Global Developmental Delay, Progressive Ataxia, and Elevated Glutamine

Mendelian MONDO:0032733 Pathograph 8 Show in embeddings browser hereditary disease inborn error of metabolism

An autosomal recessive inborn error of amino acid metabolism caused by an expansion of a GCA short tandem repeat in the 5' untranslated region of GLS, the gene encoding phosphate-activated glutaminase. The expansion reduces GLS messenger RNA transcribed from the expanded allele (probably via repeat-mediated chromatin changes), producing a relative glutaminase deficiency. Because glutaminase catalyzes the hydrolysis of glutamine to glutamate, the deficiency impairs glutamine catabolism and glutamate biosynthesis, yielding accumulation of glutamine. The three originally reported patients presented with early-onset (global) developmental delay, progressive ataxia, and elevated glutamine, with cerebellar atrophy in one. It is allelic to, but clinically distinct from, the severe neonatal-onset glutaminase deficiency (OMIM 618328) caused by biallelic loss-of-function GLS variants, and from the mechanistically opposite de novo gain-of-function (hypermorphic) GLS disorder (p.Ser482Cys) characterized by glutamate excess.

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1
Definitions
1
Inheritance
8
Pathophys.
4
Phenotypes
2
Hypotheses
1
Gaps
8
Pathograph
1
Genes
2
Medical Actions
1
Deep Research
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE
ICIMD (Inherited Metabolic Disorders)
glu gln and asp asn
📘

Definitions

1
Biochemical-plus-genetic diagnosis of GDPAG
GDPAG is suspected in a child with early-onset global developmental delay and progressive ataxia whose plasma amino acids show elevated glutamine with normal glutamate, and is confirmed by demonstrating biallelic GLS lesions. Critically, the causal 5' untranslated region GCA-repeat expansion is noncoding and is missed by standard exome sequencing; it requires genome-level or targeted repeat testing (whole-genome sequencing with a repeat-expansion caller, repeat-primed/flanking PCR).
DIAGNOSTIC_CRITERIA GLS glutaminase deficiency (GCA-repeat-expansion form)
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"Our discovery underscores the importance of careful examination of regions of the genome that are typically excluded from or poorly captured by exome sequencing."
Establishes that the causal noncoding 5'UTR repeat expansion lies in a genomic region poorly captured by exome sequencing, so diagnosis requires genome-level or targeted repeat analysis.
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
Autosomal recessive; affected individuals carry biallelic 5'UTR GCA-repeat expansions in GLS (or an expansion in trans with a loss-of-function variant).
Autosomal recessive inheritance
Show evidence (2 references)
PMID:30970188 SUPPORT Human Clinical
"The expansion was observed in three unrelated patients who presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine."
The biallelic GLS 5'UTR expansion segregates with disease in unrelated GDPAG patients, consistent with autosomal recessive inheritance.
PMID:31603991 SUPPORT Human Clinical
"GLS; GLS; EC 3.5.1.2 n = 9 bi‐allelic, AR"
This review classifies GLS (glutaminase) deficiency as a bi-allelic, autosomal recessive disorder.
◈

Mechanistic Hypotheses

2
Glutamate Deficiency (Loss-of-Function) Model
glutamate_deficiency ALTERNATIVE
Evidence balance 1 support
Because glutaminase produces glutamate — the principal excitatory neurotransmitter and precursor of GABA — from astrocyte-derived glutamine, a relative glutaminase deficiency is proposed to impair neuronal glutamate synthesis and glutamatergic (and downstream GABAergic) neurotransmission, causing the neurodevelopmental and cerebellar phenotype. This was the framing of the original report of glutaminase deficiency as an inborn error of metabolism.
Pathograph links
Impaired Glutamine Catabolism and Glutamine Accumulation -> Impaired Glutamatergic Neurotransmission INDIRECT UNKNOWN INTERMEDIATES Reduced neuronal glutamate synthesis impairs glutamatergic signaling.
Impaired Glutamatergic Neurotransmission -> Cerebellar Dysfunction and Atrophy INDIRECT UNKNOWN INTERMEDIATES Impaired glutamatergic signaling contributes to cerebellar dysfunction.
Impaired Glutamatergic Neurotransmission -> Neurodevelopmental Impairment INDIRECT UNKNOWN INTERMEDIATES Impaired glutamatergic signaling contributes to abnormal neurodevelopment.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"We report an inborn error of metabolism caused by an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
Frames the disorder as a glutaminase (glutamate-producing enzyme) deficiency.
Glutamine Accumulation Neurotoxicity Model
glutamine_neurotoxicity EMERGING
Evidence balance 1 support
An alternative model, supported by more recent clinical and biochemical studies across the glutaminase-deficiency spectrum, holds that the accumulated glutamine itself plays a key role in the neurotoxicity — analogous to the glutamine-mediated CNS injury of hepatic encephalopathy and urea cycle defects — with elevated cerebrospinal-fluid glutamine and urea-cycle-defect-like cystic brain MRI lesions reported at the severe neonatal-encephalopathy end of the glutaminase-deficiency spectrum. The two models are not mutually exclusive.
Pathograph links
Impaired Glutamine Catabolism and Glutamine Accumulation -> Glutamine Neurotoxicity INDIRECT UNKNOWN INTERMEDIATES Accumulated glutamine exerts a direct neurotoxic effect.
Glutamine Neurotoxicity -> Neurodevelopmental Impairment INDIRECT UNKNOWN INTERMEDIATES Glutamine neurotoxicity contributes to CNS injury and abnormal neurodevelopment.
Show evidence (1 reference)
PMID:41865506 SUPPORT Human Clinical
"support a key role for elevated glutamine in the neuropathogenesis of both glutaminase-deficient patients and individuals with hepatic encephalopathy and/or urea cycle defects"
Supports elevated glutamine as a key driver of neuropathogenesis in glutaminase deficiency.
?

Discussions and Knowledge Gaps

1
Should the GLS repeat-expansion form (GDPAG, OMIM 618412) and the severe neonatal-onset GLS glutaminase-deficiency encephalopathy (OMIM 618328) be modeled as one Disease entry with has_subtypes, or kept as two separate entries?
INTERPRETATION RESOLVED gdpag-vs-neonatal-form-lump-split
A lumped model is defensible: recent literature frames glutaminase deficiency as a single disorder with a broad phenotypic spectrum ranging from early-onset global developmental delay to lethal early neonatal encephalopathy (PMID:41865506), and reviews table GLS loss-of-function as one entity. However, the two ends carry distinct OMIM identities (618412 vs 618328) and mechanistically distinct lesions: a noncoding 5' UTR GCA-repeat expansion producing a relative/partial glutaminase deficiency (this entry) versus biallelic coding loss-of-function producing complete deficiency (neonatal form).
Posed by ai4c-reviewer (PR Resolved 2026-07-30T00:00:00Z
Resolution: Curator decision: keep split. This entry is scoped specifically to the repeat-expansion form (MONDO:0032733 / OMIM:618412); the severe neonatal-onset form (OMIM 618328) is to be modeled as a separate Disease entry. Raised by ai4c-reviewer on PR #7138 and adjudicated by the curator.
Show evidence (1 reference)
PMID:41865506 SUPPORT Human Clinical
"Glutaminase deficiency has recently been identified as a novel inherited metabolic disorder with a broad phenotypic spectrum ranging from early-onset global developmental delay to lethal early neonatal encephalopathy"
Documents the spectrum framing that motivates the lump/split question; the curator resolution is to keep the repeat-expansion form as a distinct entry aligned to its own OMIM/MONDO identity.
⚙

