雄性特異性轉譯調節因子CPB-1在線蟲精子生成中參與調控轉錄關閉和精子特異性胞器組成

Abstract

晚期成精作用代表了精細胞從減數分裂前期轉入中期，並得以進行分裂的階段。在這個轉變過程中，染色體和細胞質組件經歷廣泛的重新排列。雄性特有的轉譯調節因子CPB-1在粗線期的細胞質中高度表達。為了研究CPB-1在雄性生育中的功能，我們產生了一個可誘導降解CPB-1的線蟲株，以達成特定條件下的CPB-1降解。 在缺乏CPB-1的情況下，形成了初級精母細胞，但未能繼續進行分裂。對性腺的形態進行檢查顯示，CPB-1的缺乏不影響一般粗線期的染色體排列。然而，精元細胞核未能形成核小體，這是在初級精母細胞形成之前實現轉錄沉默的階段。此外，CPB-1缺失的初級精母細胞表現出轉錄活性。 我們的研究結果表明，CPB-1通過調節核小體階段的形成，在轉錄沉默中發揮作用。此外，CPB-1缺失的精原細胞缺乏細胞質顆粒，並表現出空泡狀結構，表明細胞膜胞器的異常。支持這一點的是，在缺乏CPB-1的情況下，精子特異性胞器纖維體-膜細胞器複合體(FB-MO)的結構出現高度混亂。FB-MO中的主要物質MSP蛋白有顯著的減少，並且混亂的MO結構與類似空泡的結構共定位。 綜上所述，CPB-1調控了成精作用的兩個方面的關鍵因子的轉譯：首先，調控生成核小體階段，以在形成初級精母細胞之前實現轉錄沉默；其次，在細胞質中組裝精子特異性胞器FB-MO。這些發現表明CPB-1在男性生育中參與了關鍵作用。

Late spermatogenesis represents a stage at which the spermatogenic cells transition into the M phase and are committed for division. During this transition, chromosomes and cytoplasmic components undergo extensive rearrangement. The male-specific translation regulator CPB-1 is highly expressed in the cytoplasm during the pachytene spermatogenic germline stage. To investigate the function of CPB-1 in male fertility, we generated an inducible CPB-1 degradation strain to enable controlled CPB-1 depletion. In the absence of CPB-1, primary spermatocytes were formed but failed to progress to division. Examination of germline morphology revealed that CPB-1 depletion did not affect the general early pachytene chromosome arrangement. However, spermatogenic nuclei failed to form the karyosome, a stage that allows transcription silencing before primary spermatocyte formation. Furthermore, CPB-1-depleted primary spermatocytes exhibited transcriptional activity. Our findings suggest that CPB-1 plays a role in transcriptional silencing by regulating the formation of the karyosome stage. Additionally, CPB-1-depleted spermatocytes lacked cytoplasmic granules and exhibited vacuole-like structures, indicating disorganization of cellular membranous organelles. Supporting this, the sperm-specific organelle FB-MO was highly disorganized in the absence of CPB-1. The levels of MSP, a major cargo in FB-MO, were severely reduced, and the disorganized MO structures colocalized with vacuole-like structures. In summary, CPB-1 controls the translation of key regulators in two critical aspects of spermatogenesis: first, the formation of the karyosome stage to achieve transcriptional silence before primary spermatocyte formation; second, the assembly of the sperm-specific organelle FB-MO in the cytoplasm. These findings highlight the crucial role of CPB-1 in male fertility.