Fig. 2

The clbn phenotype is caused by a mutation in rnpc3. (A) RT-PCR of full-length rnpc3 coding sequence amplifies a predominant 1.6-kb product in WT larvae (lane 4) and four aberrantly spliced transcripts in clbn^s846 (lane 5). A retroviral insertion in clbn^ZM abolishes generation of full-length rnpc3 mRNA (lane 6). Lanes 1–3 show –RT controls. (Lower) Elongation factor alpha (elfa) control. Dashed lines link the cDNA products in lanes 4 and 5 to the corresponding transcripts, shown schematically in B. The dark blue region denotes retention of 10 intronic nucleotides through use of a de novo 32 ss. (C) Two noncomplementing clbn alleles. An asterisk over T marks the position of the T′A variation, 12 nucleotides upstream of exon 14 of rnpc3, which causes the clbn^s846 phenotype. The conserved 52 ss and BPS in intron 14 (U12-type) of rnpc3 are underlined and in bold. clbn^ZM carries a retroviral insertion in the first intron of rnpc3. (D–F) Brightfield microscopy images of left lateral views of 5-dpf larvae derived from a clbn^s846 heterozygous incross that were injected at the one- to two-cell stage with 380 pg of either WT rnpc3 mRNA or a mutant mRNA retaining introns 13 and 14, corresponding to the most abundant form of rnpc3 mRNA in clbn^s846 (see B). (D) No significant overexpression phenotype in WT larvae injected with WT rnpc3 mRNA. (E) Rescue of the mutant phenotype in genotyped clbn^s846 homozygous mutant larvae injected with WT rnpc3 mRNA. (F) No rescue of the clbn mutant phenotype injected with mutant rnpc3 mRNA. (G) Noninjected control larvae from the same clutch show a near-perfect Mendelian ratio of WT to clbn larvae, whereas 96% of larvae injected with WT rnpc3 RNA appear WT at 5 dpf (P < 0.0001, Fisher’s exact test). There was no difference between uninjected and mutant rnpc3-injected groups (P = 0.9065). a, anus; e, eye; ib, intestinal bulb; sb, swim bladder; y, yolk. The brightfield images in D, E, and F were taken at the same magnification.