Pathophysiology

8
GLS 5'UTR GCA Repeat Expansion
The primary genomic lesion is an expanded GCA short tandem repeat tract in the 5' untranslated region of GLS (the gene encoding glutaminase). This noncoding expansion lies in a region typically excluded from or poorly captured by exome sequencing.
Downstream
Repeat-Mediated Chromatin Silencing of the Expanded GLS Allele The expansion drives repressive chromatin changes at the locus.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
Documents the causal 5'UTR GCA-repeat expansion, the primary genomic lesion.
Repeat-Mediated Chromatin Silencing of the Expanded GLS Allele
The expansion is associated with a relative deficiency of GLS mRNA transcribed from the expanded allele, probably resulting from repeat-mediated chromatin changes upstream of the repeat (rather than promoter DNA hypermethylation).
Downstream
Phosphate-Activated Glutaminase Deficiency Reduced GLS mRNA lowers glutaminase enzyme levels.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"The expansion was associated with a relative deficiency of GLS messenger RNA transcribed from the expanded allele, which probably resulted from repeat-mediated chromatin changes upstream of the GLS repeat."
Documents that the expansion silences the expanded GLS allele via repeat-mediated chromatin changes, reducing GLS mRNA.
Phosphate-Activated Glutaminase Deficiency
Reduced GLS expression produces a relative deficiency of phosphate-activated glutaminase, the mitochondrial enzyme that hydrolyzes glutamine to glutamate and ammonia. This is the primary enzymatic defect of the disorder.
glutaminase activity GO:0004359 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased glutaminase activity (GO:0004359). GO:0004359 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Glutamine Catabolism and Glutamine Accumulation Loss of glutaminase activity blocks hydrolysis of glutamine to glutamate.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"We report an inborn error of metabolism caused by an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
Establishes glutaminase (GLS) deficiency as the inborn error of metabolism underlying the disorder.
Impaired Glutamine Catabolism and Glutamine Accumulation
With glutaminase activity reduced, the hydrolysis of glutamine to glutamate is impaired, so glutamine catabolism falls and glutamine accumulates while glutamate biosynthesis from glutamine is diminished. Elevated glutamine is the biochemical hallmark of the disorder.
Glutamate Deficiency (Loss-of-Function) Model Glutamine Accumulation Neurotoxicity Model
L-glutamine catabolic process GO:0006543 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased L-glutamine catabolic process (GO:0006543). GO:0006543 is a biological process from the Gene Ontology. ↓ DECREASED L-glutamate biosynthetic process GO:0097054 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased L-glutamate biosynthetic process (GO:0097054). GO:0097054 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Glutamatergic Neurotransmission Reduced neuronal glutamate synthesis impairs glutamatergic signaling. Glutamate Deficiency (Loss-of-Function) Model
Glutamine Neurotoxicity Accumulated glutamine exerts a direct neurotoxic effect. Glutamine Accumulation Neurotoxicity Model
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
Documents elevated glutamine, the direct biochemical consequence of impaired glutaminase-mediated glutamine catabolism.
Glutamine Neurotoxicity
An alternative neuropathogenic mechanism holds that the accumulated glutamine is itself neurotoxic, paralleling the glutamine-mediated neurotoxicity of hepatic encephalopathy and urea cycle defects (in which glutamine accumulation drives astrocytic osmotic stress and CNS injury). Patients at the severe neonatal-encephalopathy end of the glutaminase-deficiency spectrum show elevated cerebrospinal-fluid glutamine and brain MRI cystic lesions resembling those of urea cycle defects, supporting a key role for elevated glutamine in the neuropathogenesis.
Glutamine Accumulation Neurotoxicity Model
astrocyte CL:0000127 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves astrocyte (CL:0000127). CL:0000127 is a cell type from the Cell Ontology. neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Neurodevelopmental Impairment Glutamine neurotoxicity contributes to CNS injury and abnormal neurodevelopment. Glutamine Accumulation Neurotoxicity Model
Show evidence (1 reference)
PMID:41865506 SUPPORT Human Clinical
"support a key role for elevated glutamine in the neuropathogenesis of both glutaminase-deficient patients and individuals with hepatic encephalopathy and/or urea cycle defects"
Directly supports glutamine accumulation, rather than glutamate deficiency alone, as a driver of the neuropathology in glutaminase deficiency.
Impaired Glutamatergic Neurotransmission
Neuronal glutaminase supplies glutamate, the principal excitatory neurotransmitter of the central nervous system and precursor of GABA, from astrocyte-derived glutamine via the glutamate-glutamine cycle. A relative glutaminase deficiency is expected to impair neuronal glutamate production and glutamatergic neurotransmission, a plausible mechanism linking the metabolic defect to the neurodevelopmental and cerebellar phenotype.
Glutamate Deficiency (Loss-of-Function) Model
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology. astrocyte CL:0000127 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves astrocyte (CL:0000127). CL:0000127 is a cell type from the Cell Ontology.
glutamate secretion, neurotransmission GO:0061535 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased glutamate secretion, neurotransmission (GO:0061535). GO:0061535 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Cerebellar Dysfunction and Atrophy Impaired glutamatergic signaling contributes to cerebellar dysfunction. Glutamate Deficiency (Loss-of-Function) Model
Neurodevelopmental Impairment Impaired glutamatergic signaling contributes to abnormal neurodevelopment. Glutamate Deficiency (Loss-of-Function) Model
Cerebellar Dysfunction and Atrophy
Cerebellar involvement produces progressive ataxia; one of the three originally reported patients had cerebellar atrophy on neuroimaging.
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.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"In addition to ataxia, one patient also showed cerebellar atrophy."
Documents cerebellar atrophy accompanying the ataxia in the reported patients.
Neurodevelopmental Impairment
Early-onset impairment of overall development manifesting as global developmental delay.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development"
Documents the early-onset global developmental delay.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Global Developmental Delay, Progressive Ataxia, and Elevated Glutamine 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

4
Metabolism 1
Hyperglutaminemia HP:0003217 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperglutaminemia (HP:0003217). HP:0003217 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
All three reported patients had elevated levels of glutamine.
Nervous System 3
Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
All three reported patients presented with early-onset delay in overall development.
Progressive cerebellar ataxia HP:0002073 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Progressive cerebellar ataxia (HP:0002073), qualified as course progressive. HP:0002073 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
All three reported patients presented with progressive ataxia.
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:30970188 SUPPORT Human Clinical
"In addition to ataxia, one patient also showed cerebellar atrophy."
Cerebellar atrophy was documented in one of the three patients.
🧬

Genetic Associations

1
GLS
Gene: GLS hgnc:4331 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is GLS (hgnc:4331). hgnc:4331 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (3 references)
PMID:30970188 SUPPORT Human Clinical
"an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
Identifies the causal GCA-repeat expansion in the 5'UTR of GLS.
PMID:39699045 SUPPORT Human Clinical
"expanded GCA repeats in the GLS gene can cause glutaminase deficiency with ataxia phenotype"
Confirms expanded GLS GCA repeats cause glutaminase deficiency with an ataxia phenotype; the same study established the non-expanded reference range (average ~11 repeats, range 6-33).
PMID:41865506 SUPPORT Human Clinical
"Glutaminase deficiency has recently been identified as a novel inherited metabolic disorder with a broad phenotypic spectrum ranging from early-onset global developmental delay to lethal early neonatal encephalopathy"
Establishes that GLS glutaminase deficiency spans a phenotypic spectrum, with the early-onset global-developmental-delay-with-ataxia form (this entity, MONDO:0032733) at the milder end and a lethal neonatal encephalopathy (biallelic loss-of-function/complete-deficiency alleles) at the severe end.
💊

Medical Actions

2
Supportive and Symptomatic Care
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Management is supportive and symptomatic; no disease-modifying therapy is established. Care is directed at developmental support and management of ataxia.
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. Ontology label: Genetic Counseling NCIT:C15240
Genetic counseling for this autosomal recessive disorder, including recurrence-risk counseling. Diagnosis requires detection of the noncoding 5'UTR GCA-repeat expansion, which is missed by standard exome sequencing.
🔬

Biochemical Markers

2
Plasma glutamine (INCREASED)
Context: Plasma glutamine is elevated, reflecting impaired glutaminase-mediated conversion of glutamine to glutamate. It is the diagnostic biochemical marker of the disorder.
Show evidence (1 reference)
PMID:30970188 SUPPORT Human Clinical
"presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
Elevated glutamine is the biochemical readout of the glutaminase defect.
Plasma glutamate (NORMAL)
Context: In contrast to the elevated glutamine, plasma glutamate is characteristically unaltered (normal). This dissociation — high glutamine with normal plasma glutamate — is a useful biochemical clue and reflects the fact that plasma glutamate is buffered by dietary intake and other glutamate-metabolizing enzymes even when glutaminase is deficient (a local brain glutamate deficit is not excluded).
Show evidence (1 reference)
PMID:31603991 SUPPORT Human Clinical
"Glutamate plasma levels were unaltered."
Documents that plasma glutamate is unaltered in the patients with the GLS tandem-repeat expansion, distinguishing the biochemical profile from a simple global glutamate deficit.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Ultra-rare. First reported in three unrelated patients (2019); expanded GLS GCA repeats were not detected in a screen of 349 undiagnosed ataxia patients, 1505 healthy controls, and 1236 SCA3 patients in mainland China, indicating the expansion is rare in that population.
Show evidence (1 reference)
PMID:39699045 SUPPORT Human Clinical
"Abnormal expansions of GLS GCA repeats are rare in the Chinese population."
Documents the rarity of pathogenic GLS GCA-repeat expansions.
{ }

Source YAML

click to show 
name: Global Developmental Delay, Progressive Ataxia, and Elevated Glutamine
creation_date: "2026-07-30T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: global developmental delay, progressive ataxia, and elevated glutamine
  term:
    id: MONDO:0032733
    label: global developmental delay, progressive ataxia, and elevated glutamine
parents:
- hereditary disease
- inborn error of metabolism
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  icimd_category:
  - classification_value: glu_gln_and_asp_asn
    notes: >-
      ICIMD (Ferreira et al. 2021, PMID:33340416): group "Disorders of
      glutamate/glutamine and aspartate/asparagine metabolism" under category
      "Disorders of amino acid metabolism". GLS glutaminase deficiency is a
      disorder of glutamine catabolism.
description: >
  An autosomal recessive inborn error of amino acid metabolism caused by an
  expansion of a GCA short tandem repeat in the 5' untranslated region of GLS,
  the gene encoding phosphate-activated glutaminase. The expansion reduces GLS
  messenger RNA transcribed from the expanded allele (probably via
  repeat-mediated chromatin changes), producing a relative glutaminase
  deficiency. Because glutaminase catalyzes the hydrolysis of glutamine to
  glutamate, the deficiency impairs glutamine catabolism and glutamate
  biosynthesis, yielding accumulation of glutamine. The three originally
  reported patients presented with early-onset (global) developmental delay,
  progressive ataxia, and elevated glutamine, with cerebellar atrophy in one.
  It is allelic to, but clinically distinct from, the severe neonatal-onset
  glutaminase deficiency (OMIM 618328) caused by biallelic loss-of-function GLS
  variants, and from the mechanistically opposite de novo gain-of-function
  (hypermorphic) GLS disorder (p.Ser482Cys) characterized by glutamate excess.

