Biology subjects

Reid, C. A.

Publications and source records attributed to Reid, C. A..

9 recordsLinked to original sources

bioRxiv2024

Transcriptomics-informed pharmacology identifies epigenetic and cell cycle regulators as enhancers of AAV production

Recombinant adeno-associated virus (rAAV) is a widely used viral vector for gene therapy. Despite its clinical efficacy, the manufacturing of rAAV faces challenges in productivity and quality, leading to limited availability. To address the growing demand, next-generation process development should be informed by a mechanistic understanding of the cellular response to rAAV. In this study, we performed transcriptomic analysis of 5 cell lines with variable capacities for rAAV production. Using an intersectional approach, we assessed the transcriptional response to rAAV production and compared transcriptional profiles between high and baseline producers to identify possible targets for enhancing production. Modulation of cell cycle and nucleosome components suggested a reduction of proliferative capacity and a shift toward DNA replication to support rAAV production. During rAAV production, we observed upregulation of several core functions including transcription, stress response, and Golgi and endoplasmic reticulum organization. Conversely, inhibitors of DNA-binding proteins and mitochondrial components were consistently downregulated during rAAV production. We next performed a drug connectivity analysis of these results and identified 5 classes of drugs predicted to enhance rAAV production. Validation studies confirmed the efficacy of HDAC and microtubule inhibitors. Our data uncover novel and previously identified pathways that may enhance rAAV productivity, potentially enabling a path to engineer improved processes and cell lines for higher yields and better quality rAAV production. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/599118v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1f2e93org.highwire.dtl.DTLVardef@12ab5fborg.highwire.dtl.DTLVardef@1119951org.highwire.dtl.DTLVardef@68acfb_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Gene Therapy Mediates Therapeutic Improvement in Cardiac Hypertrophy and Survival in a Murine Model of MYBPC3-Associated Cardiomyopathy

BackgroundHypertrophic cardiomyopathy (HCM) affects an estimated 600,000 people in the U.S. and is the leading cause of sudden cardiac arrest in those under 18. Loss-of-function mutations in Myosin Binding Protein C3, MYBPC3, are the most common genetic cause of HCM. The majority of MYBPC3 mutations causative for HCM result in truncations. The sarcomeric pathophysiology of the majority of HCM patients with MYBPC3 mutations appears to be due to haploinsufficiency, as the total amount of MYBPC3 protein incorporated into sarcomeres falls significantly below normal. MethodsA clear path for the treatment of haploinsufficiency is the restoration of the insufficient gene product; in this case wild-type MYBPC3. To achieve this, we engineered an AAV vector (TN-201) with superior properties for mediating cardiomyocyte-selective expression of MYBPC3 after systemic delivery. ResultsWe have demonstrated for the first time with AAV gene therapy the ability of both a mouse surrogate and TN-201, which encodes human MYBPC3 to reverse cardiac hypertrophy and systolic dysfunction and to improve diastolic dysfunction and survival in a symptomatic MYBPC3-deficient murine model of disease. Dose-ranging efficacy studies exhibited restoration of wild-type MYBPC3 protein levels and saturation of cardiac improvement at the clinically relevant dose of 3E13 vg/kg, outperforming a previously published construct. Further, we have established stable cardiac benefit for greater than one year post-injection, as well as reversal of cardiac dysfunction even in late-stage models of disease. ConclusionsOur data suggest that by restoring MYBPC3 to the sarcomere, TN-201 has the potential to slow and even reverse the course of the disease in patients with MYBPC3-associated HCM.

genetics↗

bioRxiv2024

Slc35a2 mosaic knockout impacts cortical development, dendritic arborisation, and neuronal firing in the developing brain

ObjectiveMild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) is an important cause of drug-resistant epilepsy. A significant subset of individuals diagnosed with MOGHE display somatic mosaicism for loss-of-function variants in SLC35A2, which encodes the UDP-galactose transporter. We developed a mouse model to investigate the mechanism by which disruption of this transporter leads to a malformation of cortical development. MethodsWe used in utero electroporation and CRISPR/Cas9 to knockout Slc35a2 in a subset of layer 2/3 cortical neuronal progenitors in the developing brains of fetal mice to model mosaic expression. ResultsHistology of brain tissue in the mosaic Slc35a2 knockout mice revealed the presence of upper layer-derived cortical neurons in the white matter. In contrast, oligodendrocyte patterning was unchanged. Reconstruction of single filled neurons identified altered dendritic arborisation with Slc35a2 knockout neurons having increased complexity. Whole-cell electrophysiological recordings revealed that Slc35a2 knockout neurons display reduced action potential firing and increased afterhyperpolarisation duration compared with control neurons. Mosaic Slc35a2 knockout mice also exhibited significantly increased epileptiform spiking and increased locomotion. InterpretationWe successfully generated a mouse model of mosaic Slc35a2 deficiency, which recapitulates features of the human phenotype, including impaired neuronal migration. We show that knockout in layer 2/3 cortical neuron progenitors is sufficient to disrupt neuronal excitability and increase epileptiform activity and hyperactivity in mosaic mice. Our mouse model provides a unique opportunity to investigate the disease mechanism(s) that underpin MOGHE and facilitate the development of precision therapies.

neuroscience↗

bioRxiv2024

Different fluorescent labels report distinct components of spHCN channel voltage sensor movement

Voltage clamp fluorometry was used to probe the S4 helix movement in the voltage sensing domain of the sea urchin HCN channel expressed in Xenopus oocytes. Markedly different fluorescence responses were obtained with either ALEXA-488 or MTS-TAMRA covalently linked to Cys332 at the N-terminal end of S4. With hyperpolarizing steps, ALEXA-488 fluorescence increased rapidly showing characteristics consistent with it reporting the initial inward movement of S4 in agreement with previous studies. In contrast, MTS-TAMRA fluorescence was slower and correlated with the early phase of channel opening. In addition, a slow fluorescence component was resolved with both labels that tracked the development of the mode shift or channel hysteresis. This was quantitated as an increased deactivation tail current delay with concomitantly longer activation periods and was found to depend strongly on the presence of K+ ions in the pore. This indicated that the microenvironment of the fluorescent probes attached to Cys332 was strongly influenced by conformational changes in the pore domain. Collisional quenching experiments established that ALEXA-488 was more exposed to solvent than MTS-TAMRA. This was supported by structural predictions based on homology modelling of spHCN in the closed and open conformations with covalently linked fluorophores. This study demonstrates that components of S4 movement during channel activation can be kinetically resolved using different fluorescent probes to reveal three distinct biophysical properties: voltage-sensor movement, early channel opening and mode-shift. These data support the use of different labelling probes to interrogate distinct biophysical aspects of voltage-gated membrane proteins. SummaryVoltage clamp fluorometry was used to probe the S4 helix movement in the voltage sensing domain of the spHCN channel expressed in Xenopus oocytes, labeled with either ALEXA-488 or MTS-TAMRA. Each fluorophore reported different components of S4 movement.

biophysics↗

bioRxiv2024

A precision medicine approach for HCN1 Developmental and Epileptic Encephalopathy

Pathogenic variants in HCN1 causing cation leak result in a severe developmental and epileptic encephalopathy (DEE). Current treatment options for patients with HCN1-DEE are limited and are insufficient to fully address both the seizures and clinical comorbidities of this disorder. Org 34167 is a brain penetrant broad-spectrum HCN channel inhibitor that has completed phase I clinical trials. We used a range of assays at molecular, cellular, network and behavioural levels to explore the potential of Org 34167 as a precision medicine for HCN1-DEE. Org 34167 restored the voltage sensitivity of the DEE HCN1M305L mutated channel, significantly reducing cation leak. It also restored Ih-mediated sag, hyperpolarised the resting membrane potential and reduced firing of layer V neurons from the Hcn1M294L mouse model of HCN1-DEE, which was engineered based on the HCN1M305L pathogenic variant. Additionally, Org 34167 reduced neuronal epileptiform activity and restored retinal light sensitivity in these mice, suggesting it may improve both seizures and other clinical comorbidities. However, Org 34167-mediated tremors were noted at therapeutic doses. Org 34167 was also effective at reducing cation leak caused by five additional HCN1 pathogenic variants, suggesting broader utility. Overall, these data demonstrate that a small molecule HCN inhibitor can restore channel and consequent physiological functions, positioning it as a promising precision therapeutic approach for HCN1-DEE.

neuroscience↗

bioRxiv2023

Atenolol reduces cardiac-mediated mortality in a genetic mouse model of sudden unexpected death in epilepsy

Sudden Unexpected Death in Epilepsy (SUDEP) is the leading cause of premature mortality in epilepsy. Genetic cardiac risk factors, including loss-of-function KCNH2 variants, have been linked to SUDEP. We hypothesised that seizures and LQTS interact to increase SUDEP risk. To investigate this, we crossed Kcnh2+/- and Gabrg2R43Q/+ mice that model LQTS and genetic epilepsy, respectively. Electrocorticography and electrocardiogram confirmed that Kcnh2+/- mice had a LQTS phenotype, while Gabrg2R43Q/+ mice displayed spontaneous seizures. Double mutant mice (Gabrg2R43Q/+/Kcnh2+/-) had both seizure and LQTS phenotypes that were indistinguishable from the respective single mutant mice. Survival analysis revealed that Gabrg2R43Q/+/Kcnh2+/- mice experienced a disproportionate higher rate of seizure-related death. Long-term oral administration of atenolol, a cardiac-selective {beta}-blocker, significantly improved survival in the Gabrg2R43Q/+/Kcnh2+/- mice. An additional mouse model, Hcn1M294L/+/Kcnh2+/-, based on a HCN1 developmental epileptic encephalopathy variant, also experienced a disproportionately higher rate of premature death that was rescued by atenolol. Kcnh2+/- mice also spent more time in ventricular arrhythmia during proconvulsant-induced seizures. Overall, the data implicates cardiac and loss-of-function KCNH2 variants as an important risk factor, and the potential repurposing of {beta}- blockers as a prevention strategy, for SUDEP in a subset of epilepsy patients.

