bmp4 expression is greatly expanded in boz din mutants. bmp4 expression in (a) wild-type (wt) and (b) boz din embryos at mid-gastrulation (7.5 hpf). Ventro-lateral eve1 expression and organizer-specific expression of gsc was used to distinguish (c) wild-type and (d) boz din embryos at midgastrulation (7.5 hpf). bmp4 expression in (e,g) wild-type and (f,h) boz din embryos during somitogenesis (13 hpf). (a–d) Anterior views, dorsal to right; (e,f) lateral views, dorsal to right; (g,h) ventral views. Arrowheads indicate borders of (a–d) ventro-lateral and (e–h) posterior domains of bmp4 and eve1 expression; arrow indicates (a) dorsal domain and (e,g) anterior bmp4 expression domain absent in boz din. (pm) Prechordal mesoderm; (tb) tailbud. Bar, 100 μm.