Simultaneous detection of the exon 10 polymorphism and a novel intronic single base insertion polymorphism in the XPD gene using single strand conformation polymorphism

We developed a new method based on the single strand conformation polymorphism (SSCP) technique for the detection of a G23591A (Asp312Asn) polymorphism in exon 10 of the XPD gene. In the process we also identified a novel polymorphism 23623C-ins (IVS10 + 17C-ins) in intron 10 of the same gene. With this newly developed SSCP-based method of genotyping we could detect both polymorphisms in the same assay and thus consequently determine the haplotype. In order to determine the population frequency of the novel polymorphism and the haplotype frequency, 302 healthy individuals were genotyped. The allelic frequency of the 23623C-ins intronic polymorphism was 0.16, whereas the frequency of the variant allele for the G23591A polymorphism was 0.39. Forty-three individuals (14%) were heterozygous for both polymorphisms but none carried polymorphic variants for both G23591A and 23623C-ins on the same allele. The effect of the novel intronic insertion polymorphism, which is located 16 nt downstream of the 3′-end of exon 10 of the XPD gene and involves a mononucleotide C repeat sequence, on expression remains to be determined.