BRCA1 Mutation Screening With The Protein Trunctation Test.
P. Devilee1,2, F.B.L. Hogervorst2, A. Petrij2, M. van Vliet2 E. Bakker2, G.J.B. van Ommen2, and C.J. Cornelisse1, Depts. of Pathology1, and Human Genetics2, Leiden University Hospital, Leiden.
BRCA1 is a major breast-and ovarian cancer susceptibility gene. Since BRCA1 mutation carriers have a 85% risk on developing breast cancer and 63% on ovarian cancer, mutation testing may be of potential benefit. Due to the complex genomic structure of BRCA1, rapid mutation detection is a technical challenge. Since the majority of mutations results in a premature termination of protein sysnthesis, these mutations might be detected by the Protein Truncation Test (PTT). Initially, the test was used to detect mutations in exon 11 encoding 61% of the protein. Genomic DNA from stored DNA samples or deparaffinized archival tissue is amplified using three pairs of overlapping primers which after in vitro transcription and translation yields three protein fragments. Truncated proteins are detected by their altered electrophoretic mobility. More recently, we screen the entire BRCA1 coding sequence using cDNA obtained by reversed transcription of RNA extracted from lymphocytes. To date truncating mutations in exon 11, confirmed by direct sequencing, have been detected in over 20 families. It is concluded that PTT provides a rapid test for mutations that seriously interfere with the normal function of the BRCA1 protein.