Hox 基因与昆虫体躯决定

本综述了Hox基因的组成与功能,及Hox基因决定昆虫形态进化的作用机制。     

脊椎动物基因组与基因复制研究进展

脊椎动物的出现是动物进化历史上一次质的飞跃.由于所有的脊椎动物在其胚胎发育中都呈现连续的解剖学特征,因此过去很多学者都根据现存脊椎动物的形态特征和在其发育过程中的解剖学特征假想原始脊椎动物,并推导其进化过程和起源.近年来的研究表明,通过对脊椎动物和与之亲缘关系接近的物种之间进行基因家族、染色体结构分析,可以对脊椎动物进化提供很多线索和证据.更多的研究表明,脊椎动物在进化过程中很可能发生过整体基因组的复制, 基因和/或基因组的复制可能是引起脊椎动物形体结构复杂性增加的根本原因.因此,基因和基因组的复制正在成为生物进化研究的热点问题.但这两种复制方式中哪一种是产生动物形体结构和功能复杂性增加最重要的原因尚有争论.     

ZFX基因同源序列在黄鳝基因组中的检出及其染色体定位

以大熊猫锌指蛋白基因Zfx为探针 ,在黄鳝基因组DNA中检测到一条长约 9 5kb的杂交带。依据哺乳类和爬行类动物锌指蛋白基因 (ZFX/Zfc)编码第 7～ 13个锌指结构的DNA序列保守性设计引物 ,在黄鳝基因组DNA中仅扩增到一条 5 12bp的DNA片段。将此片段克隆至载体 pBS中 ,从雌性、雄性个体中分别挑选 4个含有插入片段的白色克隆进行测序。测序结果表明 ,这些克隆中插入片段的核苷酸序列一致。该DNA片段在核苷酸水平上与人类ZFX和ZFY分别具有 88%和 87%同源性 ,但其与美洲鳄鱼Zfc的同源性可达 90 % ,而在氨基酸水平上则分别存在 95 9%、95 9%和 93 5 %的同源性 (170个氨基酸 )。该基因命名为黄鳝锌指蛋白基因Zfa ,并运用FISH将其定位于黄鳝 1号染色体 ,距离着丝粒的相对位置为 6 0 1± 0 38。通过进一步研究证明 ,黄鳝 1号染色体上存在有真兽类哺乳动物X染色质同源的保守片段 ,该保守片段有可能就是哺乳动物X染色体起源和进化的原始物质基础之一。应用哺乳动物X染色体连锁的其他基因在鱼类开展染色体比较定位研究 ,将有望促进脊椎动物性染色体进化的深入研究     

Hox基因与昆虫翅的特化

自从1978年E.B. Lewis描述了著名的果蝇双胸突变体（bithorax）以来,大量的比较发育遗传学研究为我们揭示了形态进化的遗传基础,从而使形态进化研究进入了一个新的时代。同时,Hox基因的研究也成为这一领域的焦点。本文综述了昆虫翅的起源及其特化类群翅的发育遗传学研究的最新进展。一般认为,原始的有翅昆虫胸腹部多附肢（包括翅）; 之后不同的体节受到了不同Hox的抑制,形成两对翅以及前后翅的分化; Ubx的不同表达导致了前后翅的分化,并且Ubx负责识别后翅。我们选择翅特化最为显著的3个类群——鞘翅目（T2鞘翅）、双翅目（T3平衡棒）和捻翅目（T2平衡棒）,结合Hox的表达情况讨论了翅的特化机理。目前已知双翅目和鞘翅目的翅的控制模式存在巨大差异,两种模式的比较研究对于理解翅的形态进化具有重要的意义。但是对捻翅目昆虫的研究则很少。     

