Pigmentation and testis defects in Slug-deficient mice.

(A) Pigmentation deficiencies in Slug homozygous mutant mice. Wild-type mice (+/+) with no defective pigmentation (i); the characteristic white forehead blaze in Sl/+ and W/+ mice (ii-iii); lack of pigmentation of skin in Sl homozygous mutant mice (Sl/Sl^d); and Slug homozygous mutant mice with the characteristic white forehead blaze (iv). (B) Histologic analysis of testis of wild-type and Slug mutant mice. Matched testis sections from 6-week-old wild-type mice (Slug +/+), Slug heterozygous mice (Slug +/−), Slug homozygous mice (−/−), Steel-Dickie mice23(Sl/Sl^d), and W mutant mice (W/W^v) were stained with hematoxylin and eosin. The histologic section of Slug +/+ testis shows the presence of normal seminiferous tubules (blue arrowhead) where germ cell development begins at the periphery of the tubule and where spermatogonia reside. These cells give rise to the progressively more differentiated spermatocytes and spermatids that populate the more superficial tubular layers and ultimately yield mature spermatozoa that can normally be visualized in the tubular lumina (black arrowhead). Leydig cells are present in the interstitial space (red arrowhead). As in Sl/Sl^d and W/W^v mice, there is an overall reduction in size of the seminiferous tubules in Slug−/− mice, a characteristic that can be also observed in some Slug+/− mice (Slug+/− center with normal tubules versus Slug+/− right with small tubules). In the interstitial space of Slug−/− mice, there is a reduced number of Leydig cells. On the contrary, the interstitial space of Steel-Dickie and W mutant mice testis is disproportionately increased and filled with Leydig cells. Original magnification × 40.