The limb bud Shh-Fgf feedback loop is terminated by expansion of former ZPA cells

Vertebrate limb outgrowth is driven by a positive feedback loop involving Sonic Hedgehog (Shh), Gremlin, and Fgf4. By overexpressing individual components of the loop at a time after these genes are normally down-regulated in chicken embryos, we found that Shh no longer maintains Gremlin in the posterior limb. Shh-expressing cells and their descendants cannot express Gremlin. The proliferation of these descendants forms a barrier separating the Shh signal from Gremlin-expressing cells, which breaks down the Shh-Fgf4 loop and thereby affects limb size and provides a mechanism explaining regulative properties of the limb bud.     

Progression of vertebrate limb development through SHH-mediated counteraction of GLI3

Distal limb development and specification of digit identities in tetrapods are under the control of a mesenchymal organizer called the polarizing region. Sonic Hedgehog (SHH) is the morphogenetic signal produced by the polarizing region in the posterior limb bud. Ectopic anterior SHH signaling induces digit duplications and has been suspected as a major cause underlying congenital malformations that result in digit polydactyly. Here, we report that the polydactyly of Gli3-deficient mice arises independently of SHH signaling. Disruption of one or both Gli3 alleles in mouse embryos lacking Shh progressively restores limb distal development and digit formation. Our genetic analysis indicates that SHH signaling counteracts GLI3-mediated repression of key regulator genes, cell survival, and distal progression of limb bud development.     

Hox10 and Hox11 genes are required to globally pattern the mammalian skeleton

Mice in which all members of the Hox10 or Hox11 paralogous group are disrupted provide evidence that these Hox genes are involved in global patterning of the axial and appendicular skeleton. In the absence of Hox10 function, no lumbar vertebrae are formed. Instead, ribs project from all posterior vertebrae, extending caudally from the last thoracic vertebrae to beyond the sacral region. In the absence of Hox11 function, sacral vertebrae are not formed and instead these vertebrae assume a lumbar identity. The redundancy among these paralogous family members is so great that this global aspect of Hox patterning is not apparent in mice that are mutant for five of the six paralogous alleles.     

Hoxc13 Expression Pattern in Cashmere Goat Skin During Hair Follicle Development

Hoxc13 has an important role in controlling hair formation. In this study, we examine the Hoxc13 RNA expression pattern of skin during embryo development. The result indicated that changes of the Hoxe13 gene expression and thickness of skin have a similar trend during hair follicle morphogenesis. In interpreting these results, we investigated whether the regulation motifs is in Hoxc13 intron, which is a 5.4 kb fragment. To blast with other mammals, we found a very conservative region in all mammal animals and two regions in livestock, such as cow, sheep, horse, dog, and so on, which are not in other Hox genes. We have examined putative pre-miRNA in this region, providing an entry point for elucidating currently unknown mechanisms that are required for regulating quantitative levels of Hoxc13 gene expression.     

内蒙古绒山羊Homeobox基因片段的克隆与序列分析

根据已公布的Hom eobox基因氨基酸序列保守区设计简并引物,利用PCR技术从内蒙古绒山羊血液基因组DNA中扩增Hom eobox基因家族成员。目的基因片段纯化后连接到pGEM-T载体上,经鉴定得到重组质粒。将110个重组质粒进行测序,测序结果通过与GenBank中序列比对分析,确定86条序列为Hom eobox基因,得到14个Hom eobox基因家族成员:Hoxa4,Hoxa5,Hoxa6,Hoxa7,Hoxb1,Hoxb2,Hoxb3,Hoxb6,Hoxb7,Hoxc6,Hoxd1,Hoxd3,Gbx1,Gbx2。每个基因片段由117个核苷酸组成,编码39个氨基酸。氨基酸序列非常保守,和其他物种的同源性非常高。     

Regulatory blueprint for a chordate embryo

Ciona is an emerging model system for elucidating gene networks in development. Comprehensive in situ hybridization assays have identified 76 regulatory genes with localized expression patterns in the early embryo, at the time when na?ve blastomeres are determined to follow specific cell fates. Systematic gene disruption assays provided more than 3000 combinations of gene expression profiles in mutant backgrounds. Deduced gene circuit diagrams describing the formation of larval tissues were computationally visualized. These diagrams constitute a blueprint for the Ciona embryo and provide a foundation for understanding the evolutionary origins of the chordate body plan.     

