Gene Expression In Spermatogenic Cells

长期目标是确定和表征控制雄性生殖细胞发育和功能的内在遗传程序的关键组成部分。目前应用的方法是鉴定在雄性生殖细胞中特异表达的基因，使用基因敲除方法来确定它们编码的蛋白质的作用，采用酵母双杂交测定和缺失诱变来鉴定对雄性配子发育至关重要的蛋白质-蛋白质相互作用，以及制备抗血清来确定特定基因产物的时空分布。许多基因仅在雄性生殖细胞中表达，并且正在研究选择的基因，其编码的蛋白质的功能对于配子发育和/或功能的四个新方面是必需的。(1)GAPDS和PGK 2是由生精细胞特异性基因产生的糖酵解途径中的酶，这些基因是在所有其他组织中表达的基因的直系同源物。这些酶与纤维鞘结合，纤维鞘是精子鞭毛中的细胞骨架结构。(2)AKAP 4、AKAP 3和CABYR含有蛋白激酶A（PKA）蛋白锚定位点，并且也是纤维鞘的组分。(3)鱼精蛋白1和2是高度碱性的核蛋白，在减数分裂后取代组蛋白。精子缺乏核小体，而精蛋白是其单倍体核中高度DNA压缩所必需的。(4)Cdc 20与细胞周期小体/后期促进复合物（cyclosome/anaphase-promoting complex，APC）相关，是细胞周期蛋白从中期向后期转变过程中APC依赖性蛋白水解所必需的。我们已经确定speriolin，一种新的Cdc 20结合因子在生精细胞中，可能调节Cdc 20在生精细胞减数分裂过程中的功能。前三组基因仅在精子发生的减数分裂后阶段表达，而最后一组基因在该阶段之前表达。未来的研究将确定如何旁分泌，信号转导和遗传途径有助于这些基因在生精细胞中的协调表达。

The long-term goals are to identify and characterize key components of the intrinsic genetic program that controls development and function of male germ cells. The approaches currently being applied are to identify genes expressed specifically in male germ cells, use the gene knockout approach to define the roles of the proteins they encode, employ yeast two-hybrid assays and deletion mutagenesis to identify protein-protein interactions essential for development of the male gamete, and prepare antisera to determine the temporal-spatial distribution of specific gene products. Many genes are expressed only in male germ cells and selected genes are being studied that encode proteins whose functions are essential for four novel aspects of gamete development and/or function. (1) GAPDS and PGK2 are enzymes in the glycolytic pathway produced by spermatogenic cell-specific genes that are orthologues of those expressed in all other tissues. These enzymes bind to the fibrous sheath, a cytoskeletal structure in the sperm flagellum. (2) AKAP4, AKAP3, and CABYR contain protein kinase A (PKA) protein anchoring sites and also are components of the fibrous sheath. (3) Protamines 1 and 2 are highly basic nuclear proteins that replace histones following meiosis. Sperm lack nucleosomes and the protamines are essential for the high degree of DNA compaction in their haploid nuclei. (4) Cdc20 associates with the cyclosome/anaphase-promoting complex (APC) and is essential for APC-dependent proteolysis of cell cycle proteins in the metaphase to anaphase transition. We have identified speriolin, a novel Cdc20-binding factor in spermatogenic cells that might regulate the function of Cdc20 during meiosis in the spermatogenic cells. The first three groups of genes are expressed exclusively during the post-meiotic phase of spermatogenesis, while the last gene is expressed just prior to this phase. Future studies will determine how paracrine, signal transduction, and genetic pathways contribute to the coordinate expression of these genes in spermatogenic cells.