CpG dinucleotide methylation patterns in the human androgen receptor gene and X-chromosome inactivation in peripheral blood leukocytes of phenotypically normal women

To evaluate methylation patterns in CpG dinucleotides (CpGs) of the human androgen receptor gene ( HUMARA ) and X-chromosome inactivation (XCI) status in phenotypically normal women in a general population, bisulfite genomic sequencing and methylation-specific PCR of genomic DNA extracted from peripheral blood samples of 124 phenotypically normal women were examined. CpGs methylation patterns were based on bisulfite genomic sequencing of the region containing nine CpGs in the HUMARA exon 1. The results of methylation status in CpGs from 43 independent colonies of 14 women revealed that not all CpGs were methylated even in highly methylated HUMARA alleles, and that the methylation status in CpGs varied between clones, by the position of CpGs methylation and in each subject. Evaluation of XCI was based on the method of an HUMARA (CAG)n polymorphism assay after bisulfite modification of DNA samples. The HUMARA allele size ratios of the women (82 heterozygotes) varied over a wide range and the distribution patterns of the ratios approached a 'normal distribution'. Since excessive skewing of XCI was observed in 11–12% of women, female carriers of an X-linked hereditary disease manifest its clinical symptoms or signs possibly in maximum 5–6%.