Abstract Epilepsy, a clinical diagnosis characterized by paroxysmal episodes known as seizures, affects 1% of people worldwide. Safe and patient-specific treatment is vital and can be achieved by the development of rapid pre-clinical models of for identified epilepsy genes. Epilepsy can result from either brain injury or gene mutations, and can also be induced chemically. Xenopus laevis tadpoles could be a useful model for confirmation of variants of unknown significance found in epilepsy patients, and for drug re-purposing screens that could eventually lead to benefits for patients. Here, we characterise and quantify seizure-related behaviours in X. laevis tadpoles arrayed in 24-well plates. To provoke acute seizure behaviours, tadpoles were chemically induced with either pentylenetetrazole (PTZ) or 4-aminopyridine (4-AP). To test the capacity to adapt this method for drug testing, we also exposed induced tadpoles to the anti-seizure drug valproate (VPA). Four induced seizure-like behaviours were described and manually quantified, and two of these (darting, circling) could be accurately detected automatically, using the video analysis software TopScan. Additionally, we recorded swimming trajectories and mean swimming velocity. Automatic detection showed that either PTZ or 4-AP induced darting behaviour and increased mean swimming velocity compared to untreated controls. Both parameters were significantly reduced in the presence of VPA. In particular, darting behaviour was a shown to be a sensitive measure of epileptic seizure activity. While we could not automatically detect the full range of seizure behaviours, this method shows promise for future studies, since X. laevis is a well-characterised and genetically tractable model organism.
ABSTRACT Developmental and epileptic encephalopathies (DEE) are a genetically diverse group of disorders with similar early clinical presentations. DEE65 is caused by de novo , non-synonymous, gain-of-function mutations in CYFIP2. It presents in early infancy as hypotonia, epileptic spasms and global developmental delay. While modelling loss-of-function mutations can be done using knockdown or knockout techniques to reduce the amount of functional protein, modelling gain-of-function mutations requires different approaches. Here, we show that transient ectopic expression of the Arg87Cys pathogenic variant of cyfip2 mRNA in Xenopus laevis tadpoles resulted in increased seizure-related behaviours such as rapid darting and swimming in circles. In contrast, expression of a second pathological variant, Tyr108Cys, did not alter tadpole behaviour. Expression of either pathogenic variant resulted in spontaneous epileptic activity in the brain. For both variants, neuronal hyperactivity was reduced by treating the tadpole with 5 mM of the anti-seizure drug valproate (VPA). mRNA overexpression of gain-of-function variants in X. laevis tadpoles may be useful both for understanding the aetiology of DEE and for pre-clinical drug testing.
Abstract Epilepsy, a clinical diagnosis characterised by paroxysmal episodes known as seizures, affects 1% of people worldwide. Safe and patient‐specific treatment is vital and can be achieved by the development of rapid pre‐clinical models of for identified epilepsy genes. Epilepsy can result from either brain injury or gene mutations, and can also be induced chemically. Xenopus laevis tadpoles could be a useful model for confirmation of variants of unknown significance found in epilepsy patients, and for drug re‐purposing screens that could eventually lead to benefits for patients. Here, we characterise and quantify seizure‐related behaviours in X. laevis tadpoles arrayed in 24‐well plates. To provoke acute seizure behaviours, tadpoles were chemically induced with either pentylenetetrazole (PTZ) or 4‐aminopyridine (4‐AP). To test the capacity to adapt this method for drug testing, we also exposed induced tadpoles to the anti‐seizure drug valproate (VPA). Four induced seizure‐like behaviours were described and manually quantified, and two of these (darting, circling) could be accurately detected automatically, using the video analysis software TopScan. Additionally, we recorded swimming trajectories and mean swimming velocity. Automatic detection showed that either PTZ or 4‐AP induced darting behaviour and increased mean swimming velocity compared to untreated controls. Both parameters were significantly reduced in the presence of VPA. In particular, darting behaviour was a shown to be a sensitive measure of epileptic seizure activity. While we could not automatically detect the full range of seizure behaviours, this method shows promise for future studies since X. laevis is a well‐characterised and genetically tractable model organism. image
Hydrogen sulfide (H 2 S) is an emerging neuromodulator that is considered to be a gasotransmitter similar to nitrogen oxide (NO) and carbon monoxide (CO). H 2 S exerts universal cytoprotective effects and acts as a defense mechanism in organisms ranging from bacteria to mammals. It is produced by the enzymes cystathionine β ‐synthase (CBS), cystathionine ϒ ‐lyase (CSE), 3‐mercaptopyruvate sulfurtransferase (MST), and D‐amino acid oxidase (DAO), which are also involved in tissue‐specific biochemical pathways for H 2 S production in the human body. H 2 S exerts a wide range of pathological and physiological functions in the human body, from endocrine system and cellular longevity to hepatic protection and kidney function. Previous studies have shown that H 2 S plays important roles in peripheral nerve regeneration and degeneration and has significant value during Schwann cell dedifferentiation and proliferation but it is also associated with axonal degradation and the remyelination of Schwann cells. To date, physiological and toxic levels of H 2 S in the human body remain unclear and most of the mechanisms of action underlying the effects of H 2 S have yet to be fully elucidated. The primary purpose of this review was to provide an overview of the role of H 2 S in the human body and to describe its beneficial effects.
Mothers exposed to infections during pregnancy disproportionally birth children who develop autism and schizophrenia, disorders associated with altered GABAergic function. The maternal immune activation (MIA) model recapitulates this risk factor, with many studies also reporting disruptions to GABAergic interneuron expression, protein, cellular density and function. However, it is unclear if there are species, sex, age, region, or GABAergic subtype specific vulnerabilities to MIA. Furthermore, to fully comprehend the impact of MIA on the GABAergic system a synthesised account of molecular, cellular, electrophysiological and behavioural findings was required. To this end we conducted a systematic review of GABAergic interneuron changes in the MIA model, focusing on the prefrontal cortex and hippocampus. We reviewed 102 articles that revealed robust changes in a number of GABAergic markers that present as gestationally-specific, region-specific and sometimes sex-specific. Disruptions to GABAergic markers coincided with distinct behavioural phenotypes, including memory, sensorimotor gating, anxiety, and sociability. Findings suggest the MIA model is a valid tool for testing novel therapeutics designed to recover GABAergic function and associated behaviour.
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