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。     

应用PRINS技术定位黄鳝Hox基因的研究

Hox基因是近年来发现的支持基因组复制进化理论的最有力的证据。该研究应用引物原位延伸 (PRINS)技术 ,在黄鳝有丝分裂染色体标本上开展Hox基因的定位研究。研究结果表明 ,在黄鳝染色体组中可能存在有 6个Hox基因簇 ,这些基因簇分别位于黄鳝第 1、2、3、6、8和 10号染色体 ,相对着丝粒距离分别为 2 8 2 4± 2 88、4 5 5±1 39、13 89± 2 0 3、74 32± 1.86、38 0 3± 2 .4 1和 5 8 18± 2 0 5。该研究定位黄鳝Hox基因将有助于挖掘黄鳝染色体的来源和进化特征 ,并为基因组复制进化理论提供黄鳝这一特化物种的细胞遗传学证据。     

家蚕Hox基因研究进展

Hox基因（homeobox genes）在昆虫躯体模式（body plan）的发育调控机制中扮演着重要角色,其表达具有严格的组织特异性和胚胎发育的程序性。家蚕Bombyx mori作为鳞翅目昆虫的代表,其Hox基因也陆续得到鉴定。在家蚕中存在一个拟复等位基因群--E群基因,其突变表型均与过剩斑纹和过剩附肢有关,这可能与Hox基因有着密切联系。家蚕全基因组测序完成后,发现其Hox基因簇中存在12个特有的homeobox基因（Bmshx1~Bmshx12）, 说明家蚕Hox基因可能具有独特的生物学意义。我们还利用家蚕基因芯片数据分析了Bmlab与Bmpb基因的组织表达特征。通过对家蚕Hox基因的研究,探索家蚕躯体模式建立机制,可望为解析其他鳞翅目昆虫的躯体模式的建立机制提供理论依据。本文就家蚕Hox基因的表达、功能及其与E群突变的关系等方面进行了综述。     

Hox基因及其在海胆中的研究进展

Hox(homeobox genes)基因是存在于染色体上的一段高度保守序列,其蛋白产物作为转录因子也是高度保守的。这些基因调节胚胎发育,尤其在脊椎动物前-后轴(antero-posterior axis)的发育过程中起着重要作用,并指导脊椎动物的体型形成。海胆是海洋中一类比较常见的无脊椎动物和主要的海水养殖动物,它的Hox基因对它动-植物轴(animal-vegetalaxis)的形成有调控作用,并对进化研究和养殖生产具有重要意义。综述了近年来Hox基因在海胆中的研究进展。     

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.     

基于四个Hox基因的水生蝽类昆虫（半翅目-异翅亚目：蝎蝽次目）系统发育研究

本研究选取了水生的蝎蝽次目(半翅目:异翅亚目)10科的11种为代表种,扩增了蛋白编码基因-四个Hox基因(abd-A,Dfd,Ubx和pb)的部分片段,利用最大似然法和贝叶斯方法分析了蝎蝽次目总科或科间的系统发育关系。研究结果如下:支持蝎蝽次目、潜蝽总科(盖蝽科+潜蝽科)、蝎蝽总科(负子蝽科+蝎蝽科)、蜍蝽总科(蜍蝽科+蟾蝽科)以及固蝽总科(固蝽科+蚤蝽科)的单系性;蜍蝽总科为蝎蝽次目的基部分支;仰蝽总科只包括仰蝽科,并与(固蝽总科+潜蝽总科)形成新的姐妹群关系;蝎蝽总科与划蝽总科为姐妹群;表明Hox基因在解决异翅亚目总科间或科间的系统发育关系上,是适合的分子标记。     

PcG蛋白复合体对Hox基因调节的研究

PcG蛋白广泛参与到生长、发育、增殖、分化以及肿瘤发生等重要过程.而目前为止对PcG蛋白的靶基因研究最透彻的就是Hox家族. Hox基因存在于一个高度保守的基因簇内,在调控维持正常发育及肿瘤发生中有重要作用.一般认为,PcG蛋白复合物对Hox基因进行以组蛋白表观修饰为主的沉默作用,指导Hox基因适时适地发挥功能. 同时,这个过程还需要DNA连接蛋白、ncRNA等分子的辅助.本文对Hox基因和PcG蛋白的组成和功能进行介绍,并重点归纳总结了对二者关系的经典和最新认识.     

