SLC44A1-Related Childhood-Onset Neurodegeneration

Mendelian MONDO:0030028 Pathograph 26 Show in embeddings browser Inherited Neurodegenerative Disorder Hereditary Leukoencephalopathy

An autosomal recessive childhood-onset neurodegenerative disease caused by biallelic loss-of-function variants in SLC44A1, the gene encoding choline transporter-like protein 1 (CTL1). The entity was defined in 2020 from four individuals in three unrelated families, all homozygous for frameshift alleles, and the published clinical experience remains close to that founding series. Affected individuals develop progressive ataxia, tremor, cognitive decline, dysarthria, dysphagia, optic atrophy and urinary and bowel incontinence; brain MRI shows cerebellar atrophy and leukoencephalopathy, and in a subset a low-signal globus pallidus with hyperintense streaking and a low-signal substantia nigra. CTL1 is a plasma-membrane and mitochondrial carrier that supplies the cell with the head-group substrates of the Kennedy pathway, the de novo route to the two dominant membrane phospholipids. Choline enters through CTL1, is phosphorylated, and is coupled to diacylglycerol through the CDP-choline branch to give phosphatidylcholine; the same protein was later shown to be a physiological ethanolamine transporter feeding the parallel CDP-ethanolamine branch to phosphatidylethanolamine. Losing CTL1 therefore constricts phospholipid supply at its entry step rather than at any single enzymatic reaction, which is the reason a transporter defect presents as a myelin-and-membrane disease. The mechanism deserves a precise statement, because the intuitive version of it is not what was measured. Patient fibroblasts do show diminished choline transport, but membrane phosphatidylcholine content was explicitly unchanged, and phosphatidylcholine was preserved in patient cerebrospinal fluid as well. The Kennedy pathway in CTL1-deficient cells is reduced but not absent, because the paralogue CTL2 can channel both choline and ethanolamine at lower capacity; what the cells lose is reserve and homeostatic latitude, expressed as disturbed handling of the other phospholipids and as a striking organelle phenotype (depleted free ribosomes, elongated endoplasmic reticulum, excess mitochondria and small vesicles) that chronic choline treatment reverses. The phosphatidylcholine-starvation account is supported in the oligodendrocyte lineage in vivo, where SLC44A1 loss disrupts phosphatidylcholine-pathway gene expression, inhibits phospholipid biosynthesis and alters myelin sheath lipid composition, but it is not what the accessible human tissue shows. This entry curates both readings, and the tension between them is recorded as an explicit knowledge gap rather than resolved by assertion. Therapeutically the disease is untreated, but it is one of the few neurodegenerative entities with a rational and cheap candidate substrate. Choline restored membrane lipids and organelle structure in patient fibroblasts, and citicoline restored developmental myelination in SLC44A1-deficient zebrafish and rodents. Neither result is a clinical trial, and both are curated here as preclinical.

Ask OpenScientist

Ask a research question about SLC44A1-Related Childhood-Onset Neurodegeneration. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

1
Inheritance
9
Pathophys.
11
Phenotypes
3
Gaps
26
Pathograph
1
Genes
4
Medical Actions
3
Differentials
3
Models
4
References
🏷

Classifications

Harrison's Part
NEUROLOGIC
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
All four individuals in the founding series were homozygous for SLC44A1 frameshift alleles (Asp517Metfs*19, Ser126Metfs*8, Lys90Metfs*18) arising in three unrelated families, and the report states the inheritance explicitly. Heterozygous parents are unaffected. No dominant, digenic or oligogenic mechanism has been proposed for this locus.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"we describe a novel childhood-onset neurometabolic disease caused by choline transporter deficiency with autosomal recessive inheritance"
The founding clinical report states autosomal recessive inheritance for the entity.
?

Discussions and Knowledge Gaps

3
Is the human disease actually caused by phosphatidylcholine deficiency, given that phosphatidylcholine was preserved in the accessible tissue of affected individuals?
KNOWLEDGE GAP pc_preserved_despite_transport_loss
Attached to
pathophysiology#Constrained Kennedy Pathway Phospholipid Synthesis pathophysiology#Membrane Phospholipid Homeostasis Disturbance
The intuitive account of this disease, and the one stated in most secondary summaries, is that losing the choline transporter starves membrane synthesis of its phosphatidylcholine precursor. That account is directly complicated by the founding study's own measurement: choline transport was diminished while membrane phosphatidylcholine content was unchanged, and the same group later reported that phosphatidylcholine was preserved in the cerebrospinal fluid as well as the skin fibroblasts of affected individuals. The proposed reconciliation is that the paralogue CTL2 sustains a reduced but not absent Kennedy pathway, so the cell protects its phosphatidylcholine pool by deranging the rest of its phospholipid complement. Whether the oligodendrocyte, which must build far more membrane per cell than a fibroblast and may have a different CTL2 reserve, is able to make the same trade is the open question, and the in vivo animal data suggesting it cannot are from developing rather than degenerating tissue. Resolving this changes what a biomarker would be and whether substrate repletion should be expected to work.
Show evidence (2 references)
PMID:33789160 SUPPORT In Vitro
"Paradoxically, although Cho transport and CDP-Cho Kennedy pathway were diminished, PC remained preserved in the cerebrospinal fluid and skin fibroblasts of the affected individuals"
States the paradox in the source's own words, and extends the preserved-phosphatidylcholine finding from fibroblasts to cerebrospinal fluid.
PMID:31855247 REFUTE In Vitro
"diminished choline transport yet the membrane phosphatidylcholine content remained unchanged"
Refutes the simple phosphatidylcholine-depletion model in patient fibroblasts: the transport defect is present but the expected product depletion is not.
Does the animal myelination-failure phenotype model the human disease, given that the models show a developmental hypomyelination while the human entity is a childhood-onset progressive degeneration?
HUMAN MODEL MISMATCH developmental_vs_maintenance_myelin_failure
Attached to
pathophysiology#Oligodendrocyte Maturation Failure animal_models#Zebrafish
The zebrafish and rodent data are the strongest mechanistic support in the entry: SLC44A1 is oligodendrocyte-enriched, its loss impairs oligodendroglial maturation and myelinogenesis, and citicoline rescues myelination. But the readout in those models is developmental myelination, and the citicoline result is framed by its authors as a potential therapy for developmental hypomyelination. The human phenotype is not congenital hypomyelination; it is childhood-onset progressive ataxia, tremor, cognitive decline and optic atrophy on a background of leukoencephalopathy and cerebellar atrophy, which reads as failing maintenance of established myelin plus neuronal loss. If the human lesion is maintenance rather than development, a rescue that works in a developing animal may have no window in a child who has already myelinated, and the timing of any substrate trial depends on which it is. The mouse oligodendroglial conditional knockout does not settle this either. It shows hypomyelination persisting into adulthood, which is at least consistent with an ongoing deficit, but the deletion is imposed before myelination begins, so a persistent developmental deficit and a maintenance failure are not distinguishable in it. The experiment that would separate them is an inducible deletion after myelination is complete.
Show evidence (2 references)
PMID:41317319 SUPPORT Model Organism
"supplementation with citicoline, a natural choline metabolite, restores developmental myelination in SLC44A1-deficient animals"
The rescue is reported for developmental myelination, which is the specific framing that leaves its relevance to an established, degenerating human phenotype open.
PMID:31855247 SUPPORT Human Clinical
"Clinical features included progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
The human phenotype is progressive and childhood-onset rather than congenital, which is the side of the mismatch this item documents.
Does the iron-handling vulnerability of CTL1-deficient cells explain the low-signal globus pallidus and substantia nigra seen on MRI in some affected individuals, and does brain iron actually accumulate in this disease?
KNOWLEDGE GAP iron_vulnerability_and_basal_ganglia_signal
Attached to
pathophysiology#Vulnerability to Iron-Mediated Cellular Injury phenotypes#Abnormal Basal Ganglia MRI Signal Intensity
Two findings sit next to each other in the founding report without being joined. In patient fibroblasts, chronic choline treatment protected mutant cells from acute iron overload, which says the cells handle an iron challenge worse than controls do. Separately, two of the four individuals had low signal intensity in the globus pallidus with hyperintense streaking and low signal in the substantia nigra on MRI, a pattern that visually resembles neurodegeneration with brain iron accumulation. Nothing published connects them. The cellular assay is an acute supraphysiological iron challenge in skin fibroblasts, not a measurement of iron handling in brain; no quantitative susceptibility mapping, brain iron measurement or neuropathological iron stain has been reported in any affected individual; and low T2 signal in the basal ganglia has causes other than iron, including calcium and manganese. The entry therefore draws the edge from the cellular vulnerability to the imaging finding as INDIRECT_UNKNOWN_INTERMEDIATES and records the gap here rather than asserting a chain. Resolving it matters twice over: it decides whether this entity belongs in the NBIA differential on mechanism as well as on appearance, and it decides whether brain iron could serve as a monitoring readout for a substrate-repletion trial.
Show evidence (2 references)
PMID:31855247 SUPPORT In Vitro
"Choline treatments could restore the membrane lipids, repair cellular organelles and protect mutant cells from acute iron overload."
The cellular side of the gap: an iron-handling deficit demonstrated in patient fibroblasts, in an acute overload assay rather than in brain tissue.
PMID:31855247 SUPPORT Human Clinical
"low signal intensity in globus pallidus with hyperintensive streaking and low signal intensity in substantia nigra were seen in two individuals"
The imaging side of the gap. The report describes the signal change without claiming that iron was demonstrated in patient brain, which is precisely what leaves the connection open.
⚙

