Developmental And Epileptic Encephalopathy 40

1. Disease Information

Overview. Developmental and epileptic encephalopathy 40 (DEE40) is an ultra-rare autosomal recessive mitochondrial-translation disorder caused by biallelic variants in GUF1 (GTP-binding elongation factor GUF1, chromosome 4p12). It presents as West syndrome: refractory infantile spasms beginning in the first 6 months of life with hypsarrhythmia on EEG, followed by developmental stagnation/regression and severe, lifelong neurologic impairment. It is the only human disease so far attributed to GUF1, the human homolog of bacterial elongation factor 4 (EF4/LepA), a quality-control back-translocase of the mitochondrial ribosome. The disease was delineated by Alfaiz et al. (2016) in three affected siblings of a consanguineous family (PMID:26486472).

Identifiers.

Synonyms: EIEE40 (early infantile epileptic encephalopathy-40), GUF1-related epileptic encephalopathy, GUF1-related West syndrome.

Data provenance. All clinical information derives from aggregated disease-level resources (OMIM, Orphanet, PanelApp, GenCC) and case-level primary literature — principally one deeply phenotyped sibship (PMID:26486472) plus one additional GUF1-positive patient in a Turkish targeted-NGS cohort (PMID:37820178). No EHR-derived or registry data exist.

Gene-disease validity status (important caveat). The evidence base remains thin: Genomics England PanelApp rates GUF1 AMBER on the "Early onset or syndromic epilepsy" panel (panel 402), and GenCC classifications are "Limited"/"Supportive" (HGNC:25799). A diagnostic-grade (green) rating requires ≥3 unrelated families or 2 families plus convincing functional data; DEE40 currently rests on one family with functional support plus isolated panel-cohort hits.

2. Etiology

Primary cause. Homozygous missense variant in GUF1. In the index family, exome sequencing of a consanguineous family (reported by OMIM as of Algerian origin) with three affected siblings identified a homozygous c.1825G>T / p.(Ala609Ser) transversion in exon 15, segregating with disease. Direct quote (PMID:26486472):

"We identified a homozygous variant (c.1825G>T/p.(Ala609Ser)) in the GUF1 gene in the three affected siblings."

"The variant identified in the WS family changes an alanine residue conserved in all eukaryotic organisms and positioned within the tRNA-binding moiety of this nuclear genome-encoded mitochondrial translational elongation factor."

Risk factors. - Genetic: biallelic GUF1 variants; heterozygous carriers are unaffected (autosomal recessive). - Consanguinity is the dominant epidemiologic risk factor — the index family was consanguineous, and homozygosity for an ultra-rare allele is the expected mechanism of recurrence. - Environmental risk/protective factors: none identified; no gene-environment interaction data exist (CTD has no curated GUF1 disease-chemical interactions relevant to this phenotype). A biologically plausible but unproven consideration: GUF1/EF4 function is most critical under cellular stress (temperature, nutrient limitation, ionic stress) in all model systems (PMID:18442968; PMID:24837196), suggesting physiologic stressors could modulate expressivity — this is inference, not observation.

Protective factors. None reported (no protective variants, modifier alleles, or environmental factors documented).

3. Phenotypes

All frequencies below refer to the 3 reported sibs plus OMIM's clinical synopsis; treat "3/3" as the effective denominator.

Key phenotype description (OMIM #617065 clinical summary): DEE40 is "characterized by the onset of refractory infantile spasms within the first 6 months of life"; infants "may have normal or mildly delayed development before the onset of seizures, but thereafter show developmental stagnation and severe neurologic impairment"; EEG "typically shows hypsarrhythmia, consistent with a clinical diagnosis of West syndrome."

The defining West syndrome triad, quoted exactly from the index paper (PMID:26486472):

"West syndrome (WS), defined by the triad of infantile spasms, pathognomonic hypsarrhythmia and developmental regression, is a rare epileptic disease affecting about 1:3500 live births."

