Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1PM2PM5PP3_Strong
The NM_001048174.2(MUTYH):c.1103G>T(p.Gly368Val) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.000000684 in 1,461,596 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. 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. G368S) 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]
Verdict is Pathogenic. Variant got 10 ACMG points.
PM1
In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 13 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 chr1-45331556-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 5294.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
PP3
MetaRNN computational evidence supports a deleterious effect, 0.964
Review Status: criteria provided, single submitter
Collection Method: clinical testing
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. This variant disrupts the p.Gly396 amino acid residue in MUTYH. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 11818965, 16557584, 17489848, 19793053). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 645786). This variant has not been reported in the literature in individuals affected with MUTYH-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces glycine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 396 of the MUTYH protein (p.Gly396Val). -
Jan 23, 2024
Baylor Genetics
Significance: Uncertain significance
Review Status: criteria provided, single submitter