H3K27 Demethylase, JMJD3 Controls Female Reproduction And Energy Homeostasis By Regulating Kisspeptin Signaling In Hypothalamus

Diabetes has become one of the most harmful metabolic diseases in the 21st century. High glucose levels during the long-term diabetes can lead to serious complications, including cardiovascular disease, kidney dysfunction, retinopathy, foot lesion and so on. The dysfunction of pancreatic ?-cell and decrease in ?-cell mass are crucial events in the development of diabetes. In addition to genetic predisposition, the resent studies have suggested that the epigenetic regulation may also contribute to the diabetes pathogenesis. So, a better understanding of effects and mechanisms underlying the epigenetic regulation of ? cell function and development will provide new targets for the diagnosis and treatment of diabetes. The recent discovery of H3K27me3 demethylase JMJD3 could participate in a variety of biological functions by removing the repressive H3K27me3 epigenetic modification in gene promoter and gene bodies. However, it unknown whether or not JMJD3 is involved in the pathogenesis of diabetes.In this study, we generated mice lacking Jmjd3 selectively in the pancreatic ? cell by using Rip-Cre transgeneic mice. However, the serum glucose and insulin levels were indistinguishable between knockout and control mice in both fasting and random fed conditions. The glucose tolerance test revealed no obvious difference between two groups. In addition, H & E staining of pancreatic sections indicated the normal islet morphology of knockout mice. These data suggest that the epigenetic modification mediated by JMJD3 is dispensable for the development and function of pancreatic ? cell.To our surprise, the knockout mice displayed adult-onset obesity phenotype with dramatically increased body fat mass. However, these symptoms were female specific. Further studies showed that the less locomotor activity and decreased energy expenditure but not the increased food consumption were responsible for the obesity, which was exactly the same as the estrogen deficiency induced obesity model. To investigate the role of estrogen in the generation of obesity phenotype, we performed ovariectomized surgey and estrogen replacement therapy. The results showed that the locomotor activity and energy expenditure were at the same level between knockout and control littermates. The body weight changed after ovariectomized operations were indistinguishable between two groups. Meanwhile, such obese symptom could be significantly improved by estrogen replacement therapy.As previous studies have demonstrated that RIP-Cre recombinase could also mediate the deletion of gene in specific population of hypothalamic neurons, we speculated that some dysfunction may be happened in the hypothalamus-pituitary-gonadal axis. As expected, the vaginal cytology analysis revealed the delayed puberty and irregular estrous cycle of knockout mice. In addition, the knockout mice displayed impaired fertility ability and accelerated degradation of ovarian, as well as the reduced serum estradiol levels. We also found that Jmjd3 had a similar gene expression pattern to kiss1 in female hypothalamus during puberty onset and estrous cycles. Kisspeptin has been identified as the master regulator of neuroendocrine reproductive axis in all mammalian. Result of real-time PCR showed that the expression level of Kissl was significantly reduced in AVPV nucleus of knockout mice. To investigate whether Kiss1 was the directly target gene of JMJD3 in hypothalamic neurons, we performed in vitro luciferase assay and in vivo ChIP analysis. The result showed that the Kiss1 gene promoter is activated by Jmjd3 in vitro. JMJD3 was expressed in kisspeptin neuron and recruited in vivo to the Kiss1 gene promoter. Meanwhile, the knockout mice showed increased H3K27me3 marks at the Kissl gene promoter in the AVPV nucleus.In summary, our present study indicated that the H3K27me3 demethylase JMJD3 is dispensable for pancreatic ? cell function but is an essential regulator of the female reproduction and energy homeostasis by directly regulate Kiss1 gene expression in the hypothalamic neurons.