摘要
The hair follicle is a biological oscillator that alternates growth,regression,and rest phases driven by the sequential activation of the proliferation differentiation programs of resident stem cell populations.The activation of hair follicle stem cell niches and subsequent entry into the growing phase is mainly regulated by Wnt/β-catenin signalling,while regression and resting phases are mainly regulated by Tgf-β/Bmp/Smad activity.A major question still unresolved is the nature of the molecular switch that dictates the coordinated transition between both signalling pathways.Here we have focused on the role of Endoglin(Eng),a key co-receptor for members of the Tgf-β/Bmp family of growth factors.Using an Eng haploinsufficient mouse model,we report that Eng is required to maintain a correct follicle cycling pattern and for an adequate stimulation of hair follicle stem cell niches.We further report thatβ-catenin binds to the Eng promoter depending on Bmp signalling.Moreover,we show thatβ-catenin interacts with Smad4 in a Bmp/Eng-dependent context and both proteins act synergistically to activate Eng promoter transcription.These observations point to the existence of a growth/rest switching mechanism in the hair follicle that is based on an Eng-dependent feedback cross-talk between Wnt/β-catenin and Bmp/Smad signals.
