Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM1PM2PM5
The NM_001048174.2(MUTYH):c.586G>T(p.Ala196Ser) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A196D) has been classified as Likely pathogenic.
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]
MUTYH Gene-Disease associations (from GenCC):
familial adenomatous polyposis 2
Inheritance: AD, AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), Genomics England PanelApp, ClinGen, G2P
colorectal cancer
Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen
familial ovarian cancer
Inheritance: AD, AR Classification: NO_KNOWN Submitted by: ClinGen
hereditary breast carcinoma
Inheritance: AD, AR Classification: NO_KNOWN Submitted by: ClinGen
Our verdict: Likely_pathogenic. The variant received 6 ACMG points.
PM1
In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 45 uncertain in NM_001048174.2
PM2
Very rare variant in population databases, with high coverage;
PM5
Other missense variant is known to change same aminoacid residue: Variant chr1-45332593-G-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 496104.
In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with MUTYH-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces alanine with serine at codon 224 of the MUTYH protein (p.Ala224Ser). The alanine residue is highly conserved and there is a moderate physicochemical difference between alanine and serine. -