Fig. 6
Xbp1 is required for terminal differentiation of the hatching gland. (A–D) Wild-type embryos, (E-H) Xbp1 morpholino (MO1) injected. (A, E) Live, 4 dpf embryos. Embryos injected with 5 ng MO1 (E) do not hatch from their chorions (arrow). Embryos injected with 2 ng MO2 are identical (not shown). (B, F) 40× light microscopy of fixed hatching gland tissue at 35 hpf. Embryos injected with 7.5 ng MO1 (F) have a drastic reduction in size of secretory vesicles (arrow). Single hatching gland cells are outlined. Distinct cell boundaries are present in Xbp1 MO1-injected hatching gland cells, but they are less visible in this focal plane. (C, D, G,H) Electron micrographs of hatching gland tissue (35 hpf), at 4400X (C, G) and 11 500× (D, H) magnification. Embryos injected with 7.5 ng MO1 (G) have fewer and smaller secretory vesicles (asterisk) than wild-type (C). The elaborate cisternae of the rough ER (D) are not seen in MO injected embryos (H).
Reprinted from Developmental Biology, 304(2), Bennett, J.T., Joubin, K., Cheng, S., Aanstad, P., Herwig, R., Clark, M., Lehrach, H., and Schier, A.F., Nodal signaling activates differentiation genes during zebrafish gastrulation, 525-540, Copyright (2007) with permission from Elsevier. Full text @ Dev. Biol.