Fig. 5.

Medial-to-lateral organization of the ventral neurogenic ectoderm in S. purpuratus embryos. Shown are expression patterns of nkx2.1, nkx2.2, pax2/5/8, and msx in controls (A) and in embryos treated with mBMP4 and SB for 4 h during gastrulation (B). The ventral ectodermal expression of nkx2.1 (black asterisk) disappeared (white asterisk) after drug treatment. The vegetal-ventral ectodermal expression of nkx2.2 (black arrowhead) also weakened on treatment (blank arrowhead). The brackets indicate the ectodermal expression domains. The first two columns display the late gastrula stage (2 d postfertilization, side views), while the last two columns are embryos at the pluteus larval stage (3 d postfertilization, vegetal views). Ventral is to the left in all images.