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Figure 2. xHtrA1 Blocks Head Formation and Induces Ectopic Tail-like StructuresEmbryos were injected into the animal pole of one blastomere at the 4-cell stage with 80 pg of the indicated mRNAs.(A) Uninjected tail bud embryo (dorsal view, anterior to the left).(B) xHtrA1 mRNA induces a secondary axis (arrowhead) fused with the primary body axis at the anterior end.(C) Uninjected embryo at tadpole stage.(D) xHtrA1 induces loss of head tissue and ectopic tail-like structures.(E) Histological section of xHtrA1-injected tadpole embryo. sc, spinal cord; nc, notochord; so, somites.(F and G) Ectopic N-tubulin expression in xHtrA1-induced tail outgrowth (arrowhead).(H–K) Ectopic expression of Shh and MyoD in early neurulae (dorsal view) adjacent to cells coinjected with xHtrA1 and nuclear lacZ mRNA as lineage tracer (red nuclei).(L and L′) After a single ventral injection of xHtrA1 and GFP mRNA, injected green cells populate the ectopic tail structures (arrowhead).(M and M′) Coinjection of xHtrA1 and GFP mRNA into one dorsal blastomere induces an ectopic tail outgrowth distant to injected cells.(N–Q) While xHtrA1 mRNA causes anencephaly and ectopic tail formation, xHtrA1δTrypsin or xHtrA1 (S307A) mRNA are without effects.(R) Western blot analysis of lysates from mRNA-injected embryos at stage 9 probed for xHtrA1. GAPDH is a loading control.Ectopic axial structures were induced in B, 21/88; D, 61/203; G, 15/18; I, 3/15; K, 6/19; L, 3/12; M, 4/37; O, 110/124 (head reduction), 37/124 (ectopic outgrowth), P, 0/406, and Q, 0/280 embryos. |