Quality-of-life impact. No formal QoL instruments (EQ-5D, PedsQL) have been applied to DEE40. By analogy with cohort data on epileptic encephalopathies generally, dependency is severe: in the Turkish DEE cohort containing the fourth GUF1 patient, patients with severe intellectual disability were "completely dependent on the help of their relatives in their daily life activities" (PMID:37820178).

4. Genetic/Molecular Information

Causal gene. GUF1 (HGNC:25799; NCBI Gene 60558; OMIM 617064; 4p12). Encodes a nuclear-encoded, mitochondrially targeted translation elongation factor — the human ortholog of E. coli LepA/EF4 and S. cerevisiae* Guf1. UniProt: GUF1_HUMAN (Q8N442).

Pathogenic variants. - c.1825G>T, p.(Ala609Ser) — exon 15, homozygous, germline; missense; the sole published segregating allele (PMID:26486472). ClinVar RCV000239484. Ala609 is "conserved in all eukaryotic organisms and positioned within the tRNA-binding moiety" of the protein (PMID:26486472). Functional class: neither clean loss nor gain — a conditional/context-dependent hypomorph; yeast complementation showed "the activity of GUF1(A609S) is modified in suboptimal environments" (PMID:26486472). - One additional GUF1-mutated patient was identified by a 54-gene targeted epilepsy panel in a Turkish DEE cohort (1 GUF1 hit among 48 genetically solved of 198 patients; variant details not given in the paper) (PMID:37820178). - Allele frequency: the A609S allele is absent/ultra-rare in population databases (per the original report); no recurrent or founder alleles are otherwise documented in gnomAD at appreciable frequency. - All variants reported to date are germline; there is no somatic disease association for this phenotype (mtEF4 overexpression has a separate somatic-cancer literature — see §6).

Modifier genes, epigenetics, chromosomal abnormalities. None identified. No DNA-methylation or chromatin data specific to DEE40 exist; no structural variants of GUF1 have been reported as causal.

5. Environmental Information

No environmental, lifestyle, or infectious contributors are documented for DEE40; it is a fully penetrant (within the one reported family) Mendelian mitochondrial disorder. The only environment-adjacent observation is mechanistic: GUF1/EF4 function becomes rate-limiting under stress conditions (low temperature, nutrient limitation, altered Mg²⁺) in yeast, worm, and bacterial systems — see §6.

6. Mechanism / Pathophysiology

Causal chain (ordered)

1. Biallelic GUF1 missense variant (p.Ala609Ser in the tRNA-binding domain) leads to altered activity of the mitochondrial elongation factor 4 (mtEF4/GUF1), demonstrated in yeast complementation under suboptimal conditions (PMID:26486472). (demonstrated, model system)
2. Impaired GUF1 back-translocase activity results in loss of quality control over mitochondrial translation elongation — failure to remobilize stalled mitoribosomes and to pace elongation (PMID:18442968; PMID:26486472). (demonstrated in yeast/bacteria; inferred for human)
3. Dysregulated mitochondrial translation results in synthesis of unstable/misassembled mtDNA-encoded OXPHOS subunits (PMID:27065197: "Deletion of mtEF4 accelerated mitochondrial translation at the cost of producing unstable proteins"). (demonstrated, mouse)
4. Misassembly leads to defective respiratory-chain complex biogenesis, with complex IV (cytochrome c oxidase) assembly most affected (yeast: "defects in the assembly of cytochrome oxidase," PMID:18442968; C. elegans: "disrupts the assembly of respiratory chain supercomplexes containing complex IV," PMID:24837196). (demonstrated, model systems)
5. Respiratory-chain dysfunction results in deficient oxidative phosphorylation, plus increased electron leakage and ROS production (PMID:30693836; PMID:29572227: "Knockout of mtEF4 induced respiratory chain complex defects and apoptosis"). (demonstrated in vitro/model; inferred in patients)
6. Bioenergetic failure in the developing brain leads to cortical network dysfunction and hyperexcitability, manifesting as infantile spasms with hypsarrhythmia. (inferred — this is the step the index paper frames as a hypothesis: "We suggest a new link between improper assembly of respiratory chain complexes and WS," PMID:26486472; it is consistent with the broader literature placing mitochondrial/respiratory-chain disease among infantile-spasm etiologies)
7. Ongoing epileptic activity plus chronic neuronal energy deficit result in developmental stagnation/regression and profound intellectual disability — the "developmental and epileptic" encephalopathy. (inferred; conforms to the ILAE epileptic-encephalopathy concept)

