Analysis of vertebrate organogenesis using medaka as a model system

青鳉遗传学的最新进展证明青鳉是发育和进化生物学研究的一个很好的模式系统，它可以补充斑马鱼的类似研究。日本目前正在进行大规模的诱变项目，并正在提供一个大大扩大的青鳉突变种群。本研究首先建立了突变基因的快速定位系统，然后对几个早期器官发生缺陷的青鳉突变体进行了表型和遗传分析。1. M标记系统：我们构建了一套EST遗传标记引物M-marker 2003，作为突变基因的快速定位系统。在M-marker 2003中，为每个连锁群选择了两个在北方和南方菌株之间显示长度多态性的EST标记。使用M标记的批量分离分析2003极大地促进了连锁染色体的快速鉴定（Kimura等人，2004).2. tacobo：该突变在尾芽、头部结构和鳍的发育中引起多效性效应。发现表型反映了经典和非经典wnt途径的缺陷。我们已经开始从最近的遗传标记之一，1.2厘米apart.3.toguro染色体步行：突变体显示骨骼发育的温度敏感性缺陷。我们已经把突变范围缩小到了三个连续BAC克隆所覆盖的区域。这些BAC的测序为我们提供了该区域的10个候选基因，这些候选基因正在通过吗啉代反义技术进行测试。4.头鱼（无尾）：突变体不能发育任何躯干-尾巴结构。定位克隆的结果表明，青鳉fgf受体1（fgf-r1）是引起突变的基因，本研究建立了青鳉突变基因的快速分离体系，并对重要的青鳉突变体进行了定位克隆。

Recent advances in medaka genetics have proven that the medaka is an excellent model system for developmental and evolutionary biology studies and that it can complement similar studies in zebrafish. Large-scale mutagenesis projects are now being conducted in Japan and are delivering a vastly expanded pool of medaka mutant stocks. In this project, we first established a system for rapid mapping of mutated genes, and then we performed phenotypic and genetic analyses of several medaka mutants showing defects in early organogenesis.1.M-marker system : We have constructed a set of primers of EST genetic markers, M-marker 2003, to function as a rapid mapping system for mutated genes. In M-marker 2003, two mapped EST markers showing length polymorphism between northern and southern strains were selected for each linkage group. Bulked segregation analyses with M-markers 2003 greatly facilitated rapid identification of a linked chromosome (Kimura et al., 2004).2.tacobo : The mutation causes pleiotropic effects in development of tailbud, head structures and fin. The phenotype was found to reflect defects in both canonical and non-canonical wnt pathways. We have started chromosomal walking from one of the nearest genetic markers, 1.2 cM apart.3.toguro : The mutant shows temperature-sensitive defects in skeletal development. We have narrowed down the mutation to the region that are covered by three consecutive BAC clones. The sequencing of these BACs provided us ten candidate genes in this region that are being tested by the morpholino-antisense technique.4.headfish (tail-less): The mutant fails to develop any trunk-tail structure. Positional cloning have identified that medaka fgf-receptor 1(fgf-r1) is the responsible gene for the mutant.In summary, we have established the system for rapid isolation of medaka mutated gene and positional cloning of important medaka mutants are now underway.