UNC-75 is required for the selection exon 7a from the <i>unc-32</i> exon 7 reporter in the nervous system.

<p>(<i>A</i>) Fluorescence images of the <i>ybIs1622</i> worms with the <i>unc-75</i> mutant alleles <i>yb1700</i>, <i>yb1725</i>, <i>yb1714</i> and <i>yb1701</i> with a dual-bandpass filter. Scale bar, 200 µm. (<i>B</i>) Schematic structure of the <i>unc-75</i> gene and the positions and consequence of the mutations. The ORF is colored in yellow and the regions corresponding to the three RRMs are in orange. The allele names are in the colors representing the color phenotypes. SA, splice acceptor; SD, splice donor. (<i>C</i>) Amino acid sequence alignments of the three RRMs from the CELF3–6 subfamily members <i>C. elegans</i> UNC-75, human CELF3, CELF4, CELF5 and CELF6 and the CELF1–2 subfamily members <i>C. elegans</i> ETR-1, human CELF1 and CELF2. Conserved residues are shaded in black. Residues with similar properties to the consensus are shaded in gray. The secondary structure elements determined for human CELF1 <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003337#pgen.1003337-Tsuda1" target="_blank">[51]</a>, <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003337#pgen.1003337-Teplova1" target="_blank">[52]</a> are depicted with the blue rectangles (β-sheets) and the red ellipses (α-helices) below the alignments. The highly conserved RNP1 and RNP2 motifs in each RRM are boxed in magenta. The positions of the missense mutations and the short deletion are indicated with the allele names. Note that <i>yb1725</i> generated a cryptic splice donor site almost exclusively used in the mutant, which resulted in the in-frame deletion of the 4-amino acid stretch indicated. (<i>D</i>) RT-PCR analysis of the UNC-75 mRNAs from the synchronized L1 larvae of N2 (<i>wt</i>), <i>asd-1 (yb978); fox-1 (e2643)</i> and <i>unc-75 (yb1701)</i>.