Fig. 2

Body curvature induced by injection of lbx mRNAs.

(A) Protein structure of Lbx family members with an engrailed homology domain (Eh) and homeobox domain (Hd). (B) Dorsal views of live embryos (48 hpf) injected with zebrafish lbx1a, lbx1b, or lbx2b mRNA, as well as human LBX1 or FLJ41350 mRNA, in comparison with those injected with lbx1aΔhd mRNA which lacks the homeodomain, and lbx1aΔeh, lbx1bΔeh, and lbx2Δeh mRNA which lacks the engrailed domain. Buffer was injected as a control (ctrl). Severe curvature was observed in embryos injected with lbx1a, lbx1b, and LBX1 mRNA, while mild body curvature was observed in those injected with lbx2 mRNA, but no curvature was observed in those injected with lbx genes lacking the functional domains. Bending of the body axis was not observed in embryos injected with FLJ41350. (C) Quantitative analysis of the phenotype of embryos injected with different doses of mRNA. Body curvature occurred in lbx1b, LBX1, lbx1a, and lbx2 embryos in a dose-dependent manner. lbx1b embryos presented with the highest incidence of curvature (45% for 50 pg, 59% for 100 pg, and 82% for 150 pg), and then LBX1 (29% for 50 pg, 46% for 100 pg, and 64% for 150 pg), lbx1a (24% for 50 pg, 39% for 100 pg, and 51% for 150 pg), and lbx2 (16% for 50 pg, 25% for 100 pg, and 38% for 150 pg). The incidence of curvature was less than 10% in lbx1aΔhd, lbx1aΔeh, lbx1bΔeh, lbx2Δeh, and FLJ41350 embryos regardless of dose. The data represent the mean ± standard error of three independent injections (n = 27–37). (D) Dorsal views of live larva are shown. lbx1b^+/- and lbx1b^-/- mutants as well as lbx2^+/- and lbx2^-/- mutants are comparable to WT with a straight body axis. The scale bar represents 500 µm.