Expression of the zic1, zic2, zic3, and zic4 genes in early chick embryos

We used in situ hybridization to analyze the expression patterns of the zic1-4 genes during early chick development (HH stages 7-19). The zic1-3 genes showed both overlapping and gene-specific expression patterns along the length of the dorsal neural tube and in the dorsal parts of the somites. In addition, unique expression domains of zic genes included: zic2 in the neural plate, periotic mesoderm and limb buds; zic3 in the paraxial mesoderm surrounding the neural plate, in presomitic mesoderm and in the most recently formed epithelial somites; zic2 and zic3 in developing eyes. zic4 expression was limited to dorsal fore- and midbrain regions and, unlike the expression of the zic1-3 genes, zic4 expression was not detected in the hindbrain and trunk. This was in contrast to more extensive zic4 expression in other vertebrates.The zic1-3 genes were expressed in both overlapping and unique domains within the neural tube, somites and other ectoderm and mesoderm-derived structures in the future head and trunk. zic4 expression, however, was limited to dorso-anterior regions of the future brain. This is the first comprehensive study of zic1-4 gene expression in chick embryos during neurulation and somitogenesis.The zic genes encode a family of zinc finger transcription factors. Five zic genes are typically found in vertebrates (zic1-5), where they guide a variety of developmental processes [1] and zic genes play significant roles during early neural patterning and neural crest formation [2-11]. Although zic genes may be able to partially compensate for each other [12,13], mutations in individual Zic genes in mice and humans produce distinct phenotypes [14]. For example, compromised expression of the Zic2 gene results in neural tube defects and mutation of the Zic3 gene causes left-right abnormalities in addition to less severe neural tube defects [15-23]. In addition, mutations in the Zic1 or Zic4 genes result predominantly in cerebellar abnormalities [13,24]. Collectively,