CLONING OF ZEBRAFISH VSX1 - EXPRESSION OF A PAIRED-LIKE HOMEOBOX GENEDURING CNS DEVELOPMENT

vsx1 is a homeobox gene encoding a paired-type homeodomain and a CVC d omain that was originally cloned from an adult goldfish retinal librar y. We previously reported the spatiotemporal expression pattern of vsx 1 in the adult and developing retina of zebrafish and goldfish, and we suggested that vsx1 plays a role in determining the cell fate and mai ntenance of retinal interneurons. Other related genes encoding a CVC d omain, such as vsx2 (alx) and chx10, are expressed both within and out side the retina during development. in this study, we report the cloni ng of zebrafish vsx1 and its developmental expression in both retinal and nonretinal regions of the CNS in zebrafish embryos. vsx1 expressio n was detected in a subset of hindbrain and spinal cord neurons before it was expressed in the retina. At about the same time that retinal e xpression began, the level of vsx1 was decreased in the spinal cord. T he expression of vsx1 was progressively restricted, and eventually it was detected only in the inner nuclear layer (INL) of the developing r etina. The combined expression patterns of teleost vsx1 and vsx2 (alx) during early zebrafish development encompasses the expression pattern observed for murine Chx10, and indicates a partitioning of function f or CVC genes in lower vertebrates. Dev. Genet. 23:128-141. 1998. (C) 1 998 Wiley-Liss, Inc.