Biology subjects

Robinson, K. J.

Publications and source records attributed to Robinson, K. J..

7 recordsLinked to original sources

bioRxiv2025

Mitochondrial dysfunction in Machado Joseph disease: insights from a multi-model system

Spinocerebellar ataxia type-3 (SCA3), also known as Machado Joseph disease, MJD) is a fatal, neurodegenerative disease belonging to the polyglutamine repeat disease family, caused by inheritance of an abnormal form of the ATXN3 gene, carrying a longer than usual trinucleotide repeat sequence. Within this study we explored mitochondrial function in a range of different experimental models of MJD, including transgenic zebrafish, mice and neuronal cells, to gain an understanding of mitochondrial function in the disease, and possible mechanisms of any dysfunction. Firstly, we examined the transgenic CMVMJD135 mouse model that develops impaired movement, neurodegeneration and decreased survival. We performed proteomic analysis on brain lysates extracted from a cohort of male and female WT and MJD mice, for analysis of differences in male and female mice separately. We identified that a major difference predicted by Ingenuity Pathway Analysis to be in both male and female MJD mice was related to impaired oxidative phosphorylation and mitochondrial dysfunction. We examined primary neuron cultures obtained from CMVMJD135 mice, validating the findings of the proteomic analysis, and finding changes to mitochondrial morphology, as well. We further examined a transgenic zebrafish model of MJD that expresses EGFP fused human ataxin-3 with short or long polyQ stretches (23 or 84Q, respectively) in neurons (expression driven under the elav/HuC promoter). The MJD zebrafish also exhibit altered mitochondrial electron transport chain complex protein levels, together with enhanced sensitivity to rotenone administration, which may be a valuable readout for treatment investigation studies in the future. Together, this study confirms, and extends on, the growing body of evidence suggesting that mitochondrial dysfunction plays a role in MJD, warranting investigation for therapeutic intervention.

neuroscience↗

bioRxiv2025

Gut transit and gut microbiome changes occur prior to the onset of motor impairment in a mouse model of Machado-Joseph disease

We previously identified microbial shifts prior to the onset of motor and neurological symptoms within a mouse model of the fatal neurodegenerative disease Machado-Joseph disease (MJD). Here, we aimed to explore possible mechanisms contributing to these changes within the microbiome-gut-brain axis, and whether it preceded or followed central neurodegeneration. Here, we report that pre-symptomatic male MJD mice present with significantly different microbiome communities as early as 5-weeks-old. Furthermore, we show that male MJD mice have faster total gut transit times by 9-weeks-old, prior to signs of impaired motor function by 11-weeks-old. To elucidate whether these microbial and colonic functional changes are due to the presence of pathological and morphological changes in the gut, we quantified the formation of ataxin-3 protein aggregates within the gut and examined morphological changes within the gut of pre- and early symptomatic MJD mice relative to proteinopathy in the brain. Interestingly, we observed ataxin-3 aggregates within the brains of pre-symptomatic MJD mice, with significantly more aggregates present in MJD than WT mice from 7-weeks-of-age, an earlier timepoint than previously reported, coinciding with changes within the microbiome. However, we observed no ataxin-3 protein aggregates and no changes in enteric neuron populations or morphology within the gut. Analysis of endocrine factors involved in gut motility and inflammatory markers within the small intestine of 13-week-old males revealed increased expression of genes encoding cholecystokinin (Cck), ghrelin (Ghrl), heme oxygenase (Ho1), interleukin-1 beta (Il1b), and decreased inducible nitric oxide synthase (Nos2). Together, we demonstrate for the first time that colonic dysfunction occurs after gut microbiome changes, but prior to the onset of motor impairments in male MJD mice. Our work suggests that whilst proteinopathy or morphological changes within the gut may not be involved in these changes, inflammation and related endocrine changes could have a role in the interplay between the gut and brain during MJD development, warranting further investigation.

neuroscience↗

bioRxiv2023

The Egg-Counter: A novel microfluidic platform for characterization of Caenorhabditis elegans egg-laying

Reproduction is a fundamental process that shapes the demography of every living organism yet is often difficult to assess with high precision in animals that produce large numbers of offspring. Here, we present a novel microfluidic research platform for studying Caenorhabditis elegans egg-laying. The platform provides higher throughput than traditional solid-media assays while providing a very high degree of temporal resolution. Additionally, the environmental control enabled by microfluidic animal husbandry allows for experimental perturbations difficult to achieve with solid-media assays. We demonstrate the platforms utility by characterizing C. elegans egg-laying behavior at two commonly used temperatures, 15 and 20{degrees}C. As expected, we observed a delayed onset of egg-laying at 15{degrees}C degrees, consistent with published temperature effects on development rate. Additionally, as seen in solid media studies, egg laying output was higher under the canonical 20{degrees}C conditions. While we validated the Egg-Counter with a study of temperature effects in wild-type animals, the platform is highly adaptable to any nematode egg-laying research where throughput or environmental control needs to be maximized without sacrificing temporal resolution.

animal behavior and cognition↗

bioRxiv2021

Treatment with sodium butyrate has therapeutic benefits for Machado-Joseph disease through the induction of autophagy

