Abstract
Polycystic ovary syndrome (PCOS) is a prevalent reproductive neuroendocrine disorder characterised by hyperandrogenism, anovulation and/or the presence of polycystic ovaries. It is one of the leading causes of infertility worldwide, in addition to being associated with many other comorbidities such as diabetes, insulin resistance, cardiovascular conditions and psychiatric disorders. The aetiology of PCOS is not well understood and there is currently no cure.
Previous genetic research on PCOS has focused on genes associated with steroidogenesis and metabolism, such as FSHR, LHCGR and INSR. In addition to these loci, genome-wide association studies (GWAS) have identified a GWAS signal of non-coding single nucleotide variants in the intergenic regions flanking SUOX, RPS26, ERBB3 and IKZF4 on chromosome 12. The genes in this region are not known to function in the hypothalamic-pituitary-gonadal axis or metabolism, therefore their role in the manifestation of PCOS remains elusive.
The polygenic nature of PCOS adds complexity to understanding the causality of non-coding genetic variants. These variants are predicted to influence risk through regulation of gene expression. Colocalised eQTL data links the associated PCOS genetic variants to changes in gene expression of SUOX, RPS26, ERBB3 and IKZF4 in PCOS relevant tissues (brain, immune cells and the ovary) however functional analyses are necessary to causally implicate the variant(s) in the development of PCOS.
Utilising in silico tools, twelve variants at the chromosome 12 locus were identified that overlapped transcription factor binding sites and were prioritised as putative gene regulatory variants. These prioritised variants were cloned into reporter plasmids (green fluorescent protein (GFP)), injected into 1-cell stage zebrafish embryos and observed and imaged using both epifluorescent and confocal microscopy to assess enhancer activity. We have found multiple variant regions which drive GFP expression 3 in various tissues including the developing brain and central nervous system. The stable transgenic offspring of these embryos have further confirmed these results.
Ultimately this data provides understanding of a novel locus in the manifestation of PCOS and exemplifies the importance of the non-coding genome in this complex disorder. Further study into allelic specific functional effects of the non-coding variants at this locus and others in PCOS can widen the knowledge of the molecular mechanisms underpinning PCOS as well as provide new avenues for targeted therapies