pathophysiology:
- name: GLS 5'UTR GCA Repeat Expansion
  biological_scale: MOLECULAR
  description: >
    The primary genomic lesion is an expanded GCA short tandem repeat tract in
    the 5' untranslated region of GLS (the gene encoding glutaminase). This
    noncoding expansion lies in a region typically excluded from or poorly
    captured by exome sequencing.
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
    explanation: >
      Documents the causal 5'UTR GCA-repeat expansion, the primary genomic
      lesion.
  downstream:
  - target: Repeat-Mediated Chromatin Silencing of the Expanded GLS Allele
    description: The expansion drives repressive chromatin changes at the locus.
    causal_link_type: DIRECT

- name: Repeat-Mediated Chromatin Silencing of the Expanded GLS Allele
  biological_scale: MOLECULAR
  description: >
    The expansion is associated with a relative deficiency of GLS mRNA
    transcribed from the expanded allele, probably resulting from
    repeat-mediated chromatin changes upstream of the repeat (rather than
    promoter DNA hypermethylation).
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The expansion was associated with a relative deficiency of GLS messenger RNA transcribed from the expanded allele, which probably resulted from repeat-mediated chromatin changes upstream of the GLS repeat."
    explanation: >
      Documents that the expansion silences the expanded GLS allele via
      repeat-mediated chromatin changes, reducing GLS mRNA.
  downstream:
  - target: Phosphate-Activated Glutaminase Deficiency
    description: Reduced GLS mRNA lowers glutaminase enzyme levels.
    causal_link_type: DIRECT

- name: Phosphate-Activated Glutaminase Deficiency
  biological_scale: MOLECULAR
  description: >
    Reduced GLS expression produces a relative deficiency of phosphate-activated
    glutaminase, the mitochondrial enzyme that hydrolyzes glutamine to glutamate
    and ammonia. This is the primary enzymatic defect of the disorder.
  molecular_functions:
  - preferred_term: glutaminase activity
    term:
      id: GO:0004359
      label: glutaminase activity
    modifier: DECREASED
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report an inborn error of metabolism caused by an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
    explanation: >
      Establishes glutaminase (GLS) deficiency as the inborn error of metabolism
      underlying the disorder.
  downstream:
  - target: Impaired Glutamine Catabolism and Glutamine Accumulation
    description: Loss of glutaminase activity blocks hydrolysis of glutamine to glutamate.
    causal_link_type: DIRECT

- name: Impaired Glutamine Catabolism and Glutamine Accumulation
  biological_scale: MOLECULAR
  description: >
    With glutaminase activity reduced, the hydrolysis of glutamine to glutamate
    is impaired, so glutamine catabolism falls and glutamine accumulates while
    glutamate biosynthesis from glutamine is diminished. Elevated glutamine is
    the biochemical hallmark of the disorder.
  biological_processes:
  - preferred_term: L-glutamine catabolic process
    term:
      id: GO:0006543
      label: L-glutamine catabolic process
    modifier: DECREASED
  - preferred_term: L-glutamate biosynthetic process
    term:
      id: GO:0097054
      label: L-glutamate biosynthetic process
    modifier: DECREASED
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
    explanation: >
      Documents elevated glutamine, the direct biochemical consequence of
      impaired glutaminase-mediated glutamine catabolism.
  downstream:
  - target: Impaired Glutamatergic Neurotransmission
    description: Reduced neuronal glutamate synthesis impairs glutamatergic signaling.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - glutamate_deficiency
  - target: Glutamine Neurotoxicity
    description: Accumulated glutamine exerts a direct neurotoxic effect.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - glutamine_neurotoxicity

- name: Glutamine Neurotoxicity
  biological_scale: CELLULAR
  description: >
    An alternative neuropathogenic mechanism holds
    that the accumulated glutamine is itself neurotoxic, paralleling the
    glutamine-mediated neurotoxicity of hepatic encephalopathy and urea cycle
    defects (in which glutamine accumulation drives astrocytic osmotic stress
    and CNS injury). Patients at the severe neonatal-encephalopathy end of the
    glutaminase-deficiency spectrum show elevated cerebrospinal-fluid glutamine
    and brain MRI cystic lesions resembling those of urea cycle defects,
    supporting a key role for elevated glutamine in the neuropathogenesis.
  cell_types:
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:41865506
    reference_title: "Glutaminase deficiency provides insight to the role of glutamine accumulation and neurotoxicity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "support a key role for elevated glutamine in the neuropathogenesis of both glutaminase-deficient patients and individuals with hepatic encephalopathy and/or urea cycle defects"
    explanation: >
      Directly supports glutamine accumulation, rather than glutamate
      deficiency alone, as a driver of the neuropathology in glutaminase
      deficiency.
  downstream:
  - target: Neurodevelopmental Impairment
    description: Glutamine neurotoxicity contributes to CNS injury and abnormal neurodevelopment.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - glutamine_neurotoxicity

- name: Impaired Glutamatergic Neurotransmission
  biological_scale: CELLULAR
  description: >
    Neuronal glutaminase supplies glutamate, the principal excitatory
    neurotransmitter of the central nervous system and precursor of GABA, from
    astrocyte-derived glutamine via the glutamate-glutamine cycle. A relative
    glutaminase deficiency is expected to impair neuronal glutamate production
    and glutamatergic neurotransmission, a plausible mechanism linking the
    metabolic defect to the neurodevelopmental and cerebellar phenotype.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: glutamate secretion, neurotransmission
    term:
      id: GO:0061535
      label: glutamate secretion, neurotransmission
    modifier: DECREASED
  downstream:
  - target: Cerebellar Dysfunction and Atrophy
    description: Impaired glutamatergic signaling contributes to cerebellar dysfunction.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - glutamate_deficiency
  - target: Neurodevelopmental Impairment
    description: Impaired glutamatergic signaling contributes to abnormal neurodevelopment.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - glutamate_deficiency

- name: Cerebellar Dysfunction and Atrophy
  biological_scale: TISSUE
  description: >
    Cerebellar involvement produces progressive ataxia; one of the three
    originally reported patients had cerebellar atrophy on neuroimaging.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition to ataxia, one patient also showed cerebellar atrophy."
    explanation: >
      Documents cerebellar atrophy accompanying the ataxia in the reported
      patients.

- name: Neurodevelopmental Impairment
  biological_scale: ORGANISM
  description: >
    Early-onset impairment of overall development manifesting as global
    developmental delay.
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development"
    explanation: >
      Documents the early-onset global developmental delay.

phenotypes:
- name: Global developmental delay
  category: Neurologic
  description: >
    Early-onset delay in overall development, present in all three originally
    reported patients.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
    explanation: >
      All three reported patients presented with early-onset delay in overall
      development.

- name: Progressive cerebellar ataxia
  category: Neurologic
  description: >
    Progressive ataxia was a presenting feature in all three originally reported
    patients.
  phenotype_term:
    preferred_term: Progressive cerebellar ataxia
    term:
      id: HP:0002073
      label: Progressive cerebellar ataxia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
    explanation: >
      All three reported patients presented with progressive ataxia.

- name: Cerebellar atrophy
  category: Neurologic
  description: >
    Cerebellar atrophy on neuroimaging was reported in one of the three
    originally described patients.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition to ataxia, one patient also showed cerebellar atrophy."
    explanation: >
      Cerebellar atrophy was documented in one of the three patients.

- name: Hyperglutaminemia
  category: Metabolic
  description: >
    Elevated plasma glutamine levels, the biochemical hallmark of the disorder,
    present in all three originally reported patients.
  phenotype_term:
    preferred_term: Hyperglutaminemia
    term:
      id: HP:0003217
      label: Hyperglutaminemia
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
    explanation: >
      All three reported patients had elevated levels of glutamine.

biochemical:
- name: Plasma glutamine
  presence: INCREASED
  context: >
    Plasma glutamine is elevated, reflecting impaired glutaminase-mediated
    conversion of glutamine to glutamate. It is the diagnostic biochemical
    marker of the disorder.
  biomarker_term:
    preferred_term: L-glutamine
    term:
      id: CHEBI:28300
      label: glutamine
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine"
    explanation: >
      Elevated glutamine is the biochemical readout of the glutaminase defect.

