Disease Characterization

1. Disease Information

Overview: Rare autosomal-recessive syndrome of primary microcephaly, intellectual disability/developmental delay, short stature, seizures, and biphasic impaired glucose metabolism (early hyperinsulinemic hypoglycemia evolving to young-onset insulin-deficient diabetes).
Identifiers: OMIM #616033; MONDO:0000208; Orphanet ORPHA:391408 ("Primary microcephaly–mild intellectual disability–young-onset diabetes syndrome"); gene TRMT10A OMIM *616013. No dedicated ICD-10 code; classified under rare syndromic diabetes / genetic microcephaly. MeSH: no specific descriptor (indexed under Microcephaly D008831, Dwarfism, Diabetes Mellitus).
Synonyms: MSSGM1; Microcephaly, short stature, and impaired glucose metabolism 1; TRMT10A deficiency; Young-onset diabetes with microcephaly (TRMT10A-related).
Data source: Aggregated disease-level resources (OMIM, HPO, Orphanet) built from a small number of individual-patient case reports; not EHR-derived.

2. Etiology

Causal factors: Purely genetic — biallelic loss-of-function TRMT10A variants. No environmental, infectious, or mechanical cause.
Genetic risk factors: Causal biallelic TRMT10A variants; consanguinity is a major risk context (index families were consanguineous). Carrier parents are unaffected (recessive).
Environmental risk factors: None established; disease is monogenic.
Protective factors: None described genetically or environmentally. (For the diabetes component, dietary/glycemic management is supportive, not disease-modifying.)
Gene–environment interactions: None specifically documented; β-cell demand states (puberty, growth, intercurrent illness) may modulate timing of the transition from hypoglycemia to overt diabetes, but this is inferential.

3. Phenotypes

See phenotype table above. Onset is congenital (microcephaly, developmental delay) with the glucose phenotype evolving across childhood/adolescence. Severity is moderate-to-severe for intellectual disability; variable for the metabolic component. Progression of the neurodevelopmental phenotype is largely stable (static encephalopathy), while the glucose disturbance is progressive/evolving (hypoglycemia → diabetes). Quality-of-life impact is substantial and lifelong, driven by intellectual disability, seizure burden, and the need for chronic diabetes management.

4. Genetic / Molecular Information

Causal gene: TRMT10A (HGNC:28403; Entrez 93587; ENSG00000145331; UniProt Q8TBZ6; 4q23; gene MIM 616013).
Variant classes: nonsense (p.Arg127*), missense (p.Gly206Arg, SAM-binding), splice-acceptor (c.496-1G>A), whole-gene/contiguous-gene deletions, compound-heterozygous nonsense. All biallelic.
Classification: Pathogenic/likely pathogenic per ACMG (loss-of-function is an established mechanism for this gene). ~50 P/LP in ClinVar of ~196 total.
Allele frequency: Individual pathogenic alleles are ultra-rare in gnomAD; the gene is LoF-tolerant in heterozygotes (LOEUF ≈ 1.21), consistent with recessive disease.
Origin: Germline. No somatic role.
Functional consequence: Loss of function (loss of SAM-dependent m1G9 catalytic activity).
Modifier genes / epigenetics / chromosomal abnormalities: No specific modifier genes established. The disease itself is an "epitranscriptomic" disorder (loss of a tRNA modification), but classical DNA methylation/histone changes are not the mechanism. Contiguous-gene deletions at 4q23 can extend the phenotype.

5. Environmental Information

Not applicable — MSSGM1 is a monogenic disorder with no established environmental, lifestyle, or infectious contributors.

6. Mechanism / Pathophysiology

Detailed in the Mechanistic Model above. Molecular pathway: tRNA m1G9 methylation / epitranscriptomic control of translation; downstream oxidative-stress and intrinsic apoptosis pathways. Cellular processes: oxidative stress, mitochondrial (intrinsic) apoptosis, impaired neural progenitor proliferation. Protein dysfunction: loss of function via impaired SAM binding (G206R) or absent protein (nonsense/splice/deletion). Metabolic change: β-cell failure → insulin deficiency (with an earlier hyperinsulinemic-hypoglycemic phase). Subcellular: nucleolar enzyme; mitochondrial apoptotic execution. Molecular profiling: patient iPSC-derived β-cells demonstrate tRNA-Gln hypomethylation, 5′-tRNAGln fragment accumulation, oxidative stress, and apoptosis (PMID: 30247717).

