The mutually exclusive exons of the <i>unc-32</i> gene are regulated in tissue-specific manners.

<p>(<i>A</i>) Schematic structure of the <i>unc-32</i> gene. Numbered boxes indicate exons. The position of the 3′-splice site mutation in the <i>unc-32 (e189)</i> allele is indicated. Black triangles indicate positions and directions of the exonic primers used in the RT-PCR analyses shown in (<i>B</i>). (<i>B</i>) RT-PCR analyses of <i>unc-32</i> exon 4 (left) and exon 7 (right) at the L1 and L4 larval stages. (<i>C</i>, <i>D</i>) Schematic illustration of the symmetric trio of the exon 4 reporter minigenes (<i>C</i>) and the symmetric pair of the exon 7 reporter minigenes (<i>D</i>) and the mRNA isoforms derived from them. The cDNA cassettes and the predicted ORFs for Venus/EGFP, mRFP and ECFP are colored in green, magenta and cyan, respectively. Green circles and red diamonds indicate the artificially-introduced initiation and termination codons, respectively. (<i>E</i>) Fluorescence images of an L4 larva of the exon 4 reporter worm <i>ybIs1891 [eft-3::unc-32E4a-Venus eft-3::unc-32E4b-mRFP eft-3::unc-32E4c-ECFP]</i>. E4a-Venus, E4b-mRFP and E4c-ECFP images in black-white and a merged image with pseudo colors. (<i>F</i>, <i>G</i>) Confocal images of the exon 7 reporter worms <i>ybEx1440 [eft-3::unc-32E7-EGFP eft-3::unc-32E7b-mRFP]</i>. (<i>H</i>) A fluorescence image of the <i>unc-32</i> transcriptional fusion reporter worm <i>ybEx1896 [unc-32::EGFP]</i> containing 1.7-kb of the <i>unc-32</i> promoter. int, intestine; N, neurons in head ganglia; phx, pharynx. Scale bars in (<i>E</i>), (<i>F</i>) and (<i>H</i>), 100 µm; in (<i>G</i>), 20 µm.