Gene Expression In Spermatogenic Cells

这些研究将识别和描述控制男性生殖细胞发育和功能的内在遗传程序的关键组成部分。目前正在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，使用酵母双杂交和缺失突变来鉴定对雄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。许多基因只在雄性生殖细胞中表达，目前正在研究一些编码蛋白质的基因，这些蛋白质的功能对配子发育和/或功能的四个新方面至关重要。(1)GAPDS和PGK2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同源基因。这些酶结合到纤维鞘上，这是精子鞭毛中的一种细胞骨架结构。(2)AKAP4、AKAP3和CABYR含有蛋白激酶A(PKA)蛋白锚定位点，也是纤维鞘的组成部分。(3)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，精蛋白是单倍体细胞核DNA高度致密所必需的。(4)Cdc20与环体/后期促进复合体(APC)结合，在细胞周期蛋白的中期到后期转变过程中，对APC依赖的蛋白质分解是必不可少的。我们已经在生精细胞中发现了一种新的Cdc20结合因子，它可能在生精细胞减数分裂过程中调节Cdc20的功能。前三组基因仅在精子发生的减数分裂后阶段表达，而最后一组基因恰好在这一阶段之前表达。未来的研究将确定旁分泌、信号转导和遗传途径如何有助于这些基因在生精细胞中的协调表达。

These studies will 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.