Pathophysiology

9
Biallelic SLC44A1 Loss of Function
Homozygous frameshift alleles in SLC44A1 truncate choline transporter-like protein 1. Three distinct frameshifts were reported across the three founding families, two of which (Asp517Metfs*19 and Ser126Metfs*8) gave fibroblast phenotypes that were structurally and functionally indistinguishable, arguing that the entity is driven by loss of the protein rather than by a residue-specific effect.
Downstream
Choline Transporter-Like Protein 1 Deficiency Frameshift truncation removes functional CTL1 from the membrane.
Show evidence (2 references)
PMID:31855247 SUPPORT Human Clinical
"homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and Lys90Metfs*18) in the SLC44A1 gene encoding choline transporter-like protein 1"
Identifies the causal biallelic frameshift genotype and the encoded protein.
PMID:31855247 SUPPORT In Vitro
"The Asp517Metfs*19 and Ser126Metfs*8 fibroblasts were structurally and functionally indistinguishable."
Two independent frameshift alleles converge on the same cellular phenotype, supporting a shared loss-of-function mechanism.
Choline Transporter-Like Protein 1 Deficiency
Loss of CTL1, the carrier that moves choline (and, as later shown, ethanolamine) across the plasma membrane and into mitochondria. CTL1 is enriched in oligodendrocytes, which is the expression pattern that makes a general membrane-lipid transporter behave as a white-matter disease gene.
oligodendrocyte CL:0000128 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves oligodendrocyte (CL:0000128). CL:0000128 is a cell type from the Cell Ontology.
choline transmembrane transporter activity GO:0015220 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased choline transmembrane transporter activity (GO:0015220). GO:0015220 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Reduced Cellular Choline and Ethanolamine Uptake Absent carrier protein removes the principal uptake route for both Kennedy pathway head-group substrates.
Show evidence (1 reference)
PMID:41317319 SUPPORT Model Organism
"we show that SLC44A1 is enriched in oligodendrocytes and is required for myelin development in the CNS of zebrafish and rodents"
Establishes the oligodendrocyte-enriched expression that localizes the transporter defect to the myelinating lineage.
Reduced Cellular Choline and Ethanolamine Uptake
Patient fibroblasts show diminished choline transport. The same lesion also reduces ethanolamine transport, since CTL1 was subsequently identified as a physiological ethanolamine carrier; the deficit is therefore in both head-group substrates, not choline alone.
choline transport GO:0015871 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased choline transport (GO:0015871). GO:0015871 is a biological process from the Gene Ontology. ↓ DECREASED
Experimental models
Patient-derived SLC44A1 frameshift fibroblasts PRIMARY CELL CULTURE Reproduces the transport defect directly in patient cells carrying the causal genotype.
Downstream
Constrained Kennedy Pathway Phospholipid Synthesis Substrate entry is the first committed step of de novo phospholipid synthesis, so reduced uptake constrains flux through both Kennedy branches.
Show evidence (2 references)
PMID:31855247 SUPPORT In Vitro
"Functional analysis revealed diminished choline transport yet the membrane phosphatidylcholine content remained unchanged."
Directly measures the reduced choline transport in patient fibroblasts; the same sentence records that the downstream phosphatidylcholine pool was not depleted, which is why the next node is framed as constrained flux rather than product depletion.
PMID:33789160 SUPPORT In Vitro
"The lack of CTL1 in M2 cells reduced the ethanolamine transport, the flux through the CDP-ethanolamine Kennedy pathway, and PE synthesis."
Extends the transport deficit beyond choline to ethanolamine, showing both Kennedy branches lose substrate supply.
Constrained Kennedy Pathway Phospholipid Synthesis
Reduced but not absent flux through the CDP-choline and CDP-ethanolamine branches of the Kennedy pathway. The residual flux is attributable to the paralogue CTL2, which channels both substrates at lower capacity; this is the reason bulk phosphatidylcholine is preserved in accessible patient tissue while the cell is nonetheless operating without reserve.
phosphatidylcholine biosynthetic process GO:0006656 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased phosphatidylcholine biosynthetic process (GO:0006656). GO:0006656 is a biological process from the Gene Ontology. ↓ DECREASED phosphatidylethanolamine biosynthetic process GO:0006646 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased phosphatidylethanolamine biosynthetic process (GO:0006646). GO:0006646 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Membrane Phospholipid Homeostasis Disturbance Reduced de novo supply is compensated by remodelling the rest of the phospholipid complement.
Myelin Membrane Lipid Composition Imbalance In the oligodendrocyte lineage the same constraint inhibits phospholipid biosynthesis and alters myelin sheath lipid composition.
Show evidence (3 references)
PMID:33789160 SUPPORT In Vitro
"PC and PE are synthesized de novo by CDP-Cho and CDP-Etn branches of the Kennedy pathway in which the extracellular substrates choline (Cho) and ethanolamine (Etn) are actively transported into the cell, phosphorylated, and coupled with diacylglycerols (DAGs) to form the final phospholipid product."
States the pathway architecture that makes transporter loss a biosynthetic constraint.
PMID:33789160 SUPPORT In Vitro
"CTL1-deficient cells had reduced but not absent CDP-Cho Kennedy pathway"
Supports "constrained" rather than "abolished" flux, and is the quantitative basis for the residual-capacity framing of this node.
PMID:41317319 SUPPORT Model Organism
"SLC44A1 deficiency disrupts the expression of genes involved in the phosphatidylcholine production pathway and subsequently inhibits phospholipid biosynthesis and disturbs the lipid composition of myelin sheaths"
In vivo evidence that the phosphatidylcholine branch is the one that matters for myelin, supporting the edge to the oligodendrocyte node.
Membrane Phospholipid Homeostasis Disturbance
Rather than depleting phosphatidylcholine, CTL1-deficient cells preserve it at the cost of the rest of the membrane lipid complement, and the visible consequence is an organelle phenotype: depleted free ribosomes, elongated endoplasmic reticulum, and a striking excess of mitochondria and small vesicles. Chronic choline treatment reverses it, which is the evidence that the derangement is a substrate-supply problem and not a structural one.
Experimental models
Patient-derived SLC44A1 frameshift fibroblasts PRIMARY CELL CULTURE Reproduces the compensatory membrane-lipid derangement and its organelle correlate, both reversible by choline.
Downstream
Vulnerability to Iron-Mediated Cellular Injury Membrane lipid derangement leaves mutant cells less able to withstand acute iron overload.
Show evidence (2 references)
PMID:31855247 SUPPORT In Vitro
"As part of the mechanism to preserve choline and phosphatidylcholine, choline transporter deficiency was implicated in impaired membrane homeostasis of other phospholipids."
States the compensation-at-a-cost mechanism this node represents.
PMID:31855247 SUPPORT In Vitro
"The most prominent ultrastructural changes of the mutant fibroblasts were reduced presence of free ribosomes, the appearance of elongated endoplasmic reticulum and strikingly increased number of mitochondria and small vesicles."
The measured organelle phenotype that makes this node observable.
Vulnerability to Iron-Mediated Cellular Injury
Mutant cells are less able to tolerate acute iron overload, and choline treatment protects them. This is the only cellular correlate offered for the basal ganglia and substantia nigra signal changes seen on MRI in a subset of patients; the link between the two is inferred, and is recorded as a knowledge gap (discussion iron_vulnerability_and_basal_ganglia_signal) rather than as an established chain.
Downstream
Abnormal Basal Ganglia MRI Signal Intensity Proposed, not demonstrated, correlate of the low-signal globus pallidus and substantia nigra reported in two of the four individuals.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"Choline treatments could restore the membrane lipids, repair cellular organelles and protect mutant cells from acute iron overload."
Demonstrates the iron-handling vulnerability of mutant cells and its reversal by choline.
Myelin Membrane Lipid Composition Imbalance
The lipid complement of the myelin sheath itself is altered. In vivo, SLC44A1 loss disrupts expression of the phosphatidylcholine-production genes, inhibits phospholipid biosynthesis, and changes the lipid composition of the sheaths that do form; conditional deletion in mouse oligodendroglia points to plasmalogen synthesis as one specifically inhibited arm. This is a claim about myelin lipid chemistry, separate from the claim that oligodendrocytes fail to mature, and each was measured by a different experiment.
phospholipid biosynthetic process GO:0008654 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased phospholipid biosynthetic process (GO:0008654). GO:0008654 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Slc44a1b-deficient zebrafish Zebrafish recapitulates Shows the phosphatidylcholine-production pathway disruption and the consequent change in myelin sheath lipid composition in vivo.
Oligodendroglia-specific Slc44a1 conditional knockout mouse Mouse recapitulates Metabolomic profiling of the conditional knockout identifies disrupted lipid metabolism and names plasmalogen synthesis as a specifically inhibited arm.
Downstream
Oligodendrocyte Maturation Failure A maturing oligodendrocyte must synthesize a very large membrane area in a short window, so a constrained and compositionally abnormal lipid supply is the proposed proximate reason maturation and sheath formation fail.
Show evidence (2 references)
PMID:41317319 SUPPORT Model Organism
"SLC44A1 deficiency disrupts the expression of genes involved in the phosphatidylcholine production pathway and subsequently inhibits phospholipid biosynthesis and disturbs the lipid composition of myelin sheaths"
The measured in vivo lipid-composition abnormality this node asserts, together with the biosynthetic step that produces it.
PMID:40540401 SUPPORT Model Organism
"Metabolomics profiling indicates disrupted lipid metabolism by SLC44A1 deletion, specifically inhibiting plasmalogen synthesis, a pathway vital for myelin biogenesis."
Independent mouse conditional-knockout metabolomics naming a specific inhibited lipid arm, which is why this node is stated as compositional imbalance rather than as bulk phospholipid loss.
Oligodendrocyte Maturation Failure
Oligodendroglial maturation and myelinogenesis are arrested. Time-lapse imaging in Slc44a1b-deficient zebrafish shows the failure directly and in real time, and oligodendroglia-specific Slc44a1 deletion in mouse reproduces it with shortened myelin segments and hypomyelination persisting into adulthood. This is the node at which a general membrane-lipid defect becomes a white-matter disease.
oligodendrocyte CL:0000128 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves oligodendrocyte (CL:0000128). CL:0000128 is a cell type from the Cell Ontology.
myelination GO:0042552 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased myelination (GO:0042552). GO:0042552 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Slc44a1b-deficient zebrafish Zebrafish recapitulates Reproduces the failure of oligodendroglial maturation and myelination that is proposed to underlie the human leukoencephalopathy, and does so with live imaging not obtainable in humans.
Oligodendroglia-specific Slc44a1 conditional knockout mouse Mouse recapitulates Impaired oligodendrocyte differentiation and myelination with shortened myelin segments in neonatal brain, and hypomyelination that persists into adulthood. Because the deletion is confined to oligodendroglia, the failure cannot be a downstream effect of transporter loss elsewhere in the body - which the whole-organism zebrafish model and the human genotype cannot separate.
Downstream
Leukoencephalopathy Deficient and lipid-abnormal myelin is the substrate of the imaging white-matter abnormality.
Progressive Cerebellar and Optic Pathway Degeneration Failing myelin maintenance is the proposed driver of the selective degeneration of cerebellar and optic pathways.
Show evidence (3 references)
PMID:41317319 SUPPORT Model Organism
"In vivo time-lapse imaging of Slc44a1b-deficient zebrafish reveals impaired oligodendroglial maturation and myelinogenesis."
Direct in vivo observation of the maturation and myelination failure this node asserts.
PMID:41317319 SUPPORT Model Organism
"Our findings demonstrate that SLC44A1 is essential for CNS myelination, and citicoline supplementation represents a potential therapy for developmental hypomyelination."
States the necessity of SLC44A1 for CNS myelination.
PMID:40540401 SUPPORT Model Organism
"Conditional knockout (cKO) of either SLC44A1 or SLC44A5 in oligodendroglia impairs OL differentiation and myelination in neonatal brains, with shortened myelin segment lengths."
Cell-type-specific deletion in a second species shows the maturation failure is intrinsic to oligodendroglia rather than a systemic consequence.
Progressive Cerebellar and Optic Pathway Degeneration
Selective, progressive loss of cerebellar tissue and of optic nerve axons, which is the anatomical level at which the clinical quartet of ataxia, tremor, optic atrophy and cognitive decline is generated. Cerebellar atrophy is documented on MRI in the founding series; the cell-type attributions below are anatomical localizations of the clinical and imaging findings rather than a reported histopathological cell count.
Purkinje cell CL:0000121 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Purkinje cell (CL:0000121). CL:0000121 is a cell type from the Cell Ontology. retinal ganglion cell CL:0000740 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves retinal ganglion cell (CL:0000740). CL:0000740 is a cell type from the Cell Ontology.
Downstream
Cerebellar Atrophy
Progressive Ataxia
Tremor
Dysarthria
Optic Atrophy
Cognitive Decline
Dysphagia
Urinary Incontinence
Bowel Incontinence
Show evidence (2 references)
PMID:31855247 SUPPORT Human Clinical
"Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
Documents the cerebellar tissue loss and white-matter change that this node represents.
PMID:31855247 SUPPORT Human Clinical
"Clinical features included progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
Enumerates the clinical consequences attributed to this degeneration node.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for SLC44A1-Related Childhood-Onset Neurodegeneration Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

