Figure 1.

Using BAC recombination to produce a Tg(neurog1:EGFP) transgenic line. A, Schematic showing the strategy for BAC recombination. In the BAC clone DKEY-91L18 (zK91L18) from the DanioKey library, the single coding exon of the neurog1 gene (blue bar) was replaced with an EGFP/kanamycin resistance cassette (green and black bars) by recombination using flanking homologous sequences (red bars). The EGFP gene is placed in-frame at the neurog1 start site. Schematic is not to scale. B–F, Confocal projections of live transgenic Tg(neurog1:EGFP) embryos. B, At 16 hpf, Tg(neurog1:EGFP) is expressed in developing brain, spinal neurons, and RB neurons (open arrowheads). C, By 48 hpf, Tg(neurog1:EGFP) is strongly expressed in the CNS, and DRG (arrows) neurons are visible ventral to the spinal cord along the trunk. D, In the head at 48 hpf, several regions in the brain are intensely GFP positive, including the midbrain–hindbrain boundary (arrow). A subset of cells in the trigeminal ganglia (open arrowhead) expresses Tg(neurog1:EGFP). E, GFP⁺ trigeminal ganglia neurons (open arrowheads). F, Close-up image showing GFP-expressing RB cells in the dorsal spinal cord and their associated axons (open arrowhead), cells in the spinal cord (arrowhead), and DRGs ventral to the spinal cord (arrow). G, DRGs containing a single GFP-expressing neuron (arrow) showing a centrally projecting axon (arrowhead) and a peripherally projecting axon (open arrowhead). Scale bars: B, D, 100 μm; C, 200 μm; E–G, 20 μm.