Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2PP3_Strong
The NM_001406626.1(TSC1):c.-281C>G variant causes a 5 prime UTR premature start codon gain change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).
TSC1 (HGNC:12362): (TSC complex subunit 1) This gene is a tumor suppressor gene that encodes the growth inhibitory protein hamartin. The encoded protein interacts with and stabilizes the GTPase activating protein tuberin. This hamartin-tuberin complex negatively regulates mammalian target of rapamycin complex 1 (mTORC1) signaling which is a major regulator of anabolic cell growth. This protein also functions as a co-chaperone for Hsp90 that inhibits its ATPase activity. This protein functions as a facilitator of Hsp90-mediated folding of kinase and non-kinase clients, including TSC2 and thereby preventing their ubiquitination and proteasomal degradation. Mutations in this gene have been associated with tuberous sclerosis and lymphangioleiomyomatosis. [provided by RefSeq, May 2022]
Review Status: criteria provided, single submitter
Collection Method: clinical testing
This sequence change replaces phenylalanine with leucine at codon 199 of the TSC1 protein (p.Phe199Leu). The phenylalanine residue is highly conserved and there is a small physicochemical difference between phenylalanine and leucine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with TSC1-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). 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. -
Gain of helix (P = 0.062);.;Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);.;.;Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);Gain of helix (P = 0.062);.;Gain of helix (P = 0.062);.;Gain of helix (P = 0.062);