基因信号:转录因子瀑布和分割

Drosophila) embryo.", "true", "Figure 1", "A fresh Drosophila egg shows a concentration of bicoid (bcd) expression in its anterior end.", "true", "All rights reserved.", '515', '262', '//www.scienovate.com');">

Drosophila) embryo.", "true", "Figure 1", "A fresh Drosophila egg shows a concentration of bicoid (bcd) expression in its anterior end.", "true", "All rights reserved.", '515', '262', '//www.scienovate.com');">图1:Bicoid mRNA在果蝇(果蝇)胚胎。

Drosophila) embryo.", "true", "Figure 1", "A fresh Drosophila egg shows a concentration of bicoid (bcd) expression in its anterior end.", "true", "All rights reserved.", '515', '262', '//www.scienovate.com');">新鲜果蝇卵显示集中bicoid (bcd)表达在其前结束。

©2007自然出版集团铁,&圣约翰斯顿,D。bicoidRNA本地化需要特定的绑定endosomal排序的复杂。自然 445年554 - 558 (2007)doi: 10.1038 / nature05503。保留所有权利。

在大多数分化细胞,几个级别的感应产生大量的转录因子。此外,在胚胎发展,实际的过程分化本身需要一个集成的系统的转录因子基因表达了与严格的精度和时间。在分割的情况下尤其如此。

分割是用于描述的分化模式脊椎动物和节肢动物的连续重复类似的身体解剖模块创建一个轴。在脊椎动物中,分割结果在脊柱的发展,头和四肢;在昆虫,它导致形成腹部,头部和胸腔。分割的结果被认为是有节奏的激活和失活的某些信号指示特定相关的细胞过程。这个振荡过程称为细分时钟。作为科学家了解更多关于分割时钟的计时和机制,他们还继续发现监管信息交互和信号级联。

大部分现有的基因控制的分段进行了研究使用果蝇。例如,在过去的25年里,超过40个基因已经被确认为分割中发挥作用黑腹果蝇(皮et al。,2005)。分割在果蝇是由一连串的转录因子,其中一些被发现在其他节肢动物。通常,级联系统发生在单个细胞;然而,在分割过程中,信号级联进行跨多个细胞的特定区域内发展胚胎。

hairy1 mRNA expression occurs during the formation of each somite in chick embryos.", "true", "Figure 4", "The expression pattern of the hairy1 transcription factor correlates with the formation of each individual somite. At the top row, microscopy images show hairy1 mRNA expression in chicken embryos with 15, 16, and 17 somites (dark blue). The lower row shows drawings of those same areas that clarify how hairy1 expression moves as a wave during somite formation, and embryo maturation. Hairy1 mRNA, shown in blue, starts broadly in the posterior (bottom). With time, the band of expression progresses upward and narrows as it approaches the anterior end. Eventually, it forms a narrow stripe at the posterior end of the newly formed somite (SI or SII). This entire process takes approximately 90 minutes. Scale bar 200μm.", "true", "All rights reserved.", '812', '590', 'http://www.cell.com');">

hairy1 mRNA expression occurs during the formation of each somite in chick embryos.", "true", "Figure 4", "The expression pattern of the hairy1 transcription factor correlates with the formation of each individual somite. At the top row, microscopy images show hairy1 mRNA expression in chicken embryos with 15, 16, and 17 somites (dark blue). The lower row shows drawings of those same areas that clarify how hairy1 expression moves as a wave during somite formation, and embryo maturation. Hairy1 mRNA, shown in blue, starts broadly in the posterior (bottom). With time, the band of expression progresses upward and narrows as it approaches the anterior end. Eventually, it forms a narrow stripe at the posterior end of the newly formed somite (SI or SII). This entire process takes approximately 90 minutes. Scale bar 200μm.", "true", "All rights reserved.", '812', '590', 'http://www.cell.com');">图4:一个周期性的波hairy1信使rna表达发生在每个体节的小鸡胚胎的形成。

