Endocrine Abstracts

Delayed puberty is frequently an inherited condition with a clear genetic basis, previously linked to variation in GnRH pathways genes. However, many patients do not have an identifiable genetic variant responsible for their delayed puberty and the role of epigenetic modifiers of human pubertal timing is underexplored. Robust evidence has been provided that the timing of puberty in animal models is regulated by an epigenetic mechanism of transcriptional repression. In view of the unique dynamic activity of the hypothalamic-pituitary-gonadal axis, changes in DNA methylation are highly likely to play a regulatory role in pubertal onset and timing. Genome wide DNA methylation was detected using the Illumina EPIC array, for patients (n = 92) with delayed puberty with no previously identified genetic cause, and related unaffected controls (n = 20). Analysis in R utilised dmpFinder and bumphunter packages. This revealed differentially methylated CpG sites linked to key genes involved in upstream regulation of GnRH signaling, including TAC3, SIRT1, PDYN, KMT2A, NELL2, KAT2B, NOS1 and ZNF573 which showed a difference in methylation between individuals with delayed puberty compared to controls. These differentially methylated CpG sites were identified in either enhancer or promoter regions of their corresponding genes. The top 5 CpG sites identified novel candidate genes for delayed puberty, including CADPS2. Over representation analysis identified multiple KEGG pathways previously associated with growth dysfunction as significantly altered. These included cAMP, neuroactive ligand-receptor interaction and growth hormone synthesis pathways. Differential methylation of genes related to BMI was observed, but it was not specific to patients with low or high BMI. Subsequently, pathogenic exonic variants in the genes associated with the top 10 CpG sites were identified in additional patients with delayed puberty. These findings support that changes in methylation of key GnRH regulatory genes contribute to the phenotype of delayed puberty.