Biology subjects

Heales, S.

Publications and source records attributed to Heales, S..

5 recordsLinked to original sources

bioRxiv2025

Mitochondrial stress in Fabry disease

Fabry disease (FD) is clinically heterogeneous. As some GLA variants attain similar levels of residual activity but result in a range of phenotypes, our aim is to understand factors influencing phenotypic variability. The mitochondrial unfolded protein response (mtUPR) is a stress response mechanism activated by multiple forms of mitochondrial dysfunction including accumulation of misfolded protein. As mitochondrial dysfunction has been reported, we investigated intracellular levels of heat shock protein 60 (Hsp60) by western blotting in 27 FD patients: 11 N215S (7 males) and 16 non-N215S (7 males) vs 4 heathy controls (HC, 3 males and 1 female). Serum Fibroblast Growth Factor-21 (FGF21), and Growth Differentiation Factor-15 (GDF-15) were also measured. Clinical outcomes explored included the Mainz Severity Score Index (MSSI), the Age-Adjusting Severity Scores (AASS), estimated glomerular filtration rate (eGFR) and left ventricular mass indexed to height (LVMI). Globotriaosylsphingosine (lyso-Gb3) data was available for a subset of participants. Hsp60 showed no significant differences between groups (males FD: 0.29 vs HC: 0.11, females HC: 0.26 vs FD: 0.19 Hsp60/LC), however, differences among FD patients were noted. While some had over 2-fold that of HCs, others had less than half of HCs despite genotype and gender. When analysed in terms of severity scores, the N215S group with higher levels of Hsp60 corresponded with a milder phenotype. LVMI and eGFR also seemed to improve with higher levels of Hsp60 only for this group. In terms of FGF-21 and GDF-15, lower levels showed a trend with higher Hsp60 levels and LVMI in the N215S group. To conclude, our findings suggest a potential role for mtUPR activation, as evidenced by intracellular Hsp60 levels, in modulating cardiac and renal manifestations in Fabry disease. These preliminary associations highlight the need for longitudinal studies to validate Hsp60 and mitokines as biomarkers of disease progression, aiming to inform personalized approaches that improve outcomes across Fabry disease phenotypes.

pathology↗

bioRxiv2024

Multi-Omic Analysis Reveals Lipid Dysregulation Associated with Mitochondrial Dysfunction in Parkinson's Disease Brain

Parkinsons Disease (PD) is an increasingly prevalent condition within the aging population. PD can be attributed to rare genetic mutations, but most cases are sporadic where the gene-environment interactions are unknown/likely contributory. Age related dysregulation of the glycosphingolipid degradation pathway has been implicated in the development of PD, however, our understanding of how brain lipids vary across different regions of the brain, with age and in disease stages, remains limited. In this study we profiled several phospho- and sphingolipid classes in eight distinct regions of the human brain and investigated the association of lipids with a spatio-temporal pathology gradient, utilising PD samples from early, mid, and late stages of the disease. We performed high-precision tissue sampling in conjunction with targeted LC-MS/MS and applied this to post-mortem samples from PD and control subjects. The lipids were analysed for correlations with untargeted proteomics and mitochondrial activity data, in a multi-omics approach. We concluded that the different brain regions demonstrated their own distinct profiles and also found that several lipids were correlated with age. The strongest differences between PD and controls were identified in ganglioside, sphingomyelin and n-hexosylceramides. Sphingomyelin was also found to correlate with several proteins implicated in Parkinsons disease pathways. Mitochondrial activity was correlated with the levels of several lipids in the putamen region. Finally, we identified a gradient corresponding to Braaks disease spread across the brain regions, where the areas closer to the brainstem/substantia nigra showed alterations in PC, LPC and glycosphingolipids, while the cortical regions showed changes in glycosphingolipids, specifically gangliosides, HexCer and Hex2Cer. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/604051v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@d4851eorg.highwire.dtl.DTLVardef@6f9d00org.highwire.dtl.DTLVardef@1ac9d7dorg.highwire.dtl.DTLVardef@197808e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Protein aggregation and calcium dysregulation are the earliest hallmarks of synucleinopathy in human midbrain dopaminergic neurons