neuroscience↗

bioRxiv2021

Loss-of-function variants in the cardiac Kv11.1 channel as a genetic biomarker for SUDEP

ObjectiveTo compare the frequency and impact on channel function of KCNH2 variants in SUDEP patients with epilepsy controls comprising patients older than 50 years, a group with low SUDEP risk, and establish loss-of-function KCNH2 variants as predictive biomarkers of SUDEP risk. MethodsWe searched for KCNH2 variants with a minor allele frequency of < 5%. Functional analysis in Xenopus laevis oocytes was performed for all KCNH2 variants identified. ResultsKCNH2 variants were found in 11.1% (10/90) of SUDEP individuals compared to 6.0% (20/332) of epilepsy controls (p = 0.11). Loss-of-function KCNH2 variants, defined as causing > 20% reduction in maximal amplitude, were observed in 8.9% (8/90) SUDEP patients compared to 3.3% (11/332) epilepsy controls suggesting about three-fold enrichment (nominal p = 0.04). KCNH2 variants that did not change channel function occurred at a similar frequency in SUDEP (2.2%; 2/90) and epilepsy control (2.7%; 9/332) cohorts (p > 0.99). Rare KCNH2 variants (< 1% allele frequency) associated with greater loss of function and an [~]11-fold enrichment in the SUDEP cohort (nominal p = 0.03). In silico tools were unable to predict the impact of a variant on function highlighting the need for electrophysiological analysis. ConclusionsThese data show that loss-of-function KCNH2 variants are enriched in SUDEP patients and suggest that cardiac mechanisms contribute to SUDEP risk. We propose that genetic screening in combination with functional analysis can identify loss-of-function KCNH2 variants that could act as biomarkers of an individuals SUDEP risk.

neuroscience↗

bioRxiv2020

Antisense oligonucleotide therapy for KCNT1 encephalopathy

Developmental and epileptic encephalopathies (DEE) are characterized by pharmacoresistant seizures with concomitant intellectual disability. Epilepsy of infancy with migrating focal seizures (EIMFS) is one of the most severe of these syndromes. De novo mutations in ion channels, including gain-of-function variants in KCNT1, have been found to play a major role in the etiology of EIMFS. Here, we test a potential precision therapeutic approach in KCNT1-associated DEE using a gene silencing antisense oligonucleotide (ASO) approach. The homozygous p.P924L (L/L) mouse model recapitulates the frequent, debilitating seizures and developmental compromise that are seen in patients. After a single intracerebroventricular bolus injection of a Kcnt1 gapmer ASO in symptomatic mice at postnatal day 40, seizure frequency was significantly reduced, behavioral abnormalities improved, and overall survival was extended compared to mice treated with a control ASO (non-hybridizing sequence). ASO administration at neonatal age was also well-tolerated and effective in controlling seizures and extending the lifespan of treated animals. The data presented here provides a proof of concept for ASO-based gene silencing as a promising therapeutic approach in KCNT1-associated epilepsies.

neuroscience↗

bioRxiv2019

GABA-mediated tonic inhibition differentially modulates gain in functional subtypes of cortical interneurons

The binding of GABA to extra-synaptic GABAA receptors generates tonic inhibition that acts as a powerful modulator of cortical network activity. Despite GABA being present at low levels throughout the extracellular space of the brain, previous work has shown that GABA may differentially modulate the excitability of neuron subtypes through variation in chloride gradient. Here, we introduce a distinct mechanism through which extracellular GABA can differentially modulate the excitability of neuron subtypes through variation in neuronal electrophysiological properties. Using biophysically-detailed computational models, we found that tonic inhibition enhanced the responsiveness (or gain) of models with electrophysiological features typically observed in somatostatin (Sst) interneurons and reduced gain in models with features typical for parvalbumin (Pv) interneurons. These predictions were experimentally verified using patch-clamp recordings. Further analysis revealed that differential gain modulation is also dependent upon the extent of outward rectification of the GABAA receptor-mediated tonic current. Our detailed neuron models demonstrate two subcellular consequences of tonic inhibition. First, tonic inhibition enhances somatic action potential repolarisation by increasing current flow into the dendritic compartment. This enhanced repolarisation then reduces voltage-dependent potassium currents at the soma during the afterhyperpolarisation. Finally, we show that reductions of potassium current selectively increase gain within neurons exhibiting action potential dynamics typical for Sst interneurons. Potassium currents in Pv-type interneurons are not sensitive to this mechanism as they deactivate rapidly and are unavailable for further modulation. These findings introduce a neuromodulatory paradigm in which GABA can induce a state of differential interneuron excitability through differences in intrinsic electrophysiological properties.

neuroscience↗