Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM2PP3_StrongPP5_Moderate
The NM_001354247.1(ST3GAL5):c.-321G>C variant causes a 5 prime UTR premature start codon gain change. The variant allele was found at a frequency of 0.00000124 in 1,614,092 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★).
ST3GAL5 (HGNC:10872): (ST3 beta-galactoside alpha-2,3-sialyltransferase 5) Ganglioside GM3 is known to participate in the induction of cell differentiation, modulation of cell proliferation, maintenance of fibroblast morphology, signal transduction, and integrin-mediated cell adhesion. The protein encoded by this gene is a type II membrane protein which catalyzes the formation of GM3 using lactosylceramide as the substrate. The encoded protein is a member of glycosyltransferase family 29 and may be localized to the Golgi apparatus. Mutation in this gene has been associated with Amish infantile epilepsy syndrome. Transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]
Verdict is Likely_pathogenic. Variant got 8 ACMG points.
PM2
Very rare variant in population databases, with high coverage;
PP3
MetaRNN computational evidence supports a deleterious effect, 0.989
PP5
Variant 2-85847939-C-G is Pathogenic according to our data. Variant chr2-85847939-C-G is described in ClinVar as [Pathogenic]. Clinvar id is 254245.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr2-85847939-C-G is described in Lovd as [Pathogenic].
Review Status: criteria provided, single submitter
Collection Method: clinical testing
This sequence change replaces cysteine, which is neutral and slightly polar, with serine, which is neutral and polar, at codon 195 of the ST3GAL5 protein (p.Cys195Ser). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of GM synthetase deficiency (PMID: 27232954). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 254245). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt ST3GAL5 protein function. Experimental studies have shown that this missense change affects ST3GAL5 function (PMID: 30576498). For these reasons, this variant has been classified as Pathogenic. -