Fig. 6.

smb mutants have impaired sclerotome expansion but early-forming derivatives of the sclerotome are unaffected in the smb mutant. (A) pax9 transcripts were fluorescently labeled with HCR in wild-type and smb heterozygous embryos at 22 and 24 hpf and imaged by confocal microscopy. Gray indicates the pax9⁺ domain used to quantify volume using Imaris surface rendering. (B) pax9 expression at each condition was quantified by Imaris. For 22 hpf, six wild-type and six smb heterozygous mutant animals were quantified (unpaired two-tailed t-test; P=0.8640; ns, not significant). For 24 hpf, four wild type and four smb heterozygous mutants were quantified. *P=0.0144; unpaired two-tailed t-test. (C) Heterozygous smb fish were crossed to scxa:mCherry fish, and labeled tenocytes in wild-type and smb heterozygous mutant offspring were imaged by confocal microscopy (n=5 per genotype). (D) smb heterozygous fish were crossed to her6:mCherry fish, and fin fold fibroblasts in wild-type and smb heterozygous mutant offspring were imaged by confocal microscopy (n=3 per genotype). (E) Vertebrae were imaged in Alcian Blue and Alizarin Red-stained wild types and stage-matched smb heterozygous mutants. Neural spines (ns), neural arches (na), haemal spines (hs), and haemal arches (ha) are indicated in wild type. Asterisk indicates absent haemal arch and spine; arrowheads mark fused or forked haemal arches or spines. Fisher's exact test; P<0.0001. Scale bars: 50 μm (A, top); 60 μm (A, bottom, C); 30 μm (D); 400 μm (E).