Biology subjects

Friedline, S.

Publications and source records attributed to Friedline, S..

7 recordsLinked to original sources

bioRxiv2026

Mapping and rewiring the MYBPC3 promoter for rescue of haploinsufficiency driven hypertrophic cardiomyopathy

Autosomal dominant loss-of-function variants in the gene MYBPC3 are, collectively, the most common genetic cause of hypertrophic cardiomyopathy (HCM) and are a prototype of haploinsufficient human disease. Typical for haploinsufficiency-associated genes, hundreds of unique loss-of-function pathogenic variants have been reported for MYBPC3 - therapeutic gene editing to correct each of these variants poses major regulatory and logistical hurdles. Upregulating wild-type allele expression could offer a generalizable therapeutic strategy, but the capacity to modulate native MYBPC3 transcription is unknown. Here, we present a variant-agnostic approach to rescue haploinsufficiency by mapping and rationally redesigning the MYBPC3 promoter. Using massively parallel reporter assays (MPRAs) in human induced pluripotent stem cell-derived cardiomyocytes, we performed saturation mutagenesis of the MYBPC3 promoter at single base-pair resolution. This defined a new class of clinically relevant noncoding loss-of-function variants while revealing essential cis-regulatory grammar anchored by key transcription factor binding sites (TFBSs). Furthermore, by systematically screening thousands of variant combinations, modular promoter elements, and heterologous TFBS insertions, we identified synergistic sequence edits that drive robust increases in MYBPC3 expression. Together, our findings improve the clinical interpretation of noncoding variants and establish a scalable blueprint for promoter editing to treat MYBPC3-associated HCM and other haploinsufficient diseases.

molecular biology↗

bioRxiv2026

Genomic Engineering of Gene Dosage: A Generalizable Framework for Modeling Haploinsufficiency-Mediated Human Disorders through Splicing Modulation

Heterozygous loss-of-function variants causing gene dosage reduction underlie many human genetic disorders, yet preclinical mouse models frequently fail to recapitulate human disease phenotypes due to post-translational compensation. Here, we present a generalizable framework to modulate gene dosage by alternative splicing via genome editing. By shifting proportions of transcripts toward nonsense-mediated decay, this approach enables precise titration of functional protein levels. Applying this concept to Mybpc3, we combined hypomorphic splice-altering alleles to overwhelm post-translational buffering in mice, successfully reproducing hallmark structural and functional features of human hypertrophic cardiomyopathy. Extending this concept, we engineered a portable Modulated Alternative Splice Cassette (MASC) inserted into Dsp, yielding patient-level protein reductions and characteristic arrhythmogenic cardiomyopathy pathologies, including subepicardial cardiac fibrosis and immune cell infiltration. These novel haploinsufficient models of Mybpc3 hypertrophic cardiomyopathy and Dsp arrhythmogenic cardiomyopathy will critically enable mechanistic and therapeutic testing under protein stoichiometry conditions that closely replicate the patient disorders. Finally, systematic in silico predictive modeling across 645 human haploinsufficiency-associated genes demonstrated the generalizability of MASC insertion effects on splicing across diverse tissue types. Notably, the framework developed here leaves endogenous gene expression regulatory logic intact, allowing these models to be used to develop and validate therapeutic approaches that target transcription. Overall, this strategy provides a scalable roadmap for engineering high-fidelity animal models for human diseases caused by haploinsufficiency.

genetics↗

bioRxiv2025

Activity-targeted metaproteomics enhances the ecophysiological characterization of cryptic syntrophic metabolisms

Syntrophic microbial consortia can contribute significantly to the activity and function of anoxic ecosystems, yet are often too rare to study their in situ physiologies using traditional molecular methods. Here, we combined bioorthogonal non-canonical amino acid tagging (BONCAT), stable isotope probing, and metaproteomics to improve the recovery of proteins from active members and track isotope incorporation in an anaerobic digestion community. Both click chemistry-enabled cell-sorting and direct protein pulldown coupled to metaproteomics improved recovery of isotopically labeled proteins during anaerobic acetate oxidation. Resulting labeled protein expression profiles revealed elevated activity of a rare and so-far uncharacterized syntrophic bacterium belonging to the family Natronincolaceae. BONCAT-based capture of newly translated proteins provided direct molecular evidence for the expression of a previously hypothesized oxidative glycine pathway for syntrophic acetate oxidation by this microorganism, showcasing the potential of targeted metaproteomics to characterize rare and active cells central to community metabolism in natural and engineered ecosystems.

microbiology↗

bioRxiv2025

Desmoplakin Haploinsufficiency Underlies Cell-Cell Adhesion Failure in DSP Cardiomyopathy and is Rescued by Transcriptional Activation

