Fig. 1.

Mutation of zebrafish mbnl genes resulted in decreased adult body size. (A) Primary molecular mechanism of the human genetic disorder myotonic dystrophy (DM). In unaffected individuals, free MBNL1, MBNL2 and MBNL3 proteins bind to target pre-mRNAs and regulate the inclusion of alternative exons in mRNAs. MBNL proteins suppress alternative exon inclusion in the example shown here, but they promote inclusion of other target alternative exons. In individuals with DM, MBNL proteins are sequestered by long CUG (DM1) or CCUG (DM2) repeat RNAs, which decreases their availability to bind to target pre-mRNAs and alters mRNA isoform production and downstream protein function. (B) Diagram of WT and mutant zebrafish mbnl1, mbnl2 and mbnl3 predicted coding sequences. mbnl1 mutant alleles are denoted as 1^A and 1^B, mbnl2 alleles as 2^A, and mbnl3 alleles as 3^A, 3^B and 3^C. Mutant sequences are shown in Table S2. (C) Standard length of young adult 60 days post-fertilization (dpf) WT and mbnl mutant zebrafish that were raised in the same tank. On the right are representative images of fish of each genotype taken at 76 dpf. Scale bar: 10 mm. (D,E) Standard length of 7 dpf WT and double mbnl mutant zebrafish (D) or clutchmates from an incross of 1^+/B;2^A/A;3^C/C fish (E). In C-E, each dot represents one fish and data are presented as mean±s.d. Data were analyzed by ordinary one-way ANOVA with Tukey's multiple comparisons test. Data bars that do not share the same letter above them are significantly different from one another. Raw data and statistical analysis details are in Table S5.