Notch signaling controls the balance of ciliated and secretory cell fates in developing airways

Abstract

Although there is accumulated evidence of a role for Notch in the developing lung, it is still unclear how disruption of Notch signaling affects lung progenitor cell fate and differentiation events in the airway epithelium. To address this issue, we inactivated Notch signaling conditionally in the endoderm using a Shh-Cre deleter mouse line and mice carrying floxed alleles of the Pofut1 gene, which encodes an O-fucosyltransferase essential for Notch-ligand binding. We also took the same conditional approach to inactivate expression of Rbpjk, which encodes the transcriptional effector of canonical Notch signaling. Strikingly, these mutants showed an almost identical lung phenotype characterized by an absence of secretory Clara cells without evidence of cell death, and showed airways populated essentially by ciliated cells, with an increase in neuroendocrine cells. This phenotype could be further replicated in cultured wild-type lungs by disrupting Notch signaling with a gamma-secretase inhibitor. Our data suggest that Notch acts when commitment to a ciliated or non-ciliated cell fate occurs in proximal progenitors, silencing the ciliated program in the cells that will continue to expand and differentiate into secretory cells. This mechanism may be crucial to define the balance of differentiated cell profiles in different generations of the developing airways. It might also be relevant to mediate the metaplastic changes in the respiratory epithelium that occur in pathological conditions, such as asthma and chronic obstructive pulmonary disease.

Generation of multiciliated cells in functional airway epithelia from human induced pluripotent stem cells

“…In addition, primary cilia have been observed in the luminal layers of epithelium and basal cells after lung injury (44). Inhibition of notch signaling is known to be involved in the switch from a primary ciliated cell to an MCC (24,27,28,45). DAPT inhibits notch signaling via its action on γ secretase.…”

mab21-l3 regulates cell fate specification of multiciliate cells and ionocytes

“…Because the Notch pathway is known to restrict MCC and ionocyte specification in various organs, including mouse lung 12,13 , mouse kidney 14 , zebrafish pronephros 10,11 and zebrafish skin 8,9 , the Notch/mab21-l3 signalling axis could have a conserved role in MCC/ionocyte specification in vertebrates.…”

“…Both cells are essential for human physiological processes, and malformation of them is associated with human diseases, including bronchiectasis, hydrocephalus and distal tubule acidosis 1,2 . Cell fate specifications of MCCs and ionocytes are known to be suppressed by the Notch pathway in various developing epithelia [5][6][7][8][9][10][11][12][13][14] . However, MCCspecific and ionocyte-specific transcriptional programmes are governed by different master regulators: a coiled-coil protein multicilin 15 and a forkhead transcription factor foxj1 (refs [16][17][18] for MCCs and another forkhead transcription factor foxi1 (refs 7-9,19-21) for ionocytes.…”

The building blocks of mammalian lung development

“…Ectopic expression of the active Notch intracellular domain throughout the developing airways, resulted in increased numbers of secretory (mucous-producing) cells and a decrease in ciliated cell specification (Guseh et al, 2009). Conversely, when Notch signaling was ablated throughout the entire lung epithelium by conditional deletion of Pofut1 (which attaches O-fucose to the EGF repeats of Notch), or Rbpjk (the Notch transcriptional effector), the bronchiolar epithelium largely differentiated as ciliated cells at the expense of the secretory (Clara) cells (Tsao et al, 2009;Morimoto et al, 2010). In the loss-of-function experiments, the multipotent progenitors were unaffected, alveolar development continued normally, and the mice were born with normal-sized lungs.…”