Nichola Lax - Academia.edu (original) (raw)
Papers by Nichola Lax
Mitochondrial Dysfunction in Neurodegenerative Disorders, 2016
Neuropathology and applied neurobiology, Jan 18, 2015
Mitochondrial disorders are among the most frequently inherited cause of neurological disease and... more Mitochondrial disorders are among the most frequently inherited cause of neurological disease and arise due to mutations in mitochondrial or nuclear DNA. Currently, we do not understand the specific involvement of certain brain regions or selective neuronal vulnerability in mitochondrial disease. Recent studies suggest γ-aminobutyric acid (GABA)-ergic interneurons are particularly susceptible to respiratory chain dysfunction. In this neuropathological study, we assess the impact of mitochondrial DNA defects on inhibitory interneurons in patients with mitochondrial disease. Histochemical, immunohistochemical and immunofluorescent assays were performed on post-mortem brain tissue from ten patients and ten age-matched control individuals. We applied a quantitative immunofluorescent method to interrogate complex I and IV protein expression in mitochondria within GABAergic interneuron populations in the frontal, temporal and occipital cortices. We also evaluated the density of inhibitory...
Mitochondrial Dysfunction in Neurodegenerative Disorders, 2011
Archives of …, 2012
Objective To explore the relationship between α-synuclein pathology and mitochondrial respiratory... more Objective To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain protein levels within single substantia nigra neurons. Design We examined α-synuclein and mitochondrial protein expression in substantia nigra neurons of 8 patients ...
Journal of Neuroscience, 2013
Mitochondrial defects within substantia nigra (SN) neurons are implicated in the pathogenesis of ... more Mitochondrial defects within substantia nigra (SN) neurons are implicated in the pathogenesis of Parkinson's disease. SN neurons show increased mitochondrial defects, mitochondrial DNA deletion levels, and susceptibility to such dysfunction, although the role of mitochondria in neuronal degeneration remains uncertain. In this study, we addressed this important question by exploring changes within the mitochondria of SN neurons from patients with primary mitochondrial diseases to determine whether mitochondrial dysfunction leads directly to neuronal cell loss. We counted the pigmented neurons and quantified mitochondrial respiratory activity, deficiencies in mitochondrial proteins, and the percentage of pathogenic mutations in single neurons. We found evidence of defects of both complex I and complex IV of the respiratory chain in all patients. We found that marked neuronal cell loss was only observed in a few patients with mitochondrial disease and that all these patients had mutations in polymerase gamma (POLG), which leads to the formation of multiple mitochondrial DNA deletions over time, similar to aging and Parkinson's disease. Interestingly, we detected ␣-synuclein pathology in two mitochondrial patients with POLG mutations. Our observations highlight the complex relationship between mitochondrial dysfunction and the susceptibility of SN neurons to degeneration and ␣-synuclein pathology. Our finding that the loss of SN neurons was only severe in patients with POLG mutations suggests that acquired mitochondrial defects may be less well tolerated by SN neurons than by inherited ones.
Mitochondrion, 2011
The investigational drug dichloroacetate (DCA) is dehalogenated to glyoxylate by the zeta-1 famil... more The investigational drug dichloroacetate (DCA) is dehalogenated to glyoxylate by the zeta-1 family isoform of glutathione transferase (GSTz1). This enzyme is identical to maleylacetoacetate isomerase (MAAI), the penultimate enzyme of the phenylalanine/tyrosine catabolic pathway. We tested the hypothesis that polymorphisms in the GSTz1/MAAI gene modify the kinetics of DCA and, consequently, the risk of adverse effects from the drug. Twelve healthy adults were genotyped to determine GSTz1/MAAI haplotype and received 5 days of 25 mg/kg/day oral DCA.1,2-13 C-DCA was administered on days 1 and 5, during which formal kinetic testing was done. Six children who previously participated in a randomized clinical trial of DCA for congenital lactic acidosis were also genotyped and their kinetic data reexamined in light of haplotype variations.