BackgroundTruncating variants in desmoplakin (DSPtv), are a leading cause of arrhythmogenic cardiomyopathy (ACM), often presenting with early fibrosis and arrhythmias disproportionate to systolic dysfunction. DSP is critical for cardiac mechanical integrity, linking desmosomes to the cytoskeleton to withstand contractile forces. While loss-of-function is implicated, direct evidence, both for DSP haploinsufficiency in human hearts and for the impact of mechanical stress on cardiomyocyte adhesion, has been limited, leaving the pathogenic mechanism unclear. MethodsWe analyzed explanted human heart tissue from patients with DSPtv (N=3), titin truncating variants (TTNtv, N=5), and controls (N=5) using RNA-sequencing and mass spectrometry. We generated human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) harboring patient-derived or CRISPR-Cas9 engineered DSPtv to model a range of DSP expression levels. Using a 2D cardiac muscle bundle (CMB) platform enabling live visualization of cell junctions, we developed an assay to assess cell-cell adhesion upon heightened contractile stress in response to the contractile agonist endothelin-1. CRISPR-interference (CRISPRi) was used to confirm the role of DSP loss, and CRISPR-activation (CRISPRa) was tested for therapeutic rescue. ResultsCompared to both control and TTNtv hearts, DSPtv human hearts exhibited reduced DSP at both the mRNA and protein level, as well as broadly disrupted desmosomal stoichiometry. Transcriptomic and proteomic analyses implicated cell adhesion, extracellular matrix, and inflammatory pathways. iPSC-CM models recapitulated DSP haploinsufficiency and desmosomal disruption. DSPtv CMBs showed normal baseline contractile function. However, they displayed marked cell-cell adhesion failure with contractile stress (75% failure vs. 8% in controls, p<0.001). Adhesion failure was prevented by the myosin inhibitor, mavacamten. CRISPRi-mediated DSP knockdown replicated this susceptibility to adhesion failure. Conversely, CRISPRa robustly increased DSP expression and rescued cell-cell adhesion failure in DSPtv CMBs (9% failure post-CRISPRa, p<0.001 vs. un-treated). Rescue occurred even when only the DSPII isoform was upregulated in a model with biallelic DSP transcript 1 loss of function. ConclusionsDSP haploinsufficiency is the major cause of DSP cardiomyopathy with a primary consequence of conferring vulnerability to cardiomyocyte cell-cell adhesion failure under heightened contractile stress. Transcriptional activation of DSP reverses this defect in preclinical models, establishing proof-of-concept for a potential therapeutic strategy in DSP cardiomyopathy.

genetics↗

bioRxiv2022

Eliminating Genes for a Two Component System Increases PHB Productivity in Cupriavidus basilensis 4G11 Under PHB Suppressing, Non-Stress Conditions

Species of bacteria from the genus Cupriavidus are known, in part, for their ability to produce high amounts of poly-hydroxybutyrate (PHB) making them attractive candidate bioplastic producers. The native production of PHB occurs during periods of metabolic stress, and the process regulating the initiation of PHB accumulation in these organisms is not fully understood. Screening an RB-TnSeq transposon library of Cupriavidus basilensis 4G11 allowed us to identify two genes of an apparent, uncharacterized two component system which, when omitted from the genome, are capable of increased PHB productivity in balanced, non-stress growth conditions. We observe average increases in PHB productivity of 56% and 41% relative to the wildtype parent strain, upon deleting each of two genes individually from the genome. The increased PHB phenotype disappears, however, in nitrogen-free unbalanced growth conditions suggesting the phenotype is specific to fast-growing, replete, non-stress growth. Bioproduction modeling suggests this phenotype could be due to a decreased reliance on metabolic stress induced by nitrogen limitation to initiate PHB production in the mutant strains. Such strains may allow for the use of single stage, continuous bioreactor systems, which are far simpler than PHB bioproduction schemes used previously. Bioproductivity modeling suggests that omitting this regulation in the cells may increase PHB productivity up to 24% relative to the wildtype organism when using single stage continuous systems. This work furthermore expands our understanding of the regulation of PHB accumulation in Cupriavidus, in particular the initiation of this process upon transition into unbalanced growth regimes.

genomics↗

bioRxiv2021

Biomechanics and Myofibrillar Alignment Enhance Contractile Development and Reproducibility in Stem Cell Derived Cardiac Muscle

Human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) allow novel investigations of human cardiac disease, but disorganized mechanics and immaturity of hPSC-CMs on two-dimensional (2D) surfaces have been hurdles for efficient and reproducible study of these cells. Here, we developed a platform of micron-scale 2D cardiac tissues (M2DCTs) to precisely control biomechanics in arrays of thousands of purified, independently contracting cardiac muscle strips in 2D. By defining geometry and workload in M2DCTs in this reductionist platform that does not incorporate other cell types, we show that myofibrillar alignment and auxotonic contractions at physiologic workload critically drive maturation of cardiac contractile function, calcium handling, and electrophysiology. Additionally, the organized biomechanics in this system facilitates rapid and automated extraction of contractile kinetic parameters from brightfield microscopy images, increasing the reproducibility and throughput of pharmacologic testing. Finally, we show that M2DCTs enable precise and efficient dissection of contractile kinetics in cardiomyopathy disease models.

cell biology↗

bioRxiv2020

Myofibrillar Structural Variability Underlies Contractile Function in Stem Cell-Derived Cardiomyocytes

Disease modeling and pharmaceutical testing using cardiomyocytes derived from induced pluripotent stem cell (iPSC-CMs) requires accurate assessment of contractile function. Micropatterning iPSC-CMs on elastic substrates controls cell shape and alignment to enable contractile studies, but determinants of intrinsic variability in this system have been incompletely characterized. The objective of this study was to determine the impact of myofibrillar structure on contractile function in iPSC-CMs. Automated analysis of micropatterned iPSC-CMs labeled with a cell permeant F-actin dye revealed that myofibrillar abundance is widely variable among iPSC-CMs and strongly correlates with contractile function. This variability is not reduced by subcloning from single iPSCs and is independent of iPSC-CM purification method. Controlling for myofibrillar structure reduces false positive findings related to batch effect and improves sensitivity for pharmacologic testing and disease modeling. This analysis provides compelling evidence that myofibrillar structure should be assessed concurrently in studies investigating contractile function in iPSC-CMs.

cell biology↗