Somatic hypermutability of microsatellite sequences in Turcot syndrome: Implications for forensic genetics

We investigated allelic profiles at microsatellite loci included in the AmpFlSTR® Identifiler™ kit (Applied Biosystems, Foster City, CA, USA) as well as at additional microsatellite sequences (di- and monucleotide repeats) in a family with 3 siblings affected by central nervous systems (CNS) (2 siblings) or colorectal cancer (1 sibling). Based on clinical and molecular findings, a diagnosis of type 1 Turcot syndrome was established for this family. DNA isolated from normal intestinal mucosa and peripheral leukocytes of the patient with colorectal cancer was characterized by the presence of additional peaks that were not present in parental DNA. In markers included in the AmpFlSTR® Identifiler™ kit, the sizes of the extra peaks were usually larger by one repeat unit than those of parentally derived alleles. The same peaks were observed when loci were amplified in singleplex PCR. It is important that professionals involved in forensic genetics be aware of the existence of a genetic condition that can cause a peculiar pattern of microsatellite alterations in constitutional DNA.