- name: Plasma glutamate
  presence: NORMAL
  context: >
    In contrast to the elevated glutamine, plasma glutamate is characteristically
    unaltered (normal). This dissociation — high glutamine with normal plasma
    glutamate — is a useful biochemical clue and reflects the fact that plasma
    glutamate is buffered by dietary intake and other glutamate-metabolizing
    enzymes even when glutaminase is deficient (a local brain glutamate deficit
    is not excluded).
  biomarker_term:
    preferred_term: glutamate(1-)
    term:
      id: CHEBI:29985
      label: L-glutamate(1-)
  evidence:
  - reference: PMID:31603991
    reference_title: "Inborn errors of enzymes in glutamate metabolism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glutamate plasma levels were unaltered."
    explanation: >
      Documents that plasma glutamate is unaltered in the patients with the GLS
      tandem-repeat expansion, distinguishing the biochemical profile from a
      simple global glutamate deficit.

definitions:
- name: Biochemical-plus-genetic diagnosis of GDPAG
  definition_type: DIAGNOSTIC_CRITERIA
  description: >-
    GDPAG is suspected in a child with early-onset global developmental delay
    and progressive ataxia whose plasma amino acids show elevated glutamine with
    normal glutamate, and is confirmed by demonstrating biallelic GLS lesions.
    Critically, the causal 5' untranslated region GCA-repeat expansion is
    noncoding and is missed by standard exome sequencing; it requires
    genome-level or targeted repeat testing (whole-genome sequencing with a
    repeat-expansion caller, repeat-primed/flanking PCR).
  scope: GLS glutaminase deficiency (GCA-repeat-expansion form)
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our discovery underscores the importance of careful examination of regions of the genome that are typically excluded from or poorly captured by exome sequencing."
    explanation: >
      Establishes that the causal noncoding 5'UTR repeat expansion lies in a
      genomic region poorly captured by exome sequencing, so diagnosis requires
      genome-level or targeted repeat analysis.

genetic:
- name: GLS
  gene_term:
    preferred_term: GLS
    term:
      id: hgnc:4331
      label: GLS
  relationship_type: CAUSATIVE
  notes: >
    The disorder is caused by biallelic GLS lesions involving a GCA short tandem
    repeat expansion in the 5' untranslated region of GLS, which silences the
    expanded allele and reduces glutaminase expression. Reported patients are
    either homozygous for the expansion or compound heterozygous for an
    expansion in trans with a coding loss-of-function/missense allele. GLS
    encodes phosphate-activated glutaminase (kidney-type glutaminase).
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
    explanation: >
      Identifies the causal GCA-repeat expansion in the 5'UTR of GLS.
  - reference: PMID:39699045
    reference_title: "Genetic Analysis of GCA Repeats in the GLS Gene: Implications for Undiagnosed Ataxia and Spinocerebellar Ataxia 3 in Mainland China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "expanded GCA repeats in the GLS gene can cause glutaminase deficiency with ataxia phenotype"
    explanation: >
      Confirms expanded GLS GCA repeats cause glutaminase deficiency with an
      ataxia phenotype; the same study established the non-expanded reference
      range (average ~11 repeats, range 6-33).
  - reference: PMID:41865506
    reference_title: "Glutaminase deficiency provides insight to the role of glutamine accumulation and neurotoxicity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glutaminase deficiency has recently been identified as a novel inherited metabolic disorder with a broad phenotypic spectrum ranging from early-onset global developmental delay to lethal early neonatal encephalopathy"
    explanation: >
      Establishes that GLS glutaminase deficiency spans a phenotypic spectrum,
      with the early-onset global-developmental-delay-with-ataxia form (this
      entity, MONDO:0032733) at the milder end and a lethal neonatal
      encephalopathy (biallelic loss-of-function/complete-deficiency alleles) at
      the severe end.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >
    Ultra-rare. First reported in three unrelated patients (2019); expanded GLS
    GCA repeats were not detected in a screen of 349 undiagnosed ataxia patients,
    1505 healthy controls, and 1236 SCA3 patients in mainland China, indicating
    the expansion is rare in that population.
  evidence:
  - reference: PMID:39699045
    reference_title: "Genetic Analysis of GCA Repeats in the GLS Gene: Implications for Undiagnosed Ataxia and Spinocerebellar Ataxia 3 in Mainland China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Abnormal expansions of GLS GCA repeats are rare in the Chinese population."
    explanation: >
      Documents the rarity of pathogenic GLS GCA-repeat expansions.

inheritance:
- name: Autosomal recessive inheritance
  description: >
    Autosomal recessive; affected individuals carry biallelic 5'UTR GCA-repeat
    expansions in GLS (or an expansion in trans with a loss-of-function variant).
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The expansion was observed in three unrelated patients who presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine."
    explanation: >
      The biallelic GLS 5'UTR expansion segregates with disease in unrelated
      GDPAG patients, consistent with autosomal recessive inheritance.
  - reference: PMID:31603991
    reference_title: "Inborn errors of enzymes in glutamate metabolism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GLS; GLS; EC 3.5.1.2 n = 9 bi‐allelic, AR"
    explanation: >
      This review classifies GLS (glutaminase) deficiency as a bi-allelic,
      autosomal recessive disorder.

treatments:
- name: Supportive and Symptomatic Care
  description: >
    Management is supportive and symptomatic; no disease-modifying therapy is
    established. Care is directed at developmental support and management of
    ataxia.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care

- name: Genetic Counseling
  description: >
    Genetic counseling for this autosomal recessive disorder, including
    recurrence-risk counseling. Diagnosis requires detection of the noncoding
    5'UTR GCA-repeat expansion, which is missed by standard exome sequencing.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling

mechanistic_hypotheses:
- hypothesis_group_id: glutamate_deficiency
  hypothesis_label: Glutamate Deficiency (Loss-of-Function) Model
  status: ALTERNATIVE
  description: >
    Because glutaminase produces glutamate — the principal excitatory
    neurotransmitter and precursor of GABA — from astrocyte-derived glutamine,
    a relative glutaminase deficiency is proposed to impair neuronal glutamate
    synthesis and glutamatergic (and downstream GABAergic) neurotransmission,
    causing the neurodevelopmental and cerebellar phenotype. This was the
    framing of the original report of glutaminase deficiency as an inborn error
    of metabolism.
  evidence:
  - reference: PMID:30970188
    reference_title: "Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report an inborn error of metabolism caused by an expansion of a GCA-repeat tract in the 5' untranslated region of the gene encoding glutaminase (GLS)"
    explanation: >
      Frames the disorder as a glutaminase (glutamate-producing enzyme)
      deficiency.
- hypothesis_group_id: glutamine_neurotoxicity
  hypothesis_label: Glutamine Accumulation Neurotoxicity Model
  status: EMERGING
  description: >
    An alternative model, supported by more recent clinical and biochemical
    studies across the glutaminase-deficiency spectrum, holds that the
    accumulated glutamine itself plays a key role in the neurotoxicity —
    analogous to the glutamine-mediated CNS injury of hepatic encephalopathy and
    urea cycle defects — with elevated cerebrospinal-fluid glutamine and
    urea-cycle-defect-like cystic brain MRI lesions reported at the severe
    neonatal-encephalopathy end of the glutaminase-deficiency spectrum. The two
    models are not mutually exclusive.
  evidence:
  - reference: PMID:41865506
    reference_title: "Glutaminase deficiency provides insight to the role of glutamine accumulation and neurotoxicity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "support a key role for elevated glutamine in the neuropathogenesis of both glutaminase-deficient patients and individuals with hepatic encephalopathy and/or urea cycle defects"
    explanation: >
      Supports elevated glutamine as a key driver of neuropathogenesis in
      glutaminase deficiency.

discussions:
- discussion_id: gdpag-vs-neonatal-form-lump-split
  kind: INTERPRETATION
  status: RESOLVED
  prompt: >-
    Should the GLS repeat-expansion form (GDPAG, OMIM 618412) and the severe
    neonatal-onset GLS glutaminase-deficiency encephalopathy (OMIM 618328) be
    modeled as one Disease entry with has_subtypes, or kept as two separate
    entries?
  rationale: >-
    A lumped model is defensible: recent literature frames glutaminase
    deficiency as a single disorder with a broad phenotypic spectrum ranging
    from early-onset global developmental delay to lethal early neonatal
    encephalopathy (PMID:41865506), and reviews table GLS loss-of-function as one
    entity. However, the two ends carry distinct OMIM identities (618412 vs
    618328) and mechanistically distinct lesions: a noncoding 5' UTR GCA-repeat
    expansion producing a relative/partial glutaminase deficiency (this entry)
    versus biallelic coding loss-of-function producing complete deficiency
    (neonatal form).
  resolution_note: >-
    Curator decision: keep split. This entry is scoped specifically to the
    repeat-expansion form (MONDO:0032733 / OMIM:618412); the severe
    neonatal-onset form (OMIM 618328) is to be modeled as a separate Disease
    entry. Raised by ai4c-reviewer on PR #7138 and adjudicated by the curator.
  posed_by: ai4c-reviewer (PR #7138); resolved by curator
  resolved_date: "2026-07-30T00:00:00Z"
  evidence:
  - reference: PMID:41865506
    reference_title: "Glutaminase deficiency provides insight to the role of glutamine accumulation and neurotoxicity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glutaminase deficiency has recently been identified as a novel inherited metabolic disorder with a broad phenotypic spectrum ranging from early-onset global developmental delay to lethal early neonatal encephalopathy"
    explanation: >-
      Documents the spectrum framing that motivates the lump/split question; the
      curator resolution is to keep the repeat-expansion form as a distinct entry
      aligned to its own OMIM/MONDO identity.
📚

References & Deep Research

Deep Research

1
Falcon ▸
Disease Characteristics Research Template
Edison Scientific Literature 13 citations 2026-07-30T15:41:44.883734

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

  • Disease Name: Global Developmental Delay, Progressive Ataxia, and Elevated Glutamine
  • MONDO ID: (if available)
  • Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Global Developmental Delay, Progressive Ataxia, and Elevated Glutamine covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

  • What is the disease? Provide a concise overview.
  • What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
  • What are the common synonyms and alternative names?
  • Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

  • Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
  • Risk Factors:

    Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases

  • Genetic risk factors (causal variants, susceptibility loci, modifier genes)
  • Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
  • Protective Factors:

    Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases

  • Genetic protective factors (protective variants, modifier alleles)
  • Environmental protective factors (diet, lifestyle, exposures that reduce risk)
  • Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

    Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

  • Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

    Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene

  • Pathogenic Variants:
  • Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
  • Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
  • Variant type/class (missense, frameshift, nonsense, splice-site, structural)
  • Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
  • Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
  • Functional consequences (loss of function, gain of function, dominant negative)
  • Modifier Genes: Genes that modify disease severity or expression
  • Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

    Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth

  • Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

    Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

  • Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

    Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases

  • Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

    Search first: CDC databases, WHO, PubMed, NHANES

  • Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

    Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

  • Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

    Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc

  • Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

    Search first: Gene Ontology (GO), Reactome, KEGG, PubMed

  • Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

    Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold

  • Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

    Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA

  • Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

    Search first: ImmPort, Immunome Database, IEDB, Gene Ontology

  • Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

    Search first: PubMed, Gene Ontology, Reactome

  • Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

    Search first: BRENDA, UniProt, KEGG, OMIM, PubMed

  • Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

    Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth

  • Molecular Profiling (if available):
  • Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
  • Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
  • Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
  • Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
  • Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
  • Advanced Technologies (if applicable):
  • Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
  • Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
  • Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
  • Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

  • Organ Level:
  • Primary organs directly affected
  • Secondary organ involvement (complications, secondary effects)
  • Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

    Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT

  • Tissue and Cell Level:
  • Specific tissue types affected (epithelial, connective, muscle, nervous)
  • Specific cell populations targeted (with Cell Ontology terms)

    Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB

  • Subcellular Level:
  • Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

    Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas

  • Localization:
  • Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
  • Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

  • Onset:
  • Typical age of onset (congenital, pediatric, adult, geriatric)
  • Onset pattern (acute, subacute, chronic, insidious)

    Search first: OMIM, Orphanet, HPO, PubMed

  • Progression:
  • Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
  • Progression rate (rapid, slow, variable)
  • Disease course pattern (episodic, relapsing-remitting, progressive, stable)
  • Disease duration (self-limited, chronic lifelong)

    Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM

  • Patterns:
  • Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
  • Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

  • Epidemiology:
  • Prevalence (cases per 100,000 at given time)
  • Incidence (new cases per 100,000 per year)

    Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries

  • For Genetic Etiology:
  • Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
  • Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
  • Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
  • Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
  • Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
  • Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
  • Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
  • Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
  • Population Demographics:
  • Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
  • Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
  • Geographic distribution of specific variants
  • Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
  • Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

  • Clinical Tests:
  • Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
  • Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
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  • Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
  • Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
  • Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
  • Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
  • Genetic Testing:

    Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen

  • Overview of recommended genetic testing approach
  • Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
  • Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
  • Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
  • Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
  • Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
  • Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
  • FISH > Search first: ClinVar, cytogenetics databases, PubMed
  • Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
  • Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
  • Omics-Based Diagnostics (if applicable):
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  • Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
  • Clinical Criteria:
  • Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
  • Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
  • Screening:
  • Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

  • Survival and Mortality:
  • Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
  • Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
  • Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
  • Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
  • Morbidity and Function:
  • Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
  • Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
  • Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
  • Disease Course:
  • Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
  • Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
  • Prediction:
  • Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
  • Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

  • Pharmacotherapy:
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  • Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
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  • Surgical and Interventional:
  • Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
  • Supportive and Rehabilitative:
  • Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
  • Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
  • Experimental:
  • Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
  • Treatment Outcomes:
  • Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
  • Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
  • Treatment Strategy:
  • Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
  • Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
  • Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.

13. Prevention

  • Prevention Levels:
  • Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
  • Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
  • Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
  • Immunization: Vaccine strategies (if applicable)

    Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database

  • Screening and Early Detection:
  • Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
  • Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
  • Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
  • Behavioral Interventions: Lifestyle modifications to reduce risk

    Search first: CDC, WHO, behavioral intervention databases, Cochrane Library

  • Counseling: Genetic counseling (risk assessment, family planning guidance)

    Search first: NSGC resources, ACMG guidelines, GeneReviews

  • Public Health:
  • Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
  • Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
  • Prophylaxis: Preventive medications or procedures

    Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

  • Taxonomy: Species affected (with NCBI Taxon identifiers)

    Search first: NCBI Taxonomy

  • Breed: Specific breeds affected (with VBO identifiers if applicable)

    Search first: VBO (Vertebrate Breed Ontology)

  • Gene: Orthologous genes in other species (with NCBI Gene IDs)

    Search first: NCBI Gene

  • Natural Disease:
  • Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
  • Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
  • Comparative Biology:
  • Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
  • Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
  • Transmission (if applicable):
  • Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
  • Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

  • Model Types:
  • Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
  • Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
  • Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
  • Genetic Models:
  • Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
  • Model Characteristics:
  • Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
  • Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
  • Applications:
  • Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
  • Resources:
  • Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

  • Cite primary literature (PMID preferred) for all mechanistic and clinical claims
  • Prioritize recent reviews and landmark papers
  • Include direct quotes from abstracts where possible to support key statements
  • Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Global developmental delay, progressive ataxia, and elevated glutamine (GDPAG)

Executive summary

GDPAG is an ultra-rare autosomal-recessive inborn error of glutamate–glutamine metabolism caused by biallelic loss of GLS, the gene encoding mitochondrial kidney-type glutaminase. Its defining triad is early global developmental delay, progressive ataxia, and elevated plasma glutamine with reportedly normal plasma glutamate. The best-characterized molecular cause is a large GCA repeat expansion in the GLS 5′ untranslated region (5′UTR), either homozygous or in trans with a damaging coding allele. The expansion creates repressive chromatin and reduces GLS transcription rather than causing promoter DNA hypermethylation. Published disease-specific evidence remains exceptionally small—principally three unrelated probands—so prevalence, complete phenotypic frequencies, prognosis, and treatment efficacy cannot yet be estimated reliably. (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78, richmond2020expandingtheutility pages 78-83)

domain established finding evidence type/sample confidence or limitation
Disease identity Global developmental delay, progressive ataxia, and elevated glutamine corresponds to GDPAG; OMIM 618412 is explicitly linked in retrieved literature, and Open Targets maps the disease to EFO_0010257 with GLS as the associated target (shu2023thepowerof pages 7-8, OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine) Disease database / review context High for OMIM and EFO mapping; MONDO and other identifiers were not established from retrieved evidence
Gene and inheritance Causal gene is GLS (glutaminase); the disorder is autosomal recessive, with biallelic pathogenic alleles including coding variants and/or 5′UTR GCA repeat expansions (shu2023thepowerof pages 7-8, richmond2020expandingtheutility pages 72-78) Human genetic evidence from 3 unrelated probands/families High for GLS and AR inheritance
Case count Three unrelated affected index cases/families were reported for the GLS 5′UTR GCA-repeat form of GDPAG (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78) Human case series Moderate; retrieved text summarizes the study but does not provide full demographic detail
Genotype: Family 1 Compound heterozygous: paternally inherited c.938C>T (p.Pro313Leu) plus maternally inherited 5′UTR GCA repeat expansion; expansion estimated as >90 by ExpansionHunter, rising to 246 with off-target reads; repeat PCR showed a major expansion product of ~680 repeats (richmond2020expandingtheutility pages 72-78) Human molecular genetics in 1 proband/family Moderate; different assays yielded different size estimates, reflecting technical uncertainty for large repeats
Genotype: Family 2 Homozygous 5′UTR GCA repeat expansion alleles inherited from both parents; repeat PCR showed a major expansion product of ~900 repeats (richmond2020expandingtheutility pages 72-78) Human molecular genetics in 1 proband/family Moderate; exact allele-by-allele repeat lengths were not fully resolved
Genotype: Family 3 Compound heterozygous: maternally inherited c.923dupA (p.Tyr308*) plus paternally inherited 5′UTR GCA repeat expansion; repeat PCR showed a major expansion product of ~1500 repeats (richmond2020expandingtheutility pages 72-78) Human molecular genetics in 1 proband/family Moderate; expansion size is approximate
Population repeat data In 8,295 genomes, the GLS GCA repeat had median size 14 repeats, bimodal peaks at 8 and 16; 1 person was heterozygous for an allele with >90 repeats, implying allele frequency 6.03×10^-5 for such large expanded alleles (richmond2020expandingtheutility pages 72-78) Population genome screening Moderate; based on short-read genome analysis at a difficult repeat locus
Core phenotype The GLS repeat-expansion phenotype was reported as early-onset/global developmental delay, progressive ataxia, and elevated plasma glutamine; plasma glutamate was unaltered (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78) Human clinical/biochemical evidence High for these core features; many additional phenotype details were not available in retrieved text
Biochemical marker Elevated plasma glutamine with normal plasma glutamate is the main reported disease biomarker; biochemical and flux assays supported glutaminase deficiency in patient cells (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78) Human plasma biochemistry plus fibroblast/PBM functional assays High for qualitative direction; quantitative metabolite values were not available
Enzyme deficiency Patient fibroblasts and peripheral-blood mononuclear cells showed reduced GLS activity and decreased GLS protein/expression; residual activity was present, which was proposed to explain a milder phenotype than complete ablation (richmond2020expandingtheutility pages 72-78, richmond2020expandingtheutility pages 78-83) Human patient-derived cells High for reduced activity/expression; exact activity values not extracted
Molecular mechanism The 5′UTR GCA repeat expansion did not show increased DNA methylation, but was associated with reduced H3 acetylation and H3K4me3 and increased H3K9me3, consistent with repressive chromatin and decreased GLS transcription (richmond2020expandingtheutility pages 78-83) Patient fibroblast chromatin studies High for chromatin-silencing mechanism in tested cells
Diagnostic methods Detection required methods beyond exome sequencing: singleton WGS/manual inspection, ExpansionHunter, triplet repeat–primed PCR, repeat-flanking PCR/agarose sizing, Sanger sequencing for coding variants/non-expanded alleles, plus qPCR/cDNA allelic expression and enzyme assays (richmond2020expandingtheutility pages 72-78, shu2023thepowerof pages 7-8) Human diagnostic workflow evidence High that standard ES can miss this lesion; exact clinical sensitivity/specificity not available
Distinction from other GLS disorders Retrieved literature distinguishes GDPAG from a de novo hypermorphic GLS disorder and from other severe GLS loss-of-function epileptic/neonatal phenotypes; GDPAG specifically refers here to the AR GLS deficiency with developmental delay, progressive ataxia, and elevated glutamine (rumping2020inbornerrorsof pages 3-4, rumping2020metabolicfingerprintingreveals pages 1-6) Review synthesis across GLS-associated phenotypes Moderate; distinction is clear, but retrieved sources did not fully harmonize modern nosology
Model organisms Zebrafish knockdown of GLS orthologues (glsa, glsl) caused smaller body size, curved body, and cardiac edema; prior mouse data cited in the retrieved text indicate GLS ablation impairs glutamatergic synaptic transmission and causes early death from respiratory problems, with heterozygotes showing hippocampal hypoactivity (richmond2020expandingtheutility pages 72-78, richmond2020expandingtheutility pages 78-83) Animal models Moderate; model findings support biology but do not fully recapitulate the human GDPAG phenotype
Treatment No disease-specific pharmacologic, gene, RNA, or dietary therapy for GDPAG was established in the retrieved evidence (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78) Evidence-gap assessment Low therapeutic certainty because of absence of direct interventional studies
Clinical trials No relevant interventional trials for GDPAG/glutaminase deficiency were identified; retrieved GLS trials were oncology GLS inhibitor studies and are not applicable to an enzyme-deficiency disorder (OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine) Clinical-trial search context High as a current evidence gap
Epidemiology No prevalence or incidence estimate for GDPAG was identified in retrieved disease-specific evidence; currently evidence is limited to a very small number of families/cases (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78) Evidence-gap assessment from case literature High as a gap; rarity is evident but not quantifiable from retrieved sources

