Isolation of the mouse Hox-2.9 gene; analysis of embryonic expression suggests that positional information along the anterior-posterior axis is specified by mesoderm.
Isolation of the mouse Hox-2.9 gene; analysis of embryonic expression suggests that positional information along the anterior-posterior axis is specified by mesoderm.
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发表时间：
1990-10
期刊：
影响因子：
4.6
通讯作者：
M. A. Frohman;Monica Boyle;Gail R. Martin
中科院分区：
文献类型：
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作者：
M. A. Frohman;Monica Boyle;Gail R. Martin
脊椎动物的神经管，特别是后脑，发育成节段性结构，这一点很快被人们接受。在片段形成后，神经管中的细胞不会跨越片段边界，并观察到片段特异的基因表达。然而，目前还不知道是什么位置线索指示神经管以这种受限的方式表达基因。我们克隆了一个含有小鼠同源盒的基因Hox-2.9，它在胚胎9.5岁时在神经管中的表达被限制在后脑的一段称为菱形核4的区域。对其早期发育过程中的表达模式的研究表明，在神经形成开始之前(e7.5)，Hox-2.9在胚胎中胚层的后部表达，这将参与后脑的形成。随着神经形成的开始，在神经板中也可以检测到表达，但只在表达Hox-2.9的中胚层上；在更前面的神经外胚层中检测不到，它将形成未来的中脑和前脑。在这些发现的基础上，我们认为中胚层提供了一些线索，用于指示上覆的神经外胚层沿前后轴的位置，并且HOX-2.9参与或反映了这一过程。随着神经分化的继续和单个节段的形成，在神经管中检测到第二阶段的表达，其中高水平的HOX-2.9转录本被限制在菱形结构4。在后脑区域的发育中的鳃弓单位也检测到HOX-2.9的表达，这种模式向我们暗示，在这里，中胚层也提供了诱导HOX-2.9表达的局部信号，在这种情况下，在咽内胚层和浅外胚层。总体而言，我们对HOX-2.9在后脑区的表达模式的解读表明，哺乳动物模式形成的特定机制从根本上类似于两栖动物和鸟类的模式形成-即前后位置信息由中胚层获取，中胚层诱导(神经)外胚层和内胚层的位置值，并且这两种事件都发生在有限的时间窗口内。
It is rapidly becoming accepted that the vertebrate neural tube, in particular the hindbrain, develops into a segmented structure. After segment formation, cells in the neural tube do not cross segmental boundaries, and segment-specific gene expression is observed. However, it is not known what positional cues instruct the neural tube to express genes in this restricted manner. We have cloned a murine homeobox-containing gene, Hox-2.9, whose expression in the neural tube at E9.5 is restricted to a segment of the hindbrain known as rhombomere 4. A study of its expression pattern earlier in development revealed that prior to the start of neurulation (E7.5) Hox-2.9 is expressed within a posterior to the embryonic mesoderm that will participate in hindbrain formation. With the onset of neurulation, expression then becomes detectable in the neural plate as well, but only in the part that overlies the Hox-2.9-expressing mesoderm; it is not detected in the more anterior neuroectoderm that will form the future midbrain and forebrain. On the basis of these findings, we propose that the mesoderm is providing cues that serve to instruct the overlying neuroectoderm with respect to its position along the anteroposterior axis and that Hox-2.9 participates in or reflects this process. As neurulation continues and individual segments form, a second phase of expression is detected in the neural tube in which high levels of Hox-2.9 transcripts become restricted to rhombomere 4. Hox-2.9 expression is also detected in the developing branchial arch units of the hindbrain region, in a pattern that suggests to us that here, too, mesoderm is providing a localized signal that induces Hox-2.9 expression, in this case in endoderm of the pharynx and in superficial ectoderm. In general, we interpret the expression patterns of Hox-2.9 in the hindbrain region as suggesting that the specific mechanisms of pattern formation in mammals are fundamentally similar to those of amphibians and avians - i.e. anteroposterior positional information is acquired by mesoderm, mesoderm induces positional values within (neuro-) ectoderm and endoderm, and both events occur within a restricted window of time.