Spinocerebellar ataxia type 3 (SCA3, also known as Machado Joseph disease) is a fatal neurodegenerative disease caused by expansion of the trinucleotide repeat region within the ATXN3/MJD gene. Mutation of ATXN3 causes formation of ataxin-3 protein aggregates, neurodegeneration and motor deficits. Here we investigated the therapeutic potential and mechanistic activity of sodium butyrate (SB), the sodium salt of butyric acid, a metabolite naturally produced by gut microbiota, on cultured SH-SY5Y cells and transgenic zebrafish expressing human ataxin-3 containing 84 glutamine (Q) residues to model SCA3. SCA3 SH-SY5Y cells were found to contain high molecular weight ataxin-3 species and detergent insoluble protein aggregates. Treatment with SB increased activity of the autophagy protein quality control pathway in the SCA3 cells, decreased presence of ataxin-3 aggregates and presence of high molecular weight ataxin-3 in an autophagy-dependent manner. Treatment with SB was also beneficial in vivo, improving swimming performance, increasing activity of the autophagy pathway and decreasing presence of insoluble ataxin-3 protein species in the transgenic SCA3 zebrafish. Co-treating the SCA3 zebrafish with SB and chloroquine, an autophagy inhibitor, prevented the beneficial effects of SB on zebrafish swimming, indicating that the improved swimming performance was autophagy-dependent. To understand the mechanism by which SB induces autophagy we performed proteomic analysis of protein lysates from the SB treated and untreated SCA3 SH-SY5Y cells. We found that SB treatment had increased activity of Protein Kinase A and AMPK signalling, with immunoblot analysis confirming that SB treatment had increased levels of AMPK protein and its substrates. Together our findings indicate that treatment with SB can increase activity of the autophagy pathway through a PKA/AMPK-dependent process and that this has beneficial effects in vitro and in vivo. We propose that treatment with sodium butyrate warrants further investigation as a potential treatment for neurodegenerative diseases underpinned by mechanisms relating to protein aggregation including SCA3.

neuroscience↗

bioRxiv2021

Flow cytometry allows rapid detection of protein aggregates in cell culture and zebrafish models of spinocerebellar ataxia-3

Spinocerebellar ataxia-3 (SCA3, also known as Machado Joseph Disease), is a neurodegenerative disease caused by inheritance of a ATXN3 gene containing a CAG repeat expansion, resulting in presence of a polyglutamine (polyQ) repeat expansion within the encoded human ataxin-3 protein. SCA3 is characterized by the formation of ataxin-3 protein aggregates within neurons, neurodegeneration, and impaired movement. In this study we have identified protein aggregates in both neuronal-like (SHSY5Y) cells and in vivo (transgenic zebrafish) models expressing human ataxin-3 protein containing polyQ expansion. We have adapted a flow cytometric methodology, allowing rapid quantification of detergent insoluble forms of ataxin-3 fused to a green fluorescent protein. Flow cytometric analysis revealed an increased number of detergent-insoluble ataxin-3 particles in cells and zebrafish expressing polyQ expanded ataxin-3 when compared to cells and zebrafish expressing wildtype human ataxin-3. Interestingly, a protein aggregation phenotype could be detected as early as two days of age in transgenic zebrafish, prior to the onset of a detectable movement impairment at 6 days of age, suggesting protein aggregation may be an early disease phenotype in SCA3. Further, treatment of SCA3 cells and transgenic zebrafish with compounds known to modulate the activity of the autophagy protein quality control pathway altered the number of detergent-insoluble ataxin-3 particles detected by flow cytometry. We conclude that flow cytometry is a powerful tool that can be harnessed to rapidly quantify ataxin-3 aggregates, both in vitro and in vivo, and can be utilised to screen and compare potential protein aggregate targeting therapies.

neuroscience↗

bioRxiv2021

Sodium valproate increases activity of the sirtuin pathway resulting in beneficialeffects for spinocerebellar ataxia-3 in vivo

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia-3) is a fatal neurodegenerative disease that impairs control and coordination of movement. Here we tested whether treatment with the histone deacetylase inhibitor sodium valproate (SV) prevented a movement phenotype that develops in larvae of a transgenic zebrafish model of the disease. We found that treatment with SV improved the swimming of the MJD zebrafish, increased levels of acetylated histones 3 and 4, but also increased expression of polyglutamine expanded human ataxin-3. Proteomic analysis of protein lysates generated from the treated and untreated MJD zebrafish also predicted that SV treatment had activated the sirtuin longevity signaling pathway and this was confirmed by findings of increased SIRT1 protein levels and sirtuin activity in SV treated MJD zebrafish and HEK293 cells expressing ataxin-3-84Q, respectively. Treatment with resveratrol (another compound known to activate the sirtuin pathway), also improved swimming in the MJD zebrafish. Co-treatment with SV alongside EX527, a SIRT1 activity inhibitor, prevented induction of autophagy by SV and the beneficial effects of SV on the movement in the MJD zebrafish, indicating that they were both dependent on sirtuin activity. These findings provide the first evidence of sodium valproate inducing activation of the sirtuin pathway. Further, they indicate that drugs that target the sirtuin pathway, including sodium valproate and resveratrol, warrant further investigation for the treatment of MJD and related neurodegenerative diseases.

neuroscience↗

bioRxiv2018

The Stress-Chip: A microfluidic platform for stress analysis in Caenorhabditis elegans

An organisms ability to mount a physiological response to external stressors is fundamental to its interaction with the environment. Experimental exploration of these interactions benefits greatly from the ability to maintain tight control of the environment, even under conditions in which it would be normal for the subject to flee the stressor. ere we present a nematode research platform that pairs automated image acquisition and analysis with a custom microfluidic device. This platform enables tight environmental control in low-density, single-worm arenas, which preclude animal escape while still allowing a broad range of behavioral activities. The platform is easily scalable, with two 50 arena arrays per chip and an imaging capacity of 600 animals per scanning device. Validating the device using dietary, osmotic, and oxidative stress indicates that it should be of broad use as a research platform, including eventual adaptation for additional stressors, anthelmintic-drug screening, and toxicology studies.

physiology↗