The role of melatonin and circadian rhythm genes in infertility and premature ovarian failure

Abstract

Aims: To investigate the roles melatonin and circadian rhythms play in infertility and premature ovarian failure. Methods: The melatonin receptor genes of 27 people with unexplained infertility were sequenced to see if any novel or known gene variants could be identified. A population of 93 infertile couples, 17 POF patients and 86 matched controls were genotyped to assess the frequency of gene variants within the circadian rhythm genes, melatonin synthesis genes and the melatonin receptor genes. The expression of clock genes was examined to assess the role melatonin plays in regulating clock genes in GCT cell line, COV434. The circadian rhythm genes were also observed using the expression of key clock genes over three time points in melatonin treated and untreated cells. Results: Sequencing the melatonin receptors revealed four SNPs: rs28383653 and rs8192549 in MTNR1A and rs61747139 and rs1562444 in MTNR1B. The minor allele frequency of all four SNPs was not found to be significant. Genotyping revealed a significant association between the MTNR1A SNP rs13140012 and POF (p=0.0052) this association remained significant after Bonferroni Correction. No other SNPs were found to be associated with infertility or POF. RT-qPCR did not find any significant differences in expression of clock genes in COV434 cells that were treated with melatonin or not. Some evidence of circadian rhythm expression was found in the time course data. The expression of clock genes in cells not treated with melatonin appeared to lag 6 hours behind the expression of treated cells. A significant difference in the expression of NPAS2 over the 18 hour period was found in both the treated and untreated cells (p=0.039 and p=0.0273) Conclusion: The gene variants found in the population with unexplained infertility did not appear to be an underlying cause of infertility in the entire cohort although the variants may have affected the fertility of the individual. The MTNR1A SNP rs13140012 may cause an altered transcription binding site this may also be the underlying cause of this significant association (Esposito et al., 2011).This may lead to a new area of research and a possibly changes in diagnostic techniques and treatment s for POF in the future. Melatonin did not appear to influence levels of clock gene expression in the COV434 cell line. COV434 cells express clock genes in a circadian rhythm and melatonin may play a role in initiating the expression of these genes. The analysis of clock gene expression in the ovary may lead to better understanding of how circadian rhythms affect ovarian function and overall fertility. A better understanding of the many ways melatonin affects ovarian function will allow better treatment of infertility and possibly improve outcomes of IVF procedures.