Journal of Neuropathology & Experimental Neurology, 2012
Cerebellar ataxia is a prominent clinical symptom in patients with mitochondrial DNA (mtDNA) dise... more Cerebellar ataxia is a prominent clinical symptom in patients with mitochondrial DNA (mtDNA) disease. Often this is progressive with onset in young adulthood. Here, we performed a detailed neuropathological investigation of the olivary-cerebellum in 14 genetically and clinically welldefined patients with mtDNA disease. Quantitative neuropathological investigation showed varying levels of loss of Purkinje cells, and neurons of the dentate nucleus and inferior olivary nuclei. Typically, focal Purkinje cell loss was present in patients with the m.3243A>G mutation due to the presence of microinfarcts with relative preservation of neuronal cell populations in olivary and dentate nuclei. In contrast, patients with the m.8344A>G mutation or recessive POLG mutations showed extensive and global neuronal cell loss in all 3 olivary-cerebellum areas examined. Molecular analysis of mutated mtDNA heteroplasmy levels revealed that neuronal cell loss occurred independently of the level of mutated mtDNA present within surviving neurons. High levels of neuronal respiratory chain deficiency, particularly of complex I, were detected in surviving cells; levels of deficiency were greater in regions with extensive cell loss. We found a relationship between respiratory deficiency and neuronal cell density, indicating that neuronal cell death correlates with respiratory deficiency. These findings highlight the vulnerability of the olivary-cerebellum to mtDNA defects.
Brain, 2012
Neuropathological findings in mitochondrial DNA disease vary and are often dependent on the type ... more Neuropathological findings in mitochondrial DNA disease vary and are often dependent on the type of mitochondrial DNA defect. Many reports document neuronal cell loss, demyelination, gliosis and necrotic lesions in post-mortem material. However, previous studies highlight vascular abnormalities in patients harbouring mitochondrial DNA defects, particularly in those with the m.3243A>G mutation in whom stroke-like events are part of the mitochondrial encephalopathy lactic acidosis and stroke-like episodes syndrome. We investigated microangiopathic changes in the cerebellum of 16 genetically and clinically well-defined patients. Respiratory chain deficiency, high levels of mutated mitochondrial DNA and increased mitochondrial mass were present within the smooth muscle cells and endothelial cells comprising the vessel wall in patients. These changes were not limited to those harbouring the m.3243A>G mutation frequently associated with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes, but were documented in patients harbouring m.8344A>G and autosomal recessive polymerase (DNA directed), gamma (POLG) mutations. In 8 of the 16 patients, multiple ischaemic-like lesions occurred in the cerebellar cortex suggestive of vascular smooth muscle cell dysfunction. Indeed, changes in vascular smooth muscle and endothelium distribution and cell size are indicative of vascular cell loss. We found evidence of blood-brain barrier breakdown characterized by plasma protein extravasation following fibrinogen and IgG immunohistochemistry. Reduced immunofluorescence was also observed using markers for endothelial tight junctions providing further evidence in support of blood-brain barrier breakdown. Understanding the structural and functional changes occurring in central nervous system microvessels in patients harbouring mitochondrial DNA defects will provide an important insight into mechanisms of neurodegeneration in mitochondrial DNA disease. Since therapeutic strategies targeting the central nervous system are limited, modulating vascular function presents an exciting opportunity to lessen the burden of disease in these patients.
