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Emergence of Wnt signaling during lung alveologenesis expands and maintains the type 2 alveolar epithelial cell population

ABSTRACT: Alveologenesis is the culmination of lung development and involves the correct temporal and spatial signals to generate the delicate gas exchange interface. Using a novel Wnt signaling reporter system, we have identified a Wnt-responsive alveolar epithelial sublineage arising during alveologenesis called the axin2+ alveolar type 2 cell or AT2Aaxin2. The number of AT2Aaxin2 sublineage cells increases substantially during late lung development, revealing a wave of Wnt signaling during alveologenesis. Transcriptome analysis, in vivo clonal analysis, and ex vivo lung organoid assays reveal that AT2sAaxin2s promote enhanced AT2 cellalveolar growth during generation of the alveolus compared to the overall AT2 population. Activating Wnt signaling in the AT2 lineage results in expansion of the AT2axin2 sublineageAT2s whereas inhibition of Wnt signaling inhibits AT2 cell development and shunts alveolar epithelial development towards the AT1 cell lineage. These findings reveal a novel epithelial sublineage that coordinates Wnt-dependent alveolar growthAT2 expansion required for lung alveologenesis

ORGANISM(S): Mus musculus

PROVIDER: GSE82154 | GEO | 2016/11/30

SECONDARY ACCESSION(S): PRJNA324194

REPOSITORIES: GEO

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Project description:Alveoli are thin-walled sacs that serve as the gas exchange units of the lung. They are affected in devastating lung diseases including COPD, Idiopathic Pulmonary Fibrosis, and the major form (adenocarcinoma) of lung cancer, the leading cause of cancer deaths. The alveolar epithelium is composed of two morphologically distinct cell types: alveolar type (AT) 1 cells, exquisitely thin cells across which oxygen diffuses to reach the blood, and AT2 cells, specialized surfactant-secreting cells. Classical studies suggested that AT1 cells arise from AT2 cells during development and following injury, but more recent studies suggest other sources. Here we use histological and marker analysis, lineage tracing, and clonal analysis in mice to identify alveolar progenitor and stem cells and map their locations and potential in vivo. The results show that AT1 and AT2 cells arise independently during development from a bipotential progenitor. After birth, new AT1 cells derive from rare, long-lived, self-renewing AT2 cells, each producing a slowly expanding clonal focus of regenerated alveoli contiguous with the founder AT2 cell. This stem cell function of AT2 cells is broadly activated by diffuse AT1 cell injury, and AT2 self-renewal can be induced in vitro by EGF ligands and permanently activated in vivo by AT2 cell-specific targeting of the oncogenic KrasG12D allele, efficiently transforming AT2 cells into monoclonal adenomatous tumors that rapidly enlarge and prove fatal. Thus, there is a developmental switch in alveolar progenitor cells after birth, when mature AT2 cells function as facultative stem cells that contribute to local alveolar renewal, repair, and cancer. We propose that short-range signals from dying AT1 cells regulate AT2 stem cell activity: a signal transduced by EGFR-KRAS controls AT2 self-renewal and is hijacked during oncogenic transformation, and a separate signal controls reprogramming to AT1 cell fate. To compare expression between ATII and E18 BP populations, RNA was isolated from either population purified by FACS. Two populations are analyzed with 3 biological replicates per population.

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Emergence of Wnt signaling during lung alveologenesis expands and maintains the type 2 alveolar epithelial cell population

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