Yan Wei, Ma Lang, Zilinski Carolyn A, Matzuk Martin M
Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
Biol Reprod. 2004 Jun;70(6):1619-25. doi: 10.1095/biolreprod.103.024778. Epub 2004 Feb 6.
We previously identified Gasz (a germ cell-specific gene encoding a protein containing four ankyrin repeats, a sterile-alpha motif, and a basic leucine zipper) in six mammalian species. Here, we report GASZ orthologs in pufferfish (Fugu rubripes), zebrafish (Danio verio), and frog (Xenopus laevis). Sequences of the three Gasz cDNAs were determined by database mining and 5'- and 3'-rapid amplification of cDNA ends (RACE) followed by sequencing. The three orthologous vertebrate genes encode proteins structurally similar to mammalian GASZ and contain the characteristic four ankyrin repeats (ANKs) and sterile-alpha motif (SAM). Their ANK and SAM domains share 55- 74% and 38-55% amino acid identity with those in human GASZ, respectively. Similar to human and mouse Gasz genes, pufferfish Gasz is composed of 13 exons, spanning approximately 12 kilobases, and flanked by Cftr at its 5'-end and Wnt2 at its 3'-end. Northern and Western blot analyses detect frog Gasz expression only in testis and ovary. In situ hybridization and immunohistochemical analyses show that frog Gasz mRNA and protein expression is confined to pachytene spermatocytes in the testis and to oocytes in the ovary. In frog oocytes, GASZ protein appears to localize to a cytoplasmic structure resembling the Balbiani body, a postulated mRNA transport organizer in the cytoplasm. The high evolutionary conservation and germ cell specificity suggest that GASZ plays an essential role in gametogenesis. The data presented here are important for future studies of the physiological roles of GASZ using fish and amphibians as animal models.
我们之前在六个哺乳动物物种中鉴定出了Gasz（一种生殖细胞特异性基因，编码一种包含四个锚蛋白重复序列、一个无活性α基序和一个碱性亮氨酸拉链的蛋白质）。在此，我们报告了河豚（红鳍东方鲀）、斑马鱼（斑马鱼）和青蛙（非洲爪蟾）中的GASZ直系同源基因。通过数据库挖掘以及5'-和3'-cDNA末端快速扩增（RACE）随后进行测序，确定了三种Gasz cDNA的序列。这三个直系同源脊椎动物基因编码的蛋白质在结构上与哺乳动物GASZ相似，并且包含特征性的四个锚蛋白重复序列（ANKs）和无活性α基序（SAM）。它们的ANK和SAM结构域与人类GASZ中的相应结构域分别具有55 - 74%和38 - 55%的氨基酸同一性。与人类和小鼠的Gasz基因相似，河豚的Gasz由13个外显子组成，跨度约为12千碱基，其5'-端侧翼为Cftr，3'-端侧翼为Wnt2。Northern印迹和Western印迹分析仅在睾丸和卵巢中检测到青蛙Gasz的表达。原位杂交和免疫组织化学分析表明，青蛙Gasz mRNA和蛋白质表达局限于睾丸中的粗线期精母细胞和卵巢中的卵母细胞。在青蛙卵母细胞中，GASZ蛋白似乎定位于一种类似于巴尔比亚尼体的细胞质结构，巴尔比亚尼体是细胞质中一种假定的mRNA运输组织者。高度的进化保守性和生殖细胞特异性表明GASZ在配子发生中起重要作用。此处呈现的数据对于未来以鱼类和两栖动物为动物模型研究GASZ的生理作用具有重要意义。
