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Early onset or syndromic epilepsy v4.111 ENTPD1 Arina Puzriakova Tag Q2_23_promote_green was removed from gene: ENTPD1.
Early onset or syndromic epilepsy v4.110 ENTPD1 Arina Puzriakova reviewed gene: ENTPD1: Rating: GREEN; Mode of pathogenicity: ; Publications: ; Phenotypes: ; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Early onset or syndromic epilepsy v4.109 ENTPD1 Arina Puzriakova Source NHS GMS was added to ENTPD1.
Source Expert Review Green was added to ENTPD1.
Rating Changed from Amber List (moderate evidence) to Green List (high evidence)
Early onset or syndromic epilepsy v4.37 ENTPD1 Achchuthan Shanmugasundram Tag Q2_23_promote_green tag was added to gene: ENTPD1.
Early onset or syndromic epilepsy v4.37 ENTPD1 Achchuthan Shanmugasundram Classified gene: ENTPD1 as Amber List (moderate evidence)
Early onset or syndromic epilepsy v4.37 ENTPD1 Achchuthan Shanmugasundram Added comment: Comment on list classification: As reviewed by Konstantinos Varvagiannis, there are seven unrelated cases with epilepsy. Hence, this gene can be promoted to GREEN rating in the next major update.
Early onset or syndromic epilepsy v4.37 ENTPD1 Achchuthan Shanmugasundram Gene: entpd1 has been classified as Amber List (Moderate Evidence).
Early onset or syndromic epilepsy v4.36 ENTPD1 Achchuthan Shanmugasundram reviewed gene: ENTPD1: Rating: GREEN; Mode of pathogenicity: None; Publications: 35471564; Phenotypes: Spastic paraplegia 64, autosomal recessive, OMIM:15683; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Early onset or syndromic epilepsy v2.518 ENTPD1 Konstantinos Varvagiannis gene: ENTPD1 was added
gene: ENTPD1 was added to Genetic epilepsy syndromes. Sources: Literature
Mode of inheritance for gene: ENTPD1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: ENTPD1 were set to 35471564; 28742222
Phenotypes for gene: ENTPD1 were set to Spastic paraplegia 64, autosomal recessive, OMIM:615683
Penetrance for gene: ENTPD1 were set to Complete
Review for gene: ENTPD1 was set to AMBER
Added comment: Biallelic ENTPD1 pathogenic variants cause Spastic paraplegia 64, autosomal recessive (# 615683) with DD/ID being a universal feature as suggested by the study by Calame, Herman et al. Epilepsy was also reported in 7 unrelated individuals so far with supporting evidence also from mouse model.

Consider upgrade to green rating in the ID panel, inclusion in the epilepsy panel (amber/green). Also consider adding this gene in panels for white matter disorders (which does not appear to be the case so far).

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Calame, Herman et al (2022 - PMID:35471564) describe the phenotype of 27 individuals (from 17 unrelated families) with biallelic ENTPD1 pathogenic variants. The authors collected additional information from previously reported cases and summarize the core features of the disorder.

As they highlight, the disorder has a childhood onset, with DD/ID as a universal feature (27/27 or 36/36 considering cases from the literature), progressive spastic paraparesis (36/36) [On neurological examination, abnormal reflexes were common with hyperreflexia (8/36), hyporeflexia (5/36), areflexia (3/36) or both hyperreflexia and hypo/areflexia in 20, suggesting mixed upper and lower motor neuron dysfunction]. Other features included dysarthria (in 20/27 or 27/36 overall), white matter abnormalities on brain imaging (12/22 or 15/28, in 12-13 signal abnormalities in posterior limb of internal capsule), or dysmorphisms (13/27). Some individuals had evidence of neurocognitive regression (18/27 or 21/36). Epilepsy was reported in 7 unrelated individuals within the cohort (likely 7/25 as for 2 sibs from Fam11, this was NA). Previous studies had not reported this feature.

ENTPD1 encodes ectonucleoside triphosphate diphosphohydrolase 1, involved in hydrolysis of ATP to ADP (and ADP to AMP).

While previous studies identified 5 distinct variants (2 missense and 3 pLoF), the authors describe 12 novel variants 10 of which pLoF (stopgain, stoploss, splicing) and 2 missense (one SNV and one MNV).

In silico predictions were in favor of a deleterious effect. Almost all variants were ultrarare or absent from gnomAD, although 4 were recurrent ones [NM_001776.6]: c.1109T>A / p.(Leu370*) (possibly recurrent mutation found in 4 families from Persia/Poland), c.574-6_574-3del, c.770_771del / p.(Gly257Glufs*18) (possibly founder allele from the Iberian peninsula), c.1041del / p.(Ile348Phefs*19) (?founder allele in Persia).

Variant studies:
- c.574-6_574-3del : was shown to result to skipping (complete absence) of exon 6 (RNA extracted from a whole blood sample, followed by cDNA synthesis and Sanger seq using different primer sets).
- c.401T>G / p.Met134Arg : RT-qPCR of mRNA from patient lymphoblasts showed significantly reduced mRNA levels in individuals homozygous for this variant. Protein levels were also markedly decreased upon Western blot. ENTPD1 is essential for hydrolysis of ATP to ADP and ADP to AMP, with impairment of ATPase and ADPase activity (significantly decreased phosphate production) in patient lymphoblasts.
- c.185T>G / p.Leu62* : As ENTPD1 (also known as CD39) is highly expressed in lymphocytes and polymorphonuclear leukocytes, the authors used flow cytometry on whole blood from individuals hmz for this variant, carrier parents and controls, demonstrating complete absence of ENTPD1 positive cells in affected individuals. Immunohistochemistry for ENTPD1 using paraffin sections of sural nerve demonstrated complete absence of endo and epineural vascular staining (/lack of expression).

Untargeted metabolomic analyses were performed in plasma samples from 3 affected individuals. Consistent patterns of metabolic abnormalities with alterations in lipid, nucleotide and carbohydrate metabolism were observed. Some metabolite patterns or biomarkers were indicative of inflammatory state, liver disease, insulin resistance / metabolic syndrome.

The authors cite previous mouse models suggesting hepatocellular disfunction, impaired glucose homeostasis and intestinal inflammation in ectonucleotidase deficiency (probably not specific to Entpd1). Further, the authors cite a study by Lanser et al for Entpd1-/- mice exhibiting proepileptogenic activity (2017 - PMID: 28742222 / “Disruption of the ATP/adenosine balance in CD39(-/-) mice is associated with handling-induced seizures”).

In vitro studies using a cellular model of sympathetic neurons (nerve growth factor-differentiated PC12 cells) provided evidence that ENTPD1 expression levels modulate exocytic and ischemic neurotransmitter release (cited PMID: 21325440)

Overall, the authors propose accessible diagnostic biomarkers for the disorder (e.g. flow cytometry on periperal blood cells, immunochemistry of peripheral nerve biopsies, T2 hyperintense signal in posterior limb of internal capsule, diminished ATP/ADP breakdown in lymphoblast assays, alteration in metabolic pathways) and discuss potential future developments (ASOs for splicing variant, antagonism for purinergic receptor P2X7, etc).
Sources: Literature