Ghosh Sanjay, Lasko Paul
Department of Biology, McGill University, Montreal, Quebec, Canada.
PLoS One. 2015 Apr 7;10(4):e0122519. doi: 10.1371/journal.pone.0122519. eCollection 2015.
In eukaryotes, post-transcriptional regulation of gene expression has a key role in many cellular and developmental processes. Spermatogenesis involves a complex developmental program that includes changes in cell cycle dynamics and dramatic cellular remodeling. Translational control is critical for spermatogenesis in Drosophila as many mRNAs synthesized in the spermatocytes are translated only much later during spermatid differentiation. Testes-specific translation initiation factors eIF4E-3 and eIF4G2 are essential specifically for male fertility. However, details of their roles during different stages of spermatogenesis are unknown, and the role of canonical translation initiation factors in spermatogenesis remains unexplored. In this study, we addressed the functional role of eIF4E-1, eIF4E-3, eIF4G and eIF4G2 in testes development and formation of mature sperm. Using the UAS-Gal4 system and RNA interference, we systematically knocked down these four genes in different stages of germ cell development, and in the somatic cells. Our results show that eIF4E-1 function in early germ cells and the surrounding somatic cells is critical for spermatogenesis. Both eIF4E-1 and eIF4E-3 are required in spermatocytes for chromosome condensation and cytokinesis during the meiotic stages. Interestingly, we find that eIF4G knockdown did not affect male fertility while eIF4G2 has distinct functions during spermatogenesis; it is required in early germ cells for proper meiotic divisions and spermatid elongation while its abrogation in spermatocytes caused meiotic arrest. Double knockdown of eIF4G and eIF4G2 shows that these proteins act redundantly during the early stages of spermatogenesis. Taken together, our analysis reveals spatio-temporal roles of the canonical and testes-specific translation initiation factors in coordinating developmental programs during spermatogenesis.
在真核生物中，基因表达的转录后调控在许多细胞和发育过程中起着关键作用。精子发生涉及一个复杂的发育程序，包括细胞周期动态变化和显著的细胞重塑。翻译控制对果蝇的精子发生至关重要，因为精母细胞中合成的许多mRNA直到精子细胞分化后期才被翻译。睾丸特异性翻译起始因子eIF4E - 3和eIF4G2对雄性生育能力至关重要。然而，它们在精子发生不同阶段的作用细节尚不清楚，而且经典翻译起始因子在精子发生中的作用仍未被探索。在本研究中，我们探讨了eIF4E - 1、eIF4E - 3、eIF4G和eIF4G2在睾丸发育和成熟精子形成中的功能作用。利用UAS - Gal4系统和RNA干扰技术，我们在生殖细胞发育的不同阶段以及体细胞中系统性地敲低了这四个基因。我们的结果表明，eIF4E - 1在早期生殖细胞和周围体细胞中的功能对精子发生至关重要。在减数分裂阶段，精母细胞中eIF4E - 1和eIF4E - 3都参与染色体凝聚和胞质分裂。有趣的是，我们发现敲低eIF4G并不影响雄性生育能力，而eIF4G2在精子发生过程中具有不同的功能；在早期生殖细胞中，它参与减数分裂的正常进行和精子细胞伸长，而在精母细胞中缺失会导致减数分裂停滞。同时敲低eIF4G和eIF4G2表明，这些蛋白在精子发生早期阶段发挥冗余作用。综上所述，我们的分析揭示了经典和睾丸特异性翻译起始因子在协调精子发生过程中的发育程序时的时空作用。