Brain, 2012
Defects in the mitochondrial DNA replication enzyme, polymerase , are an important cause of mitoc... more Defects in the mitochondrial DNA replication enzyme, polymerase , are an important cause of mitochondrial disease with $25% of all adult diagnoses attributed to mutations in the POLG gene. Peripheral neuronopathy is often part of the clinical syndrome and can represent the most disabling feature. In spite of this, the molecular mechanisms underlying the neuronopathy remain to be elucidated and treatment strategies are limited. In the present study, we use a combined approach comprising clinical, electrophysiological, neuropathological and molecular genetic investigations to unravel the mechanisms underpinning peripheral neuronopathy in autosomal recessive polymerase -related disease. Electrophysiological assessments documented a dorsal root ganglionopathy in all 11 cases. Of the 11 cases, eight also showed changes consistent with motor fibre loss. Detailed neuropathological investigation of two patients confirmed the electrophysiological findings, revealing atrophy of posterior columns and striking neuronal cell loss from the dorsal root ganglia, which was accompanied by severe mitochondrial biochemical abnormalities involving respiratory chain complexes I and IV due to clonally-expanded mitochondrial DNA deletions and a significant reduction in mitochondrial DNA copy number in affected neurons. We propose that the respiratory chain defects, secondary to mitochondrial DNA deletion and depletion, are likely to be responsible for pathology observed in the dorsal root ganglion and the sensory ganglionopathy documented electrophysiologically. Abbreviations: CNPase = 2 0 ,3 0 cyclic nucleotide 3 0 phosphodiesterase; COX = cytochrome c oxidase; POLG = polymerase
Archives of Neurology, 2012
To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain pro... more To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain protein levels within single substantia nigra neurons. We examined α-synuclein and mitochondrial protein expression in substantia nigra neurons of 8 patients with dementia with Lewy bodies, 5 patients with Parkinson disease, and 8 control subjects. Protein expression was determined using immunocytochemistry followed by densometric analysis. We examined single substantia nigra neurons from 5 patients with idiopathic Parkinson disease (mean age, 81.2 years), 8 patients with dementia with Lewy bodies (mean age, 75 years), and 8 neurologically and pathologically normal control subjects (mean age, 74.5 years). The control cases showed minimal Lewy body pathology and cell loss. Patients with dementia with Lewy bodies and idiopathic Parkinson disease fulfilled the clinical and neuropathologic criteria for these diseases. Our results showed that mitochondrial density is the same in nigral neurons with and without α-synuclein pathology. However, there are significantly higher levels of the respiratory chain subunits in neurons containing α-synuclein pathology. The finding of increased levels of respiratory chain complex subunits within neurons containing α-synuclein does not support a direct association between mitochondrial respiratory chain dysfunction and the formation of α-synuclein pathology.
Acta neuropathologica communications, 2016
Dementia with Lewy bodies (DLB) patients frequently experience well formed recurrent complex visu... more Dementia with Lewy bodies (DLB) patients frequently experience well formed recurrent complex visual hallucinations (RCVH). This is associated with reduced blood flow or hypometabolism on imaging of the primary visual cortex. To understand these associations in DLB we used pathological and biochemical analysis of the primary visual cortex to identify changes that could underpin RCVH. Alpha-synuclein or neurofibrillary tangle pathology in primary visual cortex was essentially absent. Neurone density or volume within the primary visual cortex in DLB was also unchanged using unbiased stereology. Microarray analysis, however, demonstrated changes in neuropeptide gene expression and other markers, indicating altered GABAergic neuronal function. Calcium binding protein and GAD65/67 immunohistochemistry showed preserved interneurone populations indicating possible interneurone dysfunction. This was demonstrated by loss of post synaptic GABA receptor markers including gephyrin, GABARAP, and ...
Neuropathology and Applied Neurobiology, 2016
Scientific reports, 2016
CLARITY enables immunofluorescent labelling and imaging of large volumes of tissue to provide a b... more CLARITY enables immunofluorescent labelling and imaging of large volumes of tissue to provide a better insight into the three dimensional relationship between cellular morphology and spatial interactions between different cell types. In the current study, we optimise passive CLARITY and immunofluorescent labelling of neurons and mitochondrial proteins in mouse and human brain tissues to gain further insights into mechanisms of neurodegeneration occurring in mitochondrial disease. This is the first study to utilise human cerebellum fixed in paraformaldehyde and cryoprotected in conjunction with formalin-fixed tissues opening up further avenues for use of archived tissue. We optimised hydrogel-embedding and passive clearance of lipids from both mouse (n = 5) and human (n = 9) cerebellum as well as developing an immunofluorescent protocol that consistently labels different neuronal domains as well as blood vessels. In addition to visualising large structures, we were able to visualise ...
