Ogawa K, Wakayama A, Kunisada T, Orii H, Watanabe K, Agata K
Department of Life Science, Faculty of Science, Himeji Institute of Technology, Hyogo, Japan.
Biochem Biophys Res Commun. 1998 Jul 9;248(1):204-9. doi: 10.1006/bbrc.1998.8915.
To investigate external signals involved in germ cell differentiation from somatic stem cells, we have tried to identify protein kinases whose expression is regulated during the process of sexualization of asexual-state planarians. It is known that in planarians germ cells differentiate from totipotent somatic stem cells called "neoblasts" during sexualization. As a first step, we have isolated twelve protein kinase genes from cDNAs of sexual-state planarians, including three non-receptor tyrosine kinases, three receptor-tyrosine kinases and three non-receptor serine/threonine kinases, and then analyzed their expression patterns during sexualization. One of them, the DjPTK1 gene, is specifically expressed in germ cells of sexual-state planarians. DjPTK1-positive cells were also detected in the mesenchymal space during the process of sexualization, and it appears that these cells migrate to the dorsal side and then differentiate into spermatogonia/spermatocytes in testis. Sequence analysis indicated that the DjPTK1 gene encodes a receptor protein tyrosine kinase belonging to the FGFR/PDGF family. These results suggest that a receptor tyrosine kinase system may be involved both at an early stage of germ cell differentiation and in a step of germ cell maturation in planarians.
为了研究参与体细胞干细胞向生殖细胞分化的外部信号，我们试图鉴定在无性状态涡虫性成熟过程中其表达受到调控的蛋白激酶。已知在涡虫中，生殖细胞在性成熟过程中从称为“新细胞”的全能体细胞干细胞分化而来。作为第一步，我们从性成熟状态涡虫的cDNA中分离出12个蛋白激酶基因，包括3个非受体酪氨酸激酶、3个受体酪氨酸激酶和3个非受体丝氨酸/苏氨酸激酶，然后分析它们在性成熟过程中的表达模式。其中一个基因DjPTK1，在性成熟状态涡虫的生殖细胞中特异性表达。在性成熟过程中，间充质空间中也检测到DjPTK1阳性细胞，这些细胞似乎迁移到背侧，然后在睾丸中分化为精原细胞/精母细胞。序列分析表明，DjPTK1基因编码一种属于FGFR/PDGF家族的受体蛋白酪氨酸激酶。这些结果表明，受体酪氨酸激酶系统可能在涡虫生殖细胞分化的早期阶段以及生殖细胞成熟过程中发挥作用。
