Fig. 2.

Lineage tracing of anterior somites in zebrafish marks OSM and SHM. Fluorescent images of primary green and photoconverted red Kaede (A-E,G,H,J). Images are from multiple embryos (e), photoconverted at either 3-5 ss (e1; A,D) or between 14 and 18 ss (e2-4; B,C,E,G,H,J). Tg(actc1b:egfp) labels muscle precursors (F,I,K). (A) Dorsal view confocal image showing photoconversion to Kaede^red in S1 of e1 at 5 ss. (B) At 36 hpf, lateral view of e2 detected Kaede^red in S1, and both anteriorly and medially migrating cells (yellow and red arrowheads, respectively). Marked cells were also observed associated with notochord (asterisks), and in neural tube as a result of photoconversion in overlying neural plate. (C) Cross-section confocal view of e3 at 45 hpf revealed medial cells localised to the oesophagus (oeso; red arrowheads; region magnified on right) and Kaede^red in close proximity to the somite (black arrowhead). Anterior cells had intense label, reminiscent of SHM (yellow arrowhead). (D) e1 at 84 hpf. Dorso-lateral view confocal images showed Kaede^red cells in close association with oesophagus. (E,F) Lateral view of e4 after photoconversion of S1+2 showing anteriorly located Kaede^red (E, yellow arrowheads) in similar position to SHM primordium in Tg(actc1b:egfp) embryos (F, yellow arrowhead). (G) Lateral view of e2 reveals Kaede^red in association with oesophagus (red arrowhead), SHM (yellow arrowhead) and common cardinal vein (magenta arrowhead) at 72 hpf. (H-K) Ventral confocal (J,K) and stereomicroscopic (H,I) views of e2 at 96 hpf showing Kaede^red in left SHM (yellow arrowheads) and pectoral fin (green arrowheads), confirmed by Tg(actc1b:egfp). Melanophore pigment is located above SHM (J,K, asterisks). ba, branchial arches; e, eye; h, heart; nt, neural tube; oeso, oesophagus; o, otic vesicle; pf, pectoral fin.