Masuya H, Sagai T, Moriwaki K, Shiroishi T
Mammalian Genetics Laboratory, National Institute of Genetics, Mishima, Japan.
Dev Biol. 1997 Feb 1;182(1):42-51. doi: 10.1006/dbio.1996.8457.
We report here that in three preaxial polydactylous mutants in the mouse, namely, 1st, 1x, and Xp1, ectopic expression of the Shh and Fgf-4 genes can be detected at the anterior margin of limb buds. These and three other mutants, namely, Rim4, Hx, and Xt1, which we described in our previous study, all appeared to form a duplicated zone of polarizing activity (ZPA) at the anterior margin of the limb bud. We studied the spatial and temporal pattern of expression of the Gli3 gene, which is affected in a loss-of-function type of mutation, Xt1. The expression domain of Gli3 appeared to be complementary to the ZPA region and the gene was expressed prior to Shh. The results support the hypothesis that GLI3 functions in the anterior portion of limb mesoderm to suppress the expression of Shh. In Drosophila, the gene ci, the fly homologue of Gli, functions to repress hh, suggesting that the negative regulation of the expression of hedgehog by genes belonging to the GLI-kruppel family has been conserved from flies to mice. Finally, we found that the polydactylous phenotype of the mutants Rim4, Xt, 1st, and 1x could be abrogated by the crossing with an inbred strain derived from wild mouse, MSM, whereas the phenotype of Xp1 could not. These results indicate the presence of a modifier gene(s) that can influence the mutant phenotype and also that the mutations could be classified into two categories with regard to the mode of interaction with the modifier gene(s). Thus, this study revealed a multigenic control in the establishment of the anteroposterior axis in mouse limb development.
我们在此报告，在小鼠的三种轴前多指突变体中，即1st、1x和Xp1，在肢芽的前缘可检测到Shh和Fgf-4基因的异位表达。这些突变体以及我们在先前研究中描述的其他三种突变体，即Rim4、Hx和Xt1，似乎都在肢芽的前缘形成了一个重复的极化活性区（ZPA）。我们研究了Gli3基因的时空表达模式，该基因在功能丧失型突变体Xt1中受到影响。Gli3的表达域似乎与ZPA区域互补，并且该基因在Shh之前表达。这些结果支持了这样的假说，即GLI3在肢中胚层的前部发挥作用以抑制Shh的表达。在果蝇中，Gli的同源基因ci发挥抑制hh的作用，这表明从果蝇到小鼠，属于GLI-克鲁ppel家族的基因对刺猬蛋白表达的负调控一直存在。最后，我们发现突变体Rim4、Xt、1st和1x的多指表型可通过与源自野生小鼠MSM的近交系杂交而消除，而Xp1的表型则不能。这些结果表明存在一个可以影响突变体表型的修饰基因，并且这些突变在与修饰基因的相互作用模式方面可分为两类。因此，本研究揭示了小鼠肢体发育中前后轴建立的多基因控制。
