The expression pattern of mab21l2 in zebrafish embryos. Mab21l2 is first expressed at the bud stage in the presumptive eye field (A, closed arrowhead), and expression expands through somitogenesis stages. At the 5-somite stage, a second expression domain in the midbrain region becomes visible (D, open arrowhead). These two domains expand, eventually forming the eyes and tectum (E–H). A section of a 24-h embryo shows peripheral expression in the tectum and in the eyes, both in the developing lens and retina. Stages are indicated in the figure, with s signifying somite. (A–H) Anterior view; (D′–H′) lateral view; (H″) section in the plane shown in (H). Gn, ganglion; Hb, hindbrain; L, lens; Ph, pharyngeal arch; R, retina; T, tectum.

Mab21l2 expression in mutant embryos. Mab21l2 expression was examined in the cyclopic mutants, cyclops (cyc) (B) and one eyed pinhead (oep) (D), and in the MHB mutants acerebellar (ace) (F), and no isthmus (noi) (H). In cyc and oep embryos, mab21l2 is still expressed in the cyclopic eye field. In the ace mutant, mab21l2 is expressed at a normal level but the shape of the expression domain in the tectum is altered (F, arrowhead). In contrast, growth of the tectum is reduced and mab21l2 expression is suppressed in the noi mutant (H, arrowhead). (A–D) Twenty-two somite stage; (E–F) 26 h stage. (A,C,E,G) are wild type embryos.