团头鲂形态发育相关基因HoxB1b的克隆及功能研究

脊椎动物Hox族基因是一类重要的生长和发育调控基因,它编码具有螺旋—转角—螺旋结构的转录因子,能与下游靶基因特定区域结合并激活表达,从而调节脊椎动物胚胎发育过程中前后轴的形态建成。利用cDNA末端快速扩增法(RACE)克隆了团头鲂(Megalobrama amblycephala)HoxB1b基因的全长cDNA序列,并研究了该基因的表达模式。结果表明:(1)团头鲂HoxB1b基因cDNA全长为1 479 bp,其中包括一个编码306个氨基酸残基的921 bp阅读框,聚类分析结果表明,该基因与斑马鱼、红鳍东方鲀、青鳉的相似度分别为89%、45%、40%,在脊椎动物中具有一定的保守性;(2)RT-PCR分析结果显示,HoxB1b在团头鲂胚胎发育过程的各时期均有稳定表达,但在成熟卵中未检测到该基因的表达,表明该基因属非母源表达类型。进一步的整胚原位杂交结果显示,HoxB1b在团头鲂不同时期胚胎存在明显的空间表达差异,受精后20 h(20 hours post fertilization,20hpf)胚胎主要在后脑表达,受精后40 h(40hpf)胚胎除了在后脑表达外,在胸鳍也检测到表达;(3)HoxB1b基因在团头...     

甜瓜果长基因fl与性别表达基因a的遗传分析及定位

【目的】 研究甜瓜2号连锁群中果长基因fl与性别表达基因a的连锁关系。分析果实长度和性别表达类型(雄花两性花同株、雌雄异花同株)的遗传规律,定位两性状基因。【方法】 以圆形甜瓜、雄花两性花同株品种西州蜜为父本,长形甜瓜、雌雄异花同株品种蛇瓜为母本杂交产生的160个BC₁(Back Cross 回交群体)单株为作图群体,研究BC₁群体中果实长度和性别类型的分布,对二者进行遗传分析。利用集团分离分析法(Bulked Segregant Analysis, BSA),用甜瓜2号连锁群上的48个SSR分子标记,对甜瓜果实长度和花性型性状进行多态性标记的筛选,对两性状基因定位。【结果】 甜瓜果实长度符合数量性状的遗传特点;雄花两性花同株与雌雄异花同株可能受双基因遗传控制。通过连锁分析,将果长基因fl定位于2号连锁群的标记SSR247159和标记SSR252089之间,遗传距离为3 cM;将性别表达基因a定位于标记SSR227156和标记CMGA36/SSR235092之间,遗传距离为3.59 cM;两区间之间的遗传距离为0。【结论】 在甜瓜西州蜜和蛇瓜的BC₁群体中,将果实长度基因fl和性别表达基因a的初步定位于不同标记区间内,证明二者不是同一基因。     

A gene expression map of the Arabidopsis root

A global map of gene expression within an organ can identify genes with coordinated expression in localized domains, thereby relating gene activity to cell fate and tissue specialization. Here, we present localization of expression of more than 22,000 genes in the Arabidopsis root. Gene expression was mapped to 15 different zones of the root that correspond to cell types and tissues at progressive developmental stages. Patterns of gene expression traverse traditional anatomical boundaries and show cassettes of hormonal response. Chromosomal clustering defined some coregulated genes. This expression map correlates groups of genes to specific cell fates and should serve to guide reverse genetics.     

小鼠早期胚胎发育过程中母源基因降解相关内源性小干扰RNA筛选与鉴定

为探究endo-siRNA在小鼠胚胎母源基因降解过程中的功能,通过生物信息学分析对小鼠母源基因和对应小RNA作筛选与鉴定,研究发现近三分之二母源基因为小RNA靶标。母源基因在早期胚胎发育过程中表达模式分析表明endo-siRNA与母源基因表达呈较强负相关,预示endo-siRNA在母源基因降解过程中具有重要功能。验证表明, endo-siRNA可在转录后水平调控母源mRNA水平,调控母源基因降解。研究结果为哺乳动物母胚转换的相关研究提供理论基础。     

