Expression of two novel zebrafish iroquois homologues (ziro1 and ziro5) during early development of axial structures and central nervous system

Previously, we reported a zebrafish iroquois gene, ziro3, and its expressio n during early embryogenesis (Mech. Dev. 87 (1999) 165). In the present stu dy, we have isolated two novel zebrafish iroquois genes, ziro1 and ziro5. h omologs of mouse Irx1 and mouse lrx5, respectively. The expression of both genes is initiated in dorsal neuroectoderm and mesoderm during gastrulation . Later, their expression appears in the central nervous system (CNS), excl uding the telencephalon and most of the diencephalon. ziro1 expression is c omplementary to that of ziroj in the notochord and later in the gut. In con trast, ziro5 expression mostly overlaps with that of ziro3. Interestingly, all three iroquois zebrafish genes are expressed in the notochord while onl y Irx3 is active in the mouse notochord. Their expression in later stages o f embryogenesis was also compared. (C) 2001 Elsevier Science Ireland Ltd. A ll rights reserved.