Biology subjects

Hepperla, A. J.

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

3 recordsLinked to original sources

bioRxiv2026

Integrin α3β1 is required for alveolar-capillary barrier formation through regulation of epithelial differentiation

Laminin-binding integrins regulate critical morphogenic processes, but their specific roles in lung development are unknown. In this study, we combined an in vivo model of epithelial 3 subunit deletion in the murine lung with a multiomics approach to investigate the role of the epithelial 3{beta}1 integrin during murine lung development. We demonstrate that 3{beta}1 integrin is dispensable for airway branching morphogenesis due to delayed epithelial expression. Instead, in vivo deletion of 3{beta}1 integrin impaired alveolar epithelial cell differentiation and disrupted alveolar-capillary barrier formation, functionally limiting gas exchange. A discontinuous alveolar BM contained abnormal collagen IV and laminin networks and widened the gap between epithelial and endothelial cells in the alveolar-capillary barrier niche. Mechanistically, mice deficient in epithelial 3{beta}1 integrin possessed an intracellular trafficking and secretion defect for BM components. Thus, integrin 3{beta}1 orchestrates the temporal maturation of alveolar epithelial cells required for organization of the alveolar-capillary barrier.

developmental biology↗

bioRxiv2021

CHD4 is recruited by GATA4 and NKX2-5 silencers to repress non-cardiac gene programs in the developing heart

The Nucleosome Remodeling and Deacetylase (NuRD) complex is one of the central chromatin remolding complexes that mediate gene repression. NuRD is essential for numerous developmental events, including heart development. Clinical and genetic studies have provided direct evidence for the role of chromodomain helicase DNA-binding protein 4 (CHD4), the catalytic component of NuRD, in congenital heart disease (CHD), including atrial and ventricular septal defects. Further, it has been demonstrated that CHD4 is essential for mammalian cardiomyocyte formation and function. A key unresolved question is how CHD4/NuRD is localized to specific cardiac targets genes, as neither CHD4 nor NuRD can directly bind DNA. Here, we coupled a bioinformatics-based approach with mass spectrometry analyses to demonstrate that CHD4 interacts with the core cardiac transcription factors GATA4, NKX2-5 and TBX5 during embryonic heart development. Using transcriptomics and genome-wide occupancy data, we have characterized the genomic landscape of GATA4, NKX2-5 and TBX5 repression and defined the direct cardiac gene targets of GATA4-CHD4, NKX2-5-CHD4 and TBX5-CHD4 complexes. These data were used to identify putative cis-regulatory elements regulated controlled by these complexes. We genetically interrogated two of these silencers in vivo, Acta1 and Myh11. We show that deletion of these silencers leads to inappropriate skeletal and smooth muscle gene mis-expression, respectively, in the embryonic heart. These results delineate how CHD4/NuRD is localized to specific cardiac loci and explicates how mutations in the broadly expressed CHD4 protein lead to cardiac specific disease states.

genomics↗

bioRxiv2020

An optogenetic switch for the Set2 methyltransferase provides evidence for rapid transcription-dependent and independent dynamics of H3K36 methylation

Histone H3 lysine 36 methylation (H3K36me) is a conserved histone modification associated with transcription and DNA repair. Although the effects of H3K36 methylation have been studied, the short-term genome-wide dynamics of H3K36me deposition and removal are not known. We established rapid and reversible optogenetic control for Set2, the sole H3K36 methyltransferase in yeast, by fusing the enzyme with the light activated nuclear shuttle (LANS) domain. Early H3K36me3 dynamics identified rapid methylation in vivo, with total H3K36me3 levels correlating with RNA abundance. Although genes exhibited disparate levels of H3K36 methylation, relative rates of H3K36me3 accumulation were largely linear and consistent across genes, suggesting a rate-limiting mechanism for H3K36me3 deposition. Removal H3K36me2/3 was also rapid and highly dependent on the demethylase Rph1. However, the per-gene rate of H3K36me3 loss weakly correlated with RNA abundance and followed exponential decay, suggesting H3K36 demethylases act in a global, stochastic manner.

molecular biology↗