hairy1 mRNA expression occurs during the formation of each somite in chick embryos.", "true", "Figure 4", "The expression pattern of the hairy1 transcription factor correlates with the formation of each individual somite. At the top row, microscopy images show hairy1 mRNA expression in chicken embryos with 15, 16, and 17 somites (dark blue). The lower row shows drawings of those same areas that clarify how hairy1 expression moves as a wave during somite formation, and embryo maturation. Hairy1 mRNA, shown in blue, starts broadly in the posterior (bottom). With time, the band of expression progresses upward and narrows as it approaches the anterior end. Eventually, it forms a narrow stripe at the posterior end of the newly formed somite (SI or SII). This entire process takes approximately 90 minutes. Scale bar 200μm.", "true", "All rights reserved.", '812', '590', 'http://www.cell.com');">的表达模式hairy1转录因子与每个体节的形成。在第一行,显微镜图像显示hairy1mRNA表达在鸡胚15日,16日和17日体节(深蓝色)。下一行显示图纸相同的领域,阐明如何hairy1表情动作像波在体节形成,胚胎成熟。Hairy1信使rna,用蓝色显示,大体上后(下)开始。随着时间的推移,乐队的表达进步向上和缩小方法前结束。最终,它形成了一个窄条纹后新成立的体节年底(SI或计划。整个过程大约需要90分钟。规模200μm酒吧。

©1997爱思唯尔有限公司Palmeirim,我。等。禽毛基因表达识别分子钟与脊椎动物分割和somitogenesis。细胞 91年639 - 648 (1997)doi: http://dx.doi.org/10.1016/s0092 - 8674 (00) 80451 - 1。保留所有权利。

hairy1 mRNA expression occurs during the formation of each somite in chick embryos.", "Figure 4", "The expression pattern of the hairy1 transcription factor correlates with the formation of each individual somite. At the top row, microscopy images show hairy1 mRNA expression in chicken embryos with 15, 16, and 17 somites (dark blue). The lower row shows drawings of those same areas that clarify how hairy1 expression moves as a wave during somite formation, and embryo maturation. Hairy1 mRNA, shown in blue, starts broadly in the posterior (bottom). With time, the band of expression progresses upward and narrows as it approaches the anterior end. Eventually, it forms a narrow stripe at the posterior end of the newly formed somite (SI or SII). This entire process takes approximately 90 minutes. Scale bar 200μm.", '812','http://www.cell.com', "In the photographs, a dark-blue stain indicates hairy1 mRNA expression. Images A, B, and C are from embryos with 15 somites. D, E, and F are images of embryos with 16 somites, and G, H, and I are images from embryos with 17 somites. Each set of three photographs shows a different stage in somite formation. The previously formed somites are at the top of the images, which is the anterior end of the embryo. The hairy1 expression in these somites appears as narrow, horizontal bands on both sides of the midline of the embryo. Hairy1 expression changes dramatically in the posterior end of the embryo. In the first image of each set (images A, D, and G), hairy1 is spread out in a broad band at the posterior end of the embryo. In the subsequent images, the band moves anteriorly and narrows until it lies adjacent to the previously formed somites. In the final images of each set (C, F, and I), a new band of hairy1 expression is starting to form at the posterior end. The schematic diagram, which is shown below the photomicrographs, has four parts to show three stages of somite formation and the beginning of the formation of the next somite. The presomatic mesoderm and the somites are shown for each stage with the posterior end, which contains the presomatic mesoderm, in the lower portion of the diagram and the somites at the top. The presomatic mesoderm is U-shaped, and the somites are depicted as ovals on both sides of the midline above the U. In stage I, an oval on each side of the midline indicates that there is a single, fully formed somite, which is labeled \"SI.\" A blue band at the bottom of the ovals indicates that hairy1 is expressed at the posterior end of the somite. The presomatic mesoderm has two regions of blue shading: a broad band covering the posterior two-thirds of the presomatic mesoderm and a narrow band, which lies a small distance from the top of the presomatic mesoderm. The top portion of the presomatic mesoderm is labeled \"S0.\" The second part of the diagram shows stage II of somite formation. Hairy1 is no longer at the posterior end of the presomatic mesoderm. Instead, it has moved anteriorly and has narrowed to about half its previous width. The second narrow band of hairy1 expression looks similar to the band in stage I, but black lines at the bottom of this narrow band indicate that a fissure is starting to separate a new somite from the presomatic mesoderm. The third part of the diagram shows that the broad band has narrowed further and has moved anteriorly. The separation of the new somite is complete. The top of the diagram shows two fully formed somites, which are labeled \"SII\" and \"SI.\" The label \"S0\" at the top of the presomatic mesoderm indicates where the next somite will form. The final illustration in the diagram shows stage I again, but with two fully formed somites. Somite formation occurs in a cycle that takes 90 minutes.")" class="inlineLinks">细节图

