Lpd functions to regulate melanoblast migration. (A) Conditional Lpd KO mice were generated by flanking exon 4 with loxP sites. Cre-mediated recombination of the loxP sites results in the removal of exon 4, creating a frame shift between exon 3 and 5 and premature termination. (B and C) Conditional Lpd KO mice crossed with β-actin-Cre mice on a mixed genetic background produced mice with a reduced body size (−20.6 ± 3.0% SEM; ****, P ≤ 0.0001, unpaired t test), which also display missing pigmentation on the ventral side (D). (E and F) To visualize melanoblasts, DCT-LacZ^tg/tg;β-actin-Cre^tg/+;Lpd^flox/flox whole-mount embryos at E14.5 were stained for β-galactosidase expression in the melanoblasts. (E) Areas within three 1 mm × 1.5 mm boxes positioned at the middle of the trunk between the fore and hind limbs were quantified in WT and KO animals. Bar, 1.5 mm. (F) Lpd KO mice show a significant reduction in the number of melanoblasts in all three boxes. Bar, 150 µm. Melanoblast numbers were reduced by ∼60%, ∼40%, and ∼30% for boxes 1, 2, and 3, respectively (20 KO or WT embryos from three litters; unpaired t test; *, P < 0.05; error bars indicate SEM). See also Fig. S4.