Hox genes and growth: early and late roles in limb bud morphogenesis.
Hox genes and growth: early and late roles in limb bud morphogenesis.
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发表时间：
1994
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通讯作者：
Bruce A. Morgan;Clifford J. Tabin
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作者：
Bruce A. Morgan;Clifford J. Tabin
近年来，分子分析已经鉴定出一些控制发育胚胎形态发生的关键基因。对这些基因的详细功能分析正在迅速使人们对胚胎形态如何调控的理解达到一个新的水平。了解这些基因在发育中发挥的作用还可以提供对形态进化的见解。脊椎动物 Hox 簇的 5' 基因在肢体形态发生过程中以复杂的模式表达。各种模型表明 Hoxd 基因指定沿肢体前后 (A-P) 轴的位置同一性。对肢体中 Hoxd 基因表达模式的仔细检查表明，在不同数字原基中表达的 Hoxd 基因的独特组合不太可能独立指定每个数字。肢体发育过程中不同时间改变 Hoxd-11 基因表达模式的影响表明，Hoxd 基因在肢体形态发生中具有不同的早期和晚期作用。在其早期作用中，Hoxd 基因参与调节未分化肢体间质的生长。连续 5' Hoxd 基因的表达限制在芽的逐渐更靠后的区域导致肢体间充质的不对称生长。在肢体发育后期，Hoxd 基因还调节新生骨骼元素的成熟。不同 Hoxd 基因之间的功能重叠程度在这些早期和晚期作用中可能不同。许多 Hox 基因对不同发育过程的联合作用导致沿 A-P 轴的模式不对称。
In recent years, molecular analysis has led to the identification of some of the key genes that control the morphogenesis of the developing embryo. Detailed functional analysis of these genes is rapidly leading to a new level of understanding of how embryonic form is regulated. Understanding the roles that these genes play in development can additionally provide insights into the evolution of morphology. The 5' genes of the vertebrate Hox clusters are expressed in complex patterns during limb morphogenesis. Various models suggest that the Hoxd genes specify positional identity along the anteroposterior (A-P) axis of the limb. Close examination of the pattern of Hoxd gene expression in the limb suggests that a distinct combination of Hoxd gene expressed in different digit primordia is unlikely to specify each digit independently. The effects of altering the pattern of expression of the Hoxd-11 gene at different times during limb development indicate that the Hoxd genes have separable early and late roles in limb morphogenesis. In their early role, the Hoxd genes are involved in regulating the growth of the undifferentiated limb mesenchyme. Restriction of the expression of successive 5' Hoxd genes to progressively more posterior regions of the bud results in the asymmetric outgrowth of the limb mesenchyme. Later in limb development, Hoxd genes also regulate the maturation of the nascent skeletal elements. The degree of overlap in function between different Hoxd genes may be different in these early and late roles. The combined action of many Hox genes on distinct developmental processes contribute to pattern asymmetry along the A-P axis.