Rspo1对雌性脊椎动物性别分化的功能

长期以来雌性脊椎动物的性别分化被认为是一个“默认”的程序.但是近些年研究发现,Rspo1基因的突变或缺失可导致哺乳动物XX型个体性反转为雄性.Rspo1在鱼类、两栖爬行类、鸟类和哺乳类动物性腺发育的不同阶段表达,其表达在雌雄个体性别分化时期有差异,是潜在的性别调控基因.Rspo1在性别发育早期可通过Wnt/β-catenin信号通路调控性腺分化相关因子的表达,影响原始生殖细胞分裂增殖、细胞周期和生长发育,参与调控性腺中体细胞的分化.本文总结了近年来Rspo1在脊椎动物中的表达调控及其在雌性性别决定方面功能的研究进展.     

Rspo1在雌性脊椎动物性别分化中的功能

长期以来雌性脊椎动物的性别分化被认为是一个"默认"的程序.但是近些年研究发现,Rspo1基因的突变或缺失可导致哺乳动物XX型个体性反转为雄性.Rspo1在鱼类、两栖爬行类、鸟类和哺乳类动物性腺发育的不同阶段表达,其表达在雌雄个体性别分化时期有差异,是潜在的性别调控基因.Rspo1在性别发育早期可通过Wnt/β-catenin信号通路调控性腺分化相关因子的表达,影响原始生殖细胞分裂增殖、细胞周期和生长发育,参与调控性腺中体细胞的分化.本文总结了近年来Rspo1在脊椎动物中的表达调控及其在雌性性别决定方面功能的研究进展.     

脊椎动物性别决定和分化的分子机制研究进展

哺乳类性别决定是多种转录因子和生长因子相继表达和相互调控的结果。SRY的表达启动雄性通路并诱导下游雄性特异基因SOX9、AMH等的表达。FOXL2在雌性未分化性腺表达,WNT-4和DAX1也在雌性性别决定或分化时期表达,表明雌性通路也是受特定基因调控的,而并非“默认通路”。鸟类的性别也是由遗传基因决定的,EFT1(雌性)和DMRT1(雄性)可能是性别决定候选基因。爬行类为温度性别决定的典型,温度可能通过调节雌激素水平和控制性别特异遗传基因表达决定性别。大部分两栖类性别受环境因素影响,但发现DMRT1和DAX1可能与其精巢发育有关。鱼类性别决定和分化方式差异很大,多种因素(遗传基因、环境因素、类固醇激素等)参与了这一过程。从青Q鳉Y染色体定位克隆的DMY,被认为是第一个非哺乳类脊椎动物雄性性别决定基因。所有这些表明脊椎动物性别决定和分化机制是多样化的。     

浅析斑马鱼性别决定的调控因素

性别决定是经典而高度保守的生物过程。在许多物种中性别决定是以遗传为基础的,个体所携带的性染色体决定了性别。然而,由于鱼类性腺发育呈现高度可变性、复杂性的特点,其性别决定机制仍未有定论。斑马鱼作为一个研究发育和疾病的重要脊椎模式动物,性别决定和分化的高度可塑性使其成为研究生理和环境因素对性腺发育影响及其作用机制的独特模型。本综述总结近年来对斑马鱼性别决定及分化过程的研究,为探索鱼类性别决定机制提供新的见解。     

早期胚胎的发育选择:性别决定

性别决定是一个复杂的发育调控过程, 早期胚胎发育过程中, 雌雄二者必居其一的发育选择是胚胎性腺形成必须的发育决定。文章综述了动物性别决定的遗传系统、性腺发生、性别决定关键基因及其作用机制, 从分子进化的角度分析了性染色体与性别决定形成机制, 提示性别决定基因在进化中总是趋向异配性染色体。     

鸡胚公母性腺差异表达基因的基因芯片杂交筛选

采用Affymetrix公司鸡基因组芯片对9日龄鸡胚公母性腺总RNA进行了芯片杂交, 并对基因表达谱进行了分析。统计结果显示, 9日龄母鸡性腺表达基因数19 368个, 公鸡性腺表达基因数19 493个; 公母性腺绝对差异表达基因,即公鸡性腺表达而母鸡性腺不表达基因145个, 母鸡性腺表达而公鸡性腺不表达基因189个。绝对差异表达基因功能分类结果显示, 参与细胞组成、细胞加工和分子结合基因占多数, 部分基因参与细胞器组成、代谢加工、生物学调控以及催化反应和细胞信号转导等。值得注意的是, 本研究发现了一些已经报道同性别决定和分化有一定关联的基因, 如ASW、CHD1和SOX9等, 同时也发现了一些未知其同性腺分化和发育有关联的基因和编码假想蛋白的表达序列。进一步分析这些基因和表达序列的生物学功能和表达模式, 将对鸟类性别决定和分化机制的了解提供有益参考。     

青鳉(Oryzias latipes)smad3的克隆与表达分析

鱼类性染色体的原始性导致性别决定基因的多样性.高等动物中的单个基因,在鱼类中因为基因组复制而产生多个同源基因,呈遗传多样性.TGF-β家族在硬骨鱼性别决定和性别分化的过程中发挥关键作用.smad3是性腺体细胞衍生因子(gsdf)的下游基因,可将TGF-β信号从细胞表面传递至细胞核.本研究从青鳉精巢和卵巢组织cDNA中克...     

