Mitochondria and the future of RASopathies: the emergence of bioenergetics

KDM5-mediated activation of genes required for mitochondrial biology is necessary for viability in Drosophila

Histone-modifying proteins play important roles in the precise regulation of the transcriptional programs that coordinate development. KDM5 family proteins interact with chromatin through demethylation of H3K4me3 as well as demethylase-independent mechanisms that remain less understood. To gain fundamental insights into the transcriptional activities of KDM5 proteins, we examined the essential roles of the single Drosophila Kdm5 ortholog during development. KDM5 performs crucial functions in the larval neuroendocrine prothoracic gland, providing a model to study its role in regulating key gene expression programs. Integrating genome binding and transcriptomic data, we identify that KDM5 regulates the expression of genes required for the function and maintenance of mitochondria, and we find that loss of KDM5 causes morphological changes to mitochondria. This is key to the developmental functions of KDM5, as expression of the mitochondrial biogenesis transcription factor Ets97D, homolog of GABPα, is able to suppress the altered mitochondrial morphology as well as the lethality of Kdm5 null animals. Together, these data establish KDM5-mediated cellular functions that are important for normal development and could contribute to KDM5-linked disorders when dysregulated.

Molecular and cellular evidence for the impact of a hypertrophic cardiomyopathy-associated RAF1 variant on the structure and function of contractile machinery in bioartificial cardiac tissues

Noonan syndrome (NS), the most common among RASopathies, is caused by germline variants in genes encoding components of the RAS-MAPK pathway. Distinct variants, including the recurrent Ser257Leu substitution in RAF1, are associated with severe hypertrophic cardiomyopathy (HCM). Here, we investigated the elusive mechanistic link between NS-associated RAF1S257L and HCM using three-dimensional cardiac bodies and bioartificial cardiac tissues generated from patient-derived induced pluripotent stem cells (iPSCs) harboring the pathogenic RAF1 c.770 C > T missense change. We characterize the molecular, structural, and functional consequences of aberrant RAF1-associated signaling on the cardiac models. Ultrastructural assessment of the sarcomere revealed a shortening of the I-bands along the Z disc area in both iPSC-derived RAF1S257L cardiomyocytes and myocardial tissue biopsies. The aforementioned changes correlated with the isoform shift of titin from a longer (N2BA) to a shorter isoform (N2B) that also affected the active force generation and contractile tensions. The genotype-phenotype correlation was confirmed using cardiomyocyte progeny of an isogenic gene-corrected RAF1S257L-iPSC line and was mainly reversed by MEK inhibition. Collectively, our findings uncovered a direct link between a RASopathy gene variant and the abnormal sarcomere structure resulting in a cardiac dysfunction that remarkably recapitulates the human disease.

Treating COVID-19: Targeting the Host Response, Not the Virus

In low- and middle-income countries (LMICs), inexpensive generic drugs like statins, ACE inhibitors, and ARBs, especially if used in combination, might be the only practical way to save the lives of patients with severe COVID-19. These drugs will already be available in all countries on the first pandemic day. Because they target the host response to infection instead of the virus, they could be used to save lives during any pandemic. Observational studies show that inpatient statin treatment reduces 28–30-day mortality but randomized controlled trials have failed to show this benefit. Combination treatment has been tested for antivirals and dexamethasone but, with the exception of one observational study in Belgium, not for inexpensive generic drugs. Future pandemic research must include testing combination generic drug treatments that could be used in LMICs.

Effects of Noonan Syndrome-Germline Mutations on Mitochondria and Energy Metabolism

Noonan syndrome (NS) and related Noonan syndrome with multiple lentigines (NSML) contribute to the pathogenesis of human diseases in the RASopathy family. This family of genetic disorders constitute one of the largest groups of developmental disorders with variable penetrance and severity, associated with distinctive congenital disabilities, including facial features, cardiopathies, growth and skeletal abnormalities, developmental delay/mental retardation, and tumor predisposition. NS was first clinically described decades ago, and several genes have since been identified, providing a molecular foundation to understand their physiopathology and identify targets for therapeutic strategies. These genes encode proteins that participate in, or regulate, RAS/MAPK signalling. The RAS pathway regulates cellular metabolism by controlling mitochondrial homeostasis, dynamics, and energy production; however, little is known about the role of mitochondrial metabolism in NS and NSML. This manuscript comprehensively reviews the most frequently mutated genes responsible for NS and NSML, covering their role in the current knowledge of cellular signalling pathways, and focuses on the pathophysiological outcomes on mitochondria and energy metabolism.

Stellera chamaejasme L. extracts in the treatment of glioblastoma cell lines: Biological verification based on a network pharmacology approach

Background

Stellera chamaejasme L (RXLD) has been demonstrated with good clinical effects and medicinal value in the treatment of cancer in vivo and in vitro. Specifically, RXLD can eliminate aggregation accumulation, which is depicted as a vital characteristic feature of intracranial tumors. The potential pharmacological mechanisms of anti-glioblastoma (GBM) have not been adequately identified.

Methods

The 3D structures of the chemical ingredients in RXLD were imported into the PharmMapper database to construct the pharmacophore models. The gene targets of GBM were obtained from databases. The pharmacophore-targets network and the protein-protein interactions (PPI) were constructed using the String database and were visualized by using Cytoscape. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were conducted using Bioconductor software. Cytoscape visualized the relationship of pathways and candidate genes to screen for key target genes. Software packages PyMOL, AutoDock, and Vina acquired the molecular docking results. In vitro experiments were undertaken to characterize RXLD extracts’ effects on A172 cell line proliferation, viability, apoptosis, cell cycle, cell wound healing, cell migration, reactive oxygen species generation, and mitochondrial membrane potential. The expression of core genes in the related pathways was detected by Western blotting.

Results

We identified 216 potential targets associated with GBM. The core components in RXLD were neochamaejasmin A, wikstrol A, isochamaejasmin, chamaejasmine, and subtoxin A. The undertaken GO enrichment analysis revealed that oxidative stress, cell proliferation, cell cycle, cell invasion, and cell migration were involved in the biological processes. The KEGG enrichment analysis revealed that the crucial pathway was MAPK pathway, while HRAS, PRKCB, MAPK9, CCND1, and TP53 were distributed in core locations. A total of seven RXLD pharmacophores demonstrated strong spontaneous docking activities with MAPK9. In vitro assays indicated that RXLD can induce apoptosis, block the cell cycle in the G2/M and S phases, inhibit cell migration via the Wnt/β-catenin pathway, and inhibited p62/Nrf2 pathway.

Conclusions

We speculate that the RAS/MAPK pathway might be an upstream pathway through which the RXLD exerts its anti-GBM effects and might be able to regulate further the Wnt/β-catenin, the oxidative stress, and the ferroptosis pathways.