Sequence, phylogeny, and RT-PCR of zebrafish RARs. A: Sequence alignment of zebrafish RARs. Alignment was performed with ClustalW. B: Phylogenetic analysis of all available full-length sequences. Another nuclear receptor, human PPAR, was defined as the outgroup. Phylogeny was constructed using the neighbor-joining method with PAUP*. Numbers on the nodes reflect bootstraps from 1,000 replicates. C: RT-PCR for the zebrafish rar genes from cDNA collected from 25 2-8 cell or 15-20 somite embryos. -RT control indicated lack of genomic DNA contamination (not shown). Asterisk indicates the newly identified gene rargb.

Comparison of zebrafish rar expression patterns from 40% epiboly through 24 hpf. ISH depicts expression patterns of raraa, rarab, rarga, and rargb. A-D: Lateral views of embryos at 40% epiboly, animal pole at the top, dorsal on the right. Arrow in A indicates dorsal expression. E-H: Lateral views at shield stage. I-L: Lateral views at 80% epiboly. Arrows in K indicate low expression around the margin. M-P: Lateral views at the tailbud stage, anterior at the top. Arrow in O indicates anterior mesendoderm expression. Arrowhead in P indicates higher anterior expression. Arrow in P indicates tailbud expression. Q-T: Lateral views at the 15-somite stage. U-X: Lateral views at 24 hpf.

Neural expression of zebrafish rar genes. ISH reveals distinct patterns of rar gene expression within and near the neural tube. Dorsal views of flatmounted embryos; rar gene expression is depicted in blue, and krox20, indicating r3 and r5, is shown in red. A: At the 5-somite stage, expression of raraa is adjacent to r5. B: At 24 hpf, raraa is expressed in the anterior spinal cord. C,D: Expression of rarab at the 5-somite stage and the 18-somite stage in the anterior spinal cord and hindbrain, with higher expression in r5and r6. E: Expression of rarga at the 5-somite stage in anterior mesendoderm (arrows) and r4 (arrowhead). F: At 24 hpf, expression of rarga has spread to the posterior hindbrain and anterior spinal cord. G: At the 10-somite stage, rargb is expressed in the lateral diencephalon (arrowhead) and the premigratory neural crest. H: At the 18-somite stage, rargb is expressed in the lateral diencephalon (arrowhead) and migrating neural crest. I: At 24 hpf, rargb is present in the pharyngeal neural crest. Numbers indicate the three streams of neural crest. Images A-F are the same magnification, and images G-I are the same magnification. Scale bar = 10 μm.

Sequence, phylogeny, and RT-PCR of zebrafish RXRs. A: Sequence alignment of zebrafish RXRs. Alignment was performed with ClustalW. B: Phylogenetic analysis of all available full-length sequences. Another nuclear receptor, human PPAR, was defined as the outgroup. Phylogeny was constructed using the neighbor-joining method with PAUP*. Numbers on the nodes reflect bootstraps from 1,000 replicates. C: RT-PCR for the zebrafish rxr genes from cDNA collected from 25 2-8 cell or 15-20 somite embryos. -RT control indicated lack of genomic DNA contamination (not shown). Arrow indicates low maternal expression of rxraa. Asterisk indicates the newly identified gene rxraa. Carrot indicates the newly identified gene rxrgb.

Comparison of zebrafish rxr expression patterns. ISH depicts expression patterns of rxraa, rxrab, rxrba, rxrbb, rxrga, and rxrgb. Lateral views at indicated stages, as in Figure 2.

Neural expression of zebrafish rxr genes. ISH reveals distinct patterns of rxr gene expression within and near the neural tube. Dorsal views of flatmounted embryos; rxr gene expression is depicted in blue, and krox20, indicating r3 and r5, is shown in red. A: At the 5-somite stage, rxraa is expressed in lateral regions of anterior spinal cord (arrows). B: At the 18-somite stage, rxraa is expressed in the neural crest (arrowheads). C: At the 5-somite stage, rxrga is expressed in the anterior spinal cord. D: At 24 hpf, rxrga is expressed in the anterior spinal cord and the neural crest (arrowheads). E: At the 10-somite stage, rxrgb is expressed in the anterior spinal cord. F: At 24 hpf, rxrgb is expressed at low levels in medial anterior spinal cord. Scale bar = 10 μm.

Unillustrated author statements