Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_ModeratePM2PP5_Moderate
The NM_000368.5(TSC1):c.1998-1G>T variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★).
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]
Verdict is Likely_pathogenic. Variant got 6 ACMG points.
PVS1
Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.012589414 fraction of the gene. Cryptic splice site detected, with MaxEntScore 4.1, offset of 15, new splice context is: cctatgttgcctttacccAGcaa. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
PM2
Very rare variant in population databases, with high coverage;
PP5
Variant 9-132904455-C-A is Pathogenic according to our data. Variant chr9-132904455-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 237706.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr9-132904455-C-A is described in Lovd as [Pathogenic].
Review Status: criteria provided, single submitter
Collection Method: clinical testing
For these reasons, this variant has been classified as Pathogenic. This variant has not been reported in the literature in an individual with a TSC1-related disease, but has been reported in an individual affected with tuberous sclerosis complex in the Leiden Open-source Variation Database (PMID: 21520333) and in a family diagnosed with tuberous sclerosis complex (Invitae). This sequence change affects an acceptor splice site in intron 15 of TSC1. It is expected to disrupt mRNA splicing and likely results in an absent or disrupted protein product. -