Table: This table condenses the strongest retrieved evidence for GLS-associated GDPAG, emphasizing what is established versus what remains uncertain. It is useful for a knowledge-base entry because it separates core disease facts from important evidence gaps.

1. Disease information

Definition. GDPAG is a Mendelian neurometabolic/neurodevelopmental disorder of glutaminase deficiency. GLS normally hydrolyzes glutamine to glutamate and ammonia; therefore, reduced GLS function impairs the first step of glutamine catabolism. GLS is expressed especially in brain and kidney, whereas the paralog GLS2 is predominantly hepatic. (rumping2020inbornerrorsof pages 3-4)

Identifiers and synonyms

  • Preferred name: Global developmental delay, progressive ataxia, and elevated glutamine.
  • Abbreviation: GDPAG.
  • OMIM: #618412.
  • Open Targets/EFO: EFO_0010257; Open Targets associates the entity with GLS/ENSG00000115419. (OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine, shu2023thepowerof pages 7-8)
  • Synonyms: GLS deficiency, glutaminase deficiency, and GLS-related GDPAG are useful descriptive alternatives.
  • MONDO, Orphanet, MeSH, ICD-10 and ICD-11: no disease-specific identifiers were established in the retrieved evidence. A knowledge base should not assign a generic ataxia, developmental-disorder, or amino-acid-metabolism code as though it were disease-specific.

Evidence granularity. The clinical evidence is patient-level data from three unrelated probands/families, subsequently summarized in disease-level reviews and databases. It is not an EHR-derived population cohort. (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78)

Nosologic caution. GDPAG should not be conflated with other allelic GLS disorders: severe neonatal/developmental and epileptic encephalopathy from other biallelic loss-of-function alleles, an optic-atrophy/ataxia phenotype associated with a homozygous exon-1 duplication, or the distinct de novo p.Ser482Cys hypermorphic disorder with glutamate excess, cataract, profound developmental delay, hypotonia, and behavioral abnormalities. (rumping2020inbornerrorsof pages 3-4, rumping2020metabolicfingerprintingreveals pages 1-6)

2. Etiology, risk, and protective factors

Primary cause

The disease is caused by germline biallelic GLS loss of function. In the three foundational families:

  1. Family 1: paternal c.938C>T (p.Pro313Leu) plus a maternal 5′UTR GCA expansion.
  2. Family 2: GCA expansions inherited from both parents.
  3. Family 3: maternal c.923dupA (p.Tyr308*) plus a paternal GCA expansion. (richmond2020expandingtheutility pages 72-78)

The repeat alleles were transmitted by clinically unaffected heterozygous parents, supporting recessive inheritance. Variants are constitutional/germline; no somatic driver has been reported. (richmond2020expandingtheutility pages 72-78)

Risk factors

  • Established genetic risk: two pathogenic GLS alleles in trans.
  • Family history/consanguinity: recurrence risk follows autosomal-recessive inheritance, but consanguinity was not documented in the retrieved case evidence.
  • Environmental, infectious, occupational, lifestyle, age, or sex risk factors: none established.
  • Modifier genes, founder effects, anticipation, or germline mosaicism: not established.

Protective factors and gene–environment interaction

No protective allele, diet, exposure, or lifestyle factor has been demonstrated. Glutamine supplementation should not be extrapolated from glutamine-synthetase deficiency: GDPAG already features glutamine accumulation, and whether that accumulation is directly neurotoxic remains unresolved. The primary study explicitly noted that the contribution of elevated glutamine to the phenotype was unclear. (richmond2020expandingtheutility pages 78-83)

3. Phenotypes

Because only three index patients define the repeat-expansion syndrome, apparent “3/3” observations describe ascertainment-defining features and should not be interpreted as stable population frequencies.

Phenotype Type and course Reported frequency Suggested HPO term
Global developmental delay Neurodevelopmental sign; early onset 3/3 in the defining series HP:0001263 Global developmental delay
Progressive ataxia Neurologic sign; progressive/neurodegenerative course 3/3 HP:0001251 Ataxia; additionally annotate progressive course in narrative
Elevated plasma glutamine Laboratory abnormality 3/3 HP:0003217 Hyperglutaminemia
Normal plasma glutamate Relevant negative biochemical finding Reported across the defining cases Record as a negative observation rather than an HPO disease feature

The review describes “early-onset delay in overall development, progressive ataxia and elevated glutamine plasma levels,” with unaltered plasma glutamate. (rumping2020inbornerrorsof pages 3-4)

Severity and quality of life. Progressive ataxia and developmental impairment are expected to compromise mobility, coordination, learning, communication, and independence, but no GDPAG-specific EQ-5D, SF-36, PROMIS, caregiver-burden, or activities-of-daily-living study has been published in the retrieved literature. Seizure frequency, behavior, speech, tone, ophthalmologic findings, hearing, dysmorphism, and growth cannot be assigned reliable frequencies from the available evidence.

4. Genetic and molecular information

Gene/protein

  • Gene: GLS; approved name glutaminase.
  • Ensembl: ENSG00000115419. (OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine)
  • Protein/function: phosphate-activated mitochondrial glutaminase; EC 3.5.1.2.
  • Isoforms: alternative splicing produces glutaminase C and kidney-type glutaminase; both are mitochondrial, with strong kidney-type glutaminase expression in cerebral cortex and kidney. (richmond2020expandingtheutility pages 78-83)

Pathogenic alleles

The disease-associated expansion lies in the 5′UTR, not in the protein-coding sequence. Repeat PCR estimated major expanded products of approximately 680, 900, and 1,500 GCA repeats in the three probands. For Family 1, short-read analysis estimated >90 repeats without off-target reads and 246 with them, illustrating that short-read estimates substantially underresolve very large expansions. (richmond2020expandingtheutility pages 72-78)

The coding alleles were:

  • c.938C>T (p.Pro313Leu): missense; experimentally associated with reduced enzyme function in the disease workflow.
  • c.923dupA (p.Tyr308*): frameshift/premature-termination allele as reported in the study text. (richmond2020expandingtheutility pages 72-78)

Clinical databases should retain the authors’ reported nomenclature while independently checking the transcript accession before importing HGVS strings. ClinVar accessions and current ACMG/AMP assertion statuses were not established by the retrieved evidence.

Population frequency

Among 8,295 genomes/16,590 alleles, the median repeat length was 14, with modes at 8 and 16. One individual carried an allele estimated at >90 repeats, corresponding to an expanded-allele frequency of 6.03×10⁻⁵ in that dataset. This is a locus-specific research estimate, not a validated carrier-frequency estimate, because short reads under-size large repetitive alleles. (richmond2020expandingtheutility pages 72-78)

Functional consequence and epigenetics

Patient fibroblasts and peripheral-blood mononuclear cells showed reduced GLS activity/protein, reduced GLS mRNA, and allelic-expression imbalance. Residual activity remained and was proposed to explain the milder course relative to complete GLS ablation. (richmond2020expandingtheutility pages 78-83, richmond2020expandingtheutility pages 72-78)

The expansion produced an epigenetic loss-of-expression mechanism:

  • no increased DNA methylation upstream or downstream of the repeat;
  • reduced activating H3 acetylation and H3K4me3;
  • enrichment of repressive H3K9me3;
  • strongest chromatin effect in the proband with two expanded alleles. (richmond2020expandingtheutility pages 78-83)

Reporter constructs containing 13, 104, or approximately 240 repeats did not reproduce a direct inhibitory effect outside the native chromosomal context. This supports chromatin-mediated silencing rather than simple repeat-dependent blockade of transcription or translation. (richmond2020expandingtheutility pages 78-83)

No disease-specific modifier gene, methylation episignature, large chromosomal abnormality, or structural rearrangement beyond the separately reported GLS exon-1 duplication phenotype has been established.

