Vitamin D receptor gene polymorphisms in persons with Down's syndrome

Background

Down syndrome (DS) is a genetic alteration caused by having three copies of chromosome 21. Variations in the presence of alleles in the vitamin D receptor (VDR) gene have been linked to a variety in the phenotype and also considered a risk factor in some populations. In the present paper, we analyze whether a variation of the BsmI polymorphism in the VDR gene is overexpressed in patients with DS and whether it is related to any phenotype of the patients.

Patients and methods

We studied the BsmI polymorphism of the vitamin D receptor in DNA from peripheral blood of 85 patients with DS and 122 controls. The detection of each phenotype is performed by amplification of the DNA sequences of intron 8 of the VDR gene by polymerase chain reaction (PCR). We analyzed the differences in distribution of the alleles in patients with DS and the correlation of the genotype to different anthropometric (age, height, body mass index) and biochemical parameters (calcium, vitamin D,{PTH hormone, bone mass).

Results

The analysis of the distribution of the BsmI polymorphism showed a higher frequency of the B allele in the DS patients with respect to controls. In the same group of patients, regression analysis showed no link with any biochemical parameter. However, the homozygous genotype bb is more frequently found in taller individuals (p=0.04) and the BB in older individuals (p=0.03).

Conclusions

The B allele of the BsmI polymorphism of the VDR gene is more frequent in people with DS. The genotypes bb and BB are more frequent in taller and longer-living DS patients respectively. This result points out the possibility that VDR genotype could influence these two phenotypic characteristics of DS patients.