Eda-activated RelB recruits an SWI/SNF (BAF) chromatin-remodeling complex and initiates gene transcription in skin appendage formation

Skin-specific Eda signaling promotes skin appendage development through NF-kB mediated gene transcription. We find that Eda triggers the formation of a novel SWI/SNF complex in which RelB is recruited through a linker protein, Tfg, to interact with the BAF45d component in SWI/SNF (BAF) chromatin remodeling complex. BAF component BAF250a is particularly enriched in skin appendages, and epidermal knockout (cKO) of BAF250a impairs skin appendage development, resulting in phenotypes similar to those of Eda-deficient mouse models. We further reveal that Eda signaling is predominantly mediated by the p50/RelB subclass of NF-kB in both human keratinocytes and mouse skin. Consistent with the phenotype of BAF250a cKO mice, downregulation of RelB, Tfg, or BAF45d arrests the growth of Meibomian gland germs in organ cultures. Transcription profiling consistently identifies several target genes regulated by Eda, RelB and SWI/SNF. In particular, we show that both RelB and SWI/SNF are indispensable for transcription of Eda target Ltb. Chromatin remodeling SWI/SNF recruited to specific gene loci by Eda-activated RelB thus provides a mediation model between an initiation signal and gene activation in organogenesis. A human keratinocyte line that stably expresses Edar protein (Edar-HaCat) was created and cultured along with the original HaCaT cell line. HaCaT cells were transfected with scrambled siRNA (Empty), while Edar-HaCat cells were transfected with scrambled siRNA (EDAR), or SMARTpooled siRNAs against hRelB (RelBi) or hBRG1 (BRG1) for 48 h prior to extraction of RNA (N = 3 biological repeats per group).