SULFATED GLYCOLIPID THAT REGULATES DEVELOPMENT OF MALE GERM CELLS

硫酸糖脂、半脂占睾丸总糖脂的90%以上，在睾丸中特异性表达。精脂是在精子发生过程中在精母细胞的高尔基膜中生物合成的。首先，一种叫做神经酰胺半乳糖转移酶（CGT）的半乳糖转移酶作用于前体甘油脂，合成中间产物半乳糖烷基丙基甘油（GaIEAG）。然后，一种称为脑苷转移酶（CST）的硫转移酶催化GaIEAG的硫酸化，合成最终产物半脂。我们发现cst缺陷小鼠的睾丸完全缺乏半脂质，精子发生在第一次减数分裂中期停止。这些发现表明，半脂对精子发生至关重要。美国99,4227-4232,2002)。接下来，我们一直在研究半脂是如何参与精子发生的。首先，我们研究了精母细胞质膜上的脂质筏中是否存在半脂质。为此，我们建立了使用密度梯度离心从小鼠睾丸中分离精母细胞的程序。结果，我们证实了半脂质包含在脂质筏中。同样，我们发现另一种磺化糖脂，硫脂也包含在脑髓鞘的脂质筏中。其次，我们开发了一种光敏碳水化合物探针，用于识别与精母细胞表面半脂相互作用的分子。我们计划将该探针引入培养的精母细胞，并在活细胞中检测这些分子。”第三，我们一直在尝试将半脂注入精小管，使睾丸恢复精子发生

The sulfated glycolipid, seminolipid occupies more than 90% of total glycolipids in the testis and is specifically expressed in the testis. Seminolipid is biosynthesized in the Golgi membranes of spermatocytes during spermatogenesis. First, a galactosyltransferase called ceramide galactosyltransferase (CGT) acts on the precursor glycerolipid, and synthesizes an intermediate product, galactosylalkylacylglycerol (GaIEAG). Then, a sulfotransferase called cerebroside sulfotransferase (CST) catalyzes the sulfation of GaIEAG, synthesizing the terminal product, seminolipid. We have found that the testes of CST-deficient mice completely lack seminolipid and spermatogenesis is arrested at the metaphase of the first meiosis. These findings indicate that seminolipid is essential for spermatogenesis (Proc.Natl.Acad.Sci.USA 99, 4227-4232, 2002). Next, we have been studying how seminolipid is involved in spermatogenesis. First, we examined the issue whether seminolipid exists in the lipid raft on the plasma membranes of spermatocytes. To this end, we had established the procedure to isolate spermatocytes from mouse testis using a density-gradient centrifugation. As a result, we confirmed that seminolipid is included in the lipid raft. Similarly, we found that another sulfated glycolipid, sulfatide is also included in the lipid raft of brain myelin sheath. Secondly, we have developed a photo-sensitive carbohydrate probe to identify the molecules that interact with seminolipid on the cell-suface of spermatocytes. We are planning to introduce this probe into cultured spermatocytes and detect such molecules in living cells. Thirdly, we have been trying to inject seminolipid into the seminiferous tubules and make the testis to resume spermatogenesis