在脊椎动物中,发展的先驱动物的骨骼系统叫做somitogenesis。因为脊椎动物的脊柱由重复单位,这些单位的发展可以比作节肢动物的分割过程。脊髓的发展,然而,是由一个振荡过程,依赖于一组基因通路中的,只有其中一些的同系物果蝇细分控制机械。

在脊椎动物脊髓的发展过程中,基因表达的振荡发生在时间的基础上。具体地说,一个信号通路中的“on”脊髓前兆时,或体节,开始形成,但“关闭”体节形成的时候就完成了。因为切口作为转录因子的浓度,它改变了它的目标在体节的前面和后面,因此建立不同的片段。

Notch通路被激活时,一种蛋白质配体信号从相邻的细胞,称为δ,结合细胞表面的缺口。在这方面,缺口作为跨膜受体。在三角洲绑定,切口的细胞中发现的细胞质从膜释放。这部分作为转录因子,它在分割中起着重要作用。级联激活几个下游基因,包括毛/分裂增强剂(他)基因编码一个转录因子。事实上,hairy1转录因子是第一个这样的决定因素是管理时间的方式;在调查中使用鸡,研究人员指出,这种蛋白质的表达与所花费的时间是一致的形成一个体节(90分钟)(图4;Palmeirimet al。,1997)。通路的负面反馈循环导致的基因表达,最终,身体发展观察胚胎期间增长的模式。Notch信号似乎主要是在脊椎动物中发现,没有证据表明它在早期昆虫分割(皮过程中发挥作用et al。,2005)。

提出了几个模型来解释在不同的生物体基因表达的振荡。在斑马鱼,Her1似乎和定期Her7转录因子可以压制自己的表达式,从而创建一个振荡对基因表达的影响(Dequeant & Pourquie, 2008)。类似的负面反馈系统由他控制的蛋白家族在老鼠也被观察到。然而,在老鼠身上,表情DNA微阵列分析还发现了大量的额外的基因表达在一个周期性的模式,似乎与分割相关的时钟。这些基因是否控制由他家族的转录因子直接或间接地通过HES-mediated下游转录因子诱导作用尚未完全清楚。

看来,母体因素的作用在果蝇不是普遍在所有昆虫,也不是常见的脊椎动物。然而,在几乎所有的昆虫和脊椎动物的级联Hox基因扮演一个角色在确定每一段和定义的一部分身体每一部分将成为(图5)。在果蝇,Hox基因的发现是通过观测的自发突变体。在特定Hox基因突变导致腿长一只苍蝇的头,翅膀,他们不应该,和许多其他身体畸形。

图5:基因在果蝇中定义部分。

两个基因簇表达(上)在一个特定地区发展中果蝇胚胎(中心)。这些基因在成人的身体飞定义段(底部)。

©2013自然教育保留所有权利。

细节图

由于广泛的实验果蝇,多少人知道这些遗传因素控制身体的模式。类似的实验与脊椎动物要复杂得多,介绍了一系列伦理问题。由于这些原因,还有小脊椎动物数据分割和振荡时钟。然而,关于特定的模式,如上面所讨论的,可以帮助研究人员开发策略来治疗疾病引起的异常节段在人类发展模式。