基于全基因组的龟鳖目Hox基因序列特征及进化分析

为对Hox基因在龟鳖目物种中进行系统地序列比较分析和进化研究，文章对目前具有染色体水平的龟鳖目基因组进行了Hox基因的鉴定,序列特征、进化和转录组分析。研究结果表明龟鳖物种的Hox基因簇是高度保守的。非重复序列的缺失导致鳖科HoxB9—HoxB13基因间区相对龟科短了10 kb。大量Hox基因编码区发生了鳖科或龟科特异的序列替换、插入和缺失。胸部骨骼发育相关的Hox基因在鳖科祖先发生了快速进化和受到正选择。Hox基因的表达具有组织、时期特异性,主要在胚胎时期的顶端外胚层嵴、背甲嵴和性腺表达。研究为龟鳖目Hox基因不同胚胎时期的多组学及表达调控分析提供了靶标,也为进一步厘清龟鳖物种演化创新提供了参考。     

成簇基因的时空表达调控

成簇基因具有不同单个基因的特性,同一簇内基因大多有类似的结构,功能以及表达模式,基因之间时空表达模式及表达量高度协调,提示同一簇基因是作为统一整体进行调节的,具有共同的调节机制。基因成簇排列是实现基因时空协调表表达的基础,是遗传信息的一种高级组织形式,具有强大的进化优势,要揭示成簇基因表达调控的基本规律,应从顺式作用元件,反式作用因子,染色质等层次,进行整体的以及多基因相互作用的研究,这些机制的阐     

Hox Genes and Axial Specification in Vertebrates

The colinear, anterior to posterior expression domains of theHox genes in vertebrate embryos is strongly correlated withregional changes in vertebral morphology. The limbs of tetrapodsare consistently aligned with specific areas of the vertebralcolumn. However, control of limb development is apparently situatedin the lateral plate mesoderm, and has been experimentally shownto be independent of an axial Hox code (Cohn et al., 1997, Nature387:97–101). We have used experimental manipulation ofchick embryos to test the causal role of Hox genes in patterningderivatives of the paraxial mesoderm. Hox expression in heterotopicallytransplanted segmental plate responds in a manner consistentwith a patterning role for these genes in the morphologicalbehavior of the transplants. Expression is maintained in dorsalparaxial regions where patterning is also intrinsic to the donorsite of the graft. However, expression is apparently lost insomite cells that migrate into the host lateral plate environmentand form appropriate host-level muscles. This arrangement couldenable increased plasticity in the evolution of transpositionalvariation in the vertebrate body plan.     

Homology, Hox Genes, and Developmental Integration

The establishment and inheritance of individualized structuralunits is a key feature of morphological evolution, embodiedin the concept of homology. In current debates, homology isoften equated with identical genetic encoding. The empiricalevidence for this assumption is ambiguous. Genetic identitycan indicate morphological identity in some cases, but severalexamples show that gene expression patterns and regulatory systemsof development may be highly conserved while morphological charactersundergo dramatic evolutionary innovation. This indicates someindependence of structural homology from its genetic and developmentalmakeup. It is proposed that phenotypic evolution depends stronglyon the epigenetic context in which genetic redundancy becomesavailable for the control of new developmental interactions.The integrated character of developmental systems may representan important factor in the origin and identity of morphologicalcharacters and can stabilize incipient structures before theirfull genetic integration. The origin of the autopod sectionof the tetrapod limb is an example which suggests that novelhomologues can arise in evolution as a consequence of changingthe epigenetic context of conserved gene function.     

