An abnormal dorsoventral pigment pattern is readily apparent in at/at; deH/deH mice, but comparison to nonmutant animals is more accurately described in terms of ventral, lateral, and dorsal regions (Figures 1G and 2A). The ventral region has short hairs with a gray base and cream-colored tip whose boundary coincides with the limb–body wall junction; both the appearance of this region and position of the boundary are approximately similar in at/at compared to at/at; deH/deH mice. The lateral region contains yellow hairs of progressively increasing length; in at/at mice, the lateral region appears as a thin yellow stripe along the flank, but in at/at; deH/deH mice, the lateral region is considerably expanded with a diffuse boundary along the dorsal flank, and a dorsal eumelanic region whose size is correspondingly reduced (Figure 2A and 2B). Total body size is smaller in mutant compared to nonmutant animals, but the proportion of body circumference occupied by the lateral region in mutant animals is increased about 2-fold, from 11.9% to 22.2% (Figure 2C). The proportion of the ventral cream-colored region is also expanded a small amount, 47.9% in mutant compared to 37.8% in nonmutant animals, but expansion of the lateral region, which occurs at all levels of the body, including the limbs and the cranium (but not the whisker pad), is the major feature responsible for the ventralized appearance caused by deH.