An Intronic Element Regulates <i>let-2</i> Alternative Splicing

<p>The top of this figure shows the alignment of C. elegans and C. briggsae sequences for the alternatively spliced region of <i>let-2</i>. Blue tracks indicate the splicing for the embryonic (top) and adult (bottom) isoforms. The purple track indicates homology between the C. briggsae and C. elegans genomes as determined by WABA. Dark purple tracks indicate regions of strong homology (>70%). The sequence of the first conserved element of intron 10 is shown. The box indicates the part deleted and replaced with the sequence GAA in the del1.2 splicing reporter construct. The lower left part of the figure shows the results of ³²P RT-PCR reactions with primers specific for the splicing reporter. Products for exon 9- or exon 10-containing messages are indicated. In embryos, only usage of exon 9 is detected for either reporter. At the L4 stage, 34% of the wild-type reporter messages contain exon 10 while del1.2 mutant messages contain only a trace amount of this exon.