Sun2^−/− mice exhibit alopecia and abnormal hair follicle structure. (A) Immunostaining of mouse back skin revealed NE localized SUN1 (also greyscale inset, arrows) was expressed in the epidermis. Asterisk indicates nonspecific staining. Dotted lines delineate hair follicles. (B) SUN2 was strongly expressed in the epidermis, dermis, and hair follicle. Dotted lines delineate hair follicles. Bar, 100 μm. (C) Sun2^−/− mice developed alopecia at P16 yet regained a normal coat by the second hair cycle (P32). (D) Hematoxylin and eosin–stained back skin from WT and Sun2^−/− mice show hair shaft breaks at P16 (IV and VI, arrow) and P18 (VIII and X, arrow). (E) Quantification of broken follicles in WT and Sun2^−/− mice. n > 160 follicles in three mice per genotype. (F and G) Immunostaining of back skin from WT and Sun2^−/− mice for keratin 6 (K6) and Hoechst illustrated acute bends in Sun2^−/− follicles (G, arrows), whereas WT follicles remained linear (F, arrow). (H) Percentage of total follicles with at least one bend <130°. n > 98 follicles in three mice per genotype. Error bars indicate SDs. Statistical significance determined by unpaired, two-tailed t test.