Fig. 6

Both overexpression and knockdown of rab23 alter asymmetric gene expression in zebrafish. (A) Dorsal views of spaw and lefty1 expression at 16 to 18-somite stage (top) and lefty1 and lefty2 expression at the 22 to 24-somite stage (bottom) in the different phenotypic classes quantified in B, C, and D. spaw expression is normally observed in the left LPM, lefty1 in the midline, and lefty2 in the left cardiac mesoderm. Injection of rab23 mRNA or rab23 MOs produced embryos with left, right, bilateral, or no gene expression in the LPM. Control embryos included those injected with phenol red (p. red) or with a control morpholino. (B) Quantification of the spaw expression pattern at the 16 to 18-somite stage. Both mRNA injected embryos and MO injected embryos showed randomized spaw expression in the LPM. The majority showed bilateral expression. (C) Quantification of spaw expression patterns at the 9 to 11-somite stage when spaw is just beginning to be expressed in the LPM. A much smaller fraction of rab23 MO injected embryos induced spaw expression at this stage compared to controls, whereas the rab23 mRNA injected fish showed a highly significant increase in the fraction of spaw-expressing embryos. (D) Quantification of lefty2 expression in the cardiac LPM at the 22 to 24-somite stage. The vast majority of mRNA-injected embryos expressed lefty2 on the left side of the heart, whereas most rab23-MO injected fish failed to express lefty2. In all assays, embryos injected with the control morpholino did not differ from those injected with phenol red alone. Statistical significance: ^NNNP<10⁶, ^NNp<10³, and ^Np<0.05 Fisherós exact test.