Description
The p.G55S variant (also known as c.163G>A), located in coding exon 2 of the MLH1 gene, results from a G to A substitution at nucleotide position 163. The glycine at codon 55 is replaced by serine, an amino acid with similar properties. The effect of this alteration in a hybrid yeast-human MLH1 has been assessed and authors report 34-66% loss of MMR compared to wild type (Ellison AR et al, Nucleic Acids Res. 2004 ; 32(18):5321-38). This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.001% (greater than 115000 alleles tested) in our clinical cohort. This amino acid position is highly conserved in available vertebrate species. This alteration is predicted to be probably damaging and deleterious by PolyPhen and SIFT in silico analyses, respectively. In addition, this alteration is predicted to be deleterious by MAPP-MMR in silico analyses (Chao E et al. Hum Mutat. 2008 Jun;29(6):852-60). Since supporting evidence is limited at this time, the clinical significance of p.G55S remains unclear.
# | Sample | Method | Observation |
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Origin | Affected | Number tested | Tissue | Purpose | Method | Individuals | Allele frequency | Families | Co-occurrences |
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1 | germline | unknown | not provided | not provided | not provided | | not provided | not provided | not provided | not provided |