Neuropharmacology, Jan 27, 2015
Increasingly in the realm of neurological disorders, particularly those involving neurodegenerati... more Increasingly in the realm of neurological disorders, particularly those involving neurodegeneration, mitochondrial dysfunction is emerging at the core of their pathogenic processes. Most of these diseases still lack effective treatment and are hampered by a shortfall in the development of novel medicines. Clearly new targets that translate well to the clinic are required. Physiological parameters in the form of neuronal network activity are increasingly being used as a therapeutic screening approach in drug development and disorders with mitochondrial dysfunction generally display neuronal network activity disturbance. However research directly linking the disturbances in neuronal network activity with mitochondrial dysfunction is only just starting to emerge. This review will summarize the breadth of knowledge linking neuronal network activity to mitochondrial dysfunction in neurodegenerative diseases and suggest potential avenues for exploration in respect to future drug development.
Annals of neurology, Jan 18, 2015
To determine the prevalence and progression of epilepsy in adult patients with mitochondrial dise... more To determine the prevalence and progression of epilepsy in adult patients with mitochondrial disease. We prospectively recruited a cohort of 182 consecutive adult patients attending a specialized mitochondrial disease clinic in Newcastle upon Tyne between Jan 1(st) 2005 and Jan 1(st) 2008. We then followed this cohort over a 7 year period, recording primary outcome measures of occurrence of first seizure, status epilepticus, stroke-like episode, and death. The overall prevalence of epilepsy in the cohort was 23.1%. The mean age of epilepsy onset was 29.4 years. The prevalence varied widely between genotypes, with several genotypes having no cases of epilepsy, a prevalence of 34.9% in the most common genotype (m.3243A>G mutation), and 92.3% in the m.8344A>G mutation. Among the cohort as a whole, focal seizures, with or without progression to bilateral convulsive seizures, was the most common seizure type. Conversely, all of the patients with the m.8344A>G mutation and epilep...
Neuropathology and applied neurobiology, Jan 4, 2015
Cerebellar ataxia is common in patients with mitochondrial disease and despite previous neuropath... more Cerebellar ataxia is common in patients with mitochondrial disease and despite previous neuropathological investigations demonstrating vulnerability of the olivocerebellar pathway in patients with mitochondrial disease, the exact neurodegenerative mechanisms are still not clear. We use quantitative quadruple immunofluorescence to enable precise quantification of mitochondrial respiratory chain protein expression in Purkinje cell bodies and their synaptic terminals in the dentate nucleus. We investigated NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 13 protein expression in twelve clinically and genetically-defined patients with mitochondrial disease and ataxia and ten age-matched controls. Molecular genetic analysis was performed to determine heteroplasmy levels of mutated mitochondrial DNA levels in Purkinje cell bodies and inhibitory synapses. Our data reveal that complex I deficiency is present in both Purkinje cell bodies and their inhibitory synapses which surround...
Mitochondrial Dysfunction in Neurodegenerative Disorders, 2016
Neuropathology and applied neurobiology, Jan 18, 2015
Mitochondrial disorders are among the most frequently inherited cause of neurological disease and... more Mitochondrial disorders are among the most frequently inherited cause of neurological disease and arise due to mutations in mitochondrial or nuclear DNA. Currently, we do not understand the specific involvement of certain brain regions or selective neuronal vulnerability in mitochondrial disease. Recent studies suggest γ-aminobutyric acid (GABA)-ergic interneurons are particularly susceptible to respiratory chain dysfunction. In this neuropathological study, we assess the impact of mitochondrial DNA defects on inhibitory interneurons in patients with mitochondrial disease. Histochemical, immunohistochemical and immunofluorescent assays were performed on post-mortem brain tissue from ten patients and ten age-matched control individuals. We applied a quantitative immunofluorescent method to interrogate complex I and IV protein expression in mitochondria within GABAergic interneuron populations in the frontal, temporal and occipital cortices. We also evaluated the density of inhibitory...
