PHB表观调控精母细胞线粒体代谢转换的作用机制研究

最新研究表明精母细胞线粒体在减数分裂前期发生代谢转换，但机制不明。申请人前期研究发现①线粒体膜蛋白PHB在精母细胞高表达。②Phb生殖细胞特异性敲除小鼠雄性不育，减数分裂在粗线期停滞，同源重组缺陷，导致无精子生成。③PHB缺失导致精母细胞线粒体融合和呼吸链复合体表达等代谢转换异常。④PHB影响精母细胞线粒体相关蛋白的转录与表达。⑤精母细胞通过PHB-JAK2轴调节组蛋白修饰，影响异染色质形成而调控相关基因的转录与表达，影响减数分裂。综上，推测PHB调控精母细胞表观修饰而影响线粒体相关基因的转录与表达，在精母细胞线粒体代谢转换过程中发挥重要表观调控作用。因此本项目将继续寻找和鉴定精母细胞PHB表观调控的下游相关基因，阐明PHB对线粒体代谢转换的作用机制。本项目将有助于推进认识表观遗传调控途径对精母细胞线粒体代谢转换所起的作用，为实现生精细胞体外命运调控和开发男性不育的治疗方法提供理论支持。

Recently, spermatocytes have been demonstrated to experience a metabolic shift during meiotic prophase I. However, its related mechanism has not yet been elucidated. Our previous studies show that (1) mitochondrial Prohibitin (PHB) is expressed higher in spermatocytes during mouse spermatogenesis. (2) After deletion of PHB specifically in the male germ cells, Phb cKO mouse are male infertile, showing that spermatocytes have meiotic pachytene arrest induced by defects in meiotic DSB repair and homologous recombination. Accordingly, no post-meiotic spermatids are produced in seminiferous tubules. (3) Loss of PHB in spermatocytes results in an impairment of mitochondrial morphology and function, for example, a significant accumulation of short and fragmented mitochondria, the reduction of the long isoform of OPA1 and respiratory complex subunits CII and CIV, and a decrease in copy numbers of mtDNA. (4) Furthermore, we found that in spermatocytes PHB is involved in the regulation of the expression of gene associated with mitochondrial pathways. (5) An axis of PHB-JAK2-H3Y41ph was found as a novel mechanism in the modulation of the heterochromatin formation in spermatocytes. It was evidenced by JAK2-mediated reduction of H3Y41ph and a retention of H3K9me3 surrounding the promoter region of gene, like evidenced meiosis-associated gene Stag3 in Phb-/- spermatocytes. Based on above findings, we proposed that mitochondrial PHB may play key roles on metabolic shift by the epigenetic regulation of histone H3Y41ph in the spermatocytes. The objectives of this study, therefore, is to further explore and identify the mitochondria-associated downstream genes and signaling pathways regulated by PHB in the spermatocytes firstly. Secondly, to clarify what the mitochondria-associated downstream genes regulated by histone H3Y41ph are also controlled by PHB indirectly. Finally, to elaborate clearly the epigenetic mechanism of PHB’s role on metabolic shift by the regulation of histone H3Y41ph in the spermatocytes. This study will help us to understand better about the epigenetic mechanism of mitochondrial PHB on metabolic shift during the development of male germ cells. The findings of this study could also support us theoretically on how to develop new therapy approach for male infertility.