BEND2在小鼠生精细胞减数分裂中的分子机制

在精子发生过程中，染色质的存在方式发生着高度动态的变化；但是，人们对其自身变化和所行使功能的具体分子机制所知甚少。我们通过生物信息学分析，发现了一个在进化上高度保守、睾丸特异表达的蛋白编码基因Bend2；初步实验显示其敲除小鼠的精子发生阻滞在偶线期精母细胞阶段，以H3K9me3为标志的异染色质状态异常。BEND2蛋白质包含2个BEN结构域，小鼠和人的基因组各自有9个基因编码含有该结构域的蛋白质，然而大部分成员的功能和作用机制不清。已知同源蛋白BEND3作为转录抑制复合物的一个成份参与异染色质的形成并抑制rDNA的转录。基于这些线索，我们的科学假说是：BEND2通过调控染色质的动态变化进而调控减数分裂期间基因表达和DNA双链断裂的修复。我们将利用多种组学和分子生物学技术结合我们建立的体外减数分裂模型阐明BEND2在减数分裂中的作用机制。

Chromatin undergoes highly dynamic reorganization during spermatogenesis. However, little is known about the underlying mechanism. We have discovered a protein coding gene named BEND2 that is highly conserved during evolution and specifically expressed in the testis through bioinformatic analyses of public transcriptomic data. Our preliminary experimental results show that the spermatogenesis of the Bend2 knockout mice arrests at zygotene spermatocyte stage and that the heterochromatin distribution of zygotene spermatocytes is aberrant. The protein product of Bend2 contains 2 BEN domains, which is also found in a total of 9 orthologous proteins in the mouse and human genomes, respectively. However, the functions of most of these proteins remain unknown. BEND3 has been reported to be a component of a transcription repressive complex that is involved in heterochromatin formation and rDNA transcription regulation. Based on these findings, we hypothesize that BEND2 plays an essential role in meiotic DNA double strand break repair and gene expression via regulating chromatin (most likely heterochromatin) reorganization in spermatogenesis. In this grant proposal, we will test this hypothesis by using omic and molecular approaches coupled with the in vitro meiosis model that we have reported lately.