Endocrine Abstracts

Whilst several key genetic contributors to the phenotype of central precocious puberty (CPP) have been recognized, many familial cases remain without clear genetic aetiology. We have identified Methyl-CpG-binding protein 2 (MECP2), a chromatin-associated transcriptional regulator with known roles in neuronal maturation, as a candidate gene for CPP. Located on chromosome Xq28, MECP2 is highly expressed in hypothalamic nuclei (arcuate, suprachiasmatic, and paraventricular) and co-localises with GnRH within GnRH neurons, suggesting a role in puberty onset through regulation of the GnRH neuronal axis. Furthermore, MECP2’s known role as an epigenetic regulator of chromatin compaction makes it an attractive candidate as a key player in the delicate regulation of pubertal onset. We have demonstrated differential expression of CPP- and Rett syndrome- associated MECP2 variants in a GT1-7 mouse neuronal GnRH-producing cell line, compared to wildtype MECP2. Studies in a GnRH reporter system demonstrated differential ability of MECP2 variants to supress GnRH promoter activity, suggesting a possible regulatory role in the GnRH neuronal network. To understand the role of MECP2 in transcriptional and epigenetic regulation of GnRH secretion, we utilised a multi-omics approach, carrying out RNAseq and ATACseq on wildtype and Mecp2-knockout GT1-7 cell lines. Analyses identified 4552 chromatin regions with differential accessibility upon loss of Mecp2 expression in vitro (3530 increased accessibility, 1022 reduced accessibility). Combination of ATACseq and RNAseq analysis identified two subsets of genes differentially regulated in Mecp2 knockout GT1-7, compared to wild-type: 487 genes appeared in both datasets, regulated by MECP2 through chromatin accessibility, and 495 were unique to RNAseq analysis, upon which MECP2 may act as a direct transcriptional regulator. Importantly, several genes identified in both datasets, including Sox11, Igsf10 and Lgr4 have known vital roles in regulation of puberty and GnRH, strongly suggesting that MECP2 contributes to regulation of pubertal onset through regulation of GnRH.