PDF(Pubmed)
Abstract：
During limb bud formation, axis polarities are established as evidenced by the spatially restricted expression of key regulator genes. In particular, the mutually antagonistic interaction between the GLI3 repressor and HAND2 results in distinct and non-overlapping anterior-distal Gli3 and posterior Hand2 expression domains. This is a hallmark of the establishment of antero-posterior limb axis polarity, together with spatially restricted expression of homeodomain and other transcriptional regulators. Here, we show that TBX3 is required for establishment of the posterior expression boundary of anterior genes in mouse limb buds. ChIP-seq and differential gene expression analysis of wild-type and mutant limb buds identifies TBX3-specific and shared TBX3-HAND2 target genes. High sensitivity fluorescent whole-mount in situ hybridisation shows that the posterior expression boundaries of anterior genes are positioned by TBX3-mediated repression, which excludes anterior genes such as Gli3, Alx4, Hand1 and Irx3/5 from the posterior limb bud mesenchyme. This exclusion delineates the posterior mesenchymal territory competent to establish the Shh-expressing limb bud organiser. In turn, HAND2 is required for Shh activation and cooperates with TBX3 to upregulate shared posterior identity target genes in early limb buds.
摘要：
在肢体芽形成过程中，关键调节基因的空间限制表达证明了轴极性。特别是,GLI3阻遏物和HAND2之间的相互拮抗相互作用导致不同且不重叠的前远端Gli3和后Hand2表达结构域.这是建立前后肢体轴极性的标志，以及同源结构域和其他转录调节因子的空间限制性表达。这里,我们表明，TBX3是建立小鼠肢芽前基因后表达边界所必需的。野生型和突变型肢芽的ChIP-seq和差异基因表达分析鉴定了TBX3特异性和共有的TBX3-HAND2靶基因。高灵敏度荧光全装原位杂交表明，前基因的后表达边界被TBX3介导的抑制定位，从后肢芽间质中排除前基因，例如Gli3，Alx4，Hand1和Irx3/5。这种排除描绘了有能力建立表达Shh的肢芽组织的后部间充质区域。反过来,HAND2是Shh激活所必需的，并与TBX3合作以上调早期肢体芽中共享的后部身份靶基因。
