Table 1.

Phenotypes of TA and TR crosses

Genotype		Phenotype
Hoxc-8 transgene
TA/++/+		Viable
TA/TA+/+		Viable
+/+TR/+		Viable
+/+TR/TR*		Viable
TA/+TR/+*†		Open eyes at birth,  viable
TA/+TR/TR†		Open eyes,  neonatal lethal
TA/TATR/+†		Open eyes,  neonatal lethal
TA/TATR/TR‡		Open eyes,  perinatal lethal
Hoxd-4 transgene
+/+TR/+		Viable
TA/+TR/+‡		Open eyes,  neonatal lethal
Isl-1 transgene
+/+TR/+		Viable
TA/+TR/+†		Posterior growth  defect

All transgenes were on the FVB inbred background. In all TA mice used, VP16 expression is controlled by the Hoxc-8 promoter (14). The generation of TR strains was reported elsewhere (15). Results were obtained as follows: ∗, with two independent TA strains:  

^†, with two independent TR stains; or  

^‡, with one combination of TA and TR strain.