Fig. 4. Depletion of XSRF leads to expansion of mesoderm. (A) XSRF morpholino oligonucleotides (MOs) specifically knockdown the translation of C-terminally Myc-tagged XSRF protein in animal cap cells. Four-cell stage embryos were injected in the animal pole region with C-terminally 6Myc-tagged XSRF RNA (2 ng) with or without CO MO (60 ng), XSRF MO1 (60 ng) or XSRF MO2 (40 ng), and then animal cap explants dissected at late blastula stages were subjected to western blotting. Uninjected, animal caps without injection; Control, animal caps injected with XSRF-6Myc only. (B-H) Phenotypes of XSRF-depleted embryos. Embryos were injected at the four-cell stage with the indicated reagents (60 ng CO MO; 60 ng XSRF MO1; 40 ng XSRF MO2; 100 pg wt XSRF) dorsally (B,D,E,G,H) or animally (C,F) and cultured to stage 31. (I-W) Knockdown of XSRF expands the expression of mesodermal markers. Four-cell stage embryos were injected in the dorsal or ventral marginal region with CO MO (60 ng), XSRF MO1 (60 ng), XSRF MO2 (40 ng) or DN XSRF (2 ng) and then analyzed at the mid-gastrula stages by in situ hybridization against Goosecoid (I,L,O,R,U), Xbra (J,M,P,S,V) or Wnt8 (K,N,Q,T,W).