Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1PM2
The NM_000548.5(TSC2):āc.4663A>Gā(p.Ser1555Gly) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,106 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (ā ). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S1555N) has been classified as Uncertain significance.
TSC2 (HGNC:12363): (TSC complex subunit 2) This gene is a tumor suppressor gene that encodes the growth inhibitory protein tuberin. Tuberin interacts with hamartin to form the TSC protein complex which functions in the control of cell growth. This TSC protein complex negatively regulates mammalian target of rapamycin complex 1 (mTORC1) signaling which is a major regulator of anabolic cell growth. Mutations in this gene have been associated with tuberous sclerosis and lymphangioleiomyomatosis. [provided by RefSeq, May 2022]
Verdict is Uncertain_significance. Variant got 4 ACMG points.
PM1
In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 15 uncertain in NM_000548.5
PM2
Very rare variant in population databases, with high coverage;
Uncertain significance, criteria provided, single submitter
clinical testing
Labcorp Genetics (formerly Invitae), Labcorp
Aug 23, 2022
This variant is not present in population databases (gnomAD no frequency). This sequence change replaces serine, which is neutral and polar, with glycine, which is neutral and non-polar, at codon 1555 of the TSC2 protein (p.Ser1555Gly). This variant has not been reported in the literature in individuals affected with TSC2-related conditions. ClinVar contains an entry for this variant (Variation ID: 1346900). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated. 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. -