Genetic Dissection of Skeletal Patterning

描述（由申请人提供）：同源异型盒基因在脊椎动物骨架形成中的关键作用已得到充分证实。关于特定Hox基因在特定骨骼区域的特异性和合作已经知道很多，但是尽管在许多实验室进行了10多年的功能实验，仍然不知道Hox转录因子实际上是如何控制椎骨身份的。在发展中的骨架的转录目标也没有被确定，一个主要的障碍，以机械的理解Hox调节途径。在这里，我提出了一个遗传学的方法来识别Hox控制的途径，在该领域的骨骼模式的一个新方向。核心假设是骨骼模式-由Hox基因调控-表现为数量性状，这是由基因-基因和基因-环境相互作用控制的。这一主张得到了我们实验室大量数据的支持，这些数据证明了骨骼中存在Hox基因功能的营养和遗传修饰剂。我们已经证明：（i）遗传因素调节Hoxb 6基因敲除小鼠骨骼异常的严重程度;（ii）表型表现受发育胚胎本身的遗传背景控制;（iii）不同的骨骼元素受到区域特异性途径的影响，这些途径在很大程度上独立运作;（iv）遗传修饰因子的数量很少，因此在实验上是容易处理的。我们现在的主要目标是通过追求以下特定目标来定义在骨骼模式中与HoxbG相互作用的遗传因素： (1)通过微卫星标记全基因组扫描，在C57 BI/6和129 Sv/Ev背景下的Hoxb 6突变体的回交中定位菌株特异性遗传修饰剂的基因组位置; (2)通过分析FVB遗传背景下的突变，确定遗传修饰剂对Hoxb 6突变体中骨骼模式表型表现的影响;以及 (3)表征已知骨骼模式介导因子的基因的表达，其在Hoxb 6突变表型发病机制中的功能。 鉴定作用于骨骼模式的修饰基因位点将揭示骨骼发育的新分子机制，并对脊椎动物身体计划的进化具有重要意义。

DESCRIPTION (provided by applicant): The crucial role of homeobox genes in patterning of the vertebrate skeleton is well established. Much is known about the specificity and cooperation of particular Hox genes in defined skeletal regions, but despite more than 10 years of functional experiments in numerous laboratories, it is still unknown how Hox transcription factors actually control vertebral identity. The transcriptional targets in the developing skeleton also have not been identified, a major obstacle to a mechanistic understanding of Hox regulated pathways. Here, I propose a genetic approach to the identification of Hox-controlled pathways; a new direction in the field of skeletal patterning. The central hypothesis is that skeletal patterning-- as regulated by Hox genes--manifests as a quantitative trait, which is controlled by gene-gene and gene-environment interactions. This proposition is supported by extensive data from our laboratory that demonstrate the existence of nutritional and genetic modifiers of Hox gene function in the skeleton. We have shown that (i) genetic factors modulate severity of skeletal anomalies in Hoxb6 knockout mice; (ii) phenotype manifestation is controlled by genetic background of the developing embryo itself; (iii) distinct skeletal elements are affected by region-specific pathways that operate largely independently; and that (iv) the number of genetic modifiers is small, and therefore experimentally tractable. Our major goal now is to define the genetic factors that interact with HoxbG in skeletal patterning by pursuit of the following Specific Aims: (1) to map the genomic location of the strain-specific genetic modifier(s) by microsatellite marker whole genome scan in a backcross of Hoxb6 mutants on C57BI/6 and 129Sv/Ev backgrounds; (2) to define the influence of genetic modifiers on manifestation of skeletal patterning phenotypes in Hoxb6 mutants by analyzing the mutation on the FVB genetic background; and (3) to characterize the expression of genes that are known mediators of skeletal patterning for their function in pathogenesis of Hoxb6 mutant phenotypes. The identification of modifier loci that act on skeletal patterning will reveal new molecular mechanisms in skeletal development and has important implications for the evolution of vertebrate body plans.