Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong
The NM_001048174.2(MUTYH):c.1016_1017delCC(p.Pro339GlnfsTer164) variant causes a frameshift change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. P339P) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.
MUTYH (HGNC:7527): (mutY DNA glycosylase) This gene encodes a DNA glycosylase involved in oxidative DNA damage repair. The enzyme excises adenine bases from the DNA backbone at sites where adenine is inappropriately paired with guanine, cytosine, or 8-oxo-7,8-dihydroguanine, a major oxidatively damaged DNA lesion. The protein is localized to the nucleus and mitochondria. This gene product is thought to play a role in signaling apoptosis by the introduction of single-strand breaks following oxidative damage. Mutations in this gene result in heritable predisposition to colorectal cancer, termed MUTYH-associated polyposis (MAP). Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Apr 2017]
Verdict is Pathogenic. Variant got 18 ACMG points.
PVS1
Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
PM2
Very rare variant in population databases, with high coverage;
PP5
Variant 1-45331745-TGG-T is Pathogenic according to our data. Variant chr1-45331745-TGG-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 406858.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
Review Status: criteria provided, single submitter
Collection Method: clinical testing
This sequence change creates a premature translational stop signal (p.Pro367Glnfs*164) in the MUTYH gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 183 amino acid(s) of the MUTYH protein. This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with MUTYH-related conditions. ClinVar contains an entry for this variant (Variation ID: 406858). This variant disrupts a region of the MUTYH protein in which other variant(s) (p.Val493Phe) have been determined to be pathogenic (PMID: 17949294, 19806110, 20618354, 25820570). This suggests that this is a clinically significant region of the protein, and that variants that disrupt it are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -
May 27, 2022
Baylor Genetics
Significance: Likely pathogenic
Review Status: criteria provided, single submitter