Biology subjects

Ernst, P.

Publications and source records attributed to Ernst, P..

6 recordsLinked to original sources

bioRxiv2026

Systematic evaluation of Cyanidioschyzon merolae across photobioreactor systems: Linking reactor design to biomass production and biochemical composition

Extremophilic red microalgae are promising platforms for sustainable biotechnology, combining robust growth under selective thermoacidophilic conditions with production of thermostable phycobiliproteins and carbon-rich biomass. However, reactor-dependent effects on growth, product formation and biomass composition remain insufficiently resolved. Here, we systematically evaluated the extremophilic red microalga Cyanidioschyzon merolae across cultivation scales and reactor formats and benchmarked its performance against the well-established Galdieria javensis and Limnospira platensis. In small-scale multi-cultivator photobioreactors and microfluidic growth chambers, C. merolae showed superior growth, reaching a maximum growth rate of 0.034 {+/-} 0.001 h-1 and 8.3 {+/-} 0.3 g l-1 cell dry weight. Microfluidic cultivation enabled growth analysis at single-cell resolution and matched growth rates obtained in photobioreactors. To identify scalable production strategies, C. merolae was further cultivated in a flat-panel photobioreactor and a custom-designed internally illuminated photobioreactor. The custom-designed photobioreactor delivered the highest biomass concentration and productivity, yielding 11.5 {+/-} 0.6 g l-1 cell dry weight and 1.07 {+/-} 0.06 g l-1 d-1, and comparable yields with regard to R-phycocyanin and R-allophycocyanin. Biomass analysis revealed substantial carbon and nitrogen contents, starch accumulation up to > 20 % of cell dry weight, and fatty acids dominated by palmitic, linoleic and oleic acids. Despite its reduced cell wall fraction, C. merolae contained structurally diverse, cultivation-dependent polysaccharides. These results establish C. merolae as a versatile chassis for thermostable pigment production and renewable feedstock generation, highlighting photobioreactor design as a key determinant of productivity and biomass quality.

microbiology↗

bioRxiv2024

HCM-associated mutations in MYH6/7 drive pathologic expression of TGF-β1 in cardiomyocytes within weeks of developmental specification

Hypertrophic cardiomyopathy (HCM) is characterized by myocyte hypertrophy, sarcomere disarray, and myocardial fibrosis, leading to significant morbidity and mortality. As the most common inherited cardiomyopathy, HCM largely results from mutations in sarcomeric protein genes. Current treatments for HCM primarily focus on alleviating late-stage symptoms, with a critical gap in the detailed understanding of early-stage deficiencies that drive disease progression. We recently showed, in monolayers of cardiomyocytes derived from human induced pluripotent stem cells (hiPSCs) with MYH7 R723C and MYH6 R725C mutations, altered expression of several extracellular matrix (ECM)-related genes with associated defects in cardiomyocyte-ECM adhesion. To better evaluate the cardiomyocyte-ECM interface and pathological ECM dynamics in early-stage HCM, here we adopted a 3D engineered heart tissue (EHT) model containing both cardiomyocytes and fibroblasts, the primary contributor to ECM remodeling. Mutant EHTs showed aberrant cardiomyocyte distribution, augmented calcium handling, and force generation compared to controls. Altered proteoglycan deposition and increased phosphorylated focal adhesion kinase (pFAK) further indicated changes in ECM composition and connectivity. Elevated transforming growth factor beta-1 (TGF-{beta}1) secretion and a higher proportion of activated fibroblasts were identified in mutant EHTs, along with sustained TGF-{beta}1 transcription specifically in mutant cardiomyocytes. Remarkably, blocking TGF-{beta}1 receptor signaling reduced fibroblast activation and contraction force to control levels. This study underscores the early interplay of mutant hiPSC-CMs with fibroblasts, wherein mutant cardiomyocytes initiate fibroblast activation via TGF-{beta}1 overexpression, independent of the immune system. These findings provide a promising foundation for developing and implementing novel strategies to treat HCM well before the manifestation of clinically detectable fibrosis and cardiac dysfunction.

bioengineering↗

bioRxiv2024

An Innovative Mitochondrial-targeted Gene Therapy for Cancer Treatment

Targeting cancer cell mitochondria holds great therapeutic promise, yet current strategies to specifically and effectively destroy cancer mitochondria in vivo are limited. Here, we introduce mLumiOpto, an innovative mitochondrial-targeted luminoptogenetics gene therapy designed to directly disrupt the inner mitochondrial membrane (IMM) potential and induce cancer cell death. We synthesize a blue light-gated channelrhodopsin (CoChR) in the IMM and co-express a blue bioluminescence-emitting Nanoluciferase (NLuc) in the cytosol of the same cells. The mLumiOpto genes are selectively delivered to cancer cells in vivo by using adeno-associated virus (AAV) carrying a cancer-specific promoter or cancer-targeted monoclonal antibody-tagged exosome-associated AAV. Induction with NLuc luciferin elicits robust endogenous bioluminescence, which activates mitochondrial CoChR, triggering cancer cell IMM permeability disruption, mitochondrial damage, and subsequent cell death. Importantly, mLumiOpto demonstrates remarkable efficacy in reducing tumor burden and killing tumor cells in glioblastoma or triple-negative breast cancer xenografted mouse models. These findings establish mLumiOpto as a novel and promising therapeutic strategy by targeting cancer cell mitochondria in vivo.

