Fig. 6

Expression pattern of zebrafish hand2. (A-F) In situ hybridization showing expression of hand2 in wild-type embryos. (A-C) Three views of the same embryo at tailbud stage (10 hpf), demonstrating hand2 expression in a continuous streak of the LPM. (A) Dorsal view of anterior part of the embryo, head at the top. (B) Dorsal view of posterior part of the embryo, tailbud at the bottom. (C) Lateral view, anterior to the left. (D,E) Two views of the same embryo at the 10-somite stage, demonstrating hand2 expression in a large portion of the LPM, with a gap (arrowheads in D) between the anterior and posterior expression domains. (D) Dorsal view of anterior part of the embryo, head at the top. (E) Dorsal view of posterior part of the embryo, tailbud at the bottom. (F) Dorsal view of the cardiogenic portion of the LPM, anterior at the top, demonstrating wider domains of hand2 expression at the 15-somite stage. (G,H) Dorsal views of the embryonic trunk at the 20-somite stage (19 hpf), anterior to the left, showing gene expression in the bilateral pectoral fin-forming regions of the LPM. hand2 expression (G) appears to overlap with a posterior portion of tbx5 expression (H). In H, intense expression of tbx5 in the dorsal retinae is visible through the yolk at the left side of the image. (I,J) Lateral views, anterior to the left, of pectoral fin buds at 32 hpf. Again, hand2 expression (I) appears to overlap with a posterior portion of tbx5 expression (J). (K) Dorsal view through the embryonic head at 28 hpf, anterior to the top. hand2 is expressed in the midline heart tube as well as within the bilateral sets of branchial arches. hand2 expression is also faintly visible in a broad sheet of LPM analogous to the gata4-expressing tissue shown in Fig. 2F. (L,M) Comparisons of hand2 expression in han mutant and wild-type embryos. Dorsal views, anterior to the top. (L) Wild-type (left) and han^s6 mutant (right) embryos at the 5-somite stage. Wild-type embryos express hand2 in the LPM; han^s6 mutant embryos do not express hand2 at this or any other stage. (M) hand2 expression at the 3-somite stage. han^c99 mutants (right) express lower levels of hand2 than wild-type siblings (left). hand2 expression levels are always reduced in han^c99 mutants, but the locations of hand2 expression are always normal.