Developmental expression pattern of zebrafish rbmx mRNA Whole-mount in situ hybridization with antisense zebrafish rbmx at the following developmental stages: a: one cell (animal pole toward top); b: 8 hpf (lateral view); c: 24 hpf (lateral view); d: 48 hpf (lateral view); e: 48 hpf cross-section of the head; f: 48 hpf (lateral view); g: 72 hpf (lateral view); h: 72 hpf (dorsal view); i: 7 dpf (lateral view). Where applicable, anterior is orientated toward the left. ba, branchial arches; ce, cerebellum; ep, epiphysis; fb, forebrain; gu, gut; hb, hindbrain; li, liver primordium; mb, midbrain; nc, notochord; ov, otic vesicle; pf, pectoral fin; re, retina; te, tectum.

rbmx knockdown in zebrafish. a: Lateral view of wildtype (wt) embryo at 48 hpf. b,c: Lateral view of embryos injected with rbmx morpholino (mo) at 48 hpf. The morphant embryos exhibit a number of phenotypes (arrows) including reduced body size, lack of jaws, delayed reabsorption of the yolk sac, defective somite patterning, curly tail and swollen pericardium. The characteristic defects in brain morphology particularly an inflated tectum and cerebral ventricle are shown in (c). d: In situ hybridization with anti-sense rbmx riboprobe of wildtype (wt) and rbmx morphant (mo) embryos at 72 hpf. e: Partial rescue of morphant (mo+re) phenotype by coinjection of rbmx-morpholino with synthetic, morpholino-resistant rbmx mRNA (lateral view at 72 hpf).

Characterization of zebrafish rbmx-morphant phenotype. Expression of otx2 (a,d), krox20 (b,e) and pax2.1 (c,f) anti-sense riboprobes at 24 hpf (a,b,c) and 48 hpf (d,e,f) in wildtype (wt) and morphant (mo) embryos, as indicated. Arrowheads indicate aberrant expression patterns of gene markers in morphant embryos. All images except of f are lateral view with anterior to the top. f is a dorsal view with anterior to the top. Dash lines indicate the relative length of the dorsoventral axis of the developing brain.