Fig. 2

Expression of tbx15 during wild type zebrafish development. (A,B) Double in situ hybridisation showing tbx15 expression (purple) at 17 hpf in the paraxial head mesenchyme, extending rostrally underneath and lateral to rhombomere 3 (r3), counterstained with krox-20 in r3 and r5 (red); (B) dorsal view. (C) At 18 hpf expression is restricted to the paraxial mesenchyme, but excluded from r5 and otic vesicles. (D,E) Somitic expression at 17 hpf in 10–11 rostral somites in the region of the horizontal myoseptum (arrows) expands to the entire somite at 27 hpf (F); (E,F) transverse sections at the level of the fifth somite. (G) Expression is detected in the first pharyngeal arch (at 24 hpf) and (H) in mesenchymal cells separating forebrain and eye. (I,J) tbx15 expression in extraocular and pharyngeal arch muscles, paraxial head mesoderm and pectoral fin bud mesenchyme at (I) 30 hpf and (J) 48 hpf. (K) Strong expression in eye and pharyngeal muscles; ventro-lateral view at 60 hpf. (L–O) tbx15 transcript in developing pectoral fins; expression is exclusively mesodermal, and at 36 h (L) is strong in the medial part of the fin bud and absent from the epidermis (arrowhead); mesodermal expression remains strong throughout the fin bud at (M) 48 hpf and (N) 3 dpf; (O) At 30 dpf tbx15 is strongly expressed in the margins and distal tips of lepidotrichs (arrowheads). (A,D,K–N) lateral views, (B,G,I,J) dorsal views, (C,E,F,H) transverse sections, (O) ventral view. am, adductor mandibulae; eom, extraocular muscles; fb, forebrain; hb, hindbrain; io, inferior oblique; lr, lateral rectus; n, notochord; ov, otic vesicle; pfb, pectoral fin bud; phm, paraxial head mesenchyme; pm, pharyngeal arch mesenchyme; r, rhombomere; sc, spinal cord; Scale bars, 100 μm.