11
Digestive 1
Dysphagia HP:0002015 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dysphagia (HP:0002015). HP:0002015 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria"
Lists dysphagia among the clinical features of the series.
Eye 1
Optic Atrophy HP:0000648 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Optic atrophy (HP:0000648), qualified as childhood onset. HP:0000648 is a phenotype from the Human Phenotype Ontology.
Onset: CHILDHOOD
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence"
Lists optic atrophy among the clinical features of the series.
Nervous System 7
Progressive Ataxia HP:0001251 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Progressive ataxia, annotated with Ataxia (HP:0001251), qualified as course progressive; childhood onset. HP:0001251 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE Onset: CHILDHOOD
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"Clinical features included progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
Lists progressive ataxia among the clinical features of the series.
Tremor HP:0001337 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tremor (HP:0001337), qualified as childhood onset. HP:0001337 is a phenotype from the Human Phenotype Ontology.
Onset: CHILDHOOD
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria"
Lists tremor among the clinical features of the series.
Cognitive Decline Mental deterioration HP:0001268 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cognitive decline, annotated with Mental deterioration (HP:0001268), qualified as course progressive; childhood onset. HP:0001268 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE Onset: CHILDHOOD
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"Clinical features included progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
Lists cognitive decline among the clinical features of the series.
Dysarthria HP:0001260 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dysarthria (HP:0001260). HP:0001260 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria"
Lists dysarthria among the clinical features of the series.
Cerebellar Atrophy HP:0001272 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebellar atrophy (HP:0001272). HP:0001272 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
Documents cerebellar atrophy on MRI in the reported individuals.
Leukoencephalopathy HP:0002352 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Leukoencephalopathy (HP:0002352). HP:0002352 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
Documents leukoencephalopathy on MRI in the reported individuals.
Abnormal Basal Ganglia MRI Signal Intensity FREQUENT HP:0012751 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Globus pallidus and substantia nigra low signal intensity on MRI, annotated with Abnormal basal ganglia MRI signal intensity (HP:0012751). HP:0012751 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"low signal intensity in globus pallidus with hyperintensive streaking and low signal intensity in substantia nigra were seen in two individuals"
2 of the 4 individuals in the series, that is 50%, which falls in the FREQUENT band (30-79%). This is the only feature in the entry for which the source gives a count, which is why it is the only one carrying a frequency value at all.
Constitutional 2
Urinary Incontinence HP:0000020 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Urinary incontinence (HP:0000020). HP:0000020 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"dysarthria, as well as urinary and bowel incontinence"
Lists urinary incontinence among the clinical features of the series.
Bowel Incontinence HP:0002607 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bowel incontinence (HP:0002607). HP:0002607 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"dysarthria, as well as urinary and bowel incontinence"
Lists bowel incontinence among the clinical features of the series.
🧬

Genetic Associations

1
SLC44A1 (Homozygous frameshift loss-of-function alleles. Three were reported in the founding series across three unrelated families: Asp517Metfs*19, Ser126Metfs*8 and Lys90Metfs*18. No missense, hypomorphic or dominant allele class has been established for this phenotype.)
Gene: SLC44A1 hgnc:18798 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SLC44A1 (hgnc:18798). hgnc:18798 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"we report on four individuals from three families with neurodegenerative disease and homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and Lys90Metfs*18) in the SLC44A1 gene encoding choline transporter-like protein 1"
Names the three homozygous frameshift alleles and the three unrelated families they arose in, which is the gene-disease association this block asserts.
🗃️

External Assertions

1
OMIM phenotype record for CONATOC
OMIM disease record OMIM:618868
OMIM phenotype entry 618868, "neurodegeneration, childhood-onset, with ataxia, tremor, optic atrophy, and cognitive decline" (CONATOC), is the source of the CONATOC acronym and is the OMIM xref carried by MONDO:0030028. Recorded as an external assertion rather than a mappings entry because DiseaseMappings has no OMIM slot; it carries only ICD-10-CM, ICD-11-F, MONDO and NCIT.
💊

Medical Actions

4
Oral Choline Supplementation
Action: choline substrate supplementationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is choline substrate supplementation, annotated with Nutritional Support (NCIT:C15433). NCIT:C15433 is a clinical intervention from the NCI Thesaurus. Ontology label: Nutritional Support NCIT:C15433
Agent: choline CHEBI:15354 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses choline (CHEBI:15354). CHEBI:15354 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Substrate repletion aimed at the transport bottleneck. Chronic choline treatment of patient fibroblasts reversed the organelle phenotype, restored membrane lipids and protected the cells against acute iron overload. This is a cellular result in patient-derived fibroblasts, not a clinical outcome: no trial of choline supplementation in this disease has been reported, and the entry does not assert clinical benefit.
Mechanism Target:
Membrane Phospholipid Homeostasis Disturbance — Restores membrane lipid composition and organelle ultrastructure in CTL1-deficient cells.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"When chronically treated with choline, those characteristics disappeared and mutant ultrastructure resembled healthy control cells."
Demonstrates reversal of the cellular phenotype this mechanism node represents.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"Choline treatments could restore the membrane lipids, repair cellular organelles and protect mutant cells from acute iron overload."
The preclinical basis for proposing choline repletion; the evidence is in vitro and does not establish clinical efficacy.
Citicoline Supplementation
Action: citicoline substrate supplementationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is citicoline substrate supplementation, annotated with Nutritional Support (NCIT:C15433). NCIT:C15433 is a clinical intervention from the NCI Thesaurus. Ontology label: Nutritional Support NCIT:C15433
Agent: citicoline CHEBI:16436 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses citicoline, annotated with CDP-choline (CHEBI:16436). CHEBI:16436 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Citicoline (CDP-choline) is the Kennedy pathway intermediate immediately downstream of choline phosphorylation, and supplementing it restored developmental myelination in SLC44A1-deficient zebrafish and rodents. Proposed on that basis as a candidate therapy for the human disease; no clinical trial in SLC44A1-related neurodegeneration has been reported.
Mechanism Target:
Oligodendrocyte Maturation Failure — Restores developmental myelination in SLC44A1-deficient animals.
Show evidence (1 reference)
PMID:41317319 SUPPORT Model Organism
"supplementation with citicoline, a natural choline metabolite, restores developmental myelination in SLC44A1-deficient animals"
Demonstrates rescue of the myelination node in two model organisms.
Supportive and Rehabilitative Care
Action: multidisciplinary supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is multidisciplinary supportive care, annotated with Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Platform: Behavioral / lifestyle
Physical and occupational therapy for progressive ataxia, speech therapy and swallowing assessment for dysarthria and dysphagia, low-vision support for optic atrophy, and continence management. This is the actual standard of care; the disease is described in the literature as lacking effective treatment.
Show evidence (1 reference)
PMID:41317319 SUPPORT Other
"childhood-onset neurodegeneration with cerebellar atrophy and leukoencephalopathy that lacks effective treatment"
States that no disease-modifying treatment exists, which is what makes supportive care the standard of care.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Platform: Other
Autosomal recessive counseling for parents of an affected child, who face a 25% recurrence risk per pregnancy, with carrier testing for at-risk relatives.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"we describe a novel childhood-onset neurometabolic disease caused by choline transporter deficiency with autosomal recessive inheritance"
The autosomal recessive inheritance established here is what determines the recurrence risk that counseling communicates.
🔬

Biochemical Markers

1
Membrane phosphatidylcholine content (Unchanged)
Context: Patient-derived skin fibroblasts and cerebrospinal fluid.
Pathograph Readouts
Readout Of Constrained Kennedy Pathway Phospholipid Synthesis Diagnostic
Not lowered. Direction is deliberately left unset: the finding is that the value was unchanged, and `BiomarkerReadoutDirectionEnum` has no value for that. This negative result is the reason the upstream node is curated as constrained flux rather than as product depletion, and it is the substance of the pc_preserved_despite_transport_loss knowledge gap.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"Functional analysis revealed diminished choline transport yet the membrane phosphatidylcholine content remained unchanged."
The measurement itself, in patient fibroblasts, alongside the transport defect that would have predicted a fall.
Show evidence (1 reference)
PMID:33789160 SUPPORT In Vitro
"Paradoxically, although Cho transport and CDP-Cho Kennedy pathway were diminished, PC remained preserved in the cerebrospinal fluid and skin fibroblasts of the affected individuals"
Extends the preserved-phosphatidylcholine result from fibroblasts to cerebrospinal fluid, so the finding is not an artefact of one accessible tissue.
🔬

Diagnosis

2
Molecular confirmation of biallelic SLC44A1 loss-of-function variants
Sequencing is the only confirmatory test. The clinical and imaging picture places the disease in the hereditary leukoencephalopathy and ataxia differential but does not distinguish it, so the diagnosis rests on finding biallelic loss-of-function SLC44A1 variants; all four published individuals were homozygous for frameshift alleles. No biochemical or metabolite test discriminates the entity - notably, phosphatidylcholine is preserved in patient cerebrospinal fluid and fibroblasts, so a normal phospholipid result does not exclude the diagnosis.
molecular genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Results: Biallelic loss-of-function SLC44A1 variants; homozygous frameshift alleles in every reported case.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"we report on four individuals from three families with neurodegenerative disease and homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and Lys90Metfs*18) in the SLC44A1 gene encoding choline transporter-like protein 1"
Establishes the genotype that confirms the diagnosis, and that every reported case was ascertained this way.
Brain MRI
The imaging handle. Cerebellar atrophy together with leukoencephalopathy is the pattern that should prompt SLC44A1 testing, and in a subset an additional low-signal globus pallidus with hyperintense streaking and low-signal substantia nigra narrows the differential further, at the cost of raising a false lead toward NBIA. MRI is suggestive, never confirmatory.
brain magnetic resonance imaging NCIT:C16809 NCI Thesaurus (NCIT)
Results: Cerebellar atrophy with leukoencephalopathy; in some individuals, low signal intensity in the globus pallidus with hyperintense streaking and in the substantia nigra.
Show evidence (2 references)
PMID:31855247 SUPPORT Human Clinical
"Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
The imaging pattern present in the reported individuals.
PMID:31855247 SUPPORT Human Clinical
"low signal intensity in globus pallidus with hyperintensive streaking and low signal intensity in substantia nigra were seen in two individuals"
The additional deep-grey signal change, present in half the series and therefore a supportive rather than a required finding.
📊

Prevalence

1
Worldwide
Cases In Literature Not yet documented
The founding series of four individuals from three families is essentially the whole published clinical experience of this entity; no prevalence or incidence estimate of any kind has been published, and MONDO:0030028 carries no Orphanet epidemiology record to band against. NOT_YET_DOCUMENTED is used in preference to a qualitative ULTRA_RARE band because there is no source to band, and rate_per_100000 is left empty for the same reason. No founder effect and no ancestry enrichment is asserted.
Show evidence (1 reference)
PMID:31855247 SUPPORT Human Clinical
"we report on four individuals from three families with neurodegenerative disease and homozygous frameshift mutations"
Establishes the size of the reported case series, which is the only occurrence information available.
🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from SLC44A1-Related Childhood-Onset Neurodegeneration:

Childhood-onset neurodegeneration with cerebellar atrophy (CONDCA, AGTPBP1)
Overlapping Features The most important differential, and the most important name confusion. CONDCA is an AGTPBP1-related recessive disease (MONDO:0032650) that also presents in childhood with cerebellar atrophy and progressive neurological decline, and the two acronyms CONATOC and CONDCA are routinely conflated. The genes, the protein families and the mechanisms are unrelated: AGTPBP1 encodes a cytosolic carboxypeptidase acting on tubulin polyglutamylation, while SLC44A1 encodes a membrane-lipid substrate transporter. Distinguish on genotype, not on phenotype.
Hereditary leukoencephalopathies and hypomyelinating leukodystrophies
Overlapping Features The leukoencephalopathy plus cerebellar atrophy on MRI places this entity in the hereditary white-matter differential, alongside the hypomyelinating leukodystrophies and Pelizaeus-Merzbacher disease. The combination of optic atrophy and prominent basal ganglia and substantia nigra signal change in a subset is the feature that should prompt SLC44A1 testing rather than a purely myelin-gene panel.
Neurodegeneration with brain iron accumulation
Overlapping Features Low globus pallidus signal with hyperintense streaking, present in two of the four reported individuals, is visually reminiscent of NBIA. The source report does not claim an eye-of-the-tiger sign and iron accumulation was not demonstrated in patient brain, but the demonstrated vulnerability of CTL1-deficient cells to acute iron overload makes the resemblance worth noting rather than dismissing.
🧫

