Endocrine Abstracts

Self-limited delayed puberty is a condition that is frequently familial with strong genetic determinants. It has been linked to coding region sequence variation by next generation sequencing of affected individuals, identifying genetic regulation of gonadotropin-releasing hormone (GnRH) pathways underlying this condition. However, the role of epigenetic modifiers of human pubertal timing is underexplored. The Hypothalamic-pituitary-gonadal (HPG) axis is unique as it is active in three phases of life: foetal, infancy and then from puberty onwards. In-between these phases of life it is dormant. This is a process highly likely to be regulated by changes in DNA methylation. We have completed DNA methylation analysis, using the Infinium Methylation EPIC array, for patients with delayed puberty who had no identified genetic cause for the condition. Quality control, annotation of CpG sites and differential methylation was completed in R Studio. This has revealed dysregulated methylation in CpG sites linked to important genes known to play a role in the control of puberty and growth. Specifically, dysregulated CpG sites were identified in both VCX and NRXN2, by analysing both differentially methylated positions (DMPs), using the software dmpFinder, and differentially methylated regions (DMR), using the software bumphunter. Key genes involved in upstream regulation of GnHR such as KISS1, TAC3, KMT2A and SIRT1 also showed increased methylation in individuals with delayed puberty. Genes associated with differentially methylated positions were then analysed to identify cellular pathways that were dysregulated. Over representation analysis identified multiple KEGG pathways previously associated with growth dysfunction as significantly altered. These included the cAMP pathway (P=8.85x10-08), the neuroactive ligand-receptor interaction pathway (P=1.63x10-05) and focal adhesion pathway (P=1.63x10-05). Our results suggest that changes in methylation of key regulatory genes contribute to the phenotype of self-limited delayed puberty in a cohort of patients.