ClinVar Genomic variation as it relates to human health

The ATM c.3118A>G (p.Met1040Val) variant has a GnomAD (v2.1.1) filtering allele frequency of 4.2% (AFR) which is above the ATM BA1 threshold of 0.5% (BA1). This variant has been observed in a homozygous state in multiple individuals without Ataxia-Telangiectasia (BP2_Strong, GTR Lab IDs: 500031, 61756). In silico protein predictors (BayesDel, score:-0.45, AGVGD, Class C0) predict that this alteration is not deleterious (BP4). In summary, this variant meets criteria to be classified as benign. ACMG/AMP criteria applied, as specified by the HBOP Variant Curation Expert Panel.

Converted during submission to Likely benign.

This variant is considered benign. This variant has been observed at a population frequency that is significantly greater than expected given the associated disease prevalence and penetrance. This variant is strongly associated with less severe personal and family histories of cancer, typical for individuals without pathogenic variants in this gene [PMID: 25085752].

Variant summary: The ATM c.3118A>G (p.Met1040Val) variant involves the alteration of a non-conserved nucleotide. 3/3 in silico tools predict a benign outcome for this variant (SNPs&GO not captured due to low reliability index). This variant was found in 459/122598 control chromosomes (10 homozygotes), predominantly observed in the African subpopulation at a frequency of 0.0413846 (428/10342, 10 homozygotes). This frequency is about 10 times the estimated maximal expected allele frequency of a pathogenic ATM variant (0.0039528), suggesting this is likely a benign polymorphism found primarily in the populations of African origin. Variant has been reported by multiple studies in both patients and healthy controls, supporting the non-pathogenic nature of this variant. In addition, multiple clinical diagnostic laboratories classified this variant as benign. Considering the high allele frequency of the variant and the homozygous occurrences in the African subpopulation, it was classified as Benign.

This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease.

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease.

This alteration is classified as benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Likely benign based on allele frequency in 1000 Genomes Project or ESP global frequency and its presence in a patient with a rare or unrelated disease phenotype. NOT Sanger confirmed.

The ATM p.Met1040Val variant was identified in 18 of 1214 proband chromosomes (frequency: 0.01) from individuals or families with breast cancer or non-Hodgkin lymphoma (Thorstenson 2001, Bretsky 2003, Sipahimalani 2007). The variant was also identified in ClinVar (benign 4x: GeneDx, Ambry Genetics, Invitae, Prevention Genetics; likely benign 3x: Mercy Hospital, Illumina, University of Chicago; not provided 1x: ITMI) unconfirmed somatic 1x: OMIM), COSMIC (2 lymphoid neoplasms, somatic status unknown), MutDB (link to UniProtKB/Swiss-Prot database, variant is unclassified with poor conservation across species), databases. The variant was not identified in the GeneInsight-COGR, LOVD 3.0, or ATM-LOVD databases. The variant was identified in control databases in 1095 (27 homozygous) of 277102 chromosomes at a frequency of 0.004 increasing the likelihood this could be a low frequency benign variant (Genome Aggregation Consortium Feb 27, 2017). The variant was identified in the following populations at a frequency greater than 1%: African in 1012 of 24020 chromosomes (freq: 0.042). The p.Met1040Val residue is conserved in in mammals but not in more distantly related organisms however computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) do not suggest a high likelihood of impact to the protein; this information is not predictive enough to rule out pathogenicity. The variant occurs outside of the splicing consensus sequence and 1 of 5 in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer, and HumanSpliceFinder) predict a greater than 10% difference in splicing; this is not very predictive of pathogenicity. In summary, based on the above information, this variant meets our laboratory's criteria to be classified as benign.