Experimental Models

1
Patient-derived SLC44A1 frameshift fibroblasts PRIMARY_CELL_CULTURE
Skin fibroblasts from individuals homozygous for Asp517Metfs*19 and Ser126Metfs*8, used to measure choline transport, membrane phospholipid content and organelle ultrastructure, and to test choline rescue.
Pathograph links
Reduced Cellular Choline and Ethanolamine Uptake recapitulates fidelity: moderate Reproduces the transport defect directly in patient cells carrying the causal genotype.
Limitations: Fibroblasts are not the affected cell type. The disease is expressed in oligodendrocytes and neurons, and the fibroblast phenotype notably does not include the phosphatidylcholine depletion that the oligodendrocyte data imply, so the model measures the transport lesion faithfully while representing its downstream consequences poorly.
Readouts
Choline transport rate in patient fibroblasts
Direction: DECREASED
Interpretation: Confirms loss of carrier-mediated choline uptake in cells with the causal genotype.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"Functional analysis revealed diminished choline transport yet the membrane phosphatidylcholine content remained unchanged."
Reports the measured reduction in choline transport in these cells.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"The Asp517Metfs*19 and Ser126Metfs*8 fibroblasts were structurally and functionally indistinguishable."
Supports treating these patient lines as an informative and reproducible model of the transport lesion.
Membrane Phospholipid Homeostasis Disturbance recapitulates fidelity: moderate Reproduces the compensatory membrane-lipid derangement and its organelle correlate, both reversible by choline.
Limitations: The compensation may be fibroblast-specific: a dividing skin fibroblast with an intact CTL2 paralogue has metabolic options that a terminally differentiated, membrane-hungry oligodendrocyte may not.
Readouts
Fibroblast organelle ultrastructure on electron microscopy
Direction: ALTERED
Interpretation: Depleted free ribosomes, elongated endoplasmic reticulum and excess mitochondria and small vesicles, normalizing with chronic choline.
Show evidence (1 reference)
PMID:31855247 SUPPORT In Vitro
"The most prominent ultrastructural changes of the mutant fibroblasts were reduced presence of free ribosomes, the appearance of elongated endoplasmic reticulum and strikingly increased number of mitochondria and small vesicles."
The measured ultrastructural readout for this mechanism node.
🐁

Animal Models

2
Slc44a1b-deficient zebrafish
Zebrafish model used for in vivo time-lapse imaging of oligodendroglial maturation and myelinogenesis, and for the citicoline rescue experiment.
Species
Zebrafish
Genotype
Slc44a1b deficient
Publication
PMID:41317319
Pathograph links
Oligodendrocyte Maturation Failure recapitulates fidelity: moderate Reproduces the failure of oligodendroglial maturation and myelination that is proposed to underlie the human leukoencephalopathy, and does so with live imaging not obtainable in humans.
Limitations: The model reports a developmental myelination failure, whereas the human disease is described as a childhood-onset progressive neurodegeneration; whether the human lesion is failed myelin development, failed myelin maintenance, or both is not settled by this model. Zebrafish carry an slc44a1 paralogue pair, so gene dosage does not map one-to-one onto the human locus.
Readouts
Oligodendroglial maturation and myelin sheath formation on time-lapse imaging
Direction: DECREASED
Interpretation: Impaired maturation and myelinogenesis in the deficient animals.
Show evidence (1 reference)
PMID:41317319 SUPPORT Model Organism
"In vivo time-lapse imaging of Slc44a1b-deficient zebrafish reveals impaired oligodendroglial maturation and myelinogenesis."
The measured in vivo readout for this mechanism node.
Show evidence (1 reference)
PMID:41317319 SUPPORT Model Organism
"we show that SLC44A1 is enriched in oligodendrocytes and is required for myelin development in the CNS of zebrafish and rodents"
Supports treating the zebrafish as informative for the human myelination mechanism, alongside rodent data.
Myelin Membrane Lipid Composition Imbalance recapitulates fidelity: moderate Shows the phosphatidylcholine-production pathway disruption and the consequent change in myelin sheath lipid composition in vivo.
Limitations: The reported measurement is of pathway gene expression and myelin lipid composition rather than of flux, so it establishes that the pathway is dysregulated without quantifying the reduction in synthetic rate. The lipid composition of a zebrafish sheath is not assumed to be quantitatively transferable to human myelin.
Readouts
Myelin sheath lipid composition
Direction: ALTERED
Interpretation: Disturbed lipid composition of myelin sheaths in deficient animals.
Show evidence (1 reference)
PMID:41317319 SUPPORT Model Organism
"SLC44A1 deficiency disrupts the expression of genes involved in the phosphatidylcholine production pathway and subsequently inhibits phospholipid biosynthesis and disturbs the lipid composition of myelin sheaths"
The measured lipid-composition readout for this mechanism node.
Oligodendroglia-specific Slc44a1 conditional knockout mouse
Cell-type-restricted deletion of Slc44a1 in mouse oligodendroglia, used to test whether the myelination defect is intrinsic to the lineage and to profile the lipid consequences by metabolomics.
Species
Mouse
Genotype
Oligodendroglial conditional Slc44a1 knockout (SLC44A1-cKO)
Publication
PMID:40540401
Pathograph links
Oligodendrocyte Maturation Failure recapitulates fidelity: moderate Impaired oligodendrocyte differentiation and myelination with shortened myelin segments in neonatal brain, and hypomyelination that persists into adulthood. Because the deletion is confined to oligodendroglia, the failure cannot be a downstream effect of transporter loss elsewhere in the body - which the whole-organism zebrafish model and the human genotype cannot separate.
Limitations: A conditional knockout is a complete, lineage-restricted null from development onward, whereas affected individuals carry a constitutive germline frameshift in every tissue; the mouse therefore models the oligodendroglial contribution rather than the disease. It also does not address the maintenance-versus-development question, since the deletion precedes myelination. The same paper shows SLC44A5 contributes in neonatal mouse oligodendroglia, and no equivalent paralogue contribution is established in humans.
Readouts
Oligodendrocyte differentiation and myelin segment length in neonatal brain
Direction: DECREASED
Interpretation: Fewer differentiated oligodendrocytes and shorter myelin segments after oligodendroglial Slc44a1 deletion.
Show evidence (1 reference)
PMID:40540401 SUPPORT Model Organism
"Conditional knockout (cKO) of either SLC44A1 or SLC44A5 in oligodendroglia impairs OL differentiation and myelination in neonatal brains, with shortened myelin segment lengths."
The measured differentiation and myelin-segment readout for this mechanism node.
Show evidence (1 reference)
PMID:40540401 SUPPORT Model Organism
"SLC44A1-cKO mice show persistent hypomyelination into adulthood whereas SLC44A5-cKO mice do not, a divergence likely attributable to age-related decline in SLC44A5 expression in oligodendroglia."
Supports treating this model as informative for the human node: the deficit is specific to SLC44A1 and does not resolve with age, which is what a model of a progressive childhood disease has to show.
Myelin Membrane Lipid Composition Imbalance recapitulates fidelity: moderate Metabolomic profiling of the conditional knockout identifies disrupted lipid metabolism and names plasmalogen synthesis as a specifically inhibited arm.
Limitations: Plasmalogen synthesis is a peroxisomal ether-lipid pathway rather than a Kennedy pathway branch, so how transporter loss reaches it is not established here, and no plasmalogen measurement has been reported in an affected individual.
Readouts
Oligodendroglial lipid metabolome
Direction: ALTERED
Interpretation: Disrupted lipid metabolism with inhibited plasmalogen synthesis.
Show evidence (1 reference)
PMID:40540401 SUPPORT Model Organism
"Metabolomics profiling indicates disrupted lipid metabolism by SLC44A1 deletion, specifically inhibiting plasmalogen synthesis, a pathway vital for myelin biogenesis."
The measured lipid-metabolome readout for this mechanism node.
{ }

Source YAML

click to show 
name: SLC44A1-Related Childhood-Onset Neurodegeneration
creation_date: "2026-09-02T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: SLC44A1-related childhood-onset neurodegeneration with ataxia, tremor,
    optic atrophy and cognitive decline
  term:
    id: MONDO:0030028
    label: neurodegeneration, childhood-onset, with ataxia, tremor, optic atrophy,
      and cognitive decline
description: >-
  An autosomal recessive childhood-onset neurodegenerative disease caused by biallelic
  loss-of-function variants in SLC44A1, the gene encoding choline transporter-like
  protein 1 (CTL1). The entity was defined in 2020 from four individuals in three
  unrelated families, all homozygous for frameshift alleles, and the published clinical
  experience remains close to that founding series. Affected individuals develop
  progressive ataxia, tremor, cognitive decline, dysarthria, dysphagia, optic atrophy
  and urinary and bowel incontinence; brain MRI shows cerebellar atrophy and
  leukoencephalopathy, and in a subset a low-signal globus pallidus with hyperintense
  streaking and a low-signal substantia nigra.

  CTL1 is a plasma-membrane and mitochondrial carrier that supplies the cell with the
  head-group substrates of the Kennedy pathway, the de novo route to the two dominant
  membrane phospholipids. Choline enters through CTL1, is phosphorylated, and is
  coupled to diacylglycerol through the CDP-choline branch to give phosphatidylcholine;
  the same protein was later shown to be a physiological ethanolamine transporter
  feeding the parallel CDP-ethanolamine branch to phosphatidylethanolamine. Losing CTL1
  therefore constricts phospholipid supply at its entry step rather than at any single
  enzymatic reaction, which is the reason a transporter defect presents as a
  myelin-and-membrane disease.

  The mechanism deserves a precise statement, because the intuitive version of it is
  not what was measured. Patient fibroblasts do show diminished choline transport, but
  membrane phosphatidylcholine content was explicitly unchanged, and phosphatidylcholine
  was preserved in patient cerebrospinal fluid as well. The Kennedy pathway in
  CTL1-deficient cells is reduced but not absent, because the paralogue CTL2 can channel
  both choline and ethanolamine at lower capacity; what the cells lose is reserve and
  homeostatic latitude, expressed as disturbed handling of the other phospholipids and
  as a striking organelle phenotype (depleted free ribosomes, elongated endoplasmic
  reticulum, excess mitochondria and small vesicles) that chronic choline treatment
  reverses. The phosphatidylcholine-starvation account is supported in the
  oligodendrocyte lineage in vivo, where SLC44A1 loss disrupts phosphatidylcholine-pathway
  gene expression, inhibits phospholipid biosynthesis and alters myelin sheath lipid
  composition, but it is not what the accessible human tissue shows. This entry curates
  both readings, and the tension between them is recorded as an explicit knowledge gap
  rather than resolved by assertion.

  Therapeutically the disease is untreated, but it is one of the few neurodegenerative
  entities with a rational and cheap candidate substrate. Choline restored membrane
  lipids and organelle structure in patient fibroblasts, and citicoline restored
  developmental myelination in SLC44A1-deficient zebrafish and rodents. Neither result
  is a clinical trial, and both are curated here as preclinical.
synonyms:
- CONATOC
- CTL1 deficiency
- choline transporter-like protein 1 deficiency
- neurodegeneration, childhood-onset, with ataxia, tremor, optic atrophy, and cognitive
  decline
parents:
- Inherited Neurodegenerative Disorder
- Hereditary Leukoencephalopathy
notes: >-
  Named entity confusion warning. This disease is frequently discussed in the same
  breath as "CONDCA" (childhood-onset neurodegeneration with cerebellar atrophy,
  MONDO:0032650, AGTPBP1), which is a different gene, a different mechanism, and a
  separate entity that dismech curates elsewhere. The acronym attached to the SLC44A1
  entity in MONDO's synonym set is CONATOC, not CONDCA. Nothing in this entry is
  derived from the AGTPBP1 literature.

  SLC44A1 also appears in dismech in a wholly unrelated somatic context: the
  SLC44A1::PRKCA fusion that defines papillary glioneuronal tumor, mentioned in
  kb/disorders/Mixed_Neuronal-Glial_Tumor.yaml. That is a somatic rearrangement in a
  neoplasm, not a germline binding, and it is not prior coverage of this disease.

  Provenance. No deep-research provider report backs this entry. The Edison/falcon
  provider returned HTTP 402 (account out of credits) and the documented claude_code
  fallback failed with "Claude Code exited with code 1" after reporting "agentapi not
  found in PATH". The entry was curated from directly retrieved primary literature,
  with every reference fetched through `just fetch-reference`.

  Scope decision. This entry is deliberately narrow, and the narrowness is a decision
  rather than an omission. The published clinical experience of CONATOC is still the
  2020 founding series of four individuals from three families (PMID:31855247); the
  other cited sources are mechanistic work on the transporter and on its role in
  myelination (PMID:33789160, PMID:41317319, PMID:40540401). A PubMed sweep of the
  whole SLC44A1 literature (2026-09-03, ~150 records) returns predominantly papers on
  the unrelated somatic SLC44A1::PRKCA fusion in glioneuronal tumours, on CTL1 as an
  oncology or pharmacology transport target, and on choline-transporter polymorphisms
  in cognition and fetal alcohol spectrum disorder. Not one of them reports an
  additional individual with the germline recessive disease. The entry therefore
  curates the four sources that bear on the entity or its mechanism and does not pad
  the reference list with papers about the gene rather than the disease. Sections that
  a larger literature would normally fill are correspondingly thin, and those absences
  are asserted rather than merely unfilled: no clinical trial of any agent has been
  registered for this disease, no natural-history cohort exists, no prevalence or
  incidence estimate has been published, and no subtypes have been proposed. Reopen
  the scope when a second independent case series appears.

  Phenotype frequency policy for this entry. All eight clinical features come from a
  single sentence in the founding report - "Clinical features included progressive
  ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as
  urinary and bowel incontinence" - which enumerates them without saying how many of
  the four individuals had each. No frequency band can be derived from it, so none of
  the eight carries a `frequency:` value. Only the basal ganglia and substantia nigra
  MRI finding does, because it is the one feature the report counts ("seen in two
  individuals", 2/4 = 50%, the FREQUENT band). An earlier draft of this entry marked
  four of the eight VERY_FREQUENT on the strength of their appearing in the disease's
  MONDO label; that is a naming fact, not an observed frequency, and it was removed.

