TP53 NM_000546.6:c.380C>T, Ser127Phe

This sequence change replaces serine, which is neutral and polar, with phenylalanine, which is neutral and non-polar, at codon 127 of the TP53 protein (p.Ser127Phe). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with clinical features of Li-Fraumeni syndrome and/or Li-Fraumeni syndrome (PMID: 32817165, 34240179; Invitae; external communication). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 182928). Advanced modeling performed at Invitae incorporating data from internal and/or published experimental studies (PMID: 12826609, 29979965, 30224644) indicates that this missense variant is expected to disrupt TP53 function. Experimental studies have shown that this missense change affects TP53 function (PMID: 12826609, 16000567, 16322298, 29979965, 30224644). This variant disrupts the p.Ser127 amino acid residue in TP53. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 29470806; Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic.

This variant is considered likely pathogenic. Functional studies indicate this variant impacts protein function [PMID: 29979965]. This variant is expected to disrupt protein structure [Myriad internal data].

The p.S127F variant (also known as c.380C>T), located in coding exon 4 of the TP53 gene, results from a C to T substitution at nucleotide position 380. The serine at codon 127 is replaced by phenylalanine, an amino acid with highly dissimilar properties. This variant was detected in a cohort of 295 women considered at high risk for breast cancer (Guindalini RSC et al. Clin Cancer Res, 2019 Mar;25:1786-1794). This variant is in the DNA binding domain of the TP53 protein and is reported to have non-functional transactivation in yeast based assays (Kato S et al. Proc Natl Acad Sci U S A, 2003 Jul;100:8424-9). Studies conducted in human cell lines indicate this alteration is deficient at growth suppression and has a dominant negative effect (Kotler E et al. Mol.Cell. 2018 Jul;71:178-190.e8; Giacomelli AO et al. Nat. Genet. 2018 Oct;50:1381-1387). Another alteration at the same codon, p.S127T (c.379T>A), has been shown to also have non-functional transactivation in yeast based assays, be deficient at growth suppression, and have a dominant negative effect (Ambry internal data; Kato S et al. Proc. Natl. Acad. Sci. USA. 2003 Jul;100:8424-9; Kotler E et al. Mol.Cell. 2018 Jul;71:178-190.e8; Giacomelli AO et al. Nat. Genet. 2018 Oct;50:1381-1387). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic.