Brislinger, M. | bioRxiv Science

bioRxiv2020

A changing signaling environment induces multiciliated cell trans-differentiation during developmental remodeling

Multiciliated cells (MCCs) are extremely highly-differentiated, presenting >100 cilia and basal bodies. We analyzed how MCCs are lost from the airway-like Xenopus embryonic epidermis during developmental tissue remodeling. We found that some MCCs undergo apoptosis, but that the majority trans-differentiate into secretory cells. Trans-differentiation involves loss of ciliary gene expression, cilia retraction and lysosomal degradation. Apoptosis and trans-differentiation are both induced by a changing signaling environment through Notch, Jak/STAT, Thyroid hormone and mTOR signaling, and trans-differentiation can be inhibited by Rapamycin. This demonstrates that even cells with extreme differentiation features can undergo direct fate conversion. Our data further suggest that the reactivation of this developmental mechanism in adults can drive tissue remodeling in human chronic airway disease, a paradigm resembling cancer formation and progression.

developmental biology↗

bioRxiv2019

ΔN-Tp63 mediates Wnt/β-catenin-induced inhibition of differentiation in basal stem cells of mucociliary epithelia

Mucociliary epithelia provide a first line of defense against pathogens in the airways and the epidermis of vertebrate larvae. Impaired regeneration and remodeling of mucociliary epithelia are associated with dysregulated Wnt/{beta}-catenin signaling in chronic airway diseases, but underlying mechanisms remain elusive and studies of Wnt signaling in mucociliary cells yield seemingly contradicting results. Employing the Xenopus mucociliary epidermis, the mouse airway, and human airway basal stem cell cultures, we characterize the evolutionarily conserved roles of Wnt/{beta}-catenin signaling in mucociliary cells in vertebrates. Wnt signaling is required in multiciliated cells for cilia formation during differentiation stages, but in Basal cells, Wnt signaling prevents specification and differentiation of epithelial cell types by activating{Delta} N-TP63 expression. We demonstrate that {Delta}N-TP63 is a master transcription factor in Basal cells, which is necessary and sufficient to mediate the Wnt-induced inhibition of differentiation and is required to retain basal stem cells during development. Chronic stimulation of Wnt signaling leads to mucociliary remodeling and Basal cell hyperplasia, but this is reversible in vivo and in vitro, suggesting Wnt inhibition as an option in the treatment of chronic lung diseases. Our work sheds light into the evolutionarily conserved regulation of stem cells and differentiation, resolves Wnt functions in mucociliary epithelia, and provides crucial insights into mucociliary development, regeneration and disease mechanisms.

developmental biology↗