  GeneReviews. Searched PubMed on 2026-09-03 with `SLC44A1 AND GeneReviews[book]` and
  with `(choline transporter[Title] OR SLC44A1[Title]) AND GeneReviews[book]`; both
  returned zero records. There is no GeneReviews chapter for this entity, so none is
  cited. This is a recorded negative search result, not an assumption from the
  entity's recency.
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    notes: >-
      Every defining feature is neurological or neuro-ophthalmological: cerebellar
      ataxia and tremor, cognitive decline, dysarthria and dysphagia, optic atrophy,
      and an MRI picture of cerebellar atrophy with leukoencephalopathy. The optic
      atrophy is degeneration of retinal ganglion cell axons, that is, central nervous
      system tissue, so a separate ophthalmological assignment is deliberately not
      made. The underlying lesion is a membrane-lipid biosynthetic defect and the
      founding report calls the entity neurometabolic, but the expressed disease is
      confined to the nervous system.
external_assertions:
- name: OMIM phenotype record for CONATOC
  source: OMIM
  assertion_type: disease_record
  external_id: OMIM:618868
  url: https://omim.org/entry/618868
  description: >-
    OMIM phenotype entry 618868, "neurodegeneration, childhood-onset, with ataxia,
    tremor, optic atrophy, and cognitive decline" (CONATOC), is the source of the
    CONATOC acronym and is the OMIM xref carried by MONDO:0030028. Recorded as an
    external assertion rather than a mappings entry because DiseaseMappings has no
    OMIM slot; it carries only ICD-10-CM, ICD-11-F, MONDO and NCIT.
references:
- reference: PMID:31855247
  title: Choline transporter-like 1 deficiency causes a new type of childhood-onset
    neurodegeneration.
- reference: PMID:33789160
  title: Choline transporter-like proteins 1 and 2 are newly identified plasma membrane
    and mitochondrial ethanolamine transporters.
- reference: PMID:41317319
  title: SLC44A1 deficiency impedes myelin development in the central nervous system.
- reference: PMID:40540401
  title: Choline transporters are required for oligodendrocyte differentiation and myelin
    sheath formation in mouse postnatal brain.
inheritance:
- name: Autosomal recessive inheritance
  description: >-
    All four individuals in the founding series were homozygous for SLC44A1 frameshift
    alleles (Asp517Metfs*19, Ser126Metfs*8, Lys90Metfs*18) arising in three unrelated
    families, and the report states the inheritance explicitly. Heterozygous parents
    are unaffected. No dominant, digenic or oligogenic mechanism has been proposed
    for this locus.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we describe a novel childhood-onset neurometabolic disease caused by
      choline transporter deficiency with autosomal recessive inheritance"
    explanation: The founding clinical report states autosomal recessive inheritance
      for the entity.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    The founding series of four individuals from three families is essentially the
    whole published clinical experience of this entity; no prevalence or incidence
    estimate of any kind has been published, and MONDO:0030028 carries no Orphanet
    epidemiology record to band against. NOT_YET_DOCUMENTED is used in preference to
    a qualitative ULTRA_RARE band because there is no source to band, and
    rate_per_100000 is left empty for the same reason. No founder effect and no
    ancestry enrichment is asserted.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we report on four individuals from three families with neurodegenerative
      disease and homozygous frameshift mutations"
    explanation: Establishes the size of the reported case series, which is the only
      occurrence information available.
pathophysiology:
- name: Biallelic SLC44A1 Loss of Function
  biological_scale: MOLECULAR
  description: >-
    Homozygous frameshift alleles in SLC44A1 truncate choline transporter-like protein
    1. Three distinct frameshifts were reported across the three founding families,
    two of which (Asp517Metfs*19 and Ser126Metfs*8) gave fibroblast phenotypes that
    were structurally and functionally indistinguishable, arguing that the entity is
    driven by loss of the protein rather than by a residue-specific effect.
  downstream:
  - target: Choline Transporter-Like Protein 1 Deficiency
    causal_link_type: DIRECT
    description: Frameshift truncation removes functional CTL1 from the membrane.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and Lys90Metfs*18)
      in the SLC44A1 gene encoding choline transporter-like protein 1"
    explanation: Identifies the causal biallelic frameshift genotype and the encoded
      protein.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The Asp517Metfs*19 and Ser126Metfs*8 fibroblasts were structurally and
      functionally indistinguishable."
    explanation: Two independent frameshift alleles converge on the same cellular
      phenotype, supporting a shared loss-of-function mechanism.
- name: Choline Transporter-Like Protein 1 Deficiency
  biological_scale: MOLECULAR
  description: >-
    Loss of CTL1, the carrier that moves choline (and, as later shown, ethanolamine)
    across the plasma membrane and into mitochondria. CTL1 is enriched in
    oligodendrocytes, which is the expression pattern that makes a general
    membrane-lipid transporter behave as a white-matter disease gene.
  molecular_functions:
  - preferred_term: choline transmembrane transporter activity
    modifier: DECREASED
    term:
      id: GO:0015220
      label: choline transmembrane transporter activity
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  downstream:
  - target: Reduced Cellular Choline and Ethanolamine Uptake
    causal_link_type: DIRECT
    description: Absent carrier protein removes the principal uptake route for both
      Kennedy pathway head-group substrates.
  evidence:
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we show that SLC44A1 is enriched in oligodendrocytes and is required
      for myelin development in the CNS of zebrafish and rodents"
    explanation: Establishes the oligodendrocyte-enriched expression that localizes
      the transporter defect to the myelinating lineage.
- name: Reduced Cellular Choline and Ethanolamine Uptake
  biological_scale: CELLULAR
  description: >-
    Patient fibroblasts show diminished choline transport. The same lesion also
    reduces ethanolamine transport, since CTL1 was subsequently identified as a
    physiological ethanolamine carrier; the deficit is therefore in both head-group
    substrates, not choline alone.
  biological_processes:
  - preferred_term: choline transport
    modifier: DECREASED
    term:
      id: GO:0015871
      label: choline transport
  downstream:
  - target: Constrained Kennedy Pathway Phospholipid Synthesis
    causal_link_type: DIRECT
    description: Substrate entry is the first committed step of de novo phospholipid
      synthesis, so reduced uptake constrains flux through both Kennedy branches.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Functional analysis revealed diminished choline transport yet the membrane
      phosphatidylcholine content remained unchanged."
    explanation: Directly measures the reduced choline transport in patient fibroblasts;
      the same sentence records that the downstream phosphatidylcholine pool was not
      depleted, which is why the next node is framed as constrained flux rather than
      product depletion.
  - reference: PMID:33789160
    reference_title: "Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The lack of CTL1 in M2 cells reduced the ethanolamine transport, the
      flux through the CDP-ethanolamine Kennedy pathway, and PE synthesis."
    explanation: Extends the transport deficit beyond choline to ethanolamine, showing
      both Kennedy branches lose substrate supply.
- name: Constrained Kennedy Pathway Phospholipid Synthesis
  biological_scale: MOLECULAR
  description: >-
    Reduced but not absent flux through the CDP-choline and CDP-ethanolamine branches
    of the Kennedy pathway. The residual flux is attributable to the paralogue CTL2,
    which channels both substrates at lower capacity; this is the reason bulk
    phosphatidylcholine is preserved in accessible patient tissue while the cell is
    nonetheless operating without reserve.
  biological_processes:
  - preferred_term: phosphatidylcholine biosynthetic process
    modifier: DECREASED
    term:
      id: GO:0006656
      label: phosphatidylcholine biosynthetic process
  - preferred_term: phosphatidylethanolamine biosynthetic process
    modifier: DECREASED
    term:
      id: GO:0006646
      label: phosphatidylethanolamine biosynthetic process
  downstream:
  - target: Membrane Phospholipid Homeostasis Disturbance
    causal_link_type: DIRECT
    description: Reduced de novo supply is compensated by remodelling the rest of the
      phospholipid complement.
  - target: Myelin Membrane Lipid Composition Imbalance
    causal_link_type: DIRECT
    description: >-
      In the oligodendrocyte lineage the same constraint inhibits phospholipid
      biosynthesis and alters myelin sheath lipid composition.
  evidence:
  - reference: PMID:33789160
    reference_title: "Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "PC and PE are synthesized de novo by CDP-Cho and CDP-Etn branches of
      the Kennedy pathway in which the extracellular substrates choline (Cho) and ethanolamine
      (Etn) are actively transported into the cell, phosphorylated, and coupled with
      diacylglycerols (DAGs) to form the final phospholipid product."
    explanation: States the pathway architecture that makes transporter loss a
      biosynthetic constraint.
  - reference: PMID:33789160
    reference_title: "Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "CTL1-deficient cells had reduced but not absent CDP-Cho Kennedy pathway"
    explanation: Supports "constrained" rather than "abolished" flux, and is the
      quantitative basis for the residual-capacity framing of this node.
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SLC44A1 deficiency disrupts the expression of genes involved in the phosphatidylcholine
      production pathway and subsequently inhibits phospholipid biosynthesis and disturbs
      the lipid composition of myelin sheaths"
    explanation: In vivo evidence that the phosphatidylcholine branch is the one that
      matters for myelin, supporting the edge to the oligodendrocyte node.
- name: Membrane Phospholipid Homeostasis Disturbance
  biological_scale: CELLULAR
  description: >-
    Rather than depleting phosphatidylcholine, CTL1-deficient cells preserve it at the
    cost of the rest of the membrane lipid complement, and the visible consequence is
    an organelle phenotype: depleted free ribosomes, elongated endoplasmic reticulum,
    and a striking excess of mitochondria and small vesicles. Chronic choline treatment
    reverses it, which is the evidence that the derangement is a substrate-supply
    problem and not a structural one.
  downstream:
  - target: Vulnerability to Iron-Mediated Cellular Injury
    causal_link_type: DIRECT
    description: Membrane lipid derangement leaves mutant cells less able to withstand
      acute iron overload.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "As part of the mechanism to preserve choline and phosphatidylcholine,
      choline transporter deficiency was implicated in impaired membrane homeostasis
      of other phospholipids."
    explanation: States the compensation-at-a-cost mechanism this node represents.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The most prominent ultrastructural changes of the mutant fibroblasts
      were reduced presence of free ribosomes, the appearance of elongated endoplasmic
      reticulum and strikingly increased number of mitochondria and small vesicles."
    explanation: The measured organelle phenotype that makes this node observable.
- name: Vulnerability to Iron-Mediated Cellular Injury
  biological_scale: CELLULAR
  description: >-
    Mutant cells are less able to tolerate acute iron overload, and choline treatment
    protects them. This is the only cellular correlate offered for the basal ganglia
    and substantia nigra signal changes seen on MRI in a subset of patients; the link
    between the two is inferred, and is recorded as a knowledge gap (discussion
    iron_vulnerability_and_basal_ganglia_signal) rather than as an established chain.
  downstream:
  - target: Abnormal Basal Ganglia MRI Signal Intensity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Proposed, not demonstrated, correlate of the low-signal globus pallidus and
      substantia nigra reported in two of the four individuals.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Choline treatments could restore the membrane lipids, repair cellular
      organelles and protect mutant cells from acute iron overload."
    explanation: Demonstrates the iron-handling vulnerability of mutant cells and its
      reversal by choline.
- name: Myelin Membrane Lipid Composition Imbalance
  biological_scale: MOLECULAR
  description: >-
    The lipid complement of the myelin sheath itself is altered. In vivo, SLC44A1 loss
    disrupts expression of the phosphatidylcholine-production genes, inhibits
    phospholipid biosynthesis, and changes the lipid composition of the sheaths that
    do form; conditional deletion in mouse oligodendroglia points to plasmalogen
    synthesis as one specifically inhibited arm. This is a claim about myelin lipid
    chemistry, separate from the claim that oligodendrocytes fail to mature, and each
    was measured by a different experiment.
  biological_processes:
  - preferred_term: phospholipid biosynthetic process
    modifier: DECREASED
    term:
      id: GO:0008654
      label: phospholipid biosynthetic process
  downstream:
  - target: Oligodendrocyte Maturation Failure
    causal_link_type: DIRECT
    description: >-
      A maturing oligodendrocyte must synthesize a very large membrane area in a short
      window, so a constrained and compositionally abnormal lipid supply is the
      proposed proximate reason maturation and sheath formation fail.
  evidence:
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SLC44A1 deficiency disrupts the expression of genes involved in the phosphatidylcholine
      production pathway and subsequently inhibits phospholipid biosynthesis and disturbs
      the lipid composition of myelin sheaths"
    explanation: The measured in vivo lipid-composition abnormality this node asserts,
      together with the biosynthetic step that produces it.
  - reference: PMID:40540401
    reference_title: "Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Metabolomics profiling indicates disrupted lipid metabolism by SLC44A1
      deletion, specifically inhibiting plasmalogen synthesis, a pathway vital for myelin
      biogenesis."
    explanation: Independent mouse conditional-knockout metabolomics naming a specific
      inhibited lipid arm, which is why this node is stated as compositional imbalance
      rather than as bulk phospholipid loss.
- name: Oligodendrocyte Maturation Failure
  biological_scale: CELLULAR
  description: >-
    Oligodendroglial maturation and myelinogenesis are arrested. Time-lapse imaging in
    Slc44a1b-deficient zebrafish shows the failure directly and in real time, and
    oligodendroglia-specific Slc44a1 deletion in mouse reproduces it with shortened
    myelin segments and hypomyelination persisting into adulthood. This is the node at
    which a general membrane-lipid defect becomes a white-matter disease.
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  biological_processes:
  - preferred_term: myelination
    modifier: DECREASED
    term:
      id: GO:0042552
      label: myelination
  downstream:
  - target: Leukoencephalopathy
    causal_link_type: DIRECT
    description: Deficient and lipid-abnormal myelin is the substrate of the imaging
      white-matter abnormality.
  - target: Progressive Cerebellar and Optic Pathway Degeneration
    causal_link_type: DIRECT
    description: Failing myelin maintenance is the proposed driver of the selective
      degeneration of cerebellar and optic pathways.
  evidence:
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In vivo time-lapse imaging of Slc44a1b-deficient zebrafish reveals impaired
      oligodendroglial maturation and myelinogenesis."
    explanation: Direct in vivo observation of the maturation and myelination failure
      this node asserts.
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our findings demonstrate that SLC44A1 is essential for CNS myelination,
      and citicoline supplementation represents a potential therapy for developmental
      hypomyelination."
    explanation: States the necessity of SLC44A1 for CNS myelination.
  - reference: PMID:40540401
    reference_title: "Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Conditional knockout (cKO) of either SLC44A1 or SLC44A5 in oligodendroglia
      impairs OL differentiation and myelination in neonatal brains, with shortened myelin
      segment lengths."
    explanation: Cell-type-specific deletion in a second species shows the maturation
      failure is intrinsic to oligodendroglia rather than a systemic consequence.
- name: Progressive Cerebellar and Optic Pathway Degeneration
  biological_scale: TISSUE
  description: >-
    Selective, progressive loss of cerebellar tissue and of optic nerve axons, which
    is the anatomical level at which the clinical quartet of ataxia, tremor, optic
    atrophy and cognitive decline is generated. Cerebellar atrophy is documented on
    MRI in the founding series; the cell-type attributions below are anatomical
    localizations of the clinical and imaging findings rather than a reported
    histopathological cell count.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  - preferred_term: retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  downstream:
  - target: Cerebellar Atrophy
    causal_link_type: DIRECT
  - target: Progressive Ataxia
    causal_link_type: DIRECT
  - target: Tremor
    causal_link_type: DIRECT
  - target: Dysarthria
    causal_link_type: DIRECT
  - target: Optic Atrophy
    causal_link_type: DIRECT
  - target: Cognitive Decline
    causal_link_type: DIRECT
  - target: Dysphagia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Urinary Incontinence
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Bowel Incontinence
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
    explanation: Documents the cerebellar tissue loss and white-matter change that
      this node represents.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features included progressive ataxia, tremor, cognitive decline,
      dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
