Biology subjects

Marian, A. J.

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

3 recordsLinked to original sources

bioRxiv2023

Histone demethylase KDM5 regulates cardiomyocyte maturation by promoting fatty acid oxidation, oxidative phosphorylation, and myofibrillar organization

RationaleHuman pluripotent stem cell-derived CMs (iPSC-CMs) are a valuable tool for disease modeling, cell therapy and to reconstruct the CM maturation process and identify, characterize factors that regulate maturation. The transition from immature fetal to adult CM entails coordinated regulation of the mature gene programming, which is characterized by the induction of myofilament and OXPHOS gene expression among others. Recent studies in Drosophila, C. elegans, and C2C12 myoblast cell lines have implicated the histone H3K4me3 demethylase KDM5 and its homologs, as a potential regulator of developmental gene program and mitochondrial function. We speculated that KDM5 may potentiate the maturation of iPSC-CMs by targeting a conserved epigenetic program that encompass mitochondrial OXPHOS and other CM specific maturation genes. ObjectivesThe purpose of this study is to determine the role of KDM5 in iPSC-CM maturation. Methods and ResultsImmunoblot analysis revealed that KDM5A, B, and C expression was progressively downregulated in postnatal cardiomyocytes and absent in adult hearts and CMs. Additionally, KDM5 proteins were found to be persistently expressed in iPSC-CMs up to 60 days after the onset of myogenic differentiation, consistent with the immaturity of these cells. Inhibition of KDM5 by KDM5-C70 -a pan-KDM5 inhibitor-resulted in differential regulation of 2,372 genes including upregulation of Fatty acid oxidation (FAO), OXPHOS, and myogenic gene programs in iPSC-CMs. Likewise, genome-wide profiling of H3K4me3 binding sites by the CUT&RUN assay revealed enriched H3K4me3 peaks at the promoter regions of FAO, OXPHOS, and sarcomere genes. Consistent with the chromatin and gene expression data, KDM5 inhibition led to increased expression of multiple sarcomere proteins, enhanced myofibrillar organization and improved calcium handling. Furthermore, inhibition of KDM5 increased H3K4me3 deposits at the promoter region of the ESRRA gene, which is known to regulate OXPHOS and cardiomyocyte maturation, and resulted in its increased RNA and protein levels. Finally, KDM5 inhibition increased baseline, peak, and spare oxygen consumption rates in iPSC-CMs. ConclusionsKDM5 regulates the maturation of iPSC-CMs by epigenetically regulating the expression of ESRRA, OXPHOS, FAO, and sarcomere genes and enhancing myofibril organization and mitochondrial function.

genomics↗

bioRxiv2023

Genetic Inactivation of Beta-Catenin Attenuates and Its Activation Aggravates Desmoplakin Cardiomyopathy

AimMutations in the DSP gene encoding desmoplakin, a constituent of the desmosomes at the intercalated discs (IDs), cause a phenotype that spans arrhythmogenic cardiomyopathy (ACM) and dilated cardiomyopathy (DCM). It is typically characterized by biventricular enlargement and dysfunction, severe myocardial fibrosis, cell death, and arrhythmias. The canonical WNT (cWNT)/{beta}-catenin signaling pathway is implicated in the pathogenesis of ACM. Given that {beta}-catenin, an indispensable co-transcriptional regulator of the cWNT pathway, is also a member of the IDs, we genetically inactivated or activated {beta}-catenin to determine its role in the pathogenesis of the desmoplakin cardiomyopathy. Methods and ResultsThe Dsp gene was conditionally deleted in cardiac myocytes concomitant with the genetic inactivation or activation of {beta}-catenin using the tamoxifen-inducible MerCreMer mice. Inactivation and activation of {beta}-catenin were achieved upon deletion of its transcriptional domain and degrons, respectively. Analysis of cardiac myocytes transcripts and proteins showed marked dysregulation of the cWNT/{beta}-catenin pathway in the DSP-deficient mouse cardiac myocytes (Myh6-McmTam:DspF/F), as indicated by increased expression of cWNT/{beta}-catenin targets along with its inhibitors and isoforms of its key co-effectors. Genetic inactivation of {beta}-catenin in the Myh6-McmTam:DspF/F mice prolonged survival, improved cardiac function, reduced cardiac arrhythmias, and attenuated myocardial fibrosis, and cell death caused by apoptosis, necroptosis, pyroptosis, i.e., PANoptosis, whereas its activation had the opposite effects. Inactivation of {beta}-catenin was associated with partial restoration of the suppressed genes involved in OXPHOS, whereas its activation has the opposite effect. The beneficial effects were independent of the changes in the transcript levels of the cWNT target genes. ConclusionThe cWNT/{beta}-catenin was markedly dysregulated in the cardiac myocytes from a mouse model of DC. Inactivation of {beta}-catenin attenuated the phenotype partly through the recovery of OXPHOS genes whereas its activation had deleterious effects. The findings suggest suppression of {beta}-catenin might be beneficial in desmoplakin-cardiomyopathy. SummaryGenetic inactivation of {beta}-catenin improved desmoplakin cardiomyopathy, in part through the restoration of expression of genes involved in oxidative phosphorylation, whereas its activation was deleterious.

genetics↗

bioRxiv2022

A human mitofusin 2 mutation causes mitophagic cardiomyopathy

Cardiac muscle has the highest mitochondrial density of any human tissue, but mitochondrial dysfunction is not a recognized cause of isolated cardiomyopathy. Here, we determined that the rare mitofusin (MFN) 2 R400Q mutation is ~20x over-represented in clinical cardiomyopathy, whereas this specific mutation is not reported as a cause of the MFN2 mutant-induced peripheral neuropathy, Charcot-Marie-Tooth disease type 2A (CMT2A). Accordingly, we interrogated the enzymatic, biophysical and functional characteristics of MFN2 Q400 versus wild-type and representative CMT2A-causing MFN2 mutants. All MFN2 mutants we studied suppressed mitochondrial fusion, the canonical MFN2 function. Compared to CMT2A mutants MFN2 R94Q and T105M that lacked catalytic GTPase activity and exhibited normal activation-induced changes in conformation, MFN2 Q400 had normal GTPase activity with impaired conformational shifting. GTPase-defective MFN2 mutants, but not MFN2 Q400, suppressed mitochondrial motility, provoked mitochondrial depolarization and reduced mitochondrial respiration. By contrast, MFN2 Q400 was uniquely defective in recruiting Parkin to mitochondria. CRISPR editing of the R400Q mutation into the mouse Mfn2 gene induced perinatal cardiomyopathy with no other organ involvement. RNA sequencing and metabolomics of cardiomyopathic Mfn2 Q400 hearts revealed signature abnormalities recapitulating experimental mitophagic cardiomyopathy. Indeed, cardiomyoblasts expressing MFN2 Q400 exhibited multiple mitophagy defects, but normal mitochondrial respiration. MFN2 Q400 is the first known natural mitophagy- and shape change-defective MFN2 mutant. Its unique profile of dysfunction evokes mitophagic cardiomyopathy, suggesting a mechanism for its enrichment in clinical cardiomyopathy.

developmental biology↗