5. Environmental information

GDPAG is a constitutional genetic disease. No toxin, radiation, pollution, occupation, smoking, alcohol, exercise, infection, or microbiome contribution is known. Environmental factors could influence general health or rehabilitation but are not established causes or modifiers. There is no zoonotic or transmissible component.

6. Mechanism and pathophysiology

Causal chain

Biallelic GLS pathogenic alleles → 5′UTR expansion-associated repressive chromatin and/or coding-allele dysfunction → reduced mitochondrial GLS transcript, protein, and activity → impaired conversion of glutamine to glutamate plus ammonia → systemic glutamine accumulation and likely altered neuronal glutamate–glutamine cycling → impaired glutamatergic synaptic function and broader amino-acid/energy/redox metabolism → abnormal neurodevelopment and progressive cerebellar motor dysfunction. The steps through reduced activity and elevated plasma glutamine are directly supported; the exact causal contribution of brain glutamine accumulation versus local glutamate deficiency remains unresolved. (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 78-83, richmond2020expandingtheutility pages 72-78)

Biological processes and pathways

Relevant pathway annotations include glutamine catabolism, glutamate biosynthesis, glutaminolysis, neurotransmitter metabolism, the glutamate–glutamine cycle, nitrogen metabolism, TCA-cycle anaplerosis, GABA synthesis, glutathione metabolism, proline/ornithine metabolism, and nucleotide synthesis. GLS links glutamine to glutamate, which can feed α-ketoglutarate/TCA metabolism and serves as a precursor of GABA and glutathione. (rumping2020metabolicfingerprintingreveals pages 1-6)

Suggested GO terms

  • GO:0006543 glutamine catabolic process
  • GO:0006537 glutamate biosynthetic process
  • GO:0006536 glutamate metabolic process
  • GO:0006099 tricarboxylic acid cycle
  • GO:0006749 glutathione metabolic process
  • GO:0007268 chemical synaptic transmission
  • GO:0043209 myelin sheath, as an anatomical cellular component of interest rather than a demonstrated GDPAG lesion

Subcellular localization: mitochondrion/mitochondrial matrix are the key compartments; suggested GO cellular-component annotation is GO:0005739 mitochondrion. (richmond2020expandingtheutility pages 78-83)

Cells and tissues

The most plausible vulnerable populations are glutamatergic neurons, cerebellar neurons including Purkinje cells, astrocytes participating in the glutamate–glutamine cycle, and neural progenitors. However, patient-specific single-cell or histopathologic evidence identifying one selectively affected cell type is unavailable. Suggested CL terms include CL:0000540 neuron, CL:0000127 astrocyte, CL:0000121 Purkinje cell, and CL:0000679 glutamatergic neuron; these should be labeled mechanistically suggested, not proven by patient tissue.

Molecular profiling

The disease study used targeted expression, enzyme, stable-isotope flux, immunoblotting, and chromatin assays. No GDPAG-specific single-cell RNA-seq, spatial transcriptomics, broad patient proteomics, lipidomics, or integrated multi-omics dataset was identified. A separate hypermorphic-GLS HEK293 metabolomics model found 109 of 12,437 mass-spectral features corresponding to endogenous metabolites significantly affected by high GLS activity, but that experiment models the opposite biochemical direction and should not be imported as a GDPAG signature. (rumping2020metabolicfingerprintingreveals pages 1-6)

7. Anatomical structures affected

Primary system: central nervous system, particularly developmental and cerebellar motor networks.

Suggested anatomy annotations:

  • brain — UBERON:0000955;
  • cerebellum — UBERON:0002037;
  • cerebral cortex — UBERON:0000956;
  • kidney — biologically relevant because of GLS expression, but not established as clinically diseased in GDPAG;
  • mitochondrion — principal subcellular compartment.

No consistent patient MRI pattern, pathology series, lateralization, peripheral-nerve lesion, or renal structural phenotype was available in the retrieved GDPAG evidence. Separate GLS-deficiency phenotypes have included cerebral edema/white-matter disease or cerebellar atrophy, but these should not be assigned automatically to GDPAG. (rumping2020inbornerrorsof pages 3-4)

8. Temporal development

Onset is pediatric/early developmental and apparently insidious rather than acute. Developmental delay is followed or accompanied by progressive ataxia, producing a chronic, lifelong neurodevelopmental-neurodegenerative course. Remission, episodic crises, stage boundaries, median progression rate, and critical therapeutic windows have not been defined. (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 78-83)

A practical, nonvalidated staging description is:

  1. Early: delayed acquisition of developmental milestones.
  2. Intermediate: emergence of coordination/gait impairment.
  3. Advanced: progressive motor disability.

This framework is inferential and should not be represented as an accepted clinical staging system.

9. Inheritance and population

Inheritance is autosomal recessive. For two carrier parents, standard Mendelian counseling gives a 25% affected, 50% carrier, and 25% non-carrier probability per pregnancy, assuming both parental alleles are correctly characterized.

Penetrance for biallelic pathogenic genotypes appears high in the reported families but cannot be quantified. Expressivity, anticipation, repeat instability across generations, sex ratio, age distribution, founder effects, geographic clustering, prevalence, and incidence are unknown. The reported expanded-allele frequency of 6.03×10⁻⁵ is not equivalent to disease prevalence or carrier frequency. (richmond2020expandingtheutility pages 72-78)

10. Diagnostics

Clinical suspicion and biochemical testing

Consider GDPAG in a child with developmental delay plus progressive ataxia, particularly when plasma amino-acid analysis shows elevated glutamine without elevated glutamate. Recommended research-informed evaluation includes:

  1. quantitative plasma amino acids, especially glutamine and glutamate;
  2. ammonia, acid–base status, liver function, lactate, and broader metabolic screening to exclude common causes of hyperglutaminemia;
  3. neurologic examination and standardized developmental assessment;
  4. brain MRI, although no GDPAG-specific radiologic criterion exists;
  5. GLS activity/flux and protein/expression assays in fibroblasts or PBMCs where available. (rumping2020inbornerrorsof pages 3-4, richmond2020expandingtheutility pages 72-78)

Genetic testing algorithm

  1. Sequence GLS coding exons and splice junctions, preferably as part of trio exome/genome analysis.
  2. If one or no GLS coding allele is found despite the biochemical phenotype, perform GLS 5′UTR GCA-repeat testing.
  3. Suitable methods include repeat-primed PCR, repeat-flanking PCR with gel/capillary sizing, Southern blot or validated long-read sequencing for very large alleles.
  4. Short-read WGS with ExpansionHunter or comparable software can flag the expansion, but exact sizing may be unreliable; the original workflow required manual read inspection and off-target-read analysis.
  5. Confirm parental phase to demonstrate biallelic inheritance. (shu2023thepowerof pages 7-8, richmond2020expandingtheutility pages 72-78)

Standard exome sequencing can miss the noncoding expansion. The 2023 review states: “Initial ES only uncovered one heterozygous and damaging variant in GLS in two probands,” whereas short-read genome sequencing identified the 5′UTR expansions. (shu2023thepowerof pages 7-8)

CMA, karyotyping, FISH, mtDNA sequencing, and generic repeat-expansion panels are not first-line confirmatory tests unless needed for the broader differential. RNA/cDNA allelic-expression analysis and chromatin assays are useful research-level functional tests, not standardized clinical criteria.

Differential diagnosis

Key alternatives include urea-cycle disorders and hepatic hyperammonemia; glutamine synthetase deficiency; SLC38A3-related developmental and epileptic encephalopathy; other GLS-associated encephalopathies; mitochondrial disease; treatable metabolic ataxias; and nonmetabolic hereditary ataxias. Distinguishing GDPAG features are the GLS genotype, reduced glutaminase function, persistent hyperglutaminemia, and progressive ataxia.

There are no validated clinical diagnostic criteria, newborn-screening program, or established population-screening assay.

11. Outcome and prognosis

No Kaplan–Meier survival analysis, life-expectancy estimate, mortality rate, or 5-/10-year outcome data exist for GDPAG. Residual enzyme activity was proposed to account for a milder phenotype than complete GLS ablation, but no validated genotype–prognosis relationship is available. (richmond2020expandingtheutility pages 78-83)

Expected morbidity centers on developmental disability and progressive loss of coordination/mobility. Published GDPAG-specific evidence does not quantify wheelchair dependence, feeding support, respiratory complications, educational attainment, adult independence, or caregiver burden. Recovery has not been documented; stabilization with supportive therapy has not been systematically studied. Candidate monitoring biomarkers are plasma glutamine and cell-based GLS activity, but neither is validated as a prognostic surrogate.

12. Treatment and current applications

There is no approved disease-modifying therapy and no relevant GDPAG clinical trial identified. Oncology trials of GLS inhibitors are mechanistically inappropriate for a GLS-deficiency disorder and must not be misclassified as therapeutic GDPAG studies. (OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine)

Present clinical management

Management is supportive and individualized:

  • developmental pediatrics and neurology follow-up;
  • physical therapy for balance, gait, strength, contracture prevention, and assistive-device assessment;
  • occupational therapy for activities of daily living;
  • speech/language therapy and augmentative communication where needed;
  • nutritional assessment and safe-swallow evaluation if indicated;
  • treatment of seizures, spasticity, pain, sleep problems, or orthopedic complications if they occur;
  • periodic plasma amino-acid monitoring, recognizing that no treatment target is validated.

