ClinVar Genomic variation as it relates to human health

The c.7926A>C variant has been reported in the literature in a cell line from an individual with ataxia-telangiectasia who also had two truncating ATM variants (Wright 1996). Experimental studies (Wright 1996) and in silico prediction tools suggest that this variant may impact splicing. This variant is not present in population databases (https://gnomad.broadinstitute.org). In silico analyses indicate this is an evolutionarily conserved residue. Thus, it is unknown at this time whether this variant increases cancer risk.

This variant is considered pathogenic. mRNA analysis has demonstrated abnormal mRNA splicing occurs [Myriad internal data]. This variant has been reported in multiple individuals with clinical features of gene-specific disease [PMID: 7792600, 8808599, 21665257].

Exonic splice variant demonstrated to result in skipping of exons 52 and/or 53, also known as exons 54 and 55 using alternate exon numbering (PMID: 7792600, 8845835, 8808599); Observed in the heterozygous state in an individual with breast cancer (PMID: 26556299); Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis indicates that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 17726045, 27304073, 16166284, 9443866, 7792600, 8808599, 30128536, 9259193, 27535533, 8845835, 26556299)

The c.7926A>C pathogenic mutation (also known as p.R2642S), located in coding exon 52 of the ATM gene, results from an A to C substitution at nucleotide position 7926. The arginine at codon 2642 is replaced by serine, an amino acid with dissimilar properties. This nucleotide position is well conserved in available vertebrate species. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. This alteration was reported in conjunction with a pathogenic ATM mutation in an individual diagnosed with ataxia-telangiectasia and was demonstrated to result in transcripts with both exon 55 skipping and exon 54 and 55 skipping (Wright J et al. Am. J. Hum. Genet. 1996 Oct;59(4):839-46, Savitsky K et al. Science, 1995 Jun;268:1749-53). In silico splice site analysis for this alteration is inconclusive. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.

This sequence change replaces arginine, which is basic and polar, with serine, which is neutral and polar, at codon 2642 of the ATM protein (p.Arg2642Ser). RNA analysis indicates that this missense change induces altered splicing and may result in an absent or altered protein product. This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with ataxia-telangiectasia and with breast cancer (PMID: 8808599, 26556299; internal data). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 215980). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be tolerated. Studies have shown that this missense change results in skipping of exon 53, and produces a non-functional protein and/or introduces a premature termination codon (internal data). For these reasons, this variant has been classified as Pathogenic.