Beermann Friedrich, Kaloulis Kostas, Hofmann Denise, Murisier Fabien, Bucher Philipp, Trumpp Andreas
Swiss Institute for Experimental Cancer Research (ISREC), Epalinges, Switzerland.
Genesis. 2006 Jan;44(1):1-6. doi: 10.1002/gene.20177.
The secreted signaling molecule fibroblast growth factor 8 (Fgf8) is an essential component of certain embryonic signaling centers including the mid-hindbrain (isthmic) organizer, the first branchial arch (BA1), and the apical ectodermal ridge (AER). In these signaling centers Fgf8 transcripts are expressed in a dynamic and transient fashion, but the mechanism by which this highly specific expression pattern is established remains largely unknown. We used DNA sequence comparisons coupled to transgenic approaches to obtain insight into the structure and function of regulatory elements in the Fgf8 locus. First, a bacterial artificial chromosome (BAC) containing the mouse Fgf8 gene partially rescues the embryonic lethality of Fgf8-deficient mice and controls Fgf8-specific gene expression of a coinjected lacZ reporter transgene. Second, sequence comparison of vertebrate Fgf8 loci revealed evolutionarily highly conserved noncoding sequences that were unexpectedly located mainly 3' of the Fgf8 coding region. Third, in transgenic mice some of these elements were sufficient to target expression to the AER, tail bud, and brain, including the isthmic organizer, indicating that they may represent Fgf8 cis-acting elements. Collectively, these data identify novel regulatory elements of the Fgf8 gene sufficient to drive expression to regions of known Fgf8 activity.
分泌型信号分子成纤维细胞生长因子8（Fgf8）是某些胚胎信号中心的重要组成部分，这些信号中心包括中后脑（峡部）组织者、第一鳃弓（BA1）和顶端外胚层嵴（AER）。在这些信号中心，Fgf8转录本以动态和短暂的方式表达，但其建立这种高度特异性表达模式的机制仍 largely未知。我们结合DNA序列比较和转基因方法来深入了解Fgf8基因座中调控元件的结构和功能。首先，包含小鼠Fgf8基因的细菌人工染色体（BAC）部分挽救了Fgf8缺陷小鼠的胚胎致死性，并控制了共注射的lacZ报告转基因的Fgf8特异性基因表达。其次，脊椎动物Fgf8基因座的序列比较揭示了进化上高度保守的非编码序列，这些序列意外地主要位于Fgf8编码区的3'端。第三，在转基因小鼠中，其中一些元件足以将表达靶向到AER、尾芽和大脑，包括峡部组织者，表明它们可能代表Fgf8顺式作用元件。总体而言，这些数据确定了Fgf8基因的新型调控元件，足以将表达驱动到已知Fgf8活性的区域。
