Evolution and Diversity in the system of development and differentiation

(1)神经系统的进化和发育机制为了了解结构脑的出现时间和方式，我们分析了一种低等无脊椎动物涡虫的中枢神经系统。我们通过构建cDNA微阵列对涡虫头部特异性基因进行了大规模筛选。结果，发现了205个具有头部部分特异性尖刺的基因，其中包括脊椎动物神经系统中的一些必需基因。前30个基因的表达模式显示出最强的峰值，这表明涡虫大脑经历了功能区域化。同源性搜索的结果是，我们发现116个克隆与已知的神经系统相关基因有显著的相似性。有趣的是，我们发现约30%的涡虫神经系统相关基因在拟南芥和酵母中具有同源序列，而拟南芥和酵母不具有神经系统。这意味着神经系统相关基因的起源大大早于神经系统的出现，这些基因可能已经被招募到神经系统。(2)发育和分化系统的进化和多样性为了研究慈鲷颌部形态在遗传水平上的多样性，我们利用DNA芯片比较了亲缘关系较近的慈鲷的基因表达水平。分析结果表明，两种慈鲷幼虫中某些基因的表达存在差异。其中一个克隆体编码一种新的astacin家族金属蛋白酶。由于一些astacin家族蛋白参与动物的形态发生，CiMP1有望参与慈鲷的物种特异性头部形态发生。在慈鲷中，我们提供了一个例子，其中选择性剪接可能在配偶选择中发挥作用，通过从单个基因产生多个mrna来实现基因功能的多样化，从而导致慈鲷物种的形成。

(1) Evolution and Developmental mechanism in Nervous systemTo understand when and how the structural brain emerged, we analyzed the central nervous system of a lower invertebrate, planarian. We conducted a large-scale screening of the head part-specific genes in the planarian by constructing a cDNA microarray. As a result, 205 genes with head part-specific spikes were found, which included some essential genes in the vertebrate nervous system. The expression patterns of the top 30 genes showing the strongest spikes implied that the planarian brain has undergone functional regionalization.As a result of homology searches, we found that 116 clones had significant similarity to known genes related to the nervous system. Interestingly, we found that 〜30% of planarian nervous system-related genes had homologous sequences in Arabidopsis and yeast, which do not possess a nervous system. This implies that the origin of nervous system-related genes greatly predated the emergence of the nervous system, and that these genes might have been recruited toward the nervous system.(2) Evolution and Diversity in the system of development and differentiationTo investigate the diversification of cichlid jaw morphology at the genetic level, we used a DNA chip to compare gene expression levels between closely related cichlid fishes. This analysis indicated that the expression of some genes differed in the larvae of two cichlid species. One such clone encodes a new astacin family metalloproteinase. Because some astacin family proteins contribute to morphogenesis in animals, CiMP1 is expected to participate in species-specific head morphogenesis in cichlids.In Cichlids, here, we provide an example in which alternative splicing may play a role in mate choice, leading to cichlid speciation through diversification of gene function by production of multiple mRNAs from a single gene.