Melanocyte-independent role of CRTC3 in melanogenesis. (A) Immunofluorescence staining using CRTC3 antibody (green) with tail skin of control and CRTC3 null mice (Bar = 50 µm). (B) mRNA levels of keratinocyte-derived melanogenic paracrine factors in the tail skin of CTRL and CRTC3 null mice and (C) in control and CRTC3KD HaCat keratinocytes. (D) Melanin content and (E) melanogenesis-related mRNA level in Mel-Ab cells co-cultured with either control or CRTC3KD keratinocytes 72 h after with or without FSK treatment. (F) Immunofluorescence staining of ACTH (red) and growth hormone (green) (left panel) and mRNA level of POMC (right panel) in the pituitary gland of CTRL and CRTC3 null mice (Bar = 100 µm). (G) Melanin content and (H) tyrosinase activity in control and CRTC3 knockdown Mel-Ab cells at 0, 24, 48, and 72 h after FSK treatment. (I) Melanin content and (J) tyrosinase activity in control and CRTC3 overexpressing Mel-Ab cells at 0, 24, 48, and 72 h after FSK treatment.