Biology subjects

Cowell, R.

Publications and source records attributed to Cowell, R..

3 recordsLinked to original sources

bioRxiv2024

Lipid-siRNA conjugate accesses a perivascular transport mechanism and achieves widespread and durable knockdown in the central nervous system

Short-interfering RNA (siRNA) has gained significant interest for treatment of neurological diseases by providing the capacity to achieve sustained inhibition of nearly any gene target. Yet, efficacious drug delivery throughout deep brain structures of the CNS remains a considerable hurdle for intrathecally administered therapeutics. We herein describe an albumin-binding lipid-siRNA conjugate that transports along meningeal and perivascular CSF pathways, leading to broad dispersion throughout the CNS parenchyma. We provide a detailed examination of the temporal kinetics of gene silencing, highlighting potent knockdown for up to five months from a single injection without detectable toxicity. Single-cell RNA sequencing further demonstrates gene silencing activity across diverse cell populations in the parenchyma and at brain borders, which may provide new avenues for neurological disease-modifying therapies.

bioengineering↗

bioRxiv2023

RNA sequencing demonstrates ex vivo neocortical transcriptomic changes induced by epileptiform activity in male and female mice

Seizures are generally associated with epilepsy but may also be a symptom of many other neurological conditions. A hallmark of a seizure is the intensity of the local neuronal activation, which can drive large-scale gene transcription changes. Such changes in the transcriptional profile are likely to alter neuronal function, thereby contributing to the pathological process. Therefore, there is a strong clinical imperative to characterie how gene expression is changed by seizure activity. To this end, we developed a simplified ex vivo technique for studying seizure-induced transcriptional changes. We compared the RNA sequencing profile in mouse neocortical tissue that had up to 3 hours of epileptiform activity induced by 4-aminopyridine (4AP), relative to control brain slices not exposed to the drug. We identified over 100 genes with significantly altered expression after 4AP treatment, including multiple genes involved in MAPK, TNF, and neuroinflammatory signalling pathways, all of which have been linked to epilepsy previously. Notably, the patterns in male and female brain slices were almost identical. Various immediate early genes were among those showing the largest upregulation. The set of down-regulated genes included ones that might be expected either to increase or to decrease neuronal excitability. In summary, we found the seizure-induced transcriptional profile to be complex, but the changes aligned well with an analysis of published epilepsy-associated genes. We discuss how simple models may provide new angles for investigating seizure-induced transcriptional changes. Significance StatementIt is well-established that strong neuronal activation results in large-scale transcriptomic changes. Understanding this process is of particular importance in epilepsy, which is characterized by paroxysmal pathological discharges. The complexity of in vivo activity patterns, however, present many difficulties for interpretation of the transcriptional changes. In contrast, ex vivo seizure models provide better experimental control and quantification of activity patterns, with lower welfare impact. Importantly, we now show that these models also replicate the transcriptional patterns previously reported in chronic human and animal epilepsy, thus validating their use in these kinds of study.

neuroscience↗

bioRxiv2022

"Leap before you look": Conditions that promote implicit visuomotor adaptation without explicit learning

When learning a novel visuomotor mapping (e.g., mirror writing), accuracy can improve quickly through explicit learning (e.g., move left to go right) but after considerable practice, implicit learning takes over, producing fast, natural movements. This implicit learning occurs automatically, but it has been unknown whether explicit learning is similarly obligatory. Using a reaching task with a 90-degree rotation between screen position and movement direction, we found that explicit learning could be "turned off" by introducing the rotation gradually (increments of 10-degrees) and instructing participants to move quickly. These specific conditions were crucial, because both explicit and implicit learning occurred if the rotation occurred suddenly, if participants were told to emphasize accuracy, or if visual feedback during movement was removed. We reached these conclusions by examining the time course of learning (e.g., whether there was fast improvement followed by a long tail of additional improvement), by examining the aftereffects of learning when the rotation was abruptly removed, and by using formal model comparison between a dual-state (explicit and implicit) versus a single-state learning model as applied to the data. Author summaryIn some situations, the relationship between motion direction and what we see is different than normal. For instance, try using a computer mouse that is held sideways (a 90-degree rotation). When first encountering this situation, people move carefully, using explicit strategies (e.g., move right to go up). However, after many learning trials, motion becomes automatic (implicit) and natural. Prior results found that implicit visuomotor learning always occurs with enough experience. In our study, we found that this is not true of explicit visuomotor learning; in some situations, explicit learning can be turned off. More specifically, we found that this occurs when the novel visuomotor situation is: 1) introduced gradually (e.g., a gradual introduction of 90-degree rotation in steps of 10 degrees); 2) when there is pressure to move quickly; and 3) with real-time onscreen views of the motion path. If any of these three components are missing, then people use explicit learning. These conclusions were reached by examining the time course of learning (e.g., whether there was both fast and slow learning as assessed with mathematical models) and by examining the tendency to automatically move in the opposite direction from the rotation when the rotation is abruptly removed after learning.

neuroscience↗