Biology subjects

Tok, S.

Publications and source records attributed to Tok, S..

4 recordsLinked to original sources

bioRxiv2026

Repeated mild traumatic brain injury does not affect sleep or epileptiform activity one-month post-injury in a knock-in mouse model of Alzheimer's disease

Traumatic brain injuries (TBIs) are associated with increased risk of neurodegenerative disease, including Alzheimers disease (AD); however, the mechanisms by which TBI promotes AD pathogenesis remain poorly understood. It also remains unclear whether post-TBI sequelae, including sleep disturbances and seizures, play a role in driving disease progression. To investigate these relationships, we employed a translational approach using the Closed-Head Injury Model of Engineered Rotational Acceleration (CHIMERA) of repeated mild TBI (rmTBI) and an AD knock-in mouse model to assess sleep, power spectral density, epileptiform activity, and A{beta} pathology one month post-injury. RmTBI caused elevated neurofilament-light and glial fibrillary acidic protein, markers of neuronal damage. Sex differences were observed in acute injury outcomes, sleep measures, and A{beta} plaque size. Specifically, females exhibited longer recovery post-injury, higher mortality, decreased non-rapid eye movement sleep duration, and larger average plaque size than males at equivalent impact energy. These findings highlight the importance of including both sexes when establishing injury severity thresholds. Future studies should incorporate validated TBI biomarkers of neural injury to define equivalent injury parameters across sexes and examine the chronic effects of rmTBI on sleep, epileptiform activity and AD pathology.

neuroscience↗

bioRxiv2025

Repetitive mild traumatic brain injury causes neuronal damage in the APP/PS1 mouse model of Alzheimer's disease without an enduring impact on amyloid pathology, sleep, or epileptiform activity

Traumatic Brain Injury (TBI) is a known risk factor for Alzheimers disease and related neurodegenerative diseases. Sleep disturbances and epileptiform abnormalities can appear after TBI and may contribute to the development of neuropathology. In this study, we characterized sleep, epileptiform activity, and neuropathology after repetitive mild traumatic brain injury (rmTBI) in a mouse model of Alzheimers disease. We used the Closed Head Impact Model of Engineered Rotational Acceleration (CHIMERA) to deliver rmTBI or sham (control) treatment to 6-month-old APP/PS1 mice (N=19). One month post-injury, we implanted electroencephalogram (EEG) and electromyographic (EMG) electrodes, recorded for 72 hours, and then collected brain tissue and blood plasma. Our assessment of sleep architecture showed that time spent in vigilance state was not affected by the rmTBI one month post-injury; however, power spectra analysis showed a shift towards higher frequencies in the rmTBI group during non-rapid eye movement (NREM) sleep. Epileptiform activity did not differ between sham and rmTBI. Compared to sham controls, the rmTBI group showed higher neurofilament light (NF-L), but not glial-fibrillary acidic protein (GFAP) in blood plasma and no change in A{beta} pathology. These results indicate sustained neurological injury in the APP/PS1 mice one month after rmTBI without affecting amyloid deposition in the brain. Our study suggests that rmTBI can induce neural injury without causing enduring sleep disruption, seizures, and exacerbation of amyloidosis in the APP/PS1 mouse model.

neuroscience↗

bioRxiv2024

Impact of Optogenetic Activation of the Thalamic Reticular Nucleus on Sleep Architecture in Mice

Alzheimers disease (AD) is a progressive neurodegenerative disorder affecting millions worldwide and is often accompanied by significant sleep disturbances, such as sleep fragmentation, early awakenings, decreased sleep efficiency, and insomnia. It has been suggested that the alterations in activity of the thalamic reticular nucleus (TRN) are closely associated with sleep disruptions in AD. Evidence suggests that activating neurons expressing gamma-aminobutyric acid (GABA) within the TRN may enhance sleep quality and potentially ameliorate neuropathology associated with AD. However, the precise mechanisms through which TRN influences sleep disruptions and AD pathophysiology remain poorly understood. In this study, we investigated whether activating GABAergic TRN neurons could alter sleep architecture in wild-type mice. Utilizing optogenetic stimulation, we observed that activation of these neurons did not significantly alter sleep state durations or delta wave power, a key indicator of Slow Wave Sleep (SWS). Furthermore, the application of a two-virus strategy inadvertently led to non-specific opsin expression beyond the targeted TRN area. We discuss the potential factors that contributed to these outcomes, providing directions for future investigations to better delineate the role of the TRN in sleep and AD.

neuroscience↗

bioRxiv2023

Improved Resolution of Highly Pathogenic Avian Influenza Virus Haemagglutinin Cleavage Site Using Oxford Nanopore R10 Sequencing Chemistry

Highly pathogenic avian influenza viruses continue to pose global risks to One Health, including agriculture, public, and animal health. Rapid and accurate genomic surveillance is critical for monitoring viral mutations, tracing transmission, and guiding interventions in near real-time. Oxford Nanopore sequencing holds promise for real-time influenza genotyping, but data quality from R9 chemistry has limited its adoption due to challenges resolving low-complexity regions such as the biologically critical hemagglutinin cleavage site, a homopolymer of basic amino acids that distinguish highly pathogenic strains. In this study, human and avian influenza isolates (n=45) from Cambodia were sequenced using both R9.4.1 and R10.4.1 flow cells and chemistries to evaluate performance between approaches. Overall, R10.4.1 yielded increased data output with higher average quality compared to R9.4.1, producing improved consensus sequences using a reference-based bioinformatics approach. R10.4.1 had significantly lower minor population insertion and deletion frequencies, driven by improved performance in low sequence complexity regions prone to insertion and deletion errors, such as homopolymers. Within the hemagglutinin cleavage site, R10.4.1 resolved the correct motif in 90% of genomes compared to only 60% with R9.4.1. Further examination showed reduced frameshift mutations in consensus sequences generated with R10.4.1 that could result in incorrectly classified virulence. Improved consensus genome quality from nanopore sequencing approaches, especially across biologically important low-complexity regions, is critical to reduce subjective hand-curation and will improve local and global genomic surveillance responses.

genomics↗