Biology subjects

Cha, B.

Publications and source records attributed to Cha, B..

5 recordsLinked to original sources

bioRxiv2025

PPARδ activation in microglia drives a transcriptional response that primes phagocytic function while countering inflammatory activation

Microglia have been implicated in neurodegeneration, though their role remains unclear, as microglia can perform protective functions or promote neuroinflammation. Numerous studies have found that the transcriptome state of microglia can indicate where they lie along this continuum. To understand regulation of microglia transcriptome state, we considered the transcription factor PPAR8, because it is highly expressed in microglia and is a therapeutic target for Alzheimers disease, (AD) a neurodegenerative disorder characterized by progressive memory loss where microglia dysfunction is involved. When we delineated the microglia transcriptome in mice treated with PPAR8 agonist, we noted that PPAR8 activation blunted expression of inflammatory mediators and migration-enhancing genes, while boosting phagocytic genes. We then examined PPAR8 function in induced transcription factor (iTF) microglia-like cells, and confirmed PPAR8 agonism increases phagocyte function while reducing pro-inflammatory cytokines and migration. To understand PPAR8 regulation upon CNS insult, we exposed iTF-microglia to apoptotic neuron debris and defined six microglia transcriptome states as a function of PPAR8 activation, and observed PPAR8 agonism can shift microglia out of a homeostatic state to a primed, disease-associated microglia-like state. As PPAR8 agonism opposed gene expression favored by PU.1, a critical transcription factor in microglial inflammation and AD pathogenesis, we examined their relationship, documented a physical interaction, and found evidence for transrepression. Finally, we tested PPAR8 agonism in Huntingtons disease and tauopathy mice, and demonstrated PPAR8 could decrease neuroinflammation in vivo. These findings suggest that PPAR8 agonist therapy may mitigate microglial dysfunction by restoring beneficial functions, while suppressing detrimental inflammation.

neuroscience↗

bioRxiv2025

Dual Probe Ligation In Situ Hybridization with Rolling-Circle Amplification for High-Plex Spatial Transcriptomics

New biological insights are increasingly dependent upon a deeper understanding of tissue architectures. Critical to such studies are spatial transcriptomics technologies, especially those amenable to analysis of the most widely available human tissue type, formalin-fixed and paraffin-embedded (FFPE) clinical specimens. Here we build on our previous oligonucleotide probe ligation-based approach to accurately analyze FFPE mRNA, which suffers from variable levels of degradation. Ligation In Situ Hybridization followed by rolling circle amplification (LISH-LocknRoll or LISH-LnR), provides a streamlined method to detect the spatial location of specific mRNA isoforms within FFPE tissue architectures. Iterative fluorescent probe hybridization and imaging enables highly multiplexed spatial transcriptomic studies, as demonstrated herein for fixed specimens from inclusion body myositis patients and pediatric rhabdomyosarcoma patients. We additionally demonstrate a system of molecular rheostats that can be used to fine tune the performance of the LISH-LnR assay. Combined with LISH-seq and LISH-QC, the LISH-LnR methodology provides a powerful approach to spatial transcriptomics.

molecular biology↗

bioRxiv2023

PROX1 inhibits PDGF-B expression to prevent myxomatous degeneration of heart valves

BackgroundCardiac valve disease (CVD) is observed in 2.5% of the general population and 10% of the elderly people. Effective pharmacological treatments are currently not available, and patients with severe CVD require surgery. PROX1 and FOXC2 are transcription factors that are required for the development of lymphatic and venous valves. We found that PROX1 and FOXC2 are expressed in a subset of valvular endothelial cells (VECs) that are located on the downstream (fibrosa) side of cardiac valves. Whether PROX1 and FOXC2 regulate cardiac valve development and disease is not known. MethodsWe used histology, electron microscopy and echocardiography to investigate the structure and functioning of heart valves from Prox1{Delta}VEC mice in which Prox1 was conditionally deleted from VECs. Isolated valve endothelial cells and valve interstitial cells were used to identify the molecular mechanisms in vitro, which were tested in vivo by RNAScope, additional mouse models and pharmacological approaches. The significance of our findings was tested by evaluation of human samples of mitral valve prolapse (MVP) and aortic valve insufficiency. ResultsHistological analysis revealed that the aortic and mitral valves of Prox1{Delta}VEC mice become progressively thick and myxomatous. Echocardiography revealed that the aortic valves of Prox1{Delta}VEC mice are stenotic. FOXC2 was downregulated and platelet-derived growth factor-B (PDGF-B) was upregulated in the VECs of Prox1{Delta}VEC mice. Conditional knockdown of FOXC2 and conditional overexpression of PDGF-B in VECs recapitulated the phenotype of Prox1{Delta}VEC mice. PDGF-B was also increased in mice lacking FOXC2 and in human MVP and insufficient aortic valve samples. Pharmacological inhibition of PDGF-B signaling with imatinib partially ameliorated the valve defects of Prox1{Delta}VEC mice. ConclusionPROX1 antagonizes PDGF-B signaling partially via FOXC2 to maintain the extracellular matrix composition and prevent myxomatous degeneration of cardiac valves. Novelty and SignificanceWhat Is Known? O_LIThe transcription factors PROX1 and FOXC2 are critical regulators of lymphatic and venous valve development. C_LIO_LIPROX1 and FOXC2 are expressed in the downstream valvular endothelial cells of heart valves. C_LI What Is New? O_LIDeletion of Prox1 from the valvular endothelial cells of mice results in enlarged and myxomatous aortic and mitral valves. Aortic valves of the mutant (Prox1{Delta}VEC) mice were stenotic. C_LIO_LIFOXC2 is partially responsible for the phenotype of Prox1{Delta}VEC mice. C_LIO_LIPROX1 and FOXC2 inhibit the expression of the cytokine PDGF-B in heart valves. C_LIO_LIHyperactivation of PDGF-B signaling results in aortic and mitral valve thickening. C_LIO_LIInhibition of PDGF-B signaling ameliorates aortic valve stenosis in Prox1{Delta}VEC mice. C_LIO_LIPDGFB is overexpressed and PROX1 is downregulated in human mitral valve prolapse (MVP) samples. C_LI Our findings suggest that PROX1 is an inhibitor of myxomatous valve disease that afflicts ~10% of the elderly population. We have also identified PDGF-B as a potential target for treating myxomatous valve disease.

