Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2
The NM_006279.5(ST3GAL3):c.343C>G(p.Arg115Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000496 in 1,614,048 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R115C) has been classified as Uncertain significance.
ST3GAL3 (HGNC:10866): (ST3 beta-galactoside alpha-2,3-sialyltransferase 3) The protein encoded by this gene is a type II membrane protein that catalyzes the transfer of sialic acid from CMP-sialic acid to galactose-containing substrates. The encoded protein is normally found in the Golgi apparatus but can be proteolytically processed to a soluble form. This protein is a member of glycosyltransferase family 29. Mutations in this gene have been associated with a form of autosomal recessive nonsymdromic cognitive disability as well as infantile epileptic encephalopathy. Multiple transcript variants encoding several different isoforms have been found for this gene. [provided by RefSeq, Jul 2017]
Verdict is Uncertain_significance. Variant got 2 ACMG points.
PM2
?
PM2 - Absent from controls (or at extremely low frequency if recessive) in Exome Sequencing Project, 1000 Genomes Project, or Exome Aggregation Consortium
Very rare variant in population databases, with high coverage;
Early infantile epileptic encephalopathy with suppression bursts Uncertain:1
Uncertain significance, criteria provided, single submitter
clinical testing
Invitae
Nov 04, 2020
This variant has not been reported in the literature in individuals with a ST3GAL3-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces arginine with glycine at codon 115 of the ST3GAL3 protein (p.Arg115Gly). The arginine residue is moderately conserved and there is a moderate physicochemical difference between arginine and glycine. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). In summary, this variant has uncertain impact on ST3GAL3 function. The available evidence is currently insufficient to determine its role in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -