Fig. 3. Growth and differentiation of wild-type (+/+) and Tbx4-mutant (-/-) allantoises. All embryos were dissected at 8.0 dpc and were at the 0- to 8-somite stages. Black arrowheads indicate the base of the allantois in all panels. (A) A summary of 8.0 dpc embryos grouped by somite number and genotype and scored for extension of the allantois as early, late or fused (see methods). Each section of the stacked bar represents the proportion of those embryos at a specific allantois stage. The number in each set is shown at the top of the bar. (B,C) Anti-phospho-Histone H3 staining showing cells undergoing mitosis. The wild-type (B) and the mutant (C) allantoises show similar numbers of mitotic cells, both in the base of the allantois and in the distal tip. (D,E) Sets of 0- to 8-somite embryos (somite number decreases to the right in each panel) TUNEL stained to indicate apoptotic cells. Although wild-type embryos (D) show few apoptotic cells, the mutant embryos (E) exhibit extensive cell death over the entire distal portion of the allantois. (F,G) Bmp4 is expressed in the base of the allantois in wild-type (F) and mutant (G) embryos. (H,I) Tbx2 is expressed in the distal two-thirds of the wild-type allantois at the 2-somite stage (H), but is extremely faint in mutant allantoises (I). (J,K) The cell adhesion molecule VCAM1 is expressed in the distal tip of the allantois in wild-type (J), but not mutant (K), embryos. (L,M) Endogenous alkaline phosphotase staining marks the PGCs, which are similar in location and number in wild-type (L) and mutant (M) embryos. (N-P) PECAM marks differentiating endothelial cells, which in the wild type appear in clumps at the 0-somite stage (N); they elongate into small vessels at the 4-somite stage (O) and resolve into a central vessel at the 8-somite stage (P). In Tbx4 mutants (N-P), normal looking clumps appear at 0 somites, whereas at 4 somites more clumps have appeared but no elongated vessels are seen. At the 8-somite stage, no central vessel is seen.

Return to article