Relevance of augmented kisspeptin signaling through H³⁶⁴ KISS1R in central precocious puberty

Understanding the pathophysiology of idiopathic central precocious puberty (ICPP) is essential, in view of its consequences on reproductive health and metabolic disorders in later life. Towards this, estimation of circulating levels of the neuropeptides, viz; Kisspeptin (Kp-10), Neurokinin B (NKB) and Neuropeptide Y (NPY), acting upstream to Gonadotropin-Releasing Hormone (GnRH), has shown promise. Insights can also be gained from functional studies on genetic variations implicated in ICPP. This study investigated the pathophysiology of ICPP in a girl by exploring the therapeutic relevance of the circulating levels of Kp-10, NKB, NPY and characterizing the nonsynonymous KISS1R variant, L³⁶⁴H, that she harbours, in a homozygous condition. Plasma levels of Kp-10, NKB and NPY before and after GnRH analog (GnRHa) treatment, were determined by ELISA. It was observed that GnRHa treatment resulted in suppression of circulating levels of Kp-10, NKB and NPY. Further, the H³⁶⁴ variant in KISS1R was generated by site directed mutagenesis. Post transient transfection of either L³⁶⁴ or H³⁶⁴ KISS1R variant in CHO cells, receptor expression was ascertained by western blotting, indirect immunofluorescence and flow cytometry. Kp-10 stimulated signalling response was also determined by phospho-ERK and inositol phosphate production. Structure-function studies revealed that, although the receptor expression in H³⁶⁴ KISS1R was comparable to L³⁶⁴ KISS1R, there was an enhanced signalling response through this variant at high doses of Kp-10. Thus, elevated levels of Kp-10, acting through H³⁶⁴ KISS1R, contributed to the manifestation of ICPP, providing further evidence that dysregulation of Kp-10/KISS1R axis impacts the onset of puberty.