Functional phylogenetic analysis of developmental mechanisms of pigment cells

本项目的研究目的如下：1.脊椎动物色素细胞分化相关基因海鞘同源物的克隆。基因及其表达模式的系统发育分析。对色素细胞发育系统的进化进行了讨论，得到以下结果。克隆了小眼球相关转录因子(MITF)基因。我们发现MITF-M是脊椎动物黑素细胞和神经脊细胞分化所必需的异构体。海鞘MITF同源物不能表达M-异构体。海鞘MITF同源物可以反式激活海鞘酪氨酸酶(TYRS)和酪氨酸酶相关蛋白(Trp)基因，也可以反式激活脊椎动物TYRS和Trp基因。另一方面，脊椎动物中只有一种MITF亚型可以反式激活海鞘色氨酸基因，这表明在脊椎动物的进化过程中已经获得了MITF-M特异的第一外显子及其调控序列。

The purpose of this project is as follows.1. Cloning of ascidian homologues for vertebrate genes involved in differentiation of pigment cells.2. Phylogenetic analysis of the genes and their expression patterns.3. Discussion of evolution of developmental systems of pigment cells.We obtained the following results.a. Putative ascidian MITF(microphthalmia-associated transcription factor) gene was cloned. We found that MITF-M is an essential isoform to allow differentiation of melanocyte from neural crest cells in vertebrates. Ascidian MITF homologue can not express the M-isoform.b. Ascidian MITF homologue can transactivate both ascidian tyrosinase (tyrs) and tyrosinase-related protein (TRP) genes but also vertebrate tyrs and TRP genes. On the other hand, only one of vertebrate MITF isoforms can transactivate the ascidian TRP gene.It is suggested that the MITF-M specific first exon and its regulatory sequence have obtained in the evolution of vertebrates.