title: A novel and rapid method of determining the effect of unclassified MLH1 genetic variants on differential allelic expression.
abstract: Germline mutations in mismatch repair genes predispose patients to Lynch Syndrome and the majority of these mutations have been detected in two key genes, MLH1 and MSH2. In particular, about a third of the missense variants identified in MLH1 are of unknown clinical significance. Using the PeakPicker software program, we have conducted a proof-of-principle study to investigate whether missense variants in MLH1 lead to allelic imbalances. Lymphocyte RNA extracted from patients harboring known MLH1 variants was used to quantify the ratio of variant to wild-type transcript, while patient lymphocyte DNA was used to establish baseline allelic expression levels. Our analysis indicated that the missense variants c.350C>T, c.793C>T, and c.1852_1853AA>GC, as well as the truncating variant c.1528C>T were all associated with significantly unbalanced allelic expression. However, the variants c.55A>T and c.2246T>C did not demonstrate an allelic imbalance. These results illustrate a novel and efficient method to investigate the pathogenicity of unclassified genetic variants discovered in mismatch repair genes, as well as genes implicated in other inherited diseases. In addition, the PeakPicker methodology has the potential to be applied in the diagnostic setting, which, in conjunction with results from other assays, will help increase both the accuracy and efficiency of genetic testing of colorectal cancer, as well as other inherited diseases.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sheron
authors.initials: S
authors.lastname: Perera
authors.forename: Brian
authors.initials: B
authors.lastname: Li
authors.forename: Soultana
authors.initials: S
authors.lastname: Tsitsikotas
authors.forename: Lily
authors.initials: L
authors.lastname: Ramyar
authors.forename: Aaron
authors.initials: A
authors.lastname: Pollett
authors.forename: Kara
authors.initials: K
authors.lastname: Semotiuk
authors.forename: Bharati
authors.initials: B
authors.lastname: Bapat
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000328:Adult; D000483:Alleles; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D053843:DNA Mismatch Repair / Q000235:genetics; D004252:DNA Mutational Analysis / Q000379:methods*; D005820:Genetic Testing / Q000379:methods*; D014644:Genetic Variation; D018095:Germ-Line Mutation; D006801:Humans; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics*; D012984:Software; D055815:Young Adult
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1