Fig. 8

Fgfrl1b is necessary for proper chondrogenesis of all ventral cartilage elements. (A) Genomic organization of fgfrl1b illustrating the Ig-like (Ig1, 2 and 3) and transmembrane (TM) domains, and the target site for the splice-blocking (SBMO) and ATG-targeting (ATGMO) morpholinos. ORF and untranslated regions highlighted by dark and light shading, respectively. The location and orientation of primers used for RT-PCR detection of altered splicing are indicated by arrows. (B) Semi-quantitative RT-PCR illustrating specific depletion of normal fgfrl1b splicing following early delivery of 0.5 and 1.0 pmol doses of SBMO (+, reverse transcriptase present; -, reverse transcriptase absent). Primer combinations are bracketed. (C–N) 4 dpf larvae stained with alcian blue. (C, D and E) Dissected ventral cartilage elements from wildtype, 1bSBMO-injected and 1bATGMO-injected larvae. (F, G and H) Dissected cranial cartilage elements from wildtype, 1bSBMO-injected and 1bATGMO-injected larvae. (I and J) Dorsal view of cartilage elements of wildtype and 1bATGMO-injected larvae presenting severe phenotype. (K and L) Dorsal view of larvae injected with sub-optimal doses of either 1aSBMO or 1bATGMO exhibiting normal chondrogenesis. (M and N) Dissected ventral and cranial cartilage elements from larvae treated with a combination of sub-optimal doses of 1aSBMO and 1bATGMO displaying absence or reduction of ceratobranchial cartilage. Abbreviations: abc, anterior basicranial commissure; cb1–5, ceratobranchial arch 1–5; ch, ceratohyal; ep, ethmoid plate; hs, hyosymplectic; m, Meckel’s cartilage; no, notochord; pc, parachordal; pq, palatoquadrate; tr, trabecula. Scale bars: 100 μm.