Fig. 4. The loss of xKaiso induces an apoptotic response in Xenopus embryos. Wild-type (A-C) and 5 ng KMO-injected (D-F) Xenopus embryos were assayed by TUNEL for the appearance of apoptotic cells. TUNEL-positive cells were not detectable in normal late blastula (A) and gastrula (B) embryos. Small numbers of apoptotic cells (arrowhead) appeared in 1-2% of wild-type embryos at late neurula stage (C). TUNEL-positive cells were detected in 11% and 15% of KMO-injected embryos at late blastula (D) and gastrula stages (E), respectively. More than 90% of KMO-injected embryos exhibited a general pattern of apoptosis at a stage corresponding to late neurula of normally developing embryos (F). Abbreviations: bp, blastopore; ant, anterior; post, posterior.