Fibroblast-specific Deletion of Yap/Taz Impairs Mouse Postnatal Dermal Development by Suppressing Collagen Production and Deposition.

The Hippo pathway effectors YAP and TAZ are key regulators of cell proliferation, apoptosis, and differentiation, thereby maintaining tissue homeostasis and controlling organ size. While their roles in epithelial tissues and cancer are well established, their role in dermal fibroblast extracellular matrix (ECM) regulation is less understood. Here, we investigated the role of Yap/Taz during postnatal skin dermis development. During postnatal growth, mouse skin steadily grows and undergoes significant surface expansion. Postnatal deletion of Yap/Taz in dermal fibroblasts, the primary cells responsible for dermal ECM homeostasis, significantly impaired dermal maturation, as evidenced by marked deficiencies in collagen synthesis and deposition. Isolated fibroblasts from Yap/Taz knockout mice showed reduced proliferation and diminished expression of Yap/Taz target genes ( Ccn2 , Col1a1 ), which were rescued by reintroduction of active Yap/Taz . RNA-seq, and spatial transcriptomics and proteomics of Yap/Taz knockout skin revealed substantial downregulation of matrisome genes, including type I ( Col1a1, Col1a2) and type III ( Col1a3 ) collagens, which together constitute more than 90% of the skin's collagen content. These findings demonstrate that Yap/Taz are essential for dermal ECM homeostasis, highlighting their therapeutic potential in skin regeneration, fibrosis, and aging-related ECM decline.