Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1PM2PP3_Strong
The NM_001048174.2(MUTYH):c.806G>T(p.Cys269Phe) variant causes a missense 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. Variant has been reported in ClinVar as Uncertain significance (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C269Y) has been classified as Uncertain significance.
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 Likely_pathogenic. Variant got 8 ACMG points.
PM1
In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 16 uncertain in NM_001048174.2
PM2
Very rare variant in population databases, with high coverage;
PP3
MetaRNN computational evidence supports a deleterious effect, 0.987
Department of Pathology and Laboratory Medicine, Sinai Health System
Significance: Uncertain significance
Review Status: no assertion criteria provided
Collection Method: clinical testing
The p.Cys297Phe variant has not been reported in the literature nor previously identified by our laboratory. The Cys residue is conserved across mammals and computational analyses (PolyPhen2, SIFT, AlignGVGD) suggest that the Phe variant may impact the protein. However, this information is not predictive enough to assume pathogenicity. The presence of this variant in combination with a reported pathogenic variant increases the likelihood that the p.Cys297Phe variant is pathogenic. In summary, based on the above information, the clinical significance of this variant cannot be determined with certainty at this time although we would lean towards a more pathogenic role for this variant. This variant is classified as a Predicted Pathogenic. -
Familial adenomatous polyposis 2 Uncertain:1
Apr 01, 2019
Department of Pathology and Laboratory Medicine, Sinai Health System
Significance: Uncertain significance
Review Status: criteria provided, single submitter