Valarché I, de Graaff W, Deschamps J
Hubrecht Laboratory, The Netherlands Institute for Developmental Biology, Utrecht.
Int J Dev Biol. 1997 Oct;41(5):705-14.
Hox genes have been shown to play a key role in the acquisition of positional identity by precursors of embryonic axial, paraxial and limb structures. This function is thought to depend on the sequential, concerted expression of these genes in time and space. However the underlying molecular mechanisms of this collinear expression are still largely unknown. So far we had identified proximal regulatory elements driving expression of Hoxb-8/LacZ transgenes in Hox-like expression patterns with rostral boundaries more posterior than those of the endogenous gene. In this work we have analyzed 30 kb of 3' genomic sequences for Hoxb-8 regulatory activity in transgenic mice. We have identified a control region in the Hoxb-5/b-4 intergenic region that rostrally extends the Hoxb-8/LacZ expression domain into the posterior hindbrain. In combination with the Hoxb-8 minimal promoter, the 3' control region drives transgene expression with boundaries more anterior than those of Hoxb-8 in the neural tube. When combined with a 4.5 kb Hoxb-8 upstream sequence, where essential proximal regulatory sequences are located, the 3' control region drives transgene expression in a domain which seems to correspond to that of the endogenous Hoxb-8. By deletion analysis we have narrowed down to 550bp the regulatory activity interacting with the Hoxb-8 minimal promoter. We discuss the possibility that this remote 3' enhancer, which is the closest regulatory region found in the cluster to rostrally extend Hoxb-8/LacZ expression, could be involved in the regulation of Hoxb-8 and interact with the proximal control elements.
已表明Hox基因在胚胎轴、体轴旁和肢体结构前体获得位置身份过程中发挥关键作用。这种功能被认为取决于这些基因在时间和空间上的顺序协同表达。然而，这种共线性表达的潜在分子机制仍 largely未知。到目前为止，我们已经鉴定出近端调控元件，它们以类似于Hox的表达模式驱动Hoxb - 8/LacZ转基因的表达，其头端边界比内源性基因的更靠后。在这项工作中，我们分析了30 kb的Hoxb - 8基因3'基因组序列在转基因小鼠中的调控活性。我们在Hoxb - 5/b - 4基因间区域鉴定出一个控制区域，它将Hoxb - 8/LacZ的表达域向前延伸至后脑后部。与Hoxb - 8最小启动子结合时，3'控制区域驱动转基因在神经管中的表达边界比Hoxb - 8的更靠前。当与位于4.5 kb Hoxb - 8上游序列（其中含有重要的近端调控序列）结合时，3'控制区域驱动转基因在一个似乎与内源性Hoxb - 8的表达域相对应的区域表达。通过缺失分析，我们已将与Hoxb - 8最小启动子相互作用的调控活性缩小至550 bp。我们讨论了这种远距离3'增强子（它是在该基因簇中发现的最靠近头端延伸Hoxb - 8/LacZ表达的调控区域）可能参与Hoxb - 8调控并与近端控制元件相互作用的可能性。
