探討精子內MENT蛋白之生化特性及生物功能

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題名:	探討精子內MENT蛋白之生化特性及生物功能 Biochemical Characterization and Functional Study of Sperm Ment Protein
作者:	劉銘
貢獻者:	生命科學系
關鍵詞:	精子 methylated in normal thymocytes protein (MENT)蛋白生殖發展受精
日期:	2020
上傳時間:	2020-10-06 13:37:48 (UTC+8)
摘要:	受精過程起於精子與卵母細胞的接觸，並在精卵細胞核的融合後終止。精子的生成起始於睾丸內，經由運輸送至附睾中繼續發展，最後在排出雄性生殖器官外後於雌性生殖道中進行獲能反應及頂體反應，方可成為成熟且具受精能力的精子。而精子內所含的分子如醣蛋白，在精子發展成熟過程中密集且大量的合成，長期以來被認為在配子發展及進行受精過程中扮演非常重要的角色。然而我們對哺乳動物精子的生化組成了解仍相當有限。因此，鑒定精子內容物及其相關分子對了解精子發展、受精及生殖是必要的。一直以來，生殖學家利用與醣類有專一辨識性的凝集素來研究哺乳類精子醣化內容物。我們的研究團隊利用花生凝集素(PNA)分離出小鼠精子內N-乙醯半乳糖胺化蛋白和可能與這些醣蛋白有相互作用的分子，再經由 LC/MS/MS質譜儀技術完成蛋白質鑑定。在小鼠精子中，我們發現內含一個特殊的38kDa蛋白質，methylated in normal thymocytes protein (MENT)，其出現在睾丸中、附睾中、獲能反應後、頂體反應後的精子。我們最新研究結果顯示，MENT的基因及蛋白質表達始於3周小鼠睪丸中，且於6周達到最高峰，而MENT蛋白質最早出現於精原母細胞中。目前生物學家對MENT蛋白了解是非常有限的，可參考之研究文獻僅有數篇之少。而目前僅知的MENT生物功能是與調控腫瘤和加速細胞增生相關，因此探討MENT在生殖中所扮演的角色是必須且前瞻的。如上述的結果及發現，我們提出來一系列的試驗，探討MENT在精子的形成、發展、成熟過程中，扮演的生物功能角色。此外，我們亦將探討MENT是否在受精過程中也參與了調控的機制。由於小鼠精子可能具有與人類同源同功能的蛋白質，故小鼠精子MENT的研究可讓我們對於人類精子生物合成有進一步的瞭解。如果實驗證明精子內的MENT的確具有與生殖相關的生物功能，所得到的資訊可以用於男性不孕症的臨床病理研究。最後，期望藉此探討精子MENT對精子發展之影響的研究成果，提供非荷爾蒙避孕藥發展的新方向。 Fertilization is a series of coordinated events involving multiple steps of mutual recognitions between haploid male and female gametes. The synthesis sperm starts in the testes and are later transit to epididymis for maturation. Ejaculated sperm are not fully functional and have to undergo capacitation and acrosome reaction to become fertile. Glycoconjugates are long thought to be essential in mammalian reproduction since the sperm glycoconjugates are extensively synthesized and modified during sperm maturation and transport. We know that glycosylated components are important in sperm development and their acquisition of fertilizing ability; nevertheless, relatively little is known about the exact biochemical composition of mammalian sperm. Therefore, it is our great interest to characterize sperm components and to define their reproductive roles and functioning in fertilization. Glycoconjugates are long thought to be essential in mammalian fertilization and the most convenient method for detecting sperm glycosylated components is the non-enzymatic lectin assay, in which the lectins can be used to recognize specific carbohydrate moieties. Recently, our research team has characterized new glycoconjugates in mouse sperm using lectin peanut agglutinin (PNA), which specifically recognizes N-acetylgalactosaminylated molecules using LC/MS/MS proteomic approach. Of analyzed samples, band with molecular weight 38 kDa was identified to be methylated in normal thymocytes protein (MENT). The protein is encoded by gene MENT and is a tumor modifier and accelerates lymphomagenesis. In our preliminary study, we confirmed the presence of MENT protein in mouse sperm from different developmental stages (testicular, epididymal, capacitated, and acrosome reacted sperm). Moreover, the gene/protein expression of MENT initiated in testis at age of week 3 and peaked at week 6. MENT was detected as early as in the spermatogonia in testes. This newly identified molecule has not yet been characterized with reproductive functions. Our finding of MENT protein present in sperm raises the question whether this molecule plays a role in sperm generation, development and maturation, during which is a window of time requiring rapid and tightly regulated cell division.In this proposed study, we will conduct a series of experiments to delineate the exact reproductive function of MENT protein and to better understand the molecular basis and changes associated with reproduction. In addition, identification and characterization of sperm component MENT may give us insights into the constituents of human sperm since homologous components are likely to be present. If MENT indeed plays a role in reproduction, this component may be used as a key molecule in studying male infertility and used as indicative parameter(s) in assessing the maturation and quality (fertilizing ability) of sperm for patients under assisted reproduction therapy. Finally, it is tempting to envision the possibility that MENT involved in sperm generation and development may be used as new targets for developing non-hormone based contraceptive control.
顯示於類別:	[生命科學系] 研究計畫

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