鲤鱼性别决定基因ccMD的鉴定及其作用机制研究

鱼类性别决定基因发掘及其作用机制不仅是生物学的前沿研究领域之一，而且对培育鱼类性控新品种具应用价值。鲤鱼是主养的鲤科鱼类代表性物种之一，雌性比雄性大。已发现的十余个鱼类性别决定基因中，没有一个来自鲤科鱼。申请人发掘出一个鲤雄性特异DNA片段，可有效鉴定黄河鲤、长江鲤和红鲤等不同类群的性别；该片段中包含一个转录本（暂命名为ccMD），特异表达于鲤鱼精巢分化早期，在分化早期达到表达峰值，随后降低；敲除ccMD的雄鲤发生性反转；结果强烈提示其可能是鲤鱼的性别决定因子。本项目拟通过体内和体外试验等研究，分析ccMD的精细表达特征；在全雄鲤中敲除ccMD或在全雌鲤中异位表达ccMD，并分析ccMD对性腺分化发育的影响；发掘ccMD直接作用的靶基因及其近、远程顺式调控元件和反式作用因子；解析鲤性别决定和分化的分子调控网络。以期阐明ccMD的性别决定功能，鉴定出第一个鲤科性别决定基因并揭示其作用机制。

Exploring sex determination genes in fish followed by uncovering their molecular mechanisms is not only a frontier area in biological research, but also of practical value for establishing precise sex controlled breeding technique, which will produce new unisexual strains with high yield traits in aquaculture. The Cyprinidae family consists of the most species among fresh water fish in the world. The common carp, Cyprinus carpio, is one of the representative aquaculture species from Cyprinidae, and females show a faster growth rate. Till now, none of the found more than ten sex determination genes in fish was from Cyprinidae. Previously, the project applier obtained a male specific DNA fragment in common carp by comparing the genome between two genders, which could identify the genders of individuals from Yellow River carp, Yangtze River carp or Xingguo red carp. In this fragment, there was a transcript coding region. The transcript was named as ccMD temporarily. It was expressed specially in the testis, reaching the peak at the initiation of sex differentiation, then declined. Ovaries were observed in the ccMD mutated male carp. The results above strongly suggested ccMD as the candidate for the sex determination gene in common carp. In this project, by means in vivo and in vitro, we will study the expression pattern of ccMD, examine the sex differentiation of ccMD mutated male common carp as well as female fish transplanted with ectopic ccMD, isolate the direct target genes of ccMD, identify the cis acting elements and the trans acting factors, analyze the molecular regulatory network of sex determination and differentiation in common carp. At the end of project, the function and its acting mechanism of ccMD in sex determination will be uncovered. ccMD is expected to be identified as the first found sex determination gene in Cyprinidae fish.