Fig. 6. Onset of ventral and posterior mesoderm defects in Tsg^-/-;Bmp7^-/- and Tsg^+/–;Bmp7^-/- compound mutants. (A,A') Ventral view of posterior primitive streak (ps) region of wild-type and mutant embryos stained with brachyury. The expression of brachyury is unchanged at 8.25 dpc in the mutant. (B,B') Side view of 8.25 dpc embryos before turning hybridized with Fgf8. Staining of the primitive streak and posterior mesoderm (pm) is fainter in the mutant. (C,C') Dorsal view of the posterior region of embryos shown in B and B', respectively. Fgf8 expression is less intense in the mutant. (D,D') High magnification view of the tailbud region of embryos stained with brachyury; in the mutant staining of tailbud mesoderm at the tip appears fainter, but notochord (n) expression is unaffected. (E,E') Bmp4 expression in side view of 9.0 dpc embryos (after turning). The allantois (al) and lateral plate mesoderm (lpm) are stained. (F,F') Higher magnification view of the tailbud region of embryos hybridized with Bmp4. The tailbud and of the allantois are abnormal in shape. Upon dissection, the allantois was found not to be fused to the chorion in the mutant (chorio-allantoic fusion has normally completed by this stage).