黄河鲤性别决定时间和相关基因表达研究

鱼类性别决定和分化机制极为复杂,通过性腺组织切片鉴定得出黄河鲤从未分化性腺发育为Ⅱ期精巢、卵巢的时间为受精后第40天到第80天。选取一些可能参与黄河鲤性别决定分化相关的基因（amh、ar、cyp19a、cyp19b、dax1、dmrt1、er、foxl2、nobox、sox9a、sox9b、zp2）进行实时荧光定量PCR分析各个基因在受精后40d、45d、50d、55d、65d和80d的表达情况。结果显示性别决定相关基因在50d都有高表达,推测45-50 d为性别决定的关键时间。ar、amh、dax1、dmrt1、sox9a、sox9b六个基因在80d雄性表达量升高,且雄性明显高于雌性,推测这些基因参与精巢分化发育过程。cyp19a、cyp19b、foxl2、nobox、zp2五个基因在80d雌性表达升高,且高于雄性,推测其可能参与卵巢分化发育。     

黄瓜性型分化的分子机制

黄瓜(Cucumis sativus)是雌雄异花植物性型分化研究的重要模式植物,近年来虽然其性型分化的分子机制研究取得了一定的成果,但其性型分化的调控机制尚未完全阐明。该文综合花器官发育基因、性别决定基因、内源激素、环境因子、性型分化假说,在分子水平构建了黄瓜性型分化的表达调控网络。同时对激素和性别决定基因协控的黄瓜单性花器官凋亡机制进行了阐述,并就miRNA在黄瓜性型分化调控中的作用进行了探讨。     

Molecular cloning and characterization of amh,dax1 and cyp19a1a genes and their response to 17α-methyltestosterone in Pengze crucian carp

The proteins encoded by amh, dax1 and cyp19a1a play important roles in gonad differentiation. Their functions have been far less studied in teleosts. In this study, the full-length cDNAs of amh, dax1 and cyp19a1a were cloned and characterized in a triploid gynogenic fish, the Pengze crucian carp. Their expression profilings in juvenile development, adult tissues and juveniles exposed to 100 ng/L 17α-methyltestosterone (MT) were investigated. Results showed that their putative proteins shared high identities to their counterparts in cyprinid fish species, respectively. The tissue distribution results indicated that amh and cyp19a1a were predominantly expressed in the ovary and dax1 was dominantly expressed in the liver. Gene profiling in the developmental stages showed that all the three target genes had a consistent highest expression at 48 days post hatching (dph). The period of 48 dph appeared to be a key time during the process of the gonad development of Pengze crucian carp. 100 ng/L MT significantly increased the mRNA expression of amh at 2- and 4-week exposures and enhanced dax1 and cyp19a1a at 6-week exposure. The present study indicated that MT could influence the gonad development in Pengze crucian carp by disturbing sex-differentiation associated gene expression. Furthermore, the present study will be of great significance to broaden the understanding of molecular mechanisms of the physiological processes of reproduction in fish.     

鱼类干扰素反应及分子调控

干扰素反应在脊椎动物抵抗病毒感染过程中发挥重要作用。近年来,鱼类干扰素抗病毒免疫反应的研究取得了重要进展,不仅克隆鉴定了一系列鱼类干扰素系统基因,而且通过功能研究揭示了鱼类具有类似于高等哺乳类的干扰素反应。但是,鱼类干扰素反应及分子调控具有自身特点。以下综述了最近这方面的研究结果。     

Genetic and genomic analyses for economically important traits and their applications in molecular breeding of cultured fish

The traits of cultured fish must continually be genetically improved to supply high-quality animal protein for human consumption.Economically important fish traits are controlled by multiple gene quantitative trait loci(QTL),most of which have minor effects,but a few genes may have major effects useful for molecular breeding.In this review,we chose relevant studies on some of the most intensively cultured fish and concisely summarize progress on identifying and verifying QTLs for such traits as growth,disease and stress resistance and sex in recent decades.The potential applications of these major-effect genes and their associated markers in marker-assisted selection and molecular breeding,as well as future research directions are also discussed.These genetic and genomic analyses will be valuable for elucidating the mechanisms modulating economically important traits and to establish more effective molecular breeding techniques in fish.     

Asymmetrical Development of the Gonads in the Embryos and Fry of the Fish, Oryzias celebensis

The development of the gonad in Oryzias celebensis was studied by light and electron microscopy. The path of PGC-migration, the time of the sex-differentiation, and the pattern of germ cell proliferation were almost identical to those in O. latipes. The most conspicuous difference was in the distribution of germ cells after migration. The gonadal anlage in O. celebensis developed only on the right side of the dorsal mesentery, although PGCs were stituated on the both sides of the embryos before migration. The testis retained its unilateral condition throughout development and acquired a unilobed shape. In the female, the right presumptive ovary developed over the mesentery, and the ovary became bilobed. Thereafter, right and left parts of the presumptive ovary fused to develop into a single ovary in the adult fish. The situation appears to be comparable to the gonadal asymmetry in birds, but the present observations suggest that the developmental processes of the asymmetrical gonads in this fish are quite different from those in birds.     

