Fig. 2. Effect of endoderm transplantation. (A,B) Diagrams of the experimental design for endoderm transplantation. Ectoderm cells were removed from early 32-cell host embryos (red twisted arrows). Donor endoderm cells were isolated from early 32-cell embryos. The isolated endoderm cells were transplanted to the ectoderm-depleted region (red arrowheads) so that the presumptive mesenchyme (A) and notochord (B) cells are sandwiched with two groups of endoderm cells. (C-N) Expression of tissue-specific markers in un-manipulated control (left column), endoderm-transplanted (middle column) and ectoderm-transplanted control (right column) embryos. (C-K) Vegetal views. (L-N) Animal views. Anterior is up. (C-E) Expression of the mesenchymespecific Mch-3 antigen in embryos in which cleavage was arrested at the 110-cell stage with cytochalasin B. Arrowhead in D indicates a muscle blastomere that ectopically expressed the Mch-3 antigen. (F-H) Expression of the muscle actin gene at the 110-cell stage. (I-K) Expression of notochord-specific Hr-Bra at the 110-cell stage. Arrowheads in J indicate cells of nerve cord lineage that ectopically expressed Hr-Bra. (L-N) Expression of neural plate-specific Hr-ETR1 in cleavage-arrested 110-cell embryos. Two rows of expression were observed in brain-lineage (arrowheads b) and nerve cord-lineage (arrowheads n) cells. The percentages at the bottom of each photo represent the proportion of embryos that ectopically expressed the Mch-3 antigen and Hr-Bra, and that showed reduced expression of actin and ETR1. Scale bar: 100 µm.