The Expression of the MouseZic1, Zic2,andZic3Gene Suggests an Essential Role forZicGenes in Body Pattern Formation

AbstractWe examined the expression ofZic1, Zic2,andZic3genes in the mouse embryo by means ofin situhybridization.Zicgenes were found as a group of genes coding for zinc finger proteins that are expressed in a restricted manner in the adult mouse cerebellum. We showed that the genes are the vertebrate homologues ofDrosophila odd-paired,which may play an essential role in parasegmental subdivision and in visceral mesoderm development. The expression of the threeZicgenes was first detected at gastrulation in a spatially restricted manner. At neurulation, the expression became restricted to the dorsal neural ectoderm and dorsal paraxial mesoderm. During organogenesis, the three genes were expressed in specific regions of several developing organs, including dorsal areas of the brain, spinal cord, paraxial mesenchyme, and epidermis, the marginal zone of the neural retina and distal regions of the developing limb. For all stages, significant differences in the spatial expression ofZic1, Zic2,andZic3were observed. Furthermore, the expression ofZicgenes inPax3, Wnt-1,andWnt-3amutant embryos suggested thatZicgenes are not primarily regulated by the three genes which were expressed in dorsal areas similar toZicgenes. However, inopen brain,a mutant with severe neural tube defects, and in theWnt-3amutant mice, the expression ofZicgenes was changed. The changed expression pattern inWnt-3amutant mice suggests thatZicgenes in the neural tube are regulated by the factors from notochord. Our findings suggest thatZicgenes are involved in many developmental processes. Furthermore, analysis of gene expression patterns in different mouse mutants indicated thatZicgenes may act upstream of many known developmental regulatory genes