Branch (tissue-specificity / compensation). In mouse, somatic tissues buffer mtEF4 loss: "Somatic tissues overcame this defect by activating mechanistic (mammalian) target of rapamycin (mTOR), thereby increasing rates of cytoplasmic translation to match rates of mitochondrial translation," whereas cells that developmentally downregulate mTOR (spermatogenic cells) undergo "cell-cycle arrest and apoptosis" (PMID:27065197). Why the human brain is vulnerable while the mouse brain is spared is an open question — plausibly the human A609S allele behaves differently from a null, and/or neuronal mTOR-mediated compensation is insufficient in the developing human cortex. This is an explicit human-model mismatch (see §15).

Supporting detail by category

• Molecular pathways: mitochondrial translation elongation and its quality control (GO:0070125 mitochondrial translational elongation; GO:0032543 mitochondrial translation); ribosomal back-translocation — "it is able to remobilize stuck ribosomes and transiently inhibit the elongation process to optimize protein synthesis" (PMID:26486472); mTOR-mediated mito-cytoplasmic translational cross-talk (PMID:27065197); oxidative phosphorylation (GO:0006119).
• Protein dysfunction: GUF1 is a ribosome-dependent GTPase (GO:0003924) "located in the mitochondrial matrix and tightly associated with the inner membrane," binding "mitochondrial ribosomes in a GTP-dependent manner" (yeast, PMID:18442968). A609S perturbs the tRNA-binding module rather than abolishing the protein.
• Cellular processes: mitoribosome rescue/fidelity; respiratory-complex assembly (GO:0033617 mitochondrial respiratory chain complex IV assembly); apoptosis upon severe OXPHOS failure (PMID:29572227).
• Metabolic changes: OXPHOS deficiency; predicted redox imbalance — mtEF4 loss "could result in cytochrome c peroxidase formation, electron leakage from electron transport chain and ROS increase" (PMID:30693836).
• Immune involvement: none.
• Cell types / anatomy: cortical neurons (CL:0000540 neuron; CL:0010012 cerebral cortex neuron) are the presumed vulnerable population, given the purely neurologic phenotype; no patient tissue studies exist.
• Molecular profiling: none in patients. In C. elegans, mtef4 deletion "induces retrograde pathways, including mitochondrial biogenesis and cytoplasmic translation reorganization" by transcriptomics (PMID:24837196). Human tissue survey: "EF4 was ubiquitous in human tissues with localization to the mitochondria (mtEF4) and performed quality control on respiratory chain biogenesis" (PMID:29572227).
• Evidence-source classification: the chain above rests on IN_VITRO (yeast complementation, human cell lines), MODEL_ORGANISM (mouse, C. elegans), and HUMAN_CLINICAL genetics (segregation in one family); no direct human biochemical confirmation (e.g., muscle respiratory-chain enzymology in a patient) has been published — a genuine knowledge gap worth recording.

7. Anatomical Structures Affected

• Organ level: brain (UBERON:0000955), specifically cerebral cortex (UBERON:0000956) as the seat of hypsarrhythmia/spasms; nervous system exclusively — no cardiac, hepatic, renal, or ophthalmologic involvement reported.
• Tissue/cell level: neurons (CL:0000540); no neuropathology has been published.
• Subcellular level: mitochondrion (GO:0005739); mitochondrial matrix (GO:0005759); mitochondrial inner membrane (GO:0005743); mitochondrial ribosome (GO:0005761).
• Lateralization: hypsarrhythmia and spasms are generalized/bilateral.