developmental biology↗

bioRxiv2020

S1PR1 regulates the quiescence of lymphatic vessels by inhibiting laminar shear stress-dependent VEGF-C signaling

During the growth of lymphatic vessels (lymphangiogenesis), lymphatic endothelial cells (LECs) at the growing front sprout by forming filopodia. Those tip cells are not exposed to circulating lymph, as they are not lumenized. In contrast, LECs that trail the growing front are exposed to shear stress, become quiescent and remodel into stable vessels. The mechanisms that coordinate the opposed activities of lymphatic sprouting and maturation remain poorly understood. Here we show that the canonical tip cell marker Delta-Like 4 (DLL4) promotes sprouting lymphangiogenesis by enhancing Vascular Endothelial Growth Factor C (VEGF-C) /VEGF Receptor 3 (VEGFR3) signaling. However, in lumenized lymphatic vessels laminar shear stress (LSS) inhibits the expression of DLL4, as well as additional tip cell markers. Paradoxically, LSS also upregulates VEGF-C/VEGFR3 signaling in LECs, but sphingosine 1-phosphate (S1P) receptor 1 (S1PR1) activity antagonizes LSS-mediated VEGF-C signaling to promote lymphatic vascular quiescence. Correspondingly, S1pr1 loss in LECs induced lymphatic vascular hypersprouting and hyperbranching, which could be rescued by reducing Vegfr3 gene dosage in vivo. In addition, S1PR1 regulates lymphatic vessel maturation by promoting membrane localization of the tight junction molecule Claudin-5. Our findings suggest a new paradigm in which LSS induces quiescence and promotes the survival of LECs by downregulating DLL4 and enhancing VEGF-C signaling, respectively. S1PR1 dampens LSS/VEGF-C signaling, thereby preventing sprouting from quiescent lymphatic vessels. These results also highlight the distinct roles that S1PR1 and DLL4 play in LECs when compared to their known roles in the blood vasculature.

developmental biology↗

bioRxiv2019

GATA2 controls lymphatic endothelial cell junctional integrity and lymphovenous valve morphogenesis through miR-126

Mutations in the transcription factor GATA2 cause lymphedema. GATA2 is necessary for the development of lymphatic valves (LVs) and lymphovenous valves (LVVs), and for the patterning of lymphatic vessels. Here, we report that GATA2 is not necessary for valvular endothelial cell (VEC) differentiation. Instead, GATA2 is required for VEC maintenance and morphogenesis. GATA2 is also necessary for the expression of cell junction molecules VE-Cadherin and Claudin5 in lymphatic vessels. We identified miR-126 as a target of GATA2, and miR-126-/- embryos recapitulate the phenotypes of mice lacking GATA2. Primary human lymphatic endothelial cells (HLECs) lacking GATA2 (GATA2{Delta}HLEC) have altered expression of Claudin5 and VE-Cadherin, and blocking miR-126 activity in HLECs phenocopies these changes in expression. Importantly, overexpression of miR-126 in GATA2{Delta}HLEC significantly rescues the cell junction defects. Thus, our work defines a new mechanism of GATA2 and uncovers miR-126 as a novel regulator of mammalian lymphatic vascular development.\n\nNon-standard abbreviationsLECs, lymphatic endothelial cells; LVs, lymphatic valves; LV-ECs, lymphatic valve-forming endothelial cells; LVVs, lymphovenous valves; LVV-ECs, lymphovenous valve-forming endothelial cells; HLEC, primary human LECs; OSS, Oscillatory shear stress; IHC, immunohistochemistry.

developmental biology↗