Hox Genes and Segmental Patterning of the Vertebrate Hindbrain

SYNOPSIS. Pattern formation in the developing hindbrain andcranio-facial region has been studied in a range of vertebrateorganisms. The developing hindbrain is transiently segmentedinto units termed rhombomeres which correspond with domainsof gene expression, lineage restriction and neuronal organizationand serve to coordinate the migration of cranial neural crestinto the adjacent branchial arches. In this paper I review thecellular and molecular events underlying both hindbrain segmentationand the acquisition of segmental identity, consolidating recentresults from different model systems. Data suggesting that thevertebrate Hox genes play an important role in specifying positionalvalue to the rhombomeres and cranial neural crest are also examined.I compare expression patterns of the Hox genes between speciesand consider the mechanisms involved in controlling their appropriatespatial regulation. In addition I describe a recently characterizedzebraflsh hindbrain segmentation mutant, Valentino; morphological,cellular and gene expression data for this mutant are helpingto further our understanding of hindbrain patterning.     

同源盒基因(Hox)与哺乳动物生殖

哺乳动物的同源盒基因（Hox）与果蝇的同源异形基因是同源基因,该基因编码的DNA片段含183碱基对,转录由61个氨基酸残基组成的蛋白质保守结构域,称同源异型域.Hox基因碱基顺序及在染色体中的位置都是高度保守的.Hox基因在体节结构分化等空间信息调控中起着重要作用,按特异的空间模式赋予每一体节其自身的特点.近年来的研究表明,Hox基因不但影响胚胎发育,而且与成体生殖系统分化有关,在着床期子宫接受态的建立及子宫蜕膜反应的发生等生殖过程中起着重要的调节作用.     

Hox and ParaHox Genes in Flatworms: Characterization and Expression

Flatworms (phylum Platyhelminthes) are favourite organisms inDevelopmental Biology and Zoology because of their extraordinarypowers of regeneration and because they may hold a pivotal placein the origin and evolution of the Bilateria. Hox genes playkey roles in both processes: setting up the new anteroposteriorpattern in the former, and as qualitative markers of phylogeneticaffinities among bilaterian phyla in the latter. We have searchedfor Hox and ParaHox genes in several flatworm groups spanningfrom freshwater triclads to marine polyclads and, more recently,in the acoels, the likely earliest extant bilaterian. We haveisolated and sequenced eight Hox genes from the freshwater tricladGirardia tigrina and three Hox and two ParaHox genes from thepolyclad Discocelis tigrina. Data from the acoels Paratomellarubra and Convoluta roscoffensis is also reported. FlatwormHox sequences and 18S rDNA sequence data support clear affinitiesof Platyhelminthes to spiralian lophotrochozoans. The basalposition of acoel flatworms supported from recent 18S rDNA data,remains still uncertain. Expression of Hox genes in intact andregenerating adult organisms show nested patterns with gradedanterior expression boundaries, or ubiquitous expression. Newapproaches to study the function of Hox genes in flatworms,such as RNA interference are briefly discussed.     

Comparative Analysis of Hox Gene Expression in the Polychaete Chaetopterus: Implications for the Evolution of Body Plan Regionalization

The Hox genes are widely regarded as candidates for involvementin major evolutionary changes in body plan organization. Weexamine Hox gene expression data for several taxa, in relationto recent work on the polychaete annelid Chaetopterus. The workin Chaetopterus shows the basic conservation of colinearityof anterior expression boundaries seen in other groups. It alsoreveals novel patterns including early expression in the larvalgrowth zone and later formation of posterior boundaries thatcorrelate with morphological transitions in the polychaete bodyplan. The polychaete gene expression pattern is compared withthose of Hox gene homologs in other taxa to reveal differencesthat represent evolutionary changes in Hox gene regulation betweenlineages. Correlations between Hox gene expression differencesand morphological differences are examined, focussing on a numberof cases in which posterior Hox gene expression boundaries correlatewith morphological transitions. Differential regulation of theseposterior expression boundaries is proposed as a possible mechanismfor changes body plan regionalization.     

Hox Genes: it's all a matter of context

Recent studies provide compelling new evidence that Hox gene effects depend on fine-structure spatial and temporal information. Further, in a specific cell type, only one or a few downstream genes may mediate Hox morphogenetic functions. If this is generally true, it will have important implications for how Hox regulatory networks operate and evolve.