Are all fishes ancient polyploids?

Euteleost fishes seem to have more copies of many genes than their tetrapod relatives. Three different mechanisms could explain the origin of these 'extra' fish genes. The duplicates may have been produced during a fish-specific genome duplication event. A second explanation is an increased rate of independent gene duplications in fish. A third possibility is that after gene or genome duplication events in the common ancestor of fish and tetrapods, the latter lost more genes. These three hypotheses have been tested by phylogenetic tree reconstruction. Phylogenetic analyses of sequences from human, mouse, chicken, frog (Xenopus laevis), zebrafish (Danio rerio) and pufferfish (Takifugu rubripes) suggest that ray-finned fishes are likely to have undergone a whole genome duplication event between 200 and 450 million years ago. We also comment here on the evolutionary consequences of this ancient genome duplication.     

Paradoxical role of C1561T glutamate carboxypeptidase II (GCPII) genetic polymorphism in altering disease susceptibility

Although olfaction could play a crucial role in underwater habitats by allowing fish to sense a variety of nonvolatile chemical signals, the importance of olfaction in species-rich cichlids is still controversial. In particular, examining whether cichlids rely on olfaction for reproduction is of primary interest to understand the mechanisms of speciation. In the present study, we explored the V1R (also known as ora) genes, which are believed to encode reproductive pheromone receptors in fish, in the genomes of Lake Victoria cichlids. By screening a bacterial artificial chromosome library, we identified all six intact V1R genes (V1R1 to V1R6) that have been reported in other teleost fish. Furthermore, RT-PCR and in situ hybridization analyses showed that all of the V1R genes were expressed in the olfactory epithelium, indicating that these receptors are functional in cichlids. These observations indicate that cichlids use V1R-mediated olfaction in some ways for their social behaviors.     

南极鱼类多样性和适应性进化研究进展

南极地区是地球上唯一未被人类活动大量影响的地区, 其极端寒冷的环境为南极生物的进化提供了“温床”。过去三千万年间, 南极鱼亚目鱼类在南极海洋逐渐变冷的过程中快速进化, 从一个温暖海域的底栖祖先分化成南极海域最为多样化的鱼类类群。由于其在南极圈内和南极圈外的各种温度区间都有分布, 因而成为研究鱼类适应性进化和耐寒机制的良好生物模型。本文综述了有关南极海域鱼类区系组成与物种多样性现状, 南极鱼亚目鱼类适应低温的一系列特化的生物学性状及其关键的遗传进化机制。现有研究表明: 南极鱼类在几千万年零度以下低温环境的进化中发生了大量基因的大规模扩增和基因表达的改变, 如铁调素、卵壳蛋白和逆转座子等118个基因发生了显著的扩增。另外, 有些从南极鱼中获得的抗寒基因已经用于提高动植物低温抗性的研究并取得了良好的效果。在今后的几年中, 将会有多个南极鱼物种的全基因组得到破译, 在低温适应相关基因的功能和进化方面的研究也会更加深入, 这些研究将深入揭示低温压力下基因组的进化规律以及鱼类低温适应的分子机制。     

鱼类免疫球蛋白基因结构及抗体多样性的遗传机制

本文对鱼类免疫球蛋白的基因结构以及抗体多样性产生的遗传机制作一综述。免疫球蛋白重链和轻链是由不同染色体上的多基因座编码的,在鱼类的不同分类单元中具有不同的基因组织方式。鱼类抗体可以识别外界为数众多的抗原,其多样性主要是由以下遗传机制产生的：种系V区编码区段的多样性、V (D) J区段组合的多样性、基因重组的不精确性、基因转换、体细胞突变以及H和L链的随机组合等。 Gene Structure and Genetic Diversity of Immunoglobulins in Fish ZHANG Yong-an,NIE Pin,ZHU Zuo-yan State Key Laboratory of Freshwater Ecology and Biotechnology,Institute of Hydrobiology,Chinese Academy of Sciences,Wuhan 430072,China Abstract:The current knowledge concerning the structure of fish immunoglobulin (Ig) genes and the genetic mechanisms in generating fish antibody diversities is reviewed.The heavy (H-) and light (L-) chains of the immunoglobulin are encoded by multigenic loci on separate chromosomes.In different taxa of fish,the Ig genes are organized in different patterns.Fish antibody can recognize various foreign antigens,and the antibody diversity is generated by the following genetic mechanisms:the sequence diversity within the segments encoding the variable domain,the combinatorial diversity of V (D) J segments,the imprecision of rearrangements,gene conversion,somatic hypermutation,and the combination of H- and L-chain. Key words：immunoglobulin; gene; antibody; diversity; fish