cancer biology↗

bioRxiv2024

Heterodimerization of Endolysin Isoforms During Bacterial Infection by Staphylococcal Phage {varphi}2638A

AO_SCPLOWBSTRACTC_SCPLOWBacteriophage endolysins targeting Gram-positive bacteria typically feature a modular architecture of one or more enzymatically active domains (EADs) and cell wall binding domains (CBDs). Several endolysins also feature internal translational start sites (iTSSs) that produce short variant (SV) isoforms alongside the full-length (FL) endolysin. While the lytic activity of endolysins and their isoforms has been extensively studied as exogenous agents, the purpose behind producing the SV isoform during the phage infection cycle remains to be explored. In this study, we used staphylococcal phage {varphi}2638A as a model to determine the interplay between its full-length endolysin, Ply2638A, and its SV isoform during phage infection. X-ray crystallography structures and AlphaFold-generated models enabled elucidation of individual functions of the M23 endopeptidase, central amidase, and SH3b domains of Ply2638A. Production of the SV isoform (amidase and SH3b) was confirmed during phage infection and shown to form a heterodimer complex with Ply2638A via inter-amidase domain interactions. Using genetically engineered phage variants, we show that production of both isoforms provides an advantage during phage infection as phages producing only one isoform presented impaired lytic activity, which could be partly restored through recombinant protein complementation of the missing isoform. Importantly, when applied as an antimicrobial protein against Staphylococcus aureus in culture, the activity of Ply2638A remained constant regardless of SV isoform complementation. Drawing from our findings, we propose that SV isoform production provides its biological advantage upon endolysin entry to the periplasmic space to ensure optimal peptidoglycan degradation prior to cell wall lysis and progeny phage release.

molecular biology↗

bioRxiv2019

Novel anti-somatostatin receptor 2 antibody-drug conjugate for neuroendocrine cancer therapy

Neuroendocrine (NE) cancers include a diverse spectrum of hormone-secreting neoplasms that arise from the endocrine and nervous systems. Current chemo- and radio- therapies have marginal curative benefits. This study aimed to develop an innovative antibody-drug conjugate (ADC) to effectively treat NE tumors (NETs). We first confirmed that somatostatin receptor 2 (SSTR2) is an ideal surface target by analyzing 38 patient-derived NET tissues, 33 normal organs, and 3 NET cell lines. We then developed a new monoclonal antibody (mAb, IgG1 and kappa) to target two extracellular domains of SSTR2, which showed strong and specific surface binding to NETs. The ADC was constructed by conjugating the anti-SSTR2 mAb and antimitotic monomethyl auristatin E. In vitro evaluations indicated that the ADC can effectively bind, internalize, release payload, and kill NET cells effectively. Finally, the ADC was evaluated in vivo using a NET xenografted mouse model to determine cancer targeting, maximal tolerated dosage, pharmacokinetics, and anti-cancer efficacy. The anti-SSTR2 ADC was able to exclusively target and kill NETs with minimal toxicity and high stability in vivo. This study demonstrates that the anti-SSTR2 mAb-based ADC has high therapeutic values for NET therapy.

bioengineering↗

bioRxiv2018

Precisely control mitochondrial membrane potential with light to manipulate cell fate decisions

Mitochondrial dysfunction has been implicated in many pathological conditions and diseases. The normal functioning of mitochondria relies on maintaining the inner mitochondrial membrane (IMM) potential (a.k.a. {Delta}{Psi}m) that is essential for ATP synthesis, Ca2+ homeostasis, redox balance and regulation of other key signaling pathways such as mitophagy and apoptosis. However, the detailed mechanisms by which {Delta}{Psi}m regulates cellular function remain incompletely understood, partially due to difficulty of manipulating {Delta}{Psi}m with spatiotemporal resolution, reversibility, or cell type specificity. To address this need, we have developed a next-generation optogenetic-based technique for controllable mitochondrial depolarization with light. We demonstrate successful targeting of the heterologous Channelrhodopsin-2 (ChR2) fusion protein to the IMM and formation of functional cationic channels capable of light-induced selective {Delta}{Psi}m depolarization and mitochondrial autophagy. Importantly, we for the first time show that optogenetic-mediated mitochondrial depolarization can be well-controlled to differentially influence the fate of cells expressing mitochondrial ChR2: while sustained moderate light illumination induces substantial apoptotic cell death, transient mild light illumination elicits cytoprotection via mitochondrial preconditioning. Finally, we show that Parkin overexpression exacerbates, instead of ameliorating, mitochondrial depolarization-mediated cell death in HeLa cells. In summary, we provide evidence that the described mitochondrial-targeted optogenetics may have a broad application for studying the role of mitochondria in regulating cell function and fate decision.

cell biology↗