黄鳝基因组中存在酪氨酸蛋白激酶受体基因同源序列

近年的研究表明,酪氨酸蛋白激酶受体通过其细胞膜外部的结构域与细胞外的信号分子配体结合后,激活本身位于细胞质内的激酶结构域,磷酸化的酪酸进而激活下游一系列信号分子。这些分子的激活引起细胞内基因表达的改变,最终导致细胞本身表型状态的变化。本文发现并研究了存在于鱼类中的酪氨酸蛋白激酶受体基因的同源序列matk。实验用黄鳝和胡子鲇为集市采购。PCR扩增采用人SRY基因编码区的一对引物,分别为：5′CCCGAATTCGACAATGCAATCATATGCTTCTGC3′和5′CTGTAGCGGTCCCGTTGCTGCGGTG3′。分别制备雌雄性黄鳝基因组DNA,进行PCR扩增。2％琼脂糖凝胶电泳分析表明,雌雄性样品中均可见到约250bp的扩增带。将雄性的扩增产物matk重组pUC13载体上。对其进行测序,结果表明：matk与人SRY和SRY盒基因序列无同源性,而与最近才报道的大鼠酪氨酸蛋白受体基因ptk3cDNA5′端序列具有56％的序列一致性（图1）。有报导,人与鼠的酪氨酸蛋白激酶受体基因DDR和ptk3存在96％的同源性。表明这种酪氨酸蛋白受体基因具有很强的保守性。以matk为探针,对经过EcoRI酶切过的雌雄黄鳝的胡子鲇（为对照）的基因组DNA进行Southern印迹分析。杂交结果（图2）显示：实验组的雌雄性黄鳝中,在3．3Kb和2．2Kb处均有两条一致的杂交带;而对照组中没有杂交带。说明黄鳝中存在酪氨酸蛋白激酶受体同源序列,有两个抟。类似地：果蝇和线虫的胰岛素受体基因scvenless和EGF／TGF－α等在哺乳动物中均有各自的同源基因－rasl和lin－3等。本研究结果有助于了解信号传导机制及其在水生动物到陆生动物中的进化模式。     

运用PRINS和体细胞杂种克隆板对猪新微卫星的定位

In this study, two new microsatellites HAU02 and HAU06, which are screened and cloned. HUA02 and HAU06 are repectively mapped in lq23-27 and 6q11-21 by means of PRINS (primed in situ labeling) and somatic cell hybrid (SCH) panel techniques, we discussed their advantage and disadvantage in gene mapping. These two means provide us more techniques in gene mapping, and the locations of these new microsatellites accumulate more resource for Porcine Physical Map.     

鱼类特异的基因组复制及鱼类多样性(英文)

过去的研究认为在脊椎动物的进化历程中曾发生了两次基因组复制.而最近的系统发生学和比较基因组学研究提出辐鳍鱼还发生了第3次基因组复制,即鱼类特异的基因组复制(The fish-specific genome dupli-cation).目前,基因组复制是生物进化研究中的热点问题.硬骨鱼是世界上现存鱼类中最多的一类,由多于现存脊椎动物半数的物种组成,在形态和生理适应类型上表现了明显的差异.硬骨鱼在进化上的成功和惊人的生物多样性可能与它们的基因组复杂性有关.     

利用脉冲电场凝胶电泳测定小鼠CK-4、Hox3.1和Hox3.3基因间的距离

利用脉冲电场凝胶电泳(PFGE,Pulse Field Gel Electrophoresis)和Southern印迹杂交,测定了小鼠第15染色体上Ⅱ型细胞角蛋白CK-4基因与含同源区序列的Hox 3.3基因之间的最大距离为130kb。Hox 3.3和Hox 3.1基因之间的距离不超过50kb。同时还确定了这三个基因所在的1100kb DNA片段上MluⅠ、NotⅠ、SacⅡ、SolⅠ和SfiⅠ五种限制酶的物理图。     

Hox基因及其进化机制的研究进展

Hox基因是生物体内一类重要的发育调控基因家族.Hox基因高度保守,通常成簇存在,编码一类转录因子,在个体胚胎发育中起着重要的调控作用.近期研究表明,基因复制、基因序列变异及选择压力对Hox基因簇的产生和进化有重要作用,同时调节元件和协同进化对Hox基因的进化也有重要影响.     

鱼类特异的基因组复制

辐鳍鱼类是脊椎动物中种类最多、分布最广的类群,其基因组大小不等。过去的观点认为,在脊椎动物进化历程中曾发生了两次基因组复制。近期的系统基因组学研究资料进一步提出,在大约350百万年,辐鳍鱼还发生了第三次基因组复制,即鱼类特异的基因组复制(fish-specificgenomeduplication,FSGD),且发生的时间正处在“物种极度丰富”的硬骨鱼谱系(真骨总目)和“物种贫乏”的谱系(辐鳍鱼纲基部的类群)出现分歧的时间点,表明FSGD与硬骨鱼物种和生物多样性的增加有关。进一步开展鱼类比较基因组学和功能基因组学研究将进一步验证FSGD这一假说。     

