Single-cell sequencing WT and PADI4 cKO skin, P1
Tissue formation requires a coordinated balance of progenitor cell proliferation and differentiation. Posttranslational protein modifications have emerged as a mechanism utilized to regulate progenitor cell state transitions. Herein, we exploit the well characterized and stereotyped hair follicle development to delineate the function of PADI4; an enzyme converting peptidylarginine to citrulline. Single cell-sequencing places Padi4 in both progenitor and differentiated hair lineage cells during hair follicle development. We show that the absence of PADI4 induces gene expression across hair follicle cell clusters, suggesting that PADI4 acts to negatively impact transcription. In addition, we establish PADI4 as a negative regulator of proliferation, acting of LEF1-positive hair shaft committed progenitor cells. Mechanistically, PADI4 citrullinates proteins associated with mRNA-processing and ribosomal biogenesis, and lack of PADI4 promotes protein synthesis and rRNA transcription in vivo, in both hair follicle progenitor and committed lineage cells. Characterizing key translational effectors, we demonstrate that PADI4 interacts with 4E-BP1 and reveal a crosstalk between PADI4 activity and 4E-BP1 phosphorylation. We report that PADI4 contributes to hair follicle development by repressing progenitor cell proliferation and translational activity. This work sheds new light on how posttranslational modifications impact progenitor cell states and tissue formation. Overall design: At postnatal day 1, K14-Cre Padi4 fl/fl, tdTOMATO  mouse back skins were dissected and used for single-cell preparation. tdTOMATO cells were isolated and used for library preparation.