Biology subjects

Zepp, J. A.

Publications and source records attributed to Zepp, J. A..

3 recordsLinked to original sources

bioRxiv2023

Dynamic Hippo pathway activity underlies mesenchymal differentiation during lung alveolar morphogenesis

Alveologenesis, the final stage in lung development, substantially remodels the distal lung, expanding the alveolar surface area for efficient gas exchange. Secondary crest myofibroblasts (SCMF) exist transiently in the neonatal distal lung and are critical for alveologenesis. However, the pathways that regulate SCMF function, proliferation, and temporal identity remain poorly understood. To address this, we purified SCMFs from reporter mice, performed bulk RNA-sequencing, and found dynamic changes in Hippo-signaling components during alveologenesis. We deleted Hippo effectors, Yap/Taz, from Acta2-expressing SCMFs at the onset of alveologenesis, causing a significant arrest in alveolar development. Using scRNA-seq, we identified a distinct cluster of cells in mutant lungs with altered expression of marker genes associated with proximal mesenchymal cell types, airway smooth muscle (ASM), and alveolar duct myofibroblasts (DMF). Using lineage tracing, we show that neonatal Acta2-expressing SCMFs give rise to adult DMFs and that Yap/Taz mutants have an increase of persisting DMF-like cells in the alveolar ducts. Our findings identify plasticity in neonatal lung myofibroblasts and demonstrate that Yap/Taz are critical for maintaining lineage commitment along the proximal-distal axis.

developmental biology↗

bioRxiv2023

Dysregulated alveolar epithelial maintenance in Hermansky-Pudlak syndrome pulmonary fibrosis

Hermansky-Pudlak syndrome (HPS) is a genetic disorder of endosomal protein trafficking associated with pulmonary fibrosis in specific subtypes, including HPS-1 and HPS-2. Single mutant HPS1 and HPS2 mice display increased fibrotic sensitivity while double mutant HPS1/2 mice exhibit spontaneous fibrosis with aging, which has been attributed to HPS mutations in alveolar epithelial type II (AT2) cells. We utilized HPS mouse models and human lung tissue to investigate mechanisms of AT2 cell dysfunction driving fibrotic remodeling in HPS. Starting at 8 weeks of age, HPS mice exhibited progressive loss of AT2 cell numbers. HPS AT2 cell function was impaired ex vivo and in vivo. Incorporating AT2 cell lineage tracing in HPS mice, we observed aberrant differentiation with increased AT2-derived alveolar epithelial type I cells. Transcriptomic analysis of HPS AT2 cells revealed elevated expression of genes associated with aberrant differentiation and p53 activation. Lineage tracing and organoid modeling studies demonstrated that HPS AT2 cells were primed to persist in a Krt8+ reprogrammed transitional state, mediated by p53 activity. Intrinsic AT2 progenitor cell dysfunction and p53 pathway dysregulation are novel mechanisms of disease in HPS-related pulmonary fibrosis, with the potential for early targeted intervention before the onset of fibrotic lung disease.

cell biology↗

bioRxiv2022

A CXCL12 morphogen gradient uncovers lung endothelial heterogeneity and promotes distal vascular growth

In adults, there is a growing amount of data uncovering the cellular diversity of the pulmonary circulation and mechanisms governing vascular repair after injury, however, molecular and cellular mechanisms contributing to the morphogenesis and growth of the pulmonary vasculature during embryonic development are less clear. Importantly, deficits in vascular development lead to a large number of lung diseases in children, indicating a need to uncover fetal programs that promote pulmonary vascular growth. To address this, we used a transgenic mouse reporter for expression of Cxcl12, an arterial hallmark gene, and performed single-cell RNA sequencing on isolated Cxcl12-DsRed+ endothelium to assess cellular heterogeneity within pulmonary endothelium. Combining cell annotation, gene ontology analysis, and spatial transcriptomics allowed us to segregate the developing artery into spatially and functionally distinct novel subpopulations. In addition, expression of Cxcl12 suggests a morphogen gradient from arteries to capillaries, suggesting directed cell migration for pulmonary vascular development. Disruption of this gradient led to abnormal branching and pulmonary vascular hypoplasia. These data provide evidence for arterial endothelial functional heterogeneity and reveal conserved signaling mechanisms essential for pulmonary vascular development.

developmental biology↗