    explanation: Enumerates the clinical consequences attributed to this degeneration
      node.
genetic:
- name: SLC44A1
  association: >-
    Homozygous frameshift loss-of-function alleles. Three were reported in the founding
    series across three unrelated families: Asp517Metfs*19, Ser126Metfs*8 and
    Lys90Metfs*18. No missense, hypomorphic or dominant allele class has been
    established for this phenotype.
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: SLC44A1
    term:
      id: hgnc:18798
      label: SLC44A1
  inheritance:
  - name: Autosomal recessive inheritance
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
  notes: >-
    hgnc:18798 is SLC44A1, solute carrier family 44 member 1, encoding choline
    transporter-like protein 1 (CTL1). The gene is separately and unrelatedly known
    to medicine as the 5' partner of the somatic SLC44A1::PRKCA fusion that defines
    papillary glioneuronal tumor; that is a rearrangement in tumour tissue and has no
    bearing on this germline recessive disease.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we report on four individuals from three families with neurodegenerative
      disease and homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and
      Lys90Metfs*18) in the SLC44A1 gene encoding choline transporter-like protein 1"
    explanation: Names the three homozygous frameshift alleles and the three unrelated
      families they arose in, which is the gene-disease association this block asserts.
phenotypes:
- name: Progressive Ataxia
  category: Neurological
  description: Progressive cerebellar ataxia, reported in the founding series and one
    of the four features named in the disease's MONDO label.
  phenotype_term:
    preferred_term: Progressive ataxia
    term:
      id: HP:0001251
      label: Ataxia
    clinical_course: PROGRESSIVE
    onset:
      onset_category: CHILDHOOD
      notes: >-
        Childhood onset is asserted for the disease as a whole by the founding report
        and by the MONDO label, not measured separately for this feature.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features included progressive ataxia, tremor, cognitive decline,
      dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
    explanation: Lists progressive ataxia among the clinical features of the series.
- name: Tremor
  category: Neurological
  description: Tremor, one of the four features named in the disease's MONDO label.
  phenotype_term:
    preferred_term: Tremor
    term:
      id: HP:0001337
      label: Tremor
    onset:
      onset_category: CHILDHOOD
      notes: >-
        Childhood onset is asserted for the disease as a whole by the founding report
        and by the MONDO label, not measured separately for this feature.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy,
      dysarthria"
    explanation: Lists tremor among the clinical features of the series.
- name: Cognitive Decline
  category: Neurological
  description: >-
    Progressive loss of previously acquired cognitive function. Bound to HP:0001268
    Mental deterioration, which is HPO's term for decline from an attained level, in
    preference to any term implying static intellectual disability.
  phenotype_term:
    preferred_term: Cognitive decline
    term:
      id: HP:0001268
      label: Mental deterioration
    clinical_course: PROGRESSIVE
    onset:
      onset_category: CHILDHOOD
      notes: >-
        Childhood onset is asserted for the disease as a whole by the founding report
        and by the MONDO label, not measured separately for this feature.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features included progressive ataxia, tremor, cognitive decline,
      dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
    explanation: Lists cognitive decline among the clinical features of the series.
- name: Optic Atrophy
  category: Ophthalmological
  description: Optic atrophy, reflecting degeneration of retinal ganglion cell axons;
    one of the four features named in the disease's MONDO label.
  phenotype_term:
    preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
    onset:
      onset_category: CHILDHOOD
      notes: >-
        Childhood onset is asserted for the disease as a whole by the founding report
        and by the MONDO label, not measured separately for this feature.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary
      and bowel incontinence"
    explanation: Lists optic atrophy among the clinical features of the series.
- name: Dysarthria
  category: Neurological
  description: Dysarthria, consistent with the cerebellar and white-matter involvement.
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy,
      dysarthria"
    explanation: Lists dysarthria among the clinical features of the series.
- name: Dysphagia
  category: Neurological
  description: Swallowing difficulty, a bulbar consequence of the progressive
    neurodegeneration and a major determinant of nutritional and aspiration risk.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy,
      dysarthria"
    explanation: Lists dysphagia among the clinical features of the series.
- name: Urinary Incontinence
  category: Genitourinary
  description: Urinary incontinence reported as part of the clinical picture.
  phenotype_term:
    preferred_term: Urinary incontinence
    term:
      id: HP:0000020
      label: Urinary incontinence
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dysarthria, as well as urinary and bowel incontinence"
    explanation: Lists urinary incontinence among the clinical features of the series.
- name: Bowel Incontinence
  category: Gastrointestinal
  description: Bowel incontinence reported as part of the clinical picture.
  phenotype_term:
    preferred_term: Bowel incontinence
    term:
      id: HP:0002607
      label: Bowel incontinence
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dysarthria, as well as urinary and bowel incontinence"
    explanation: Lists bowel incontinence among the clinical features of the series.
- name: Cerebellar Atrophy
  category: Imaging
  description: Cerebellar atrophy on brain MRI, the imaging correlate of the ataxia
    and tremor.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
    explanation: Documents cerebellar atrophy on MRI in the reported individuals.
- name: Leukoencephalopathy
  category: Imaging
  description: >-
    Diffuse white-matter abnormality on brain MRI. This is the finding that ties the
    clinical entity to the oligodendrocyte and myelin biology of SLC44A1, and it is
    the feature that places the disease in the hereditary leukoencephalopathy
    differential.
  phenotype_term:
    preferred_term: Leukoencephalopathy
    term:
      id: HP:0002352
      label: Leukoencephalopathy
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
    explanation: Documents leukoencephalopathy on MRI in the reported individuals.
- name: Abnormal Basal Ganglia MRI Signal Intensity
  category: Imaging
  description: >-
    Low signal intensity in the globus pallidus with hyperintense streaking, and low
    signal intensity in the substantia nigra, seen in two of the four reported
    individuals. Bound to the generic basal ganglia signal term rather than to the
    NBIA-specific eye-of-the-tiger term, which the source does not claim. Whether this
    reflects mineral accumulation was not established.
  phenotype_term:
    preferred_term: Globus pallidus and substantia nigra low signal intensity on MRI
    term:
      id: HP:0012751
      label: Abnormal basal ganglia MRI signal intensity
  frequency: FREQUENT
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "low signal intensity in globus pallidus with hyperintensive streaking
      and low signal intensity in substantia nigra were seen in two individuals"
    explanation: >-
      2 of the 4 individuals in the series, that is 50%, which falls in the FREQUENT
      band (30-79%). This is the only feature in the entry for which the source gives
      a count, which is why it is the only one carrying a frequency value at all.
biochemical:
- name: Membrane phosphatidylcholine content
  biomarker_term:
    preferred_term: membrane phosphatidylcholine content
  presence: Unchanged
  context: Patient-derived skin fibroblasts and cerebrospinal fluid.
  notes: >-
    Deliberately left unbound. `biomarker_term` takes an NCIT term, and NCIT has no
    analyte term for membrane phosphatidylcholine: the candidates it does offer are an
    enzyme (NCIT:C202874 Phosphatidylcholine-Sterol Acyltransferase), two pathway terms
    (NCIT:C28751, NCIT:C91316), a ratio measurement (NCIT:C147420) and the commercial
    dietary mixture lecithin (NCIT:C68386). None of them names the quantity that was
    measured, so no term is bound rather than a near-miss one.
  readouts:
  - target: Constrained Kennedy Pathway Phospholipid Synthesis
    relationship: READOUT_OF
    endpoint_context: DIAGNOSTIC
    description: >-
      Membrane phosphatidylcholine is the product of the CDP-choline branch and is the
      obvious readout of it, which is what makes the result informative.
    interpretation: >-
      Not lowered. Direction is deliberately left unset: the finding is that the value
      was unchanged, and `BiomarkerReadoutDirectionEnum` has no value for that. This
      negative result is the reason the upstream node is curated as constrained flux
      rather than as product depletion, and it is the substance of the
      pc_preserved_despite_transport_loss knowledge gap.
    evidence:
    - reference: PMID:31855247
      reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Functional analysis revealed diminished choline transport yet the membrane
        phosphatidylcholine content remained unchanged."
      explanation: The measurement itself, in patient fibroblasts, alongside the
        transport defect that would have predicted a fall.
  evidence:
  - reference: PMID:33789160
    reference_title: "Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Paradoxically, although Cho transport and CDP-Cho Kennedy pathway were
      diminished, PC remained preserved in the cerebrospinal fluid and skin fibroblasts
      of the affected individuals"
    explanation: >-
      Extends the preserved-phosphatidylcholine result from fibroblasts to
      cerebrospinal fluid, so the finding is not an artefact of one accessible tissue.
diagnosis:
- name: Molecular confirmation of biallelic SLC44A1 loss-of-function variants
  description: >-
    Sequencing is the only confirmatory test. The clinical and imaging picture places
    the disease in the hereditary leukoencephalopathy and ataxia differential but does
    not distinguish it, so the diagnosis rests on finding biallelic loss-of-function
    SLC44A1 variants; all four published individuals were homozygous for frameshift
    alleles. No biochemical or metabolite test discriminates the entity - notably,
    phosphatidylcholine is preserved in patient cerebrospinal fluid and fibroblasts, so
    a normal phospholipid result does not exclude the diagnosis.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  results: >-
    Biallelic loss-of-function SLC44A1 variants; homozygous frameshift alleles in every
    reported case.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we report on four individuals from three families with neurodegenerative
      disease and homozygous frameshift mutations (Asp517Metfs*19, Ser126Metfs*8, and
      Lys90Metfs*18) in the SLC44A1 gene encoding choline transporter-like protein 1"
    explanation: Establishes the genotype that confirms the diagnosis, and that every
      reported case was ascertained this way.
- name: Brain MRI
  description: >-
    The imaging handle. Cerebellar atrophy together with leukoencephalopathy is the
    pattern that should prompt SLC44A1 testing, and in a subset an additional low-signal
    globus pallidus with hyperintense streaking and low-signal substantia nigra narrows
    the differential further, at the cost of raising a false lead toward NBIA. MRI is
    suggestive, never confirmatory.
  diagnosis_term:
    preferred_term: brain magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  results: >-
    Cerebellar atrophy with leukoencephalopathy; in some individuals, low signal
    intensity in the globus pallidus with hyperintense streaking and in the substantia
    nigra.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain MRI demonstrated cerebellar atrophy and leukoencephalopathy."
    explanation: The imaging pattern present in the reported individuals.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "low signal intensity in globus pallidus with hyperintensive streaking
      and low signal intensity in substantia nigra were seen in two individuals"
    explanation: The additional deep-grey signal change, present in half the series and
      therefore a supportive rather than a required finding.
treatments:
- name: Oral Choline Supplementation
  description: >-
    Substrate repletion aimed at the transport bottleneck. Chronic choline treatment
    of patient fibroblasts reversed the organelle phenotype, restored membrane lipids
    and protected the cells against acute iron overload. This is a cellular result in
    patient-derived fibroblasts, not a clinical outcome: no trial of choline
    supplementation in this disease has been reported, and the entry does not assert
    clinical benefit.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: choline substrate supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: choline
      term:
        id: CHEBI:15354
        label: choline
  target_mechanisms:
  - target: Membrane Phospholipid Homeostasis Disturbance
    description: Restores membrane lipid composition and organelle ultrastructure in
      CTL1-deficient cells.
    evidence:
    - reference: PMID:31855247
      reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "When chronically treated with choline, those characteristics disappeared
        and mutant ultrastructure resembled healthy control cells."
      explanation: Demonstrates reversal of the cellular phenotype this mechanism node
        represents.
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Choline treatments could restore the membrane lipids, repair cellular
      organelles and protect mutant cells from acute iron overload."
    explanation: The preclinical basis for proposing choline repletion; the evidence
      is in vitro and does not establish clinical efficacy.
- name: Citicoline Supplementation
  description: >-
    Citicoline (CDP-choline) is the Kennedy pathway intermediate immediately downstream
    of choline phosphorylation, and supplementing it restored developmental myelination
    in SLC44A1-deficient zebrafish and rodents. Proposed on that basis as a candidate
    therapy for the human disease; no clinical trial in SLC44A1-related
    neurodegeneration has been reported.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: citicoline substrate supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: citicoline
      term:
        id: CHEBI:16436
        label: CDP-choline
  target_mechanisms:
  - target: Oligodendrocyte Maturation Failure
    description: Restores developmental myelination in SLC44A1-deficient animals.
    evidence:
    - reference: PMID:41317319
      reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "supplementation with citicoline, a natural choline metabolite, restores
        developmental myelination in SLC44A1-deficient animals"
      explanation: Demonstrates rescue of the myelination node in two model organisms.
  notes: >-
    The preferred_term deliberately names citicoline while the bound NCIT term is the
    broader Nutritional Support action, because NCIT's clinical-intervention subtree
    has no citicoline-specific action term; the agent identity is carried by the
    CHEBI-bound therapeutic_agent instead. CHEBI:16436 is CDP-choline, of which
    citicoline is the pharmaceutical name.
- name: Supportive and Rehabilitative Care
  description: >-
    Physical and occupational therapy for progressive ataxia, speech therapy and
    swallowing assessment for dysarthria and dysphagia, low-vision support for optic
    atrophy, and continence management. This is the actual standard of care; the
    disease is described in the literature as lacking effective treatment.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: multidisciplinary supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "childhood-onset neurodegeneration with cerebellar atrophy and leukoencephalopathy
      that lacks effective treatment"
    explanation: States that no disease-modifying treatment exists, which is what makes
      supportive care the standard of care.
- name: Genetic Counseling
  description: >-
    Autosomal recessive counseling for parents of an affected child, who face a 25%
    recurrence risk per pregnancy, with carrier testing for at-risk relatives.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we describe a novel childhood-onset neurometabolic disease caused by
      choline transporter deficiency with autosomal recessive inheritance"
    explanation: The autosomal recessive inheritance established here is what determines
      the recurrence risk that counseling communicates.
experimental_models:
- name: Patient-derived SLC44A1 frameshift fibroblasts
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: >-
    Skin fibroblasts from individuals homozygous for Asp517Metfs*19 and Ser126Metfs*8,
    used to measure choline transport, membrane phospholipid content and organelle
    ultrastructure, and to test choline rescue.
  modeled_mechanisms:
  - target: Reduced Cellular Choline and Ethanolamine Uptake
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the transport defect directly in patient cells carrying the causal
      genotype.
    limitations: >-
      Fibroblasts are not the affected cell type. The disease is expressed in
      oligodendrocytes and neurons, and the fibroblast phenotype notably does not
      include the phosphatidylcholine depletion that the oligodendrocyte data imply,
      so the model measures the transport lesion faithfully while representing its
      downstream consequences poorly.
    readouts:
    - name: Choline transport rate in patient fibroblasts
      target: Reduced Cellular Choline and Ethanolamine Uptake
      direction: DECREASED
      interpretation: Confirms loss of carrier-mediated choline uptake in cells with
        the causal genotype.
      evidence:
      - reference: PMID:31855247
        reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Functional analysis revealed diminished choline transport yet the
          membrane phosphatidylcholine content remained unchanged."
        explanation: Reports the measured reduction in choline transport in these
          cells.
    evidence:
    - reference: PMID:31855247
      reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The Asp517Metfs*19 and Ser126Metfs*8 fibroblasts were structurally
