Fig. 1. Although loss of Sdc1 alters keratinocyte growth characteristics, Sdc1-null keratinocytes retain their epithelial morphology and keratin expression. (A,B) Equivalent numbers of primary wt (+/+) and Sdc1-null (–/–) keratinocytes were plated out and grown for the times indicated; in A keratinocytes are viewed with phase-contrast optics at 3 days after being placed in culture, and in B the numbers of adherent primary +/+ and –/– keratinocytes were counted at the indicated days. Data are plotted as the mean ± s.e.m.; ^*, significantly more Sdc1-null keratinocytes per dish than wt keratinocytes at days 3 and 10. Bar in A, 10 µm. (C) Studies using [³H]thymidine showed that at day 7, Sdc1-null keratinocytes proliferated more than wt keratinocytes, even after controlling for differences in keratinocyte density. (D) Triple-labeling using FITC-labeled phalloidin (green) for F-actin, K14 (red) for intermediate filament protein keratin 14, and DAPI (blue) for nuclei in +/+ keratinocytes (a-d) and on –/– keratinocytes (e-h). The localization of K14 appears similar in wt and Sdc1-null keratinocytes. Sdc1-null keratinocytes show thicker cortical actin filament bundles that localized prominently at keratinocyte peripheries compared with wt keratinocytes. ^*, regions shown magnified in d and h to better emphasize the actin cortical filaments. Bar in D, 4 µm (a-c and e-g) and 1.3 µm (d and h).