Fig. 6. (A-C) Genetic interaction between Dkk1 and Lrp6 indicated by rescue of postaxial polysyndactyly in double mutants. All mice are homozygous for the doubleridge allele, Dkk1^d. The extra digit in the doubleridge single mutant is marked by the arrow. The frequency of partial and complete rescue is dependent on Lrp genotype (Table 2). E16.5 forelimbs were stained with alcian blue to reveal skeletal elements.