8. Temporal Development

• Onset: infantile — refractory spasms within the first 6 months of life (OMIM); development before onset normal or mildly delayed.
• Progression: epileptic-encephalopathy pattern — seizure onset is followed by developmental stagnation and regression; thereafter the course is one of static severe impairment (profound ID, absent language) rather than documented ongoing neurodegeneration. Seizures are refractory.
• Course pattern: chronic, lifelong; no remissions reported.
• Critical period: infancy — as for all infantile-spasm syndromes, the window for hormonal/vigabatrin therapy is early; whether prompt treatment alters outcome in DEE40 specifically is unknown (spasms were refractory in the reported family).

9. Inheritance and Population

• Inheritance: autosomal recessive (HP:0000007). Homozygosity in a consanguineous family; parents unaffected carriers.
• Penetrance/expressivity: apparently complete penetrance and consistent expressivity within the single sibship (3/3 affected homozygotes); no inter-familial comparison possible.
• Anticipation, germline mosaicism, founder effects: none reported; A609S may represent a private allele.
• Consanguinity: central — the index family was consanguineous; expect DEE40 predominantly in populations with elevated autozygosity.
• Carrier frequency: unknown; presumably extremely low.
• Epidemiology: ultra-rare — 4 reported patients worldwide (3 sibs, PMID:26486472; 1 Turkish panel case, PMID:37820178). For context, West syndrome of all causes affects "about 1:3500 live births" (PMID:26486472). Sex ratio in reported cases includes both sexes (the index sibship included male and female children). Suggested dismech prevalence class: CASES_IN_LITERATURE.

10. Diagnostics

• Electrophysiology: EEG is the pivotal test — hypsarrhythmia (interictal) with epileptic spasms; evolution should be followed as West syndrome can transform to other encephalopathy patterns (Lennox-Gastaut evolution is seen in 20–48% of West syndrome generally, PMID:37820178).
• Imaging: brain MRI to exclude structural etiologies; in the DEE cohort containing a GUF1 patient, "There was no structural anomaly that could cause a seizure" (PMID:37820178). No DEE40-specific imaging signature is established.
• Laboratory/biochemical: standard metabolic screening is typically unrevealing ("Metabolic examination tests were performed in all patients, and no specific findings indicative of a disease were detected," PMID:37820178). Respiratory-chain enzymology (muscle/fibroblast) is mechanistically rational (predicted complex IV assembly defect) but has not been reported in a patient.
• Genetic testing (the diagnostic mainstay):
• Exome/genome sequencing — how the index family was solved ("we exome-sequenced the members of a consanguineous family affected with isolated WS," PMID:26486472).
• Targeted NGS epilepsy panels — GUF1 is included on commercial and academic EIEE/DEE panels (e.g., the 54-gene Turkish panel, PMID:37820178; GTR lists GUF1 clinical tests under Gene 60558). Trio testing to confirm segregation and biallelic phase.
• CMA/karyotype/FISH/mtDNA/repeat testing: not informative for GUF1 point variants (though mtDNA testing belongs in the differential workup of mitochondrial epilepsy).
• Variant interpretation caution: given PanelApp AMBER / GenCC Limited status, a novel biallelic GUF1 variant in a DEE patient should be reported conservatively (often VUS-to-likely-pathogenic territory) unless functional or segregation data are strong.
• Differential diagnosis: the full West-syndrome gene spectrum (CDKL5, ARX, STXBP1, KCNQ2, TBC1D24, SLC25A22, etc.) and mitochondrial epilepsies (mtDNA mutations such as m.8993T>G, nuclear mitochondrial-translation defects — e.g., TSFM, RARS2); tuberous sclerosis and structural/metabolic causes must be excluded per ILAE criteria.
• Screening: not part of newborn screening; carrier/cascade testing appropriate within an affected family.

