Severe microcephaly

Gene: PPP1R35

Comment on list classification: Rating this gene as Red, but with a watchlist tag, until more evidence is available.

Created: 25 Mar 2021, 3:23 p.m. | Last Modified: 25 Mar 2021, 3:23 p.m.

Panel Version: 2.104

Conference poster (Genomics of Rare Disease 2021) - 'Biallelic frameshift indel in PPP1R35 as a cause of primary microcephaly' by Dawood et al, Baylor College of Medicine -

Proband from a Turkish consanguineous family with primary microcephaly (-4.3 SD at birth, -6.1 SD by 42 months) and GDD. Brain imaging showed thinning of corpus collosum, mild cerebellar volume loss, increased extra-axial CSF spaces, pachygyria, dysmorphic ventricular system and delayed myelination of the internal capsule. Exome sequencing revealed a biallelic frameshifting indel in the PPP1R35 gene (c.753_*3delGGAAGCGTAGACCinsCG; p.Trp251Cysfs*22), resulting in deletion of the canonical stop codon in the last exon. Sequencing of unaffected parents and 2 unaffected sibs confirmed segregation with the phenotype. Droplet digital PCR demonstrated expression of mutant mRNA, with comparable gene expression levels observed for mutant and wild-type alleles in fibroblasts.

Authors note a second Iranian consanguineous family in literature with two sibs with microcephaly and the same, p.Trp251Cysfs*22 variant - however, this paper could not be found in PubMed.
Sources: Other

Created: 25 Mar 2021, 3:23 p.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Primary microcephaly