7. Anatomical Structures Affected

Organ level: Brain (primary — UBERON:0000955), pancreas/pancreatic islets (UBERON:0000006, islet of Langerhans), skeletal system (short stature; UBERON:0001434). Secondary: kidney (hypoplastic kidneys in expansion reports; UBERON:0002113), reproductive/endocrine axis (delayed puberty).
Body systems: Nervous, endocrine, musculoskeletal.
Cell level: Pancreatic β-cells (CL:0000169); neural progenitors/radial glia (CL:0000047).
Subcellular: Nucleolus (GO:0005730), mitochondrion (GO:0005739).
Localization: Microcephaly is bilateral/symmetric (small brain overall). No lateralization.

8. Temporal Development

Onset: Congenital neurodevelopmental features (microcephaly, developmental delay). Glucose phenotype evolves: hyperinsulinemic hypoglycemia in infancy/childhood; diabetes typically young-onset (childhood–young adulthood).
Progression: Neurodevelopmental component static; metabolic component progressive (β-cell decline). Seizures may be intermittent/episodic.
Course: Chronic, lifelong.
Critical periods: Prenatal/early-postnatal brain growth (microcephaly window); adolescence/growth-related metabolic demand may precipitate diabetes.

9. Inheritance and Population

Epidemiology: Ultra-rare; only a handful of families reported worldwide. No formal prevalence/incidence estimate possible.
Inheritance: Autosomal recessive; biallelic (homozygous in consanguineous families, or compound heterozygous).
Penetrance: Appears high/complete for the neurodevelopmental core in biallelic individuals; expressivity of the metabolic phenotype is variable (hypoglycemia vs diabetes; occasionally absent).
Consanguinity: Strongly associated — a major ascertainment context.
Founder effects / carrier frequency: No established founder allele; carrier frequency not formally estimated (individual alleles ultra-rare in gnomAD).
Demographics: Reported across multiple ancestries (European, Asian — the c.496-1G>A case was the first in an Asian/Chinese patient, PMID: 33067246). No strong sex bias reported (autosomal); some reports note female patients with delayed puberty/amenorrhea.

10. Diagnostics

Recommended approach: Molecular genetic testing is definitive — whole-exome sequencing (WES) or targeted panels (syndromic/monogenic diabetes, microcephaly, intellectual disability panels) that include TRMT10A; chromosomal microarray to detect whole-gene/contiguous-gene deletions. Single-gene TRMT10A sequencing where the syndrome is clinically suspected.
Clinical/laboratory: Fasting/OGTT glucose and insulin (documenting hypoglycemia and/or hyperglycemia); C-peptide; anti-GAD65 negativity helps distinguish from type 1 diabetes (0/3 positive in reported families); HbA1c. Brain MRI documenting microcephaly (± structural findings). Growth/skeletal assessment (osteoporosis, scoliosis).
Differential diagnosis: MSSGM2 (PPP1R15B/CReP, OMIM #616817) — the closest molecular differential; Wolcott-Rallison syndrome (EIF2AK3/PERK — neonatal diabetes + epiphyseal dysplasia + hepatic dysfunction); MEDS (IER3IP1 — microcephaly with simplified gyration, epilepsy, neonatal diabetes, PMID: 24138066); other syndromic monogenic diabetes (reviewed PMID: 33832649: "diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects"); primary microcephaly syndromes.
Screening: Cascade carrier testing in consanguineous families; prenatal/preimplantation testing where the familial variant is known.

11. Outcome / Prognosis

Survival/mortality: No formal survival data; the disorder is chronic but not reported as classically lethal in infancy (contrast Wolcott-Rallison, where hepatic failure is life-threatening). Long-term risks derive from diabetes complications and seizure/neurodevelopmental morbidity.
Morbidity/function: Substantial lifelong disability from intellectual disability, developmental delay, seizures, and chronic diabetes management. Short stature and skeletal fragility add morbidity.
Prognostic factors: Genotype (complete LoF vs hypomorphic), presence/severity of seizures, and metabolic control likely influence outcome; formal prognostic models do not exist given rarity.