        and functionally indistinguishable."
      explanation: Supports treating these patient lines as an informative and
        reproducible model of the transport lesion.
  - target: Membrane Phospholipid Homeostasis Disturbance
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the compensatory membrane-lipid derangement and its organelle
      correlate, both reversible by choline.
    limitations: >-
      The compensation may be fibroblast-specific: a dividing skin fibroblast with an
      intact CTL2 paralogue has metabolic options that a terminally differentiated,
      membrane-hungry oligodendrocyte may not.
    readouts:
    - name: Fibroblast organelle ultrastructure on electron microscopy
      target: Membrane Phospholipid Homeostasis Disturbance
      direction: ALTERED
      interpretation: Depleted free ribosomes, elongated endoplasmic reticulum and
        excess mitochondria and small vesicles, normalizing with chronic choline.
      evidence:
      - reference: PMID:31855247
        reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "The most prominent ultrastructural changes of the mutant fibroblasts
          were reduced presence of free ribosomes, the appearance of elongated endoplasmic
          reticulum and strikingly increased number of mitochondria and small vesicles."
        explanation: The measured ultrastructural readout for this mechanism node.
animal_models:
- name: Slc44a1b-deficient zebrafish
  species: Zebrafish
  genotype: Slc44a1b deficient
  publication: PMID:41317319
  description: >-
    Zebrafish model used for in vivo time-lapse imaging of oligodendroglial maturation
    and myelinogenesis, and for the citicoline rescue experiment.
  modeled_mechanisms:
  - target: Oligodendrocyte Maturation Failure
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the failure of oligodendroglial maturation and myelination that is
      proposed to underlie the human leukoencephalopathy, and does so with live imaging
      not obtainable in humans.
    limitations: >-
      The model reports a developmental myelination failure, whereas the human disease
      is described as a childhood-onset progressive neurodegeneration; whether the
      human lesion is failed myelin development, failed myelin maintenance, or both is
      not settled by this model. Zebrafish carry an slc44a1 paralogue pair, so gene
      dosage does not map one-to-one onto the human locus.
    readouts:
    - name: Oligodendroglial maturation and myelin sheath formation on time-lapse imaging
      target: Oligodendrocyte Maturation Failure
      direction: DECREASED
      interpretation: Impaired maturation and myelinogenesis in the deficient animals.
      evidence:
      - reference: PMID:41317319
        reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In vivo time-lapse imaging of Slc44a1b-deficient zebrafish reveals
          impaired oligodendroglial maturation and myelinogenesis."
        explanation: The measured in vivo readout for this mechanism node.
    evidence:
    - reference: PMID:41317319
      reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "we show that SLC44A1 is enriched in oligodendrocytes and is required
        for myelin development in the CNS of zebrafish and rodents"
      explanation: Supports treating the zebrafish as informative for the human
        myelination mechanism, alongside rodent data.
  - target: Myelin Membrane Lipid Composition Imbalance
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Shows the phosphatidylcholine-production pathway disruption and the consequent
      change in myelin sheath lipid composition in vivo.
    limitations: >-
      The reported measurement is of pathway gene expression and myelin lipid
      composition rather than of flux, so it establishes that the pathway is
      dysregulated without quantifying the reduction in synthetic rate. The lipid
      composition of a zebrafish sheath is not assumed to be quantitatively
      transferable to human myelin.
    readouts:
    - name: Myelin sheath lipid composition
      target: Myelin Membrane Lipid Composition Imbalance
      direction: ALTERED
      interpretation: Disturbed lipid composition of myelin sheaths in deficient
        animals.
      evidence:
      - reference: PMID:41317319
        reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "SLC44A1 deficiency disrupts the expression of genes involved in the
          phosphatidylcholine production pathway and subsequently inhibits phospholipid
          biosynthesis and disturbs the lipid composition of myelin sheaths"
        explanation: The measured lipid-composition readout for this mechanism node.
- name: Oligodendroglia-specific Slc44a1 conditional knockout mouse
  species: Mouse
  genotype: Oligodendroglial conditional Slc44a1 knockout (SLC44A1-cKO)
  publication: PMID:40540401
  description: >-
    Cell-type-restricted deletion of Slc44a1 in mouse oligodendroglia, used to test
    whether the myelination defect is intrinsic to the lineage and to profile the lipid
    consequences by metabolomics.
  modeled_mechanisms:
  - target: Oligodendrocyte Maturation Failure
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Impaired oligodendrocyte differentiation and myelination with shortened myelin
      segments in neonatal brain, and hypomyelination that persists into adulthood.
      Because the deletion is confined to oligodendroglia, the failure cannot be a
      downstream effect of transporter loss elsewhere in the body - which the
      whole-organism zebrafish model and the human genotype cannot separate.
    limitations: >-
      A conditional knockout is a complete, lineage-restricted null from development
      onward, whereas affected individuals carry a constitutive germline frameshift in
      every tissue; the mouse therefore models the oligodendroglial contribution rather
      than the disease. It also does not address the maintenance-versus-development
      question, since the deletion precedes myelination. The same paper shows SLC44A5
      contributes in neonatal mouse oligodendroglia, and no equivalent paralogue
      contribution is established in humans.
    readouts:
    - name: Oligodendrocyte differentiation and myelin segment length in neonatal brain
      target: Oligodendrocyte Maturation Failure
      direction: DECREASED
      interpretation: Fewer differentiated oligodendrocytes and shorter myelin segments
        after oligodendroglial Slc44a1 deletion.
      evidence:
      - reference: PMID:40540401
        reference_title: "Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Conditional knockout (cKO) of either SLC44A1 or SLC44A5 in oligodendroglia
          impairs OL differentiation and myelination in neonatal brains, with shortened myelin
          segment lengths."
        explanation: The measured differentiation and myelin-segment readout for this
          mechanism node.
    evidence:
    - reference: PMID:40540401
      reference_title: "Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "SLC44A1-cKO mice show persistent hypomyelination into adulthood whereas
        SLC44A5-cKO mice do not, a divergence likely attributable to age-related decline
        in SLC44A5 expression in oligodendroglia."
      explanation: >-
        Supports treating this model as informative for the human node: the deficit is
        specific to SLC44A1 and does not resolve with age, which is what a model of a
        progressive childhood disease has to show.
  - target: Myelin Membrane Lipid Composition Imbalance
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Metabolomic profiling of the conditional knockout identifies disrupted lipid
      metabolism and names plasmalogen synthesis as a specifically inhibited arm.
    limitations: >-
      Plasmalogen synthesis is a peroxisomal ether-lipid pathway rather than a Kennedy
      pathway branch, so how transporter loss reaches it is not established here, and
      no plasmalogen measurement has been reported in an affected individual.
    readouts:
    - name: Oligodendroglial lipid metabolome
      target: Myelin Membrane Lipid Composition Imbalance
      direction: ALTERED
      interpretation: Disrupted lipid metabolism with inhibited plasmalogen synthesis.
      evidence:
      - reference: PMID:40540401
        reference_title: "Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Metabolomics profiling indicates disrupted lipid metabolism by SLC44A1
          deletion, specifically inhibiting plasmalogen synthesis, a pathway vital for myelin
          biogenesis."
        explanation: The measured lipid-metabolome readout for this mechanism node.
differential_diagnoses:
- name: Childhood-onset neurodegeneration with cerebellar atrophy (CONDCA, AGTPBP1)
  description: >-
    The most important differential, and the most important name confusion. CONDCA is
    an AGTPBP1-related recessive disease (MONDO:0032650) that also presents in
    childhood with cerebellar atrophy and progressive neurological decline, and the
    two acronyms CONATOC and CONDCA are routinely conflated. The genes, the protein
    families and the mechanisms are unrelated: AGTPBP1 encodes a cytosolic
    carboxypeptidase acting on tubulin polyglutamylation, while SLC44A1 encodes a
    membrane-lipid substrate transporter. Distinguish on genotype, not on phenotype.
- name: Hereditary leukoencephalopathies and hypomyelinating leukodystrophies
  description: >-
    The leukoencephalopathy plus cerebellar atrophy on MRI places this entity in the
    hereditary white-matter differential, alongside the hypomyelinating leukodystrophies
    and Pelizaeus-Merzbacher disease. The combination of optic atrophy and prominent
    basal ganglia and substantia nigra signal change in a subset is the feature that
    should prompt SLC44A1 testing rather than a purely myelin-gene panel.
- name: Neurodegeneration with brain iron accumulation
  description: >-
    Low globus pallidus signal with hyperintense streaking, present in two of the four
    reported individuals, is visually reminiscent of NBIA. The source report does not
    claim an eye-of-the-tiger sign and iron accumulation was not demonstrated in
    patient brain, but the demonstrated vulnerability of CTL1-deficient cells to acute
    iron overload makes the resemblance worth noting rather than dismissing.
discussions:
- discussion_id: pc_preserved_despite_transport_loss
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is the human disease actually caused by phosphatidylcholine deficiency, given that
    phosphatidylcholine was preserved in the accessible tissue of affected individuals?
  rationale: >-
    The intuitive account of this disease, and the one stated in most secondary
    summaries, is that losing the choline transporter starves membrane synthesis of its
    phosphatidylcholine precursor. That account is directly complicated by the founding
    study's own measurement: choline transport was diminished while membrane
    phosphatidylcholine content was unchanged, and the same group later reported that
    phosphatidylcholine was preserved in the cerebrospinal fluid as well as the skin
    fibroblasts of affected individuals. The proposed reconciliation is that the
    paralogue CTL2 sustains a reduced but not absent Kennedy pathway, so the cell
    protects its phosphatidylcholine pool by deranging the rest of its phospholipid
    complement. Whether the oligodendrocyte, which must build far more membrane per cell
    than a fibroblast and may have a different CTL2 reserve, is able to make the same
    trade is the open question, and the in vivo animal data suggesting it cannot are
    from developing rather than degenerating tissue. Resolving this changes what a
    biomarker would be and whether substrate repletion should be expected to work.
  attaches_to:
  - pathophysiology#Constrained Kennedy Pathway Phospholipid Synthesis
  - pathophysiology#Membrane Phospholipid Homeostasis Disturbance
  evidence:
  - reference: PMID:33789160
    reference_title: "Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Paradoxically, although Cho transport and CDP-Cho Kennedy pathway were
      diminished, PC remained preserved in the cerebrospinal fluid and skin fibroblasts
      of the affected individuals"
    explanation: States the paradox in the source's own words, and extends the
      preserved-phosphatidylcholine finding from fibroblasts to cerebrospinal fluid.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "diminished choline transport yet the membrane phosphatidylcholine content
      remained unchanged"
    explanation: >-
      Refutes the simple phosphatidylcholine-depletion model in patient fibroblasts:
      the transport defect is present but the expected product depletion is not.
- discussion_id: developmental_vs_maintenance_myelin_failure
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Does the animal myelination-failure phenotype model the human disease, given that
    the models show a developmental hypomyelination while the human entity is a
    childhood-onset progressive degeneration?
  rationale: >-
    The zebrafish and rodent data are the strongest mechanistic support in the entry:
    SLC44A1 is oligodendrocyte-enriched, its loss impairs oligodendroglial maturation
    and myelinogenesis, and citicoline rescues myelination. But the readout in those
    models is developmental myelination, and the citicoline result is framed by its
    authors as a potential therapy for developmental hypomyelination. The human
    phenotype is not congenital hypomyelination; it is childhood-onset progressive
    ataxia, tremor, cognitive decline and optic atrophy on a background of
    leukoencephalopathy and cerebellar atrophy, which reads as failing maintenance of
    established myelin plus neuronal loss. If the human lesion is maintenance rather
    than development, a rescue that works in a developing animal may have no window in
    a child who has already myelinated, and the timing of any substrate trial depends
    on which it is. The mouse oligodendroglial conditional knockout does not settle
    this either. It shows hypomyelination persisting into adulthood, which is at least
    consistent with an ongoing deficit, but the deletion is imposed before myelination
    begins, so a persistent developmental deficit and a maintenance failure are not
    distinguishable in it. The experiment that would separate them is an inducible
    deletion after myelination is complete.
  attaches_to:
  - pathophysiology#Oligodendrocyte Maturation Failure
  - animal_models#Zebrafish
  evidence:
  - reference: PMID:41317319
    reference_title: "SLC44A1 deficiency impedes myelin development in the central nervous system."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "supplementation with citicoline, a natural choline metabolite, restores
      developmental myelination in SLC44A1-deficient animals"
    explanation: >-
      The rescue is reported for developmental myelination, which is the specific
      framing that leaves its relevance to an established, degenerating human
      phenotype open.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features included progressive ataxia, tremor, cognitive decline,
      dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence."
    explanation: >-
      The human phenotype is progressive and childhood-onset rather than congenital,
      which is the side of the mismatch this item documents.
- discussion_id: iron_vulnerability_and_basal_ganglia_signal
  kind: KNOWLEDGE_GAP
  prompt: >-
    Does the iron-handling vulnerability of CTL1-deficient cells explain the
    low-signal globus pallidus and substantia nigra seen on MRI in some affected
    individuals, and does brain iron actually accumulate in this disease?
  rationale: >-
    Two findings sit next to each other in the founding report without being joined.
    In patient fibroblasts, chronic choline treatment protected mutant cells from
    acute iron overload, which says the cells handle an iron challenge worse than
    controls do. Separately, two of the four individuals had low signal intensity in
    the globus pallidus with hyperintense streaking and low signal in the substantia
    nigra on MRI, a pattern that visually resembles neurodegeneration with brain iron
    accumulation. Nothing published connects them. The cellular assay is an acute
    supraphysiological iron challenge in skin fibroblasts, not a measurement of iron
    handling in brain; no quantitative susceptibility mapping, brain iron measurement
    or neuropathological iron stain has been reported in any affected individual; and
    low T2 signal in the basal ganglia has causes other than iron, including calcium
    and manganese. The entry therefore draws the edge from the cellular vulnerability
    to the imaging finding as INDIRECT_UNKNOWN_INTERMEDIATES and records the gap here
    rather than asserting a chain. Resolving it matters twice over: it decides whether
    this entity belongs in the NBIA differential on mechanism as well as on
    appearance, and it decides whether brain iron could serve as a monitoring readout
    for a substrate-repletion trial.
  attaches_to:
  - pathophysiology#Vulnerability to Iron-Mediated Cellular Injury
  - phenotypes#Abnormal Basal Ganglia MRI Signal Intensity
  evidence:
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Choline treatments could restore the membrane lipids, repair cellular
      organelles and protect mutant cells from acute iron overload."
    explanation: >-
      The cellular side of the gap: an iron-handling deficit demonstrated in patient
      fibroblasts, in an acute overload assay rather than in brain tissue.
  - reference: PMID:31855247
    reference_title: "Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "low signal intensity in globus pallidus with hyperintensive streaking
      and low signal intensity in substantia nigra were seen in two individuals"
    explanation: >-
      The imaging side of the gap. The report describes the signal change without
      claiming that iron was demonstrated in patient brain, which is precisely what
      leaves the connection open.
📚

References & Deep Research

References

4
PMID:31855247
Choline transporter-like 1 deficiency causes a new type of childhood-onset neurodegeneration.
No top-level findings curated for this source.
PMID:33789160
Choline transporter-like proteins 1 and 2 are newly identified plasma membrane and mitochondrial ethanolamine transporters.
No top-level findings curated for this source.
PMID:41317319
SLC44A1 deficiency impedes myelin development in the central nervous system.
No top-level findings curated for this source.
PMID:40540401
Choline transporters are required for oligodendrocyte differentiation and myelin sheath formation in mouse postnatal brain.
No top-level findings curated for this source.