ROLE OF XHOX HOMEOBOX GENES IN XENOPUS DEVELOPMENT

发育生物学最近的一个焦点是分离和研究基因 对细胞的命运和模式做出关键决定， 胚胎发生果蝇的遗传学研究表明， 含有同源框DNA结合基序的蛋白质参与这种 其他基因，如脊椎动物Myo-D基因，也具有决定性作用。 发育调节剂的强制性质。我们建议研究 非洲爪蟾胚胎的区域特化和模式形成 重点研究Xhox-1同源盒基因和Myo-D基因。 在以前的工作中，我们设计了一种过表达测定来解决 Xhox-1A基因的功能，并证明它很可能是 参与体节的形成。体节发生是一个初级体节 形成脊椎动物身体运动的事件。这一发现很重要 因为这是脊椎动物功能的第一个指标 同源框基因，它满足了广泛的期望，同源框基因 将参与重要的发展活动。我们建议研究 进一步研究了Xhox-1A和相关基因的作用。Xhox-1B，在体节中 阵我们将使用抗体在细胞分辨率上进行研究 这些基因的正常表达模式。此外，我们将设计 Xhox-1基因的显性作用突变体，其将用于 拮抗内源性基因的作用，从而扰乱 以新的方式进行体节发生。我们还将探讨同源异型盒基因的功能 通过研究Xhox-1A蛋白与 DNA.我们相信，从长远来看，这种生化方法将 揭示了稳定的发育变化是如何受到影响的。 在非洲爪蟾中，大部分体节组织变成肌肉。一无所知 关于肌肉组织的模式（体节发生）如何与 对肌肉血统的承诺。有证据表明Myo-D基因 在这个承诺步骤中是有指导意义的。我们将描述 在早期发育过程中表达非洲爪蟾Myo-D，并试图 设计功能性试验来测试Myo-D基因表达是否可以 多能的胚胎外胚层直接进入肌肉谱系。 这些实验旨在研究细胞的具体例子， 脊椎动物发育中的承诺和模式。此外，我们将 采取一种更普遍的方法来解决区域性的基本问题， 在胚胎中发生。我们将筛选一个原肠形成前的cDNA 具有发育上感兴趣的基因的探针的文库， 同源异型盒基因，相信他们中的许多人将显示有限的空间 表达，并将在早期阶段指示细胞定型区。 这一建议的力量在于，我们已经有了一个 我们研究的同源异型盒基因的功能测定， 我们可以将这些研究与丰富的细胞和 非洲爪蟾胚胎的发育信息。

A recent focus of development biology has been to isolate and study genes through to make critical decisions of cell fate and patterning in embryogenesis. Genetic studies in Drosophila indicate that genes containing the homeobox DNA-binding motif participate in such decisions.Other genes such as the vertebrate Myo-D gene, also have the compelling properties of developmental regulators. We propose to study regional specification and pattern formation in Xenopus embryos using as a focus the Xhox-1 homeobox genes and the Myo-D gene. In previous work we devised an overexpression assay to address the function of the Xhox-1A gene and demonstrated that it is likely to be involved in somite formation. Somitogenesis is a primary segmentation event which shapes the vertebrate body play. This finding is significant because it is the very first indication of a function for a vertebrate homeobox gene and it fulfills the broad expectation that homeobox genes will participate in critical developmental events. We propose to study further the role of Xhox-1A and a linked gene. Xhox-1B, in somite formation. We will use antibodies to investigate at cellular resolution the normal expression pattern of these genes. Furthermore, we will design dominant-acting mutants of the Xhox-1 genes which will be used to antagonize the action of the endogenous genes and thus perturb somitogenesis in new ways. We will also approach homeobox gene function at the biochemical level by studying the binding of Xhox-1A protein to DNA. We believe that in the long term this biochemical approach will reveal how stable developmental changes are affected. In Xenopus, most of the somite tissue becomes muscle. Nothing is known about how the patterning of muscle tissue (somitogenesis) meshes with commitment to the muscle lineage. Evidence suggests that the Myo-D gene is instructive in this commitment step. We will characterize the expression of the Xenopus Myo-D during early development and attempt to devise functional assays to test whether Myo-D gene expression can commit multipotent, embryonic ectoderm directly into the muscle lineage. These experiments are designed to investigate specific examples of cell commitment and patterning in vertebrate development. In addition, we will take a more general approach to the fundamental problem of how regional specification occurs in embryos. We will screen a pre-gastrulation cDNA library with probes for developmentally interesting genes such as other homeobox genes, believing that many of them will show restricted spatial expression and will indicate zones of cell commitment at early stages. The strength of this proposal lies in the fact that we already have a functional assay for the homeobox genes that we study and in the fact that we can relate these studies to the wealth of cellular and developmental information available for Xenopus embryos.