Post-transcriptional regulation of development

生产可育精子需要表达精子发育不同阶段所需的1000多种蛋白质。例如，一些蛋白质在精子发育的早期起作用，以确保精子含有正确数量的染色体。其他蛋白质在精子发育后期起作用，形成鞭子状的尾巴，在受精过程中将精子推向卵子。尽管最近在了解精子细胞如何发育方面取得了进展，但人们对蛋白质如何在正确的地点和时间形成可育精子知之甚少。我们最近发现，一种名为eIF 4 E-3的因子控制着果蝇精子发育过程中的蛋白质合成。eIF 4 E-3是调节蛋白质合成起始的保守蛋白质家族的成员。在缺乏eIF 4 E-3的情况下，一些精子蛋白的表达低于正常水平，干扰细胞分裂和精子发育，导致男性不育。出乎意料的是，典型eIF 4 E（果蝇中的eIF 4 E-1）的敲除类似于eIF 4 E-3的丢失，表明eIF 4 E-3和eIF 4 E-1可能调节类似的蛋白质。然而，eIF 4 E-3缺少重要的氨基酸，这表明它可能与eIF 4 E-1不同。此外，果蝇还产生另外三种睾丸特异性eIF 4 E蛋白，eIF 4 E-4、eIF 4 E-5和eIF 4 E-7。该实验将结合细胞生物学、遗传学、分子生物学和生物化学等技术，探索eIF 4 E-3的作用和调控机制，确定其他eIF 4 E的作用，并鉴定这些eIF 4 E在精子发育过程中调控的靶基因。*** 我们的实验，这将是第一个系统地表征果蝇雄性生殖系的翻译调控机制，将集中在以下具体目标：*1。分析eIF 4 E-3在精子发生中的作用及调控。* 我们将使用荧光显微镜来研究eIF 4 E-3突变体中的缺陷，并将其与eIF 4 E-1的缺失进行比较。我们将工程敲除eIF 4 E-4，-5和-7，并研究它们在精子发生中的作用。我们将使用遗传杂交来测试eIF 4 E-3和eIF 4 E-1是否具有重叠或独特的作用，并进行拯救实验来测试eIF 4 E-3中缺失的氨基酸的显著性。2.研究睾丸特异性eIF 4F复合物及其靶点。* 我们将使用免疫共沉淀（co-IP）来鉴定睾丸中存在的蛋白质合成复合物。我们将使用质谱来测试eIF 4 E-3的序列变化是否影响其调节。我们将进行RNA co-IP，以鉴定优先与睾丸中表达的五种eIF 4 E中的每一种相关的mRNA组。重要性：我们的实验将揭示翻译控制在果蝇雄性生殖细胞发育中的作用和机制，并将揭示动物发育过程中特化细胞分化关键步骤的翻译控制调节的广泛原则。

Production of fertile sperm requires expression of more than 1000 proteins that are needed at different stages of sperm development. For example, some proteins act early in sperm development to ensure the sperm contains the correct number of chromosomes. Other proteins act later in sperm development to form the whip-like tail that propels the sperm towards the egg during fertilization. Despite recent progress in understanding how sperm cells develop, little is known about how proteins are made at the right place and time to form fertile sperm. We recently discovered that a factor called eIF4E-3 controls protein synthesis during sperm development in fruit flies. eIF4E-3 is a member of a conserved family of proteins that regulates initiation of protein synthesis. In the absence of eIF4E-3, some sperm proteins are expressed at lower than normal levels, interfering with cell division and sperm development and causing male sterility. Unexpectedly, knockdown of the canonical eIF4E (eIF4E-1 in flies) resembles loss of eIF4E-3, suggesting eIF4E-3 and eIF4E-1 may regulate similar proteins. However, eIF4E-3 is missing important amino acids, suggesting it may be regulated differently from eIF4E-1. In addition, fruit flies make three other testis-specific eIF4E proteins, eIF4E-4, -5 and -7. The proposed experiments will use a combination of cell biology, genetics, molecular biology and biochemistry to discover the role and regulation of eIF4E-3, determine the roles of the other eIF4Es, and identify target genes regulated by these eIF4Es during sperm development. *** Our experiments, which will be the first to systematically characterize mechanisms of translational regulation in the fruit fly male germline, will focus on the following specific aims:*******1. Analyze the role and regulation of eIF4E-3 in spermatogenesis. ***We will use fluorescence microscopy to study the defects in eIF4E-3 mutants, and to compare them with loss of eIF4E-1. We will engineer knockouts of eIF4E-4, -5 and -7 and study their roles in spermatogenesis. We will use genetic crosses to test whether eIF4E-3 and eIF4E-1 have overlapping or unique roles, and perform rescue experiments to test the significance of the amino acids that are missing in eIF4E-3.******2. Investigate testis-specific eIF4F complexes and their targets. ***We will use co-immunoprecipitation (co-IP) to identify the protein synthesis complexes present in testes. We will use mass spectrometry to test whether sequence changes in eIF4E-3 affect its regulation. We will carry out RNA co-IPs to identify sets of mRNAs that preferentially associate with each of the five eIF4Es expressed in testes.******Significance: Our experiments will reveal the role and mechanism of translational control in fruit fly male germ cell development and will uncover broad principles underlying translational control regulation of key steps in differentiation of specialized cells during animal development.**