Wnt5a Promotes AT1 and Represses AT2 Lineage-Specific Gene Expression in a Cell-Context-Dependent Manner

Abstract

Lung maturation is not limited to proper structural development, but also includes differentiation and functionality of various highly specialized alveolar cell types. Alveolar type 1 cells (AT1s) occupy nearly 95% of the alveolar surface and are critical for establishing efficient gas exchange in the mature lung. AT1 cells arise from progenitors specified during the embryonic stage as well as alveolar epithelial progenitors expressing surfactant protein C (Sftpc pos cells) during postnatal and adult stages. Previously, we found that Wnt5a, a non-canonical Wnt ligand, is required for differentiation of AT1 cells during the saccular phase of lung development. To further investigate the role of Wnt5a in AT1 cell differentiation, we generated and characterized a conditional Wnt5a gain-of-function mouse model. Neonatal Wnt5a gain-of-function disrupted alveologenesis through inhibition of cell proliferation. In this setting Wnt5a downregulated beta-catenin-dependent canonical Wnt signaling, repressed AT2 (anti-AT2) and promoted AT1 (pro-AT1) lineage-specific gene expression. In addition, we identified two subpopulations of Sftpc high and Sftpc low alveolar epithelial cells. In Sftpc low cells, Wnt5a exhibits pro-AT1 and anti-AT2 effects, concurrent with inhibition of canonical Wnt signaling. Interestingly, in the Sftpc high subpopulation, although increasing AT1 lineage-specific gene expression, Wnt5a gain-of-function did not change AT2 gene expression, nor inhibit canonical Wnt signaling. Using primary epithelial cells isolated from human fetal lungs we demonstrate that this property of Wnt5a is evolutionarily conserved. Wnt5a therefore serves as a selective regulator that ensures proper AT1/AT2 balance in the developing lung.

Atf3 defines a population of pulmonary endothelial cells essential for lung regeneration

“…In mice induced after H1N1 injury, however, the percentage of Atf3-positive pulmonary ECs in the distal lung was dramatically increased ( Figure 2C ). Although Atf3 expression has been reported in proliferating AT2 cells in mice infected with Streptococcus pneumoniae (Ali et al, 2022), we did not observe an increase in Atf3-positive AT2 cells or in Atf3-positive mesenchymal cells following influenza infection ( Figure 2 – S2A-B ). Our data also show that the increase in Atf3-expressing (CD45 - /tdTm + ) cells that we observed after H1N1 was specific to the endothelial compartment, and a similar increase did not occur in CD31 - non-ECs ( Figure 2C, Figure 2 – S2C-D ).…”

“…Temporal changes in TF expression may also alter the choice to proliferate or differentiate within a certain cell population. Specific TFs also differentially regulate activation of signaling pathways in the lung known to affect progenitor function, including Wnt signaling (Barkauskas et al, 2013; Frank et al, 2016; Li et al, 2022; Liberti et al, 2021; Nabhan et al, 2018; Wang et al, 2016; Zacharias et al, 2018).…”

Matrix fibroblast function during alveolarization is dependent on GATA6

“…PDGFRA + fibroblasts support alveolar type 2 (AT2) and alveolar type 1 (AT1) cell differentiation during alveolarization, homeostasis and injury repair (15,42,43,49,50).…”

“…PDGFRA + fibroblasts support alveolar type 2 (AT2) and alveolar type 1 (AT1) cell differentiation during alveolarization, homeostasis and injury repair (15, 42, 43, 49, 50). Immunohistochemistry for the AT2 cell marker proSPC and AT1 cell markers HOPX and AGER were performed on control and GATA6 PDGFRAΔ/Δ lungs at PN7 and PN28 (Fig.…”

WNT through the Ranks: A Mesenchymal FOXF1-WNT5A Axis Sways Hierarchical Decisions in Alveolar Epithelial Development

“…Wnt5a expression has been shown to be induced during AEC2-to-AEC1 differentiation in vitro upon treatment with IGF-I (insulin-like growth factor 1) ( 16 ). Moreover, in vivo studies have shown that loss of function of Wnt5a impairs AEC1 differentiation ( 15 ), while gain of function of WNT5a promotes AEC2-to-AEC1 differentiation ( 17 ). The latter study also showed that WNT5A inhibits canonical WNT signaling in a subset of AEC2s defined by low expression of Sftpc (surfactant protein C) ( 17 ).…”