12. Treatment

No disease-specific or curative therapy exists. Management is symptomatic and supportive.
Glucose management: Insulin for the diabetic phase; management of hyperinsulinemic hypoglycemia in the earlier phase (dietary/glycemic strategies, and hyperinsulinism-directed therapy where indicated). Regular endocrinology follow-up given the evolving phenotype.
Neurodevelopmental: Early intervention, special education, physical/occupational/speech therapy; anti-seizure medication for epilepsy.
Skeletal/endocrine: Management of osteoporosis, scoliosis; assessment/management of delayed puberty.
Experimental/rational targets: Because the mechanism involves oxidative stress and tRNA-fragment–mediated β-cell apoptosis, antioxidant and anti-apoptotic strategies are conceptually attractive but unproven. For the related ISR biology (relevant to MSSGM2 and shared translational-stress mechanisms), ISR modulation (e.g., ISRIB) reverses cognitive deficits across disease models (PMID: 33258451: "treatment with the drug-like small-molecule ISR inhibitor ISRIB reverses ISR activation in the brain"), providing a rationale worth exploring — though it targets the eIF2α/PPP1R15B axis rather than tRNA methylation directly. NCIT-type intervention categories: Insulin therapy, Anticonvulsant therapy, Physical/Occupational/Speech therapy, Supportive care.
Genetic counseling is central (25% recurrence risk per pregnancy for carrier couples).

13. Prevention

Primary prevention: None (monogenic). Genetic counseling and reproductive options (carrier screening in consanguineous families, prenatal/preimplantation genetic testing) are the principal preventive tools.
Secondary prevention: Early molecular diagnosis enables anticipatory monitoring for the transition from hypoglycemia to diabetes, and early neurodevelopmental intervention.
Tertiary prevention: Optimized diabetes control to prevent microvascular complications; seizure control; skeletal health maintenance.

14. Other Species / Natural Disease

Orthologs: Yeast Trm10 (the founding ortholog; SAM-dependent tRNA m1G9 methyltransferase); conserved across eukaryotes. Mouse Trmt10a, zebrafish orthologs.
Natural disease: No well-characterized naturally occurring animal disease equivalent is established (no OMIA entry documented here). The mechanism (tRNA m1G9 methylation) is evolutionarily conserved, making cross-species modeling informative.

15. Model Organisms

Cellular/in vitro (primary): Patient iPSC-derived β-cells were used to establish the mechanism (tRNA-Gln hypomethylation, 5′-tRNAGln fragments, oxidative stress, intrinsic apoptosis) — the most directly disease-relevant model (PMID: 30247717). In vitro enzymatic assays defined the G206R SAM-binding/catalytic defect (PMID: 25053765).
Yeast (Trm10): Foundational model for m1G9 methyltransferase biology and complementation assays.
Model utility: iPSC-β-cell and yeast systems recapitulate the enzymatic and cell-death phenotypes well; a faithful whole-organism model capturing microcephaly + biphasic glucose phenotype simultaneously is a gap. Mouse/zebrafish knockouts would be the logical next step for the neurodevelopmental component.

Evidence Base

PMID	Study	Evidence type	Supports
24204302	Igoillo-Esteve 2013, PLoS Genet — TRMT10A mutation in young-onset diabetes and primary microcephaly	Human clinical + molecular	Gene discovery (TRMT10A), core phenotype, tissue expression (brain/islet); OMIM source for #616033
25053765	Gillis 2014, J Med Genet — TRMT10A dysfunction...	Human clinical + in vitro enzymology	Second family, G206R abolishes m1G9 activity via SAM-binding defect, biphasic glucose phenotype (hyperinsulinemic hypoglycemia)
30247717	Cosentino 2018, Nucleic Acids Res — β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes	Patient iPSC-β-cell + in vitro	Definitive mechanism: G9 methyltransferase, tRNAGln/tRNAiMet targets, oxidative stress, intrinsic apoptosis, 5′-tRNAGln fragments mediate β-cell death
33067246	2020 case report	Human clinical	Splice variant c.496-1G>A; first Asian/Chinese patient; allelic spectrum
26159176	Abdulkarim 2015, Diabetes — PPP1R15B missense	Human clinical + functional	Defines MSSGM2 (PPP1R15B), the principal differential; shared eIF2α/β-cell mechanism
24138066	IER3IP1 / MEDS case report	Human clinical	Differential diagnosis (microcephaly + neonatal diabetes)
33832649	Review — Molecular mechanisms of β-cell dysfunction in monogenic diabetes	Review	Places MSSGM1 among syndromic monogenic diabetes
33258451	Krukowski 2020 — ISRIB reverses age-related memory decline	Model organism (mouse)	Therapeutic rationale for ISR modulation (relevant to shared translational-stress biology / MSSGM2)

Note on evidence source types: The core gene–disease and mechanistic claims are supported by human clinical reports (24204302, 25053765, 33067246) and patient-derived in vitro work (30247717, iPSC-β-cells; enzymology in 25053765). The ISR/therapeutic material (33258451 and related) is model-organism evidence and is offered as rationale, not established therapy.

