Belting H G, Shashikant C S, Ruddle F H
Department of Molecular, Cellular, and Developmental Biology, Yale University, POB 208103, New Haven, CT 06520, USA.
Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):2355-60. doi: 10.1073/pnas.95.5.2355.
Differential Hox gene expression between vertebrate species has been implicated in the divergence of axial morphology. To examine this relationship, we have compared expression and transcriptional regulation of Hoxc8 in chicken and mouse. In both species, expression of Hoxc8 in the paraxial mesoderm and neural tube is associated with midthoracic and brachial identities, respectively. During embryogenesis, there is a temporal delay in the activation of Hoxc8 in chicken compared with mouse. As a result, chicken Hoxc8 expression in the paraxial mesoderm is at a posterior axial level, extending over a smaller domain compared with mouse Hoxc8 expression. This finding is consistent with a shorter thoracic region in chicken compared with mouse. In addition, the chicken Hoxc8 early enhancer, differing from its mouse counterpart in only a few specific nucleotides, directs a reporter gene expression to a more posterior domain in transgenic mouse embryos. These findings are consistent with the concept that the diversification of axial morphology has been achieved through changes in cis-regulation of developmental control genes.
脊椎动物物种之间Hox基因的差异表达与轴向形态的分化有关。为了研究这种关系，我们比较了鸡和小鼠中Hoxc8的表达和转录调控。在这两个物种中，Hoxc8在近轴中胚层和神经管中的表达分别与胸中部和臂部特征相关。在胚胎发育过程中，与小鼠相比，鸡的Hoxc8激活存在时间延迟。因此，与小鼠Hoxc8表达相比，鸡近轴中胚层中Hoxc8的表达处于更靠后的轴向水平，且延伸范围更小。这一发现与鸡的胸段区域比小鼠短是一致的。此外，鸡的Hoxc8早期增强子与小鼠的对应物仅在少数几个特定核苷酸上有所不同，在转基因小鼠胚胎中，它将报告基因的表达导向更靠后的区域。这些发现与轴向形态的多样化是通过发育控制基因顺式调控的变化实现这一概念是一致的。