Suggested MAXO annotations include MAXO:0000011 physical therapy, MAXO:0000010 occupational therapy, speech-language therapy, developmental assessment, genetic counseling, biochemical surveillance, and assistive-device use; local ontology versions should be checked before production import.

Experimental concepts

Potential future strategies include GLS gene replacement, activation of the silenced expanded allele, epigenome editing, or repeat-targeted approaches. None has reached a GDPAG preclinical efficacy study or human trial. Because GLS participates in neurotransmission, redox balance, and systemic metabolism, both under-correction and overactivation could be harmful; the distinct hypermorphic GLS syndrome demonstrates this dosage sensitivity. (rumping2020inbornerrorsof pages 3-4, rumping2020metabolicfingerprintingreveals pages 1-6, richmond2020expandingtheutility pages 78-83)

13. Prevention

The disease is not preventable through vaccination, diet, or lifestyle. Evidence-based prevention is reproductive/genetic rather than environmental:

  • cascade testing of relatives after defining the familial alleles;
  • carrier testing that includes the 5′UTR repeat, not coding sequencing alone;
  • prenatal diagnosis using chorionic-villus or amniotic-fluid DNA;
  • preimplantation genetic testing for monogenic disease;
  • counseling regarding autosomal-recessive recurrence.

Secondary/tertiary prevention consists of early diagnosis, developmental intervention, fall prevention, mobility support, and surveillance for complications. No newborn-screening recommendation or prophylactic medication exists.

14. Other species and natural disease

No naturally occurring GLS-related GDPAG has been established in companion animals, livestock, or wildlife, and no breed/VBO association is known. The disorder is noninfectious and has no zoonotic potential. Orthologous GLS biology is conserved in vertebrates, supporting comparative modeling, but induced models should not be represented as natural veterinary disease.

15. Model organisms

Zebrafish

Knockdown of glsa, glsl, or both caused smaller body size, body curvature, and cardiac edema. This supports developmental dependence on GLS but does not specifically reproduce the human triad or the 5′UTR chromatin lesion. (richmond2020expandingtheutility pages 72-78)

Mouse

Cited mouse studies indicate that complete Gls ablation partially impairs glutamatergic synaptic transmission and causes early death from respiratory dysfunction, whereas heterozygous deficiency produces hippocampal hypoactivity. These findings support a dosage-sensitive role in neuronal transmission and respiration but model more severe or carrier states rather than the residual-activity human GDPAG genotype. (richmond2020expandingtheutility pages 78-83)

Human cells

Patient fibroblasts and PBMCs reproduce reduced mRNA/protein/activity, altered glutamine-to-glutamate flux, allelic imbalance, and expansion-associated chromatin repression. Attempts to generate neuronal cells from patient fibroblasts were unsuccessful, limiting direct study of human neuronal pathophysiology. (richmond2020expandingtheutility pages 78-83, richmond2020expandingtheutility pages 72-78)

Useful future models include isogenic repeat-expanded iPSCs, induced glutamatergic neurons, cerebellar/Purkinje organoids, repeat-length knock-in mice, and CRISPR-corrected rescue lines.

Recent developments and evidence appraisal

The most relevant 2023–2024 development is diagnostic rather than therapeutic. A 2023 review used GDPAG as a paradigm showing that phenotype-plus-biochemistry can direct genome analysis toward pathogenic noncoding variants missed by exome sequencing. (shu2023thepowerof pages 7-8)

Recent GLS literature has also broadened the allelic spectrum, including 2024 reports of coding-variant developmental/epileptic encephalopathy and mechanistically distinct de novo GLUL/GLS-pathway disorders; these developments reinforce the need to classify disease by variant mechanism and biochemical direction, rather than treating all glutamine-pathway phenotypes as interchangeable. However, no 2023–2024 publication retrieved here materially expanded the GDPAG repeat-expansion cohort, established prevalence, or tested treatment.

Key source notes, dates, URLs, and quotations

  1. Rumping et al., “Inborn errors of enzymes in glutamate metabolism,” Journal of Inherited Metabolic Disease, published November 2020. DOI/URL: https://doi.org/10.1002/jimd.12180. Disease-specific review statement: “Three other unrelated patients with GLS deficiency, as a consequence of tandem repeat expansion in GLS, presented with early-onset delay in overall development, progressive ataxia and elevated glutamine plasma levels.” It further reports that plasma glutamate was unaltered. PMID was not available in the retrieved record. (rumping2020inbornerrorsof pages 3-4)

  2. Shu, Maroilley & Tarailo-Graovac, “The Power of Clinical Diagnosis for Deciphering Complex Genetic Mechanisms in Rare Diseases,” Genes, published January 2023. DOI/URL: https://doi.org/10.3390/genes14010196. Exact retrieved text: “Kuilenburg et al. identified GCA-REs in the 5′UTR region of the GLS by SR-GS. Initial ES only uncovered one heterozygous and damaging variant in GLS in two probands who presented with global developmental delay, progressive ataxia, and elevated glutamine (GDPAG; OMIM #618412).” PMID was not present in the retrieved record. (shu2023thepowerof pages 7-8)

  3. Richmond, “Expanding the utility of whole genome sequencing in the diagnosis of rare genetic disorders,” University of British Columbia thesis/ArXiv, January 2020. DOI/URL: https://doi.org/10.14288/1.0394775. This retrieved full text supplied the detailed repeat sizes, population analysis, functional assays, and chromatin mechanism. Its conclusion states: “The expansion in the 5′ untranslated region of GLS, which encodes glutaminase, results in reduced expression and glutaminase deficiency.” This is not a peer-reviewed primary journal article and has no PMID; it is therefore best treated as detailed supporting primary-study documentation. (richmond2020expandingtheutility pages 78-83, richmond2020expandingtheutility pages 72-78)

  4. Rumping et al., “Metabolic fingerprinting reveals extensive consequences of GLS hyperactivity,” BBA—General Subjects, accepted November 4, 2019 and published in the 2020 volume. DOI/URL: https://doi.org/10.1016/j.bbagen.2019.129484. This is mechanistically informative but models GLS hyperactivity, not GDPAG deficiency. (rumping2020metabolicfingerprintingreveals pages 1-6)

Knowledge-base conclusions

The high-confidence entry is: GDPAG (OMIM 618412) is an autosomal-recessive GLS loss-of-function disorder characterized by early developmental delay, progressive ataxia, and hyperglutaminemia. Large 5′UTR GCA expansions silence GLS through repressive histone remodeling and can occur homozygously or in trans with a coding pathogenic allele. Diagnosis requires biochemical phenotyping plus explicit repeat-expansion analysis because standard exome sequencing may miss the causal allele. All broader phenotype frequencies, natural-history estimates, imaging signatures, epidemiology, prognosis, and disease-modifying treatments remain insufficiently characterized.

References

  1. (rumping2020inbornerrorsof pages 3-4): Lynne Rumping, Esmee Vringer, Roderick H. J. Houwen, Peter M. van Hasselt, Judith J. M. Jans, and Nanda M. Verhoeven‐Duif. Inborn errors of enzymes in glutamate metabolism. Journal of Inherited Metabolic Disease, 43:200-215, Nov 2020. URL: https://doi.org/10.1002/jimd.12180, doi:10.1002/jimd.12180. This article has 33 citations and is from a peer-reviewed journal.

  2. (richmond2020expandingtheutility pages 72-78): Phillip Andrew Richmond. Expanding the utility of whole genome sequencing in the diagnosis of rare genetic disorders. ArXiv, Jan 2020. URL: https://doi.org/10.14288/1.0394775, doi:10.14288/1.0394775. This article has 0 citations.

  3. (richmond2020expandingtheutility pages 78-83): Phillip Andrew Richmond. Expanding the utility of whole genome sequencing in the diagnosis of rare genetic disorders. ArXiv, Jan 2020. URL: https://doi.org/10.14288/1.0394775, doi:10.14288/1.0394775. This article has 0 citations.

  4. (shu2023thepowerof pages 7-8): Li Shu, Tatiana Maroilley, and Maja Tarailo-Graovac. The power of clinical diagnosis for deciphering complex genetic mechanisms in rare diseases. Genes, 14:196, Jan 2023. URL: https://doi.org/10.3390/genes14010196, doi:10.3390/genes14010196. This article has 9 citations.

  5. (OpenTargets Search: Global developmental delay, progressive ataxia, and elevated glutamine): Open Targets Query (Global developmental delay, progressive ataxia, and elevated glutamine, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

  6. (rumping2020metabolicfingerprintingreveals pages 1-6): Lynne Rumping, Mia L. Pras-Raves, Johan Gerrits, Yuen Fung Tang, Marcel A. Willemsen, Roderick H.J. Houwen, Gijs van Haaften, Peter M. van Hasselt, Nanda M. Verhoeven-Duif, and Judith J.M. Jans. Metabolic fingerprinting reveals extensive consequences of gls hyperactivity. Mar 2020. URL: https://doi.org/10.1016/j.bbagen.2019.129484, doi:10.1016/j.bbagen.2019.129484. This article has 10 citations and is from a peer-reviewed journal.

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