黄鳝激素敏感性脂肪酶基因Hsl染色体原位杂交定位

动物脂肪组织中的甘油三酯在数量上是最重要的储存能源。Hsl基因所编码的激素敏感性脂肪酶是一种多功能酶。它通过催化水解储存在脂肪组织中的甘油三酯,以及卵巢、肾上腺、睾丸和胎盘中的胆固醇酯,在机体能量供应和类固醇生成作用中发挥重要作用。本研究以放射性同位素和地高辛标记重组质粒pBS中所含猪Hsl基因作为探针,分别与Pst Ⅰ酶切的黄鳝基因组总DNA和有丝分裂染色体标本进行Southern杂交和荧光原位杂交(FISH)。结果显示,Southern杂交呈现一条带,片段长度约为11.5kb。同时,应用FISH定位Hsl基因于黄鳝5号染色体,相对着丝粒距离为78.35±1.26。该定位结果与应用“特定染色体DNA池”定位黄鳝Hsl基因结果相符,且定位结果更为精细。表明在淡水鱼类黄鳝基因组中存在Hsl基因,另一方面也首次提供黄鳝5号染色体上FISH杂交信息,从而为增加黄鳝染色体组中已知的遗传标记和建立高精度遗传图谱奠定基础。 Abstract:Adipose tissue triacylglycerols are the quantitatively most important source of stored energy in animals.Hormone-sensitive lipase encoded by hormone-sensitive lipase gene (Hsl) is a multifunctional enzyme that catalyzes the hydrolysis of triacylglycerol stored in adipose tissue and cholesterol esters in the adrenals,ovaries,testes and macrophages.Using pig Hsl gene inserted into pBS labeled by the radioactive isotope and the digoxigenin as the probes respectively,one band,11.5kb,has been shown to hybridized with total DNA of rice field eel digested with Pst Ⅰby Southern blotting and Hsl gene has been assigned to metaphase chromosome 5,at the position of 78.35±1.26 from the c entromere in rice field eel by fluorescent in situ hybridization (FISH).The mapping results are corresponding to that of “specific-chromosomal DNA pool”obtained by chromosome microisolation used to map gene and the mapping result is more accurate.The results of the study further illustrate the importance of the presence of Hsl gene in rice field eel genome and provide the first FISH mapping data for rice field eel chromosome 5.The current studies would advance the addition of known genetic markers and the construction of high resolution genetic map in rice field eel genome.     

The Hox Paradox: More complex(es) than imagined

An understanding of the origin of different body plans requires knowledge of how the genes and genetic pathways that control embryonic development have evolved. The Hox genes provide an appealing starting point for such studies because they play a well-understood causal role in the regionalization of the body plan of all bilaterally symmetric animals. Vertebrate evolution has been characterized by gene, and possibly genome, duplication events, which are believed to have provided raw genetic material for selection to act upon. It has recently been established that the Hox gene organization of ray-finned fishes, such as the zebrafish, differs dramatically from that of their lobe-finned relatives, a group that includes humans and all the other widely used vertebrate model systems. This unusual Hox gene organization of zebrafish is the result of a duplication event within the ray-finned fish lineage. Thus, teleosts, such as zebrafish, have more Hox genes arrayed over more clusters (or "complexes") than do tetrapod vertebrates. Here, I review our understanding of Hox cluster architecture in different vertebrates and consider the implications of gene duplication for Hox gene regulation and function and the evolution of different body plans.     

黄鳝Nup93基因的分子克隆及其在性腺和肾的显著表达

核孔蛋白（Nucleoporins,Nups）是核孔复合体（Nuclear pore complexes,NPC）的重要组成成分,核孔复合体可以控制细胞内信号分子在核质问的双向转运,从而控制基因表达、细胞增殖和分化。在构建的黄鳝精巢SMART cDNA文库中,采用差异筛选的方法得到黄鳝核孔蛋白家族中Nup93基因的3’端片段,根据此段序列设计引物,使用兼并PCR和5＇RACE方法克隆得到此基因的全长cDNA。序列比对显示该基因与酵母Nic96、斑马鱼Nup93和人类Nup93的同源性分别为36．5％、94．6％和90．5％。进化树分析显示,黄鳝Nup93与其他鱼类的Nup93归为一支。采用荧光定量PCR方法对不同性别黄鳝的性腺和其他组织内该基因的表达作定量分析发现,Nup93在性腺和肾中的表达量远高于其他组织,而且表达量存在一定的性别差异。这一结果提示Nup93可能与性腺发育相关。     