11. Outcome / Prognosis

• Survival: no mortality data; the reported sibs survived infancy. Life expectancy unquantified.
• Morbidity: severe — profound intellectual disability, absent language, motor impairment (axial hypotonia + peripheral spasticity, poor fine motor skills), refractory epilepsy; full dependency for activities of daily living is expected from the DEE literature (PMID:37820178).
• Prognostic factors: none established within DEE40 (n too small). Extrapolating from West syndrome generally, etiology and treatment latency drive outcome; genetically determined ("symptomatic") West syndrome carries the poorer developmental prognosis, and DEE40's reported course fits that pattern.
• Complications: evolution toward other epileptic encephalopathy patterns (LGS risk after infantile spasms is 20–48% in general cohorts, PMID:37820178); feeding difficulties with attendant nutritional risk.
• Recovery potential: none demonstrated; developmental stagnation persisted despite management in the reported family.

12. Treatment

There is no disease-specific or mechanism-directed therapy. Management follows standard-of-care for infantile spasms/West syndrome and supportive care for severe DEE.

• Pharmacogenomics: none specific to GUF1.
• Advanced therapeutics: no gene therapy, ASO, or clinical trial (no NCT identifiers) targets GUF1/DEE40. A speculative mechanistic lead — mTOR-pathway modulation of the mitochondrial/cytoplasmic translation balance (PMID:27065197) — has not been tested therapeutically and cuts both ways (compensation in mouse required mTOR activation).
• Treatment response: the defining feature is refractoriness of the spasms; no DEE40-specific response rates exist.

13. Prevention

• Primary prevention: none for the disorder itself; genetic counseling in consanguineous families is the actionable lever.
• Secondary prevention: early recognition of spasms and prompt EEG — critical for all infantile-spasm syndromes; rapid genetic diagnosis (panel/exome) ends the diagnostic odyssey and informs counseling ("Understanding the genetic etiology is vital for genetic counseling and, maybe, the future development of remedies for the etiology," PMID:37820178).
• Tertiary prevention: aggressive seizure management to limit encephalopathic impact; standard DEE complication surveillance (nutrition, orthopedic sequelae of spasticity).
• Reproductive options: carrier testing of relatives, prenatal diagnosis, and PGT are technically feasible once the familial variants are known.
• Vaccination, public-health, and behavioral prevention: not applicable.

14. Other Species / Natural Disease

No naturally occurring GUF1-deficiency disease is documented in companion animals or wildlife (no OMIA entry). The gene is, however, among the most anciently conserved translation factors, and the comparative biology is unusually rich:

• E. coli LepA/EF4: the founding member; "the bacterial elongation factor LepA was identified as critical for the accuracy of in vitro translation reactions" (PMID:18442968); structural and single-molecule work established back-translocation (Qin et al., Cell 2006; Evans et al., PNAS 2008; Liu et al., PNAS 2011). In vivo, LepA contributes to tellurite resistance and is required for H. pylori growth in acid — fitness under stress, not viability.
• S. cerevisiae Guf1: mitochondrial matrix GTPase; deletion causes "cold- and heat-sensitive growth defects on non-fermentable carbon sources… especially pronounced under nutrient-limiting conditions" and "defects in the assembly of cytochrome oxidase," with synthetic sickness with oxa1 insertase mutants (PMID:18442968). This is the system used to functionally test the patient allele (PMID:26486472).
• C. elegans mtEF4: "mtef4 deletion leads to self-brood size reduction, growth delay and mitochondrial dysfunction," and at 15 °C "reduces mitochondrial translation and disrupts the assembly of respiratory chain supercomplexes containing complex IV" (PMID:24837196).
• Mouse Guf1/mtEF4: knockout "causes testis-specific dysfunction in oxidative phosphorylation, leading to male infertility" (PMID:27065197); a prior report similarly found loss of Guf1 impairs sperm mitochondrial function (Piao & Jin, Biol Reprod 2015). NCBI Taxon suggestions: NCBITaxon:9606 (human), NCBITaxon:10090 (mouse), NCBITaxon:6239 (C. elegans), NCBITaxon:4932 (S. cerevisiae), NCBITaxon:562 (E. coli).
• Evolutionary note: EF4 has long been called a paradox — "highly conserved, yet of no physiological significance?" (Zhang & Qin, Biochem J 2013) — because deletions across taxa lack overt phenotypes under optimal conditions; DEE40 supplies the missing organismal significance in humans.