Mutations in the SNCA gene cause autosomal dominant Parkinsons disease (PD), with progressive loss of dopaminergic neurons in the substantia nigra, and accumulation of aggregates of -synuclein. However, the sequence of molecular events that proceed from the SNCA mutation during development, to its end stage pathology is unknown. Utilising human induced pluripotent stem cells (hiPSCs) with SNCA mutations, we resolved the temporal sequence of pathophysiological events that occur during neuronal differentiation in order to discover the early, and likely causative, events in synucleinopathies. We adapted a small molecule-based protocol that generates highly enriched midbrain dopaminergic (mDA) neurons (>80%). We characterised their molecular identity using single-cell RNA sequencing and their functional identity through the synthesis and secretion of dopamine, the ability to generate action potentials, and form functional synapses and networks. RNA velocity analyses confirmed the developmental transcriptomic trajectory of midbrain neural precursors into mDA neurons using our approach, and identified key driver genes in mDA neuronal development. To characterise the synucleinopathy, we adopted super-resolution methods to determine the number, size and structure of aggregates in SNCA-mutant mDA neurons. At one week of differentiation, prior to maturation to mDA neurons of molecular and functional identity, we demonstrate the formation of small aggregates; specifically, {beta}-sheet rich oligomeric aggregates, in SNCA-mutant midbrain immature neurons. The aggregation progresses over time to accumulate phosphorylated aggregates, and later fibrillar aggregates. When the midbrain neurons were functional, we observed evidence of impaired physiological calcium signalling, with raised basal calcium, and impairments in cytosolic and mitochondrial calcium efflux. Once midbrain identity fully developed, SNCA-mutant neurons exhibited bioenergetic impairments, mitochondrial dysfunction and oxidative stress. During the maturation of mDA neurons, upregulation of mitophagy and autophagy occured, and ultimately these multiple cellular stresses lead to an increase in cell death by six weeks post-differentiation. Our differentiation paradigm generates an efficient model for studying disease mechanisms in PD, and highlights that protein misfolding to generate intraneuronal oligomers is one of the earliest critical events driving disease in human neurons, rather than a late-stage hallmark of the disease.

neuroscience↗

bioRxiv2018

Gene therapy in argininosuccinic aciduria

Argininosuccinate lyase (ASL) belongs to the liver-based urea cycle detoxifying ammonia, and the citrulline-nitric oxide cycle synthesising nitric oxide (NO). ASL-deficient patients present argininosuccinic aciduria characterised by hyperammonaemia and a multi-organ disease with neurocognitive impairment. Current therapeutic guidelines aim to control ammonaemia without considering the systemic NO imbalance. Here, we observed a neuronal disease with oxidative/nitrosative stress in ASL-deficient mouse brains. A single systemic injection of gene therapy mediated by an adeno-associated viral vector serotype 8 (AAV8) in adult or neonatal mice demonstrated the long-term correction of the urea cycle and the citrulline-NO cycle in the brain, respectively. The neuronal disease persisted if ammonaemia only was normalised but was dramatically reduced after correction of both ammonaemia and neuronal ASL activity. This was correlated with behavioural improvement and a decrease of the cortical cell death rate. Thus, the cerebral disease in argininosuccinic aciduria involves neuronal oxidative/nitrosative stress not mediated by hyperammonaemia, which is reversed by AAV gene transfer targeting the brain and the liver, acting on two different metabolic pathways via a single vector delivered systemically. This approach provides new hope for hepatocerebral metabolic diseases.

genetics↗

bioRxiv2017

Mitochondrial impairment and rescue in riboflavin responsive neuropathy

Brown-Vialetto-Van Laere syndrome (BVVLS) represents a phenotypic spectrum of motor, sensory, and cranial nerve neuropathy, often with ataxia, optic atrophy and respiratory problems leading to ventilator-dependence. Loss-of-function mutations in two riboflavin transporter (RFVT) genes, SLC52A2 and SLC52A3, have recently been linked to BVVLS. However, the genetic frequency, neuropathology and downstream consequences of RFVT mutations have previously been undefined. By screening a large cohort of 132 patients with early-onset severe sensory, motor and cranial nerve neuropathy we confirmed the strong genetic link between RFVT mutations and BVVLS, identifying twenty-two pathogenic mutations in SLC52A2 and SLC52A3, fourteen of which were novel. Brain and spinal cord neuropathological examination of two cases with SLC52A3 mutations showed classical symmetrical brainstem lesions resembling pathology seen in mitochondrial disease, including severe neuronal loss in the lower cranial nerve nuclei, anterior horns and corresponding nerves, atrophy of the spinothalamic and spinocerebellar tracts and posterior column-medial lemniscus pathways. Mitochondrial dysfunction has previously been implicated in an array of neurodegenerative disorders. Since riboflavin metabolites are critical components of the mitochondrial electron transport chain (ETC), we hypothesized that reduced riboflavin transport would result in impaired mitochondrial activity, and confirmed this using in vitro and in vivo models. ETC complex I and complex II activity were decreased in SLC52A2 patient fibroblasts, while global knockdown of the single Drosophila RFVT homologue revealed reduced levels of riboflavin, downstream metabolites, and ETC complex I activity. RFVT knockdown in Drosophila also resulted in severely impaired locomotor activity and reduced lifespan, mirroring patient pathology, and these phenotypes could be partially rescued using a novel esterified derivative of riboflavin. Our findings indicate mitochondrial dysfunction as a downstream consequence of RFVT gene defects in BVVLS and validate riboflavin esters as a potential therapeutic strategy.

neuroscience↗