Fig. 5 . Mi-2ß depletion causes severe effects on hair follicle morphogenesis. (A) Hematoxylin and Eosin-stained sagittal sections of dorsal skin from WT and mutant at E18.5 and P1. The number next to the follicles designates their developmental stage according to Hardy (Hardy, 1992). (B,C) The number of hair follicles per unit length (B) and the percentage of follicles at distinct developmental stages (C) were evaluated from E18.5 through P1. The number of hair follicles in the mutant was reduced by approximately 50% relative to WT from E18.5 through P1. At E18.5 in the WT, primary follicles have developed to stage 3 or 4, whereas secondary follicles have reached stage 1-2. In the mutant, a reduction was detected from stage 3a onwards. By P1 in the WT, primary, secondary and tertiary follicles have developed to stages 5-6, 3-4, and 1-2, respectively. However, by P1 in the mutant, follicles at stage 1 and after stage 3c were severely reduced relative to WT.