Development of Analytical Tests for Detection of Pathogenicity and Identification of Molecular Defects in Unclear Genetic Variants of the DNA Mismatch Repair Gene MSH2 in Lynch Syndrome

• Applicant: Privatdozent Dr. Guido Plotz
• Subject Area: Gastroenterology ; Human Genetics
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270558391

Inactivating mutations of the MSH2 gene cause Lynch syndrome, a heritable cancer predisposition. Identification of an inactivating mutation in MSH2 in a patient enables predictive diagnosis and targeted cancer surveillance in family members. However, in a significant portion of MSH2 variants it is unclear if they are inactivating and therefore pathogenic. These "variants of uncertain significance" (VUS) need to be classified in order to establish a diagnosis. In most cases, this classification requires a functional analyses of the variant MSH2 gene or protein in the laboratory. However, currently there are no functional tests available which comprise evidence-based reference limits or classifiers that allow translating the test result into a pathogenicity statement. In this project, it is planned to analyze genetic MSH2 variants identified in cancer patients. These variants are introduced into MSH2 expression vectors and are expressed in cell culture or in vitro. Functional analyses are then performed and comprise (for example): expression level (RNA and protein), protein stability, catalytic activity, subcellular localization, interaction with protein partners and others. Besides VUS, variants with known clinical status (pathogenic or neutral) are included as controls to establish reference limits or identify classifiers for the assays. This will allow to translate functional results of the VUS into pathogenicity statements suitable for use in clinical diagnosis.In parallel to establishing test systems for clinical applications, the molecular defects identified in the different variants will serve to guide a thourough analysis of the MSH2 protein functions, including its protein interaction surfaces, DNA binding modes and ATPase cycle.

• DFG Programme: Research Grants