15. Model Organisms

Resources: MGI (Guf1), WormBase, SGD (GUF1/YLR289W), IMPC. Applications: the yeast complementation assay is the established readout for classifying new GUF1 missense variants — directly relevant to resolving future VUS. Unmet model need: no neuronal or brain-conditional model (e.g., patient iPSC-derived neurons, knock-in A609S mouse) exists; this is the experiment that would close the largest gap in the causal chain (step 6, §6).

Key open questions / knowledge gaps (for KB curation)

1. Single-family gene-disease association (PanelApp AMBER, GenCC Limited) — additional unrelated biallelic families with phenotype detail are the rate-limiting evidence.
2. No patient-level biochemical confirmation of respiratory-chain (complex IV) deficiency in any DEE40 patient tissue — the central mechanistic step is model-inferred.
3. Human-model mismatch: mouse null has no neuro phenotype; mechanism of human brain vulnerability (allele behavior vs. compensation capacity) is unresolved.
4. No natural-history, imaging, or treatment-response data beyond the index sibship.

Sources: - OMIM #617065 — Developmental and Epileptic Encephalopathy 40 - OMIM *617064 — GTP-Binding Elongation Factor GUF1 - Alfaiz et al. 2016, Eur J Hum Genet — West syndrome caused by homozygous GUF1 variant (PMID:26486472) - PMC version of Alfaiz et al. 2016 - Bauerschmitt et al. 2008, J Biol Chem — yeast Guf1 promotes mitochondrial protein synthesis under suboptimal conditions (PMID:18442968) - Gao et al. 2016, Nat Struct Mol Biol — mtEF4 knockout mouse, spermatogenesis (PMID:27065197) - Yang et al. 2014, BBA — C. elegans mtEF4 and respiratory dysfunction (PMID:24837196) - Zhu et al. 2018, Cancer Res — human EF4 as mitochondrial translation switch (PMID:29572227) - Li & Qin 2018, Free Radic Res — mtEF4, OXPHOS complexes and ROS (PMID:30693836) - Bariş et al. 2023, Rev Assoc Med Bras — targeted NGS in pediatric DEE, incl. 1 GUF1 patient (PMID:37820178) - Genomics England PanelApp — GUF1, Early onset or syndromic epilepsy panel (AMBER) - Genomics England PanelApp — GUF1, Mitochondrial disorders panel - GenCC — GUF1 (HGNC:25799) classifications - ClinGen — GUF1 curation results - NIH Genetic Testing Registry — GUF1 (Gene 60558) - Orphanet — GUF1 gene page (Infantile spasms syndrome, ORPHA:3451) - MalaCards — Developmental and Epileptic Encephalopathy 40 - GeneCards — GUF1

Reference Validation

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All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• GO:0003924 (1 mention) - the report calls it "Protein dysfunction: GUF1 is a ribosome-dependent GTPase"; GO calls it GTPase activity**
• CL:0000540 (2 mentions) - the report calls it "Tissue/cell level: neurons"; CL calls it neuron**

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

• UBERON:0000955 (1 mention) - the report calls it "Organ level: brain"; UBERON calls it brain**, and lists "the brain" among its other names
• GO:0005739 (1 mention) - the report calls it "Subcellular level: mitochondrion"; GO calls it mitochondrion**
• NCBITaxon:6239 (1 mention) - the report calls it "C. elegans"; NCBITaxon calls it Caenorhabditis elegans, and lists "Rhabditis elegans" among its other names
• NCBITaxon:4932 (1 mention) - the report calls it "S. cerevisiae"; NCBITaxon calls it Saccharomyces cerevisiae, and lists "Mycoderma cerevisiae" among its other names

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.