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Intellectual disability v3.1519 IMPDH2 Ivone Leong Tag Q3_21_rating was removed from gene: IMPDH2.
Intellectual disability v3.1519 IMPDH2 Sarah Leigh commented on gene: IMPDH2
Intellectual disability v3.1519 IMPDH2 Ivone Leong Source Expert Review Green was added to IMPDH2.
Rating Changed from Amber List (moderate evidence) to Green List (high evidence)
Intellectual disability v3.1300 IMPDH2 Arina Puzriakova Classified gene: IMPDH2 as Amber List (moderate evidence)
Intellectual disability v3.1300 IMPDH2 Arina Puzriakova Added comment: Comment on list classification: New gene added by Zornitza Stark. This gene is not yet associated with a relevant phenotype in OMIM or G2P, but sufficient unrelated cases with relevant phenotype to rate Green at the next GMS review. Neurodevelopmental delay is an early feature that may be evident prior to other manifestations (plausible that other cases may develop dystonic signs later in life) and so inclusion on this panel is warranted.
Intellectual disability v3.1300 IMPDH2 Arina Puzriakova Gene: impdh2 has been classified as Amber List (Moderate Evidence).
Intellectual disability v3.1299 IMPDH2 Arina Puzriakova Tag Q3_21_rating tag was added to gene: IMPDH2.
Intellectual disability v3.1299 IMPDH2 Arina Puzriakova reviewed gene: IMPDH2: Rating: GREEN; Mode of pathogenicity: None; Publications: 33098801; Phenotypes: ; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Intellectual disability v3.1216 IMPDH2 Zornitza Stark gene: IMPDH2 was added
gene: IMPDH2 was added to Intellectual disability. Sources: Literature
Mode of inheritance for gene: IMPDH2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: IMPDH2 were set to 33098801
Phenotypes for gene: IMPDH2 were set to Neurodevelopmental disorder with dystonia
Review for gene: IMPDH2 was set to GREEN
Added comment: 6 unrelated individuals
1x individual in a dystonia cohort index case with infancy-onset dystonia and other neurological manifestations with a de-novo missense variant, c.338G>A (p.Gly113Glu) in IMPDH2, predicted to disrupt an invariant residue within the cystathionine-β-synthase (CBS) domain pair of the encoded protein.
IMPDH2 encodes IMPDH2, a key enzyme in the purine biosynthetic pathway, expressed throughout the brain and not linked previously to any human Mendelian condition.
1x individual with a de-novo substitution, c.337G>A (p.Gly113Arg), was found in in-house whole-exome sequencing data from 500 individuals with neurodevelopmental disorders. Through GeneMatcher, de novo variants identified:
3 x missense: c.729G>C (p.Gln243His), c.619G>C (p.Gly207Arg), and c.619G>A (p.Gly207Arg)
1 x deletion: c.478_480delTCC (p.Ser160del)
The six variants were predicted to be deleterious and none of them seen in control databases. All affected conserved amino acids and resided in and around the cystathionine-β-synthase domain pair.
The described variants are situated in and around the CBS domain pair, a regulatory element in which clustering of pathogenic missense variants has already been shown for the homologue of IMPDH2, IMPDH1.

All individuals shared similar neurodevelopmental phenotypes. Apart from the dystonia cohort index case, one participant had evidence of dystonic posturing.

Modelling of the variants on 3D protein structures revealed spatial clustering near specific functional sites, predicted to result in deregulation of IMPDH2 activity. Additionally, thermal-shift assays showed that the c.619G>A (p.Gly207Arg) variant, identified as within the CBS domain pair, and c.729G>C (p.Gln243His), which is in close vicinity, affected the stability or folding behaviour of IMPDH2.
Sources: Literature