Localizations of γ-Actins in Skin, Hair, Vibrissa, Arrector Pili Muscle and Other Hair Appendages of Developing Rats

Six isoforms of actins encoded by different genes have been identified in mammals including alpha-cardiac, alpha-skeletal, alpha-smooth muscle (alpha-SMA), beta-cytoplasmic, gamma-smooth muscle (gamma-SMA), and gamma-cytoplasmic actins (gamma-CYA). In a previous study we showed the localization of alpha-SMA and other cytoskeletal proteins in the hairs and their appendages of developing rats (Morioka K., et al. (2011) Acta Histochem. Cytochem. 44, 141-153), and herein we determined the localization of gamma type actins in the same tissues and organs by immunohistochemical staining. Our results indicate that the expression of gamma-SMA and gamma-CYA is suggested to be poor in actively proliferating tissues such as the basal layer of the epidermis and the hair matrix in the hair bulb, and as well as in highly keratinized tissues such as the hair cortex and hair cuticle. In contrast, the expression of gamma-actins were high in the spinous layer, granular layer, hair shaft, and inner root sheath, during their active differentiations. In particular, the localization of gamma-SMA was very similar to that of alpha-SMA. It was located not only in the arrector pili muscles and muscles in the dermis, but also in the dermal sheath and in a limited area of the outer root sheath in both the hair and vibrissal follicles. The gamma-CYA was suggested to be co-localized with gamma-SMA in the dermal sheath, outer root sheath, and arrector pili muscles. Sparsely distributed dermal cells expressed both types of gamma-actin. The expression of gamma-actins is suggested to undergo dynamic changes according to the proliferation and differentiation of the skin and hair-related cells.