Table 1

In vitro recombination of 8.25- to 8.5-dpc mouse tissues demonstrates that endothelial signals induce pancreatic differentiation in isolated endoderm. Tissues used for Pdx1analysis are taken from progeny of matings of mice heterozygous for a lacZ insertion into the Pdx1 locus with ICR mice (half should contain the insertion). Ratios of explants expressing insulin (as determined by antibody staining) and Pdx1 (as determined by LacZ staining) versus total number of explants are shown. n.d., not done.

Recombined tissuesInsulin-expressing explants/total number of explantsPdx1-expressing explants/total number of explants
Endoderm + aorta7/1017/36
Endoderm0/5 0/8
Endoderm + umbilical artery3/6 4/8
Endoderm + mesenchyme3/6 3/6
Endoderm + notochord0/6 4/16
Endoderm + neural tube0/7 0/1
Aorta + neural tube0/3 n.d.
Aorta + somites0/4 n.d.