Chan, S. F. | Search bioRxiv

bioRxiv2024

Desmoplakin mutations in cardiac fibroblasts cause TGF?1-mediated pathological fibrogenesis in desmoplakin cardiomyopathy via beclin-1 regulation

BackgroundPathological fibrosis is a major finding in cardiovascular diseases and can result in arrhythmia and heart failure. Desmosome gene mutations can lead to arrhythmogenic cardiomyopathy (ACM). Among ACM, pathogenic desmoplakin (DSP) variants cause a distinctive cardiomyopathy with excessive cardiac fibrosis that could precede ventricular dysfunction. DSP variants are also linked to other fibrotic diseases. Whether DSP plays any role in pathological fibrosis remain unknown. MethodsMesenchymal stromal cells (MSCs) are resident fibroblast-like cells that are responsible for fibrogenesis in most organs, including hearts. We first used unbiased genome-wide analyses to generate cardiac fibroblasts-like, induced pluripotent stem cell-derived MSCs from normal donors and ACM patients with DSP mutations. We then studied the fibrogenic responses of cardiac MSCs to transforming growth factor beta-1 (TGF-{beta}1) using Western/Co-IP, autophagy assay, gene knockdowns/over-expressions, genomic analyses, mouse DSP knockdown models, immunostaining, and qPCR. ResultsTGF{beta}1 induced excessive accumulations of vimentin (VIM)/fibrillar collagens, and over-activated fibrotic genes in DSP-mutant MSCs when compared to normal MSCs. In normal MSCs, VIMs bind to wild-type DSP during normal fibrogenesis after TGF{beta}1. DSP-mutant MSCs exhibited a haplo-insufficient phenotype with increased DSP-unbound VIMs that sequestered beclin-1 (BECN1) from activating autophagy and caveolin-1 (CAV1)-mediated endocytosis. Decreased autophagy caused collagen accumulations and diminished CAV1 endocytosis resulted in abnormal CAV1 plaque formation that over-activated fibrotic genes [COL1A1, COL3A1, and fibronectin (FN)] via heightened p38 activities after TGF{beta}1. Genome-wide analysis and DSP knockdown in mouse fibroblasts confirmed this novel role of DSP mutations in pathological fibrosis. Overexpression of VIM-binding domains of DSP could suppress pathological fibrosis by increasing collagen autophagic degradation and decreasing fibrotic gene expressions. ConclusionsOur data reveal that DSP deficiency in MSCs/fibroblasts leads to exaggerated fibrogenesis in DSP-cardiomyopathy by decreasing BECN1 availability for autophagy and CAV1-endocytosis. Overexpression of VIM binding domains of DSP could be a new strategy to treat pathological fibrosis.

cell biology↗

bioRxiv2020

Aberrant gliogenesis and excitation in MEF2C autism patient hiPSC-neurons and cerebral organoids

MEF2C has been shown to be a critical transcription factor for neurodevelopment, whose loss-of-function mutation in humans results in MEF2C haploinsufficiency syndrome (MHS), a severe form of autism spectrum disorder (ASD)/intellectual disability (ID). Here, we use patient hiPSC-derived cerebrocortical neurons and cerebral organoids to characterize MHS deficits. Unexpectedly, we found an aberrant micro-RNA-mediated gliogenesis pathway that contributes to decreased neurogenesis. We also demonstrate network-level hyperexcitability in neurons, as evidenced by excessive synaptic and extrasynaptic activity contributing to excitatory/inhibitory (E/I) imbalance. Notably, the extrasynaptic NMDA receptor antagonist, NitroSynapsin, corrects this aberrant electrical activity associated with abnormal phenotypes. During neurodevelopment, MEF2C regulates many ASD-associated gene networks suggesting that our approach may lead to personalized therapy for multiple forms of ASD. One sentence summaryAutism-like MEF2C+/- patient hiPSC models show miRNA-mediated overproduction of astrocytes and hyperactivity of neurons.

neuroscience↗