Molecular Cloning of the Rice Field Eel Nup 93 with Predominant Expression in Gonad and Kidney

Nucleoporins (Nups) are important components of nuclear pore complexes (NPCs). NPCs control gene expression, cells proliferation and differentiation by mediating exchange of cellular signal molecules on both nuclear and cytoplasmic sides. Using subtractive screening, 3'end fragment of Nup 93 from the testis cDNA library of the rice field eel was obtained. Full-length cDNA of the gene was further cloned by degenerate PCR and 5'RACE methods. Sequence analysis indicated that the homology of the rice field eel Nup 93 were 36.5% with yeast Nic 96, 94.6% and 90.5% with Nup 93 of zebrafish and human, respectively. Phylogenetic analysis showed that the rice field eel Nup 93 fits with Nup 93 of the other fishes. Real-time PCR result showed that expression of Nup 93 in gonads and kidney were much higher than in other tissues, and different expression quantities among gonads of three sexes were also observed, suggesting that Nup 93 may involve in gonad development.     

The fates of zebrafish Hox gene duplicates

In his 1970 book, Susumu Ohno stressed the importance of gene duplication in the evolution of the vertebrate genome and body plan. He elaborated the idea that duplication events provide novel genetic material on which evolution may act. Data are accumulating to show that extensive duplication events, perhaps incorporating the duplication of entire genomes, occurred in the lineage leading to teleost fishes. These duplications may have been pivotal in the explosive radiation of this highly successful vertebrate group. Thus, the teleosts provide us with an ideal opportunity to investigate the fates and functions of duplicated genes. A convenient system for these studies is the zebrafish, Danio rerio, which has become a popular genetic and embryological model.     

The "fish-specific" Hox cluster duplication is coincident with the origin of teleosts

The Hox gene complement of zebrafish, medaka, and fugu differs from that of other gnathostome vertebrates. These fishes have seven to eight Hox clusters compared to the four Hox clusters described in sarcopterygians and shark. The clusters in different teleost lineages are orthologous, implying that a "fish-specific" Hox cluster duplication has occurred in the stem lineage leading to the most recent common ancestor of zebrafish and fugu. The timing of this event, however, is unknown. To address this question, we sequenced four Hox genes from taxa representing basal actinopterygian and teleost lineages and compared them to known sequences from shark, coelacanth, zebrafish, and other teleosts. The resulting gene genealogies suggest that the fish-specific Hox cluster duplication occurred coincident with the origin of crown group teleosts. In addition, we obtained evidence for an independent Hox cluster duplication in the sturgeon lineage (Acipenseriformes). Finally, results from HoxA11 suggest that duplicated Hox genes have experienced diversifying selection immediately after the duplication event. Taken together, these results support the notion that the duplicated Hox genes of teleosts were causally relevant to adaptive evolution during the initial teleost radiation.     

Cloning and Characterization of a Rice Field Eel vasa-Like Gene cDNA and Its Expression in Gonads During Natural Sex Transformation

The vasa (vas)-related gene encodes an RNA helicase protein member of the DEAD-box family and plays key roles in germ-cell formation in higher metazoans. Using degenerate PCR and RACE, we cloned the vasa gene of the rice field eel (Monopterus albus), which is homologous to the Drosophila vasa gene. We named it ma-vas (Monopterus albus vas). Ma-vas encodes a protein of 618 amino acids, which contains all of the known characteristics of vasa homologs. RT-PCR analysis revealed that ma-vas was exclusively expressed in the gonads of the female, intersex, and male. During gonadal natural sex reversal, ma-vas is expressed in oocytes at all stages of oogenesis, in degenerating oocytes of ovotestis, and in spermatogonia and spermatocytes at early stages. The vasa positive signal was also observed in the peripheral layer of late ovary. It was not found, however, in that layer of the testis. Alkaline phosphatase (AKP) staining on the ovary and testis also indicated that some cells had differentiational potential in the peripheral layer of the ovary, suggesting that spermatogonia might arise from cells with AKP and vasa-positive staining in the peripheral layer of the female gonad.