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. Author manuscript; available in PMC: 2018 Oct 9.
Published in final edited form as: Dev Cell. 2017 Oct 9;43(1):48–59.e5. doi: 10.1016/j.devcel.2017.09.003

Figure 7. Model showing how Yap maintains and generates basal like stem cells by activating the stromal niche during homeostasis and epithelial regeneration.

Figure 7

(A) During homeostasis, basal stem/progenitor cells are only found in the trachea, where they maintain themselves by inducing Fgf10 expression in the tracheal stromal niche downstream of Yap. Ilk positively regulates the Hippo pathway in conducting airway epithelial cells to maintain their quiescence by inhibiting Yap-mediated activation of Fgf10 expression in ASMCs.

(B) Hippo pathway inactivation in conducting non-cartilaginous airway epithelium in response to injury or by deleting Ilk (4) or Mst1/2 (5) results in nuclear Yap localization, increased epithelial Wnt7b expression and Fgf10 expression in ASMCs, which reciprocally breaks epithelial quiescence. The Fgf10-expressing basal stem cell niche extends into the non-cartilaginous airways allowing for BSC mobilization into the lower conducting airways upon airway epithelial Ilk deletion. Alternatively, Fgf10 released by the activated ASMC niche could drive the differentiation of LNEPs, which are scattered along the lower conducting airways, into the basal stem/progenitor cell lineage.