The skin serves as a powerful barrier against microbial, physical, and chemical insults and is maintained through constant proliferation and differentiation of epidermal cells. However, the mechanisms that regulate skin homeostasis are not fully understood. In this episode, Hisahiro Yoshida describes the development and characterization of a strain of mice that exhibit progressive pruritic dermatitis due to the presence of a mutation that results in hyperactivation of JAK1 tyrosine kinase. Treatment of these mice with JAK1 inhibitors delayed disease onset, indicating that JAK1-mediated signaling plays an important role in maintenance of skin barrier function.
Skin homeostasis is maintained by the continuous proliferation and differentiation of epidermal cells. The skin forms a strong but flexible barrier against microorganisms as well as physical and chemical insults; however, the physiological mechanisms that maintain this barrier are not fully understood. Here, we have described a mutant mouse that spontaneously develops pruritic dermatitis as the result of an initial defect in skin homeostasis that is followed by induction of a Th2-biased immune response. These mice harbor a mutation that results in a single aa substitution in the JAK1 tyrosine kinase that results in hyperactivation, thereby leading to skin serine protease overexpression and disruption of skin barrier function. Accordingly, treatment with an ointment to maintain normal skin barrier function protected mutant mice from dermatitis onset. Pharmacological inhibition of JAK1 also delayed disease onset. Together, these findings indicate that JAK1-mediated signaling cascades in skin regulate the expression of proteases associated with the maintenance of skin barrier function and demonstrate that perturbation of these pathways can lead to the development of spontaneous pruritic dermatitis.
Takuwa Yasuda, Toshiyuki Fukada, Keigo Nishida, Manabu Nakayama, Masashi Matsuda, Ikuo Miura, Teruki Dainichi, Shinji Fukuda, Kenji Kabashima, Shinji Nakaoka, Bum-Ho Bin, Masato Kubo, Hiroshi Ohno, Takanori Hasegawa, Osamu Ohara, Haruhiko Koseki, Shigeharu Wakana, Hisahiro Yoshida