Amano Takanori, Sagai Tomoko, Tanabe Hideyuki, Mizushina Yoichi, Nakazawa Hiromi, Shiroishi Toshihiko
Mammalian Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan.
Dev Cell. 2009 Jan;16(1):47-57. doi: 10.1016/j.devcel.2008.11.011. Epub 2008 Dec 18.
The expression of Sonic hedgehog (Shh) in mouse limb buds is regulated by a long-range enhancer 1 Mb upstream of the Shh promoter. We used 3D-FISH and chromosome conformation capture assays to track changes at the Shh locus and found that long-range promoter-enhancer interactions are specific to limb bud tissues competent to express Shh. However, the Shh locus loops out from its chromosome territory only in the posterior limb bud (zone of polarizing activity or ZPA), where Shh expression is active. Notably, while Shh mRNA is detected throughout the ZPA, enhancer-promoter interactions and looping out were only observed in small fractions of ZPA cells. In situ detection of nascent Shh transcripts and unstable EGFP reporters revealed that active Shh transcription is likewise only seen in a small fraction of ZPA cells. These results suggest that chromosome conformation dynamics at the Shh locus allow transient pulses of Shh transcription.
音猬因子（Shh）在小鼠肢芽中的表达受Shh启动子上游1 Mb处一个远距离增强子的调控。我们使用三维荧光原位杂交（3D-FISH）和染色体构象捕获分析来追踪Shh基因座的变化，发现远距离启动子-增强子相互作用是肢芽组织中能够表达Shh的细胞所特有的。然而，Shh基因座仅在Shh表达活跃的后肢芽（极化活性区或ZPA）中从其染色体区域环出。值得注意的是，虽然在整个ZPA中都能检测到Shh mRNA，但增强子-启动子相互作用和环出仅在一小部分ZPA细胞中观察到。对新生Shh转录本和不稳定的EGFP报告基因的原位检测表明，活跃的Shh转录同样仅在一小部分ZPA细胞中可见。这些结果表明，Shh基因座处的染色体构象动态变化允许Shh转录产生瞬时脉冲。
