BMP15 gene promoter methylation status in the active and inactive X chromosome in sheep

For economic reasons as well as animal breeding of farm animals, fertility rate is of particular importance. Bone morphogenetic protein15 (BMP15) is one of the genes that associated with fertility in sheep. BMP15 is located on the X chromosome and one of the X chromosomes is inactivated in female mammals because of dosage compensation comparing to males. This study aimed to evaluate the methylation status of BMP15 promoter on the inactive X chromosome. To do this, samples were taken from ovaries of 22 nonpregnant, and 8 pregnant ewes. DNA and RNA was extracted from the follicles. Using specific primers for the bisulfite converted DNA and wild type, DNA, the methylation status of the cytosine was investigated. Expression of this gene in pregnant and nonpregnant group was also studied. Results showed that promoter of BMP15 is not methylated even in inactive chromosome and unlike most genes in this chromosome escapes from methylation. This shows that despite the inactivation of one of the X chromosomes, both alleles of this gene in mutant homozygous individuals are active and this resemble the functional pattern of the genes that are located on autosomal chromosomes. Expression of the gene in different physiological steps supports this. Results showed that mRNA expression of the gene among pregnant and nonpregnant groups was not significantly different. It seems that, inactivating an allele of BMP15 in early life of animal permanently will make the mutant homozygotes to be fertile.