|
Fig. 2 Ptk7 overexpression disrupts embryonic patterning and morphogenesis and inhibits exogenous Wnt/β-catenin activity. (A) Lateral view of uninjected control embryos at 36 hpf. (B,C) Embryos injected with ptk7 (400 pg) mRNA at the one-cell stage exhibit axial morphogenesis (B) and dorsoventral patterning defects (C). (D,E) Whole-mount in situ hybridisation (WISH) demonstrating chordin (chd) expression in control (D) and ptk7 (400 pg) mRNA-injected (E) embryos at shield stage (animal pole view, dorsal right). Arrowhead indicates lateral expansion of chd expression in embryos overexpressing Ptk7. (F,G) WISH of vox expression in control (F) and ptk7 (400 pg) mRNA-injected (G) embryos at shield stage (lateral view, dorsal right). (H,I) WISH for axin2 in control (H) and ptk7 (400 pg) mRNA-injected (I) embryos at bud stage (lateral view). Reduced vox and axin2 expression is observed in embryos overexpressing Ptk7. (J) Overexpression of wnt8 (10 pg) disrupts CNS pattern, as demonstrated by loss of eyes and reduced forebrain at 36 hpf. Co-injection of ptk7 (300 pg) mRNA can largely rescue these wnt8-induced phenotypes. (K) Schematic of Ptk7 mutant isoforms generated for structure-function and rescue experiments. (L) Quantification of phenotypes observed upon injection of wnt8 (10 pg) mRNA, and upon co-injection of wnt8 with full length ptk7 (300 pg), ptk7ΔICD (200 pg), ptk7 egfrTM (300 pg), ptk7ΔECD (150 pg) and ptk7 ECD (200 pg) mRNA. mRNA concentrations were adjusted to yield equimolar amounts of truncated/mutant Ptk7 protein. Embryos were scored as being ‘eyeless’ if the eye was either completely absent or <25% the size of uninjected controls.