Nohno T, Kawakami Y, Wada N, Ishikawa T, Ohuchi H, Noji S
Department of Molecular Biology, Department of Biochemistry I, Kawasaki Medical School, 577 Matsushima, Kurashiki, 701-01, Japan.
Biochem Biophys Res Commun. 1997 Sep 18;238(2):506-11. doi: 10.1006/bbrc.1997.7320.
We have isolated the chicken homeobox genes LH-2A and LH-2B encoding two related LIM domain-containing homeodomain proteins and examined the expression pattern during chick limb development. LH-2A is most closely related to human and rat LH-2, while LH-2B is less conserved. Although both LH-2A and LH-2B are expressed in the limb mesenchyme throughout stage 16 to stage 32, LH-2A transcripts are detectable in the distal limb bud and LH-2B transcripts are detectable in the anterior limb bud. Signals from the apical ectodermal ridge positively regulate LH-2A expression, since removal of the apical ectoderm resulted in the rapid reduction of LH-2A expression in the distal limb mesenchyme. Ectopic expression of the sonic hedgehog gene in the anterior margin of the limb bud resulted in the rapid reduction of LH-2B expression accompanying respecification of the positional value to the posterior phenotype. These results suggest that LH-2A and LH-2B play important roles in the determination and specification of the proximal-distal and anterior-posterior positional values, respectively.
我们分离出了编码两种相关的含LIM结构域同源结构域蛋白的鸡同源框基因LH-2A和LH-2B，并研究了它们在鸡胚肢体发育过程中的表达模式。LH-2A与人类和大鼠的LH-2关系最为密切，而LH-2B的保守性较低。尽管LH-2A和LH-2B在整个第16阶段到第32阶段都在肢体间充质中表达，但LH-2A转录本在远端肢芽中可检测到，而LH-2B转录本在前肢芽中可检测到。来自顶端外胚层嵴的信号正向调节LH-2A的表达，因为去除顶端外胚层会导致远端肢体间充质中LH-2A表达迅速降低。肢体芽前缘中sonic hedgehog基因的异位表达导致LH-2B表达迅速降低，同时位置值重新指定为后表型。这些结果表明，LH-2A和LH-2B分别在近端-远端和前后位置值的确定和指定中发挥重要作用。
