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Figure 1. Depletion of Xlefty Results in Exogastrulation(A) Xnr2 and (B) Xlefty are dorsally expressed in complementary adjacent domains at stage 10.5. Vegetal views, with dorsal at the top. Arrowheads indicate the dorsal lip. (C) Model of Nodal signaling at the dorsal lip in the presence (left) or absence (right) of Lefty function. Arrows represent the extent of Nodal signaling response away from the dorsal lip; vegetal view. (D–G) Xlefty depletion by MO injection results in exogastrulation that is rescued by coinjection of an Xlefty DNA construct that lacks the MO-targeted sequence. (D) Uninjected embryo (59/60 normal). (E) Exogastrulae from injection of 8 pmol anti-Xlefty MO (49/60 exogastrulated). Complete exogastrula on left, partial exogastrula on right. The arrowhead indicates the pigmented ectoderm at the posterior end (confirmed by in situ hybridization, Supplementary Figure S3) of the complete exogastrula. Complete exogastrulae (24/60) exhibited no morphologically obvious neural plate during neurulation and no dorsal closure after neurulation, whereas partial exogastrulae (25/60) had a morphologically recognizable neural plate and ≤50% dorsal closure over the yolk. (F) Injection of 100 pg CS2+/Xlefty DNA results in aberrant development but not exogastrulation (0/46 exogastrulated). (G) Coinjection of 8 pmol anti-Xlefty MO + 100 pg CS2+/Xlefty DNA rescues gastrulation (1/60 exogastrulated). Post-neurula embryos with neural plate closure and >50% dorsal closure over the yolk were scored as rescued. (D, F, and G) Left lateral view at stage 26, with anterior to the left. For exogastrulae (E), shown is a dorsal view at stage 26, with anterior at the top. |
