Mutation screening of APC gene in patients with Familial Adenomatous Polyposis by Conformation Sensitive Gel Electrophoresis (CSGE)

Objectives: Familial Adenomatous Polyposis (FAP) is an autosomal dominant predisposition to colon cancer. This hereditary genetic disease is characterized by more than 100 adenomatous polyps in colon and rectum. Additional features may include desmoids tumors, polyps in the upper gastrointestinal tract, osteomas and Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE). A mutation in APC (Adenomatous Polyposis Coli) is found in the majority of cases. Mutation detection and genetic analysis of APC in this syndrome is highly recommended as the penetrance is almost 100% by 40 years of age. The APC gene expanding on 5q21-q22 has 15 exons and has an ORF with 8538 nucleotides which codes a protein with 2843 amino acids.
Materials and Methods: 5 families among 150 families were selected according to accepted diagnosis criteria of FAP. CSGE (Conformation Sensitive Gel Electrophoresis) technique for the first time was set up to screen mutations in all 15 exons of APC gene by this technique. Direct sequencing was used as gold standard to confirm CSGE results.
Results: CSGE analysis showed electrophoresis migration anomalies and heteroduplex formation in exon 15 of APC in all patients. Further analysis by direct sequencing characterized these heteroduplexes as deleterious mutations. These mutations can be classified as non sense, frame shift and deletion.
Conclusion: For the first time, CSGE technique was set up for mutation screening of coding and some parts of non coding regions of APC. In comparison with other screening methods, this technique has many advantages so it can be used in routine clinical laboratories. As mutation detection in APC is laborious, needs high tech technology and is expensive, finding sensitive and cost effective mutation screening technique would have direct positive effect on clinical management of families with familial susceptibility to colon cancer.