Identification of a novel Tru9 I polymorphism in the human vitamin D receptor gene.

We found a novel Tru9 I restriction polymorphism in intron 8 of the vitamin D receptor (VDR) gene in healthy French Caucasians. It corresponds to a substitution of A for G at nucleotide +443 bp from the end of exon 8. The allelic frequency of G and A in 151 unrelated subjects was 0.894 and 0.106, respectively. This polymorphism is located in the reverse primer binding site of primers that have been frequently used in the literature to genotype a BsmI restriction polymorphism. The presence of the Tru9I A allele may result in allele drop-out when the BsmI restriction fragment length polymorphism (RFLP) is genotyped with the original set of primers. This novel Tru9I polymorphism may be useful for analysis of the VDR gene.