FIGURE 4

FIGURE 4

Proliferating progenitor cells within the rhombomere centers shift their division mode over time. (A–D) Tg[BCP:H2B-GFP] embryos were pulsed with EdU at the indicated intervals and chased for 6 h to analyze the position of the derivatives of cells that underwent the S-phase. EdU is depicted in magenta, hindbrain boundaries in blue, and fabp7a cells enriched in the center of the rhombomeres in green. (A–D) Dorsal projections with anterior to the top. White arrowheads indicate the rhombomere boundaries. (a–d, a’–d’, a’’–d’’) Transverse views of (A–D) through the center of r4 displaying either the EdU cells (a–d), the fabp7a cells (a’–d’), or the merge of both (a’’–d’’). ov, otic vesicle. (E) Analysis of the progenitor cell division mode within the rhombomere centers. Scheme depicting the multicolor clonal growth experimental approach. Tg[HuC:GFP] embryos at the 8-cell stage were injected with the hsp:zebrabow construct and heat-shocked 1 h before the imaging time. Embryos were in vivo imaged at 36 hpf or 42 hpf (t0), and then at 48 hpf or 54 hpf (tf), respectively. The cell division mode was analyzed in all the clones. (F) Transverse projections generated at t0 and tf showing examples of the three observed clonal cell behaviors: a cell undergoing symmetric proliferative division (PP, red cell not expressing HuC at t0 and the daughter cells not expressing it at tf; white asterisks), a cell undergoing asymmetric division (PN, red cell not expressing HuC at t0, with only one of the daughters expressing HuC at tf; white asterisks), and a cell undergoing symmetric neurogenic division (NN, white cell not expressing HuC at t0, but both daughters expressing HuC at tf; white asterisks). The neuronal differentiation domain is displayed in yellow. (G,H) Stacked bar graphs showing the percentage of PP (orange), PN (blue), and NN (gray) cell division modes in the rhombomere centers between two different time intervals: 36–48 hpf (G; n = 11 cells, N = 4 embryos) and 42–54 hpf (H; n = 13 cells N = 5 embryos).