Figure 2.

Cre/loxP strategy successfully creates a functionally null M6P/IGF2R allele. A: Wild-type (WT) and M6P/IGF2R knockout (KO) mice at 18.5 days of gestation. Embryos inheriting a deleted M6P/IGF2R exon 10 allele from their mothers (KO) exhibited an overgrowth phenotype. They also frequently displayed extra post-axial digits on the fore and/or hind limbs (arrowhead); shorter, blunter tails often with a characteristic kink in the tip (*); and extravasation of overgrown abdominal organs (arrow). B: Wet weight measurements demonstrate that knockout (KO) embryos (n = 12) and their corresponding placentas are significantly (P < 0.0001) larger than those in WT mice (n = 20); standard errors of the mean are shown. C: Western blot analysis performed on tail tips from the 18.5-day-old embryos confirmed the absence of M6P/IGF2R protein in KO mice.