Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2
The ENST00000361392.9(ST3GAL3):c.123G>A(p.Lys41Lys) variant causes a synonymous change. The variant allele was found at a frequency of 0.00000372 in 1,614,066 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar 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]
Genetic Services Laboratory, University of Chicago
Significance: Uncertain significance
Review Status: criteria provided, single submitter
Collection Method: clinical testing
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Early infantile epileptic encephalopathy with suppression bursts Uncertain:1
Jul 19, 2022
Labcorp Genetics (formerly Invitae), Labcorp
Significance: Uncertain significance
Review Status: criteria provided, single submitter
Collection Method: clinical testing
In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. This sequence change falls in intron 2 of the ST3GAL3 gene. It does not directly change the encoded amino acid sequence of the ST3GAL3 protein. It affects a nucleotide within the consensus splice site. This variant is present in population databases (rs759128744, gnomAD 0.007%). This variant has not been reported in the literature in individuals affected with ST3GAL3-related conditions. ClinVar contains an entry for this variant (Variation ID: 436872). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. -