Limitations and Knowledge Gaps

Ultra-rarity. Only a handful of families are reported worldwide, precluding formal estimates of prevalence, incidence, penetrance, expressivity, survival, and prognosis. All quantitative frequencies come from very small numerator/denominator counts (e.g., 3/3, 6/6).
Ascertainment/consanguinity bias. Index families were consanguineous, which may bias the reported phenotypic spectrum and allele types (homozygous LoF).
Mechanism–phenotype gaps. The β-cell death mechanism is well established in patient iPSC-β-cells, but the neural progenitor / microcephaly mechanism is inferred from tissue expression and analogy rather than demonstrated with the same rigor. The molecular basis of the biphasic glucose phenotype (why hypoglycemia precedes diabetes) is not fully explained.
No faithful whole-organism model simultaneously capturing microcephaly + short stature + biphasic glucose phenotype is documented, limiting preclinical therapeutic testing.
Nosological confusion. The strong phenotypic overlap and shared Orphanet term with PPP1R15B/MSSGM2 (and, more broadly, other eIF2α-pathway disorders) has historically led to gene mis-attribution — this report explicitly corrects MSSGM1 → TRMT10A.
No disease-specific therapy exists; therapeutic rationale (ISR modulation, antioxidants) is extrapolated from related biology and not validated in TRMT10A disease.

Proposed Follow-up Experiments / Actions

Establish a whole-organism model. Generate Trmt10a knockout / patient-variant knock-in mice (and/or zebrafish) to test recapitulation of microcephaly, short stature, and the biphasic glucose phenotype; characterize neural progenitor proliferation/apoptosis in developing cortex.
Dissect the neural mechanism. Use patient iPSC-derived neural progenitors/organoids to test whether tRNA-Gln hypomethylation and 5′-tRNA fragments drive progenitor apoptosis/premature differentiation, mirroring the β-cell findings.
Explain the biphasic glucose phenotype. Longitudinal functional studies (iPSC-β-cells and, if modeled, animal islets) tracking insulin secretion dynamics over "developmental time" to determine why hyperinsulinemic hypoglycemia precedes β-cell failure/diabetes.
Therapeutic screening. Test antioxidants and inhibitors of the intrinsic apoptotic pathway, and tRNA-fragment–targeting strategies, for β-cell rescue in patient iPSC-β-cells; evaluate whether SAM supplementation or substrate-stabilizing approaches partially restore modification for hypomorphic alleles.
Genotype–phenotype registry. Assemble an international TRMT10A patient registry (variant type, glucose trajectory, neurodevelopmental outcomes, renal/skeletal features) to refine penetrance/expressivity and support natural-history-informed management guidelines.
Diagnostic guidance. Ensure TRMT10A is included on syndromic diabetes, microcephaly, and intellectual-disability gene panels, with CMA to capture whole-gene deletions; formalize anti-GAD65 negativity + biphasic glucose pattern as clinical flags prompting testing.

Report compiled from a five-iteration autonomous investigation (13 confirmed findings, 46 papers reviewed). Core gene–disease attribution corrected to TRMT10A for MSSGM1 (OMIM #616033); PPP1R15B assigned to MSSGM2 (OMIM #616817) as the principal differential.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	12
Resolved	12
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	12
On topic	11
Off topic	0

All extracted references resolved successfully.

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Mappings

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Biochemical Markers

Diagnosis

Prevalence

Differential Diagnoses

Related Datasets

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

2. Etiology

3. Phenotypes

Neurological/developmental

Growth/skeletal

Endocrine/metabolic (the defining "impaired glucose metabolism" component)

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Ontology Term Suggestions for Knowledge-Base Curation

Reference Validation

Key Findings

Finding 1 — MSSGM1 is an autosomal-recessive TRMT10A disorder (gene–disease correction)

Finding 2 — Molecular mechanism: loss of tRNA m1G9 methyltransferase activity → tRNA fragmentation → β-cell death

Finding 3 — Core phenotype and biphasic glucose dysregulation

Finding 4 — Allelic spectrum and population genetics

Phenotype Table (HPO annotations, OMIM:616033)

Mechanistic Model / Interpretation

Section-by-Section Disease Characterization

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Reference Validation