Tbx5基因在漠斑牙鲆（Paralichthys olivaceus）变态前的表达

鲽形目鱼类仔鱼经过变态后形成眼睛和偶鳍等器官左右不对称的稚鱼。Tbx家族成员参与脊椎动物心脏、肢体和眼等器官的发育,而Tbx基因与鲽形目鱼类变态的关系目前尚无报道。我们运用扫描电镜和软硬骨染色等方法对出膜后2d（变态早期）和26d（变态前期）的牙鲆仔鱼的形态进行观察,牙鲆出膜后2d胸鳍原基出现,出膜后26d胸鳍发育成熟,而在出膜后26d胸鳍和腹鳍仍呈现左右对称。我们克隆了牙鲆Tbx5基因的CDS序列,该序列编码的多肽具有部分T-box保守结构域,与斑马鱼Tbx5同源性高达93%。系统进化分析显示：这段CDS序列与硬骨鱼的Tbx5基因聚为一支,但与四足动物Tbx5相分离。整体原位杂交显示出膜后26d的牙鲆仔鱼中,Tbx5基因不仅在胸鳍、眼背侧、脊柱和尿囊表达,且在胸鳍和眼背侧的表达呈现左右不对称,左侧面（有眼侧）的表达量均高于右侧面（无眼侧）的表达量。综上结果暗示,牙鲆Tbx5基因可能参与了变态过程中眼睛与胸鳍左右不对称的形成。 研究亮点： 鲽形目鱼类都经历变态发育过程,产生显著的左右不对称形态,但调控该过程的分子机制尚不清楚。本文对牙鲆变态初期仔鱼进行了形态学观察,并对牙鲆Tbx5进行克隆及其表达分析,并探讨Tbx5与牙鲆仔鱼眼睛与胸鳍不对称变态过程的关系,为进一步研究牙鲆变态机制奠定基础。     

牙鲆早期发育和变态期间Pitx2基因的表达(英文)

Pitx2基因被认为是脊椎动物中调节内脏器官左右不对称的关键转录因子。为进一步探讨牙鲆变态期间的左右不对称是否也受Pitx2的左特异活性调节,采用逆转录聚合酶链式反应(RT-PCR),拟在变态的牙鲆的头部组织中克隆编码Pitx2基因的部分cDNA序列,并通过以18s rRNA为内标的半定量RT-PCR研究其在牙鲆早期发育和变态期间的表达情况。克隆和测序的结果表明Pitx2在牙鲆早期发育和变态期间也存在基因表达;而半定量的结果表明它的左特异性功能很可能在变态的早期阶段发挥作用。但是,牙鲆变态期间的右眼移动是否受Pitx2的左特异活性调控,以及变态期间的左右不对称和内脏器官的左右不对称是否拥有相同的分子机制,仍需进一步研究。     

牙鲆早期发育和变态期间Pitx2基因的表达

Pitx2基因被认为是脊椎动物中调节内脏器官左右不对称的关键转录因子。为进一步探讨牙鲆变态期间的左右不对称是否也受Pitx2的左特异活性调节,采用逆转录聚合酶链式反应(RT-PCR),拟在变态的牙鲆的头部组织中克隆编码Pitx2基因的部分cDNA序列,并通过以18s rRNA为内标的半定量RT-PCR研究其在牙鲆早期发育和变态期间的表达情况。克隆和测序的结果表明Pitx2在牙鲆早期发育和变态期间也存在基因表达;而半定量的结果表明它的左特异性功能很可能在变态的早期阶段发挥作用。但是,牙鲆变态期间的右眼移动是否受Pitx2的左特异活性调控,以及变态期间的左右不对称和内脏器官的左右不对称是否拥有相同的分子机制,仍需进一步研究。     

Genome-wide identification and expression analysis of GDSL esterase/lipase genes in tomato

The GDSL esterase/lipase family contains many functional genes that perform important biological functions in growth and development, morphogenesis, seed oil synthesis, and defense responses in plants. The expression of GDSL esterase/lipase genes can respond to biotic and abiotic stresses. Although GDSL esterase/lipase family genes have been identified and studied in other plants, they have not been identified and their functions remain unclear in tomato. This study is the first to identify 80 G...