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Steward, L.

Publications and source records attributed to Steward, L..

2 recordsLinked to original sources
bioRxiv2025

Botulinum Neurotoxin A1 Signaling in Pain Modulation within Human Sensory Neurons

Botulinum neurotoxin type A1 (BoNT/A1) is an effective treatment for chronic migraine, but its direct mechanism of action on human sensory neurons has not been fully elucidated. While rodent studies on dorsal root ganglion (DRG) and trigeminal ganglion (TG) show that BoNT/A1 inhibits neurotransmission, including calcitonin gene-related peptide (CGRP) release, by cleaving SNAP-25, only one previous study has assessed its effect on human DRG neurons. The objective of this study was to understand the mechanism of action of BoNT/A1 in cultured human sensory neurons and assess, using RNA sequencing, the transcriptomic consequences of BoNT/A1 treatment. Using DRGs obtained from organ donors the expression of key targets, including SNAP25, SV2C, & CALCA, was validated by mining existing transcriptomic datasets as well as immunohistochemistry. Cultured dissociated human DRG neurons treated with BoNT/A1 were used to examine cleavage of SNAP25, release of CGRP and transcriptomic changes after BoNT/A1 treatment. SV2C was found to be widely expressed in human DRG neurons in a pattern that completely overlapped with CGRP expression. Consistent with this finding, BoNT/A1 disrupted SNARE protein complexes in human DRG neurons as demonstrated by SNAP-25 cleavage in most somatosensory neurons and a reduction in capsaicin-evoked CGRP release, indicating impaired vesicle fusion. Moreover, Bulk RNA sequencing experiments revealed downregulated expression of a large subset of genes responsible for neurotransmitter and neuropeptide release from neurons suggesting a novel mechanism through which BoNT/A regulates neurotransmission. These results provide new insight into the molecular mechanisms by which BoNT/A may exert its pain-relieving effects in humans.

neuroscience↗
bioRxiv2024

Discovery of novel compounds and target mechanisms using a high throughput, multiparametric phenotypic screen in a human neuronal model of Tuberous Sclerosis

Tuberous sclerosis complex (TSC) is a rare genetic disorder caused by mutations in the mTOR pathway genes TSC1 or TSC2. TSC can affect multiple organs including the brain, and most patients (75-90%) present with seizures during early childhood and intractable epilepsy throughout life. mTOR inhibitors, part of the current standard of care, lack the optimal characteristics to fully address patient phenotypes. Here, we report on the application of our all-optical electrophysiology platform for phenotypic screening in a human neuronal model of TSC. We used CRISPR/Cas9-isogenic TSC2-/- iPS cell lines to identify disease-associated changes to neuronal morphology, transcript expression and neuronal excitability. We established a robust multiparametric electrophysiological phenotype which we then validated in TSC patient-derived neurons. We used this phenotype to conduct a screen of [~]30,000 small molecule compounds in human iPS cell-derived neurons and identified chemical scaffolds that rescued the functional TSC disease parameters. Confirmed hits may act via different mechanisms than direct mTOR pathway inhibition. This strategy provides molecular starting points for therapeutic development in TSC and a framework for phenotype discovery and drug screening in other neurological disorders.

neuroscience↗