Mitochondrial Dysfunction in Neurodegenerative Disorders, 2011
Archives of …, 2012
Objective To explore the relationship between α-synuclein pathology and mitochondrial respiratory... more Objective To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain protein levels within single substantia nigra neurons. Design We examined α-synuclein and mitochondrial protein expression in substantia nigra neurons of 8 patients ...
Journal of Neuroscience, 2013
Mitochondrial defects within substantia nigra (SN) neurons are implicated in the pathogenesis of ... more Mitochondrial defects within substantia nigra (SN) neurons are implicated in the pathogenesis of Parkinson's disease. SN neurons show increased mitochondrial defects, mitochondrial DNA deletion levels, and susceptibility to such dysfunction, although the role of mitochondria in neuronal degeneration remains uncertain. In this study, we addressed this important question by exploring changes within the mitochondria of SN neurons from patients with primary mitochondrial diseases to determine whether mitochondrial dysfunction leads directly to neuronal cell loss. We counted the pigmented neurons and quantified mitochondrial respiratory activity, deficiencies in mitochondrial proteins, and the percentage of pathogenic mutations in single neurons. We found evidence of defects of both complex I and complex IV of the respiratory chain in all patients. We found that marked neuronal cell loss was only observed in a few patients with mitochondrial disease and that all these patients had mutations in polymerase gamma (POLG), which leads to the formation of multiple mitochondrial DNA deletions over time, similar to aging and Parkinson's disease. Interestingly, we detected ␣-synuclein pathology in two mitochondrial patients with POLG mutations. Our observations highlight the complex relationship between mitochondrial dysfunction and the susceptibility of SN neurons to degeneration and ␣-synuclein pathology. Our finding that the loss of SN neurons was only severe in patients with POLG mutations suggests that acquired mitochondrial defects may be less well tolerated by SN neurons than by inherited ones.
Mitochondrion, 2011
The investigational drug dichloroacetate (DCA) is dehalogenated to glyoxylate by the zeta-1 famil... more The investigational drug dichloroacetate (DCA) is dehalogenated to glyoxylate by the zeta-1 family isoform of glutathione transferase (GSTz1). This enzyme is identical to maleylacetoacetate isomerase (MAAI), the penultimate enzyme of the phenylalanine/tyrosine catabolic pathway. We tested the hypothesis that polymorphisms in the GSTz1/MAAI gene modify the kinetics of DCA and, consequently, the risk of adverse effects from the drug. Twelve healthy adults were genotyped to determine GSTz1/MAAI haplotype and received 5 days of 25 mg/kg/day oral DCA.1,2-13 C-DCA was administered on days 1 and 5, during which formal kinetic testing was done. Six children who previously participated in a randomized clinical trial of DCA for congenital lactic acidosis were also genotyped and their kinetic data reexamined in light of haplotype variations.
Journal of Neuropathology & Experimental Neurology, 2012
Cerebellar ataxia is a prominent clinical symptom in patients with mitochondrial DNA (mtDNA) dise... more Cerebellar ataxia is a prominent clinical symptom in patients with mitochondrial DNA (mtDNA) disease. Often this is progressive with onset in young adulthood. Here, we performed a detailed neuropathological investigation of the olivary-cerebellum in 14 genetically and clinically welldefined patients with mtDNA disease. Quantitative neuropathological investigation showed varying levels of loss of Purkinje cells, and neurons of the dentate nucleus and inferior olivary nuclei. Typically, focal Purkinje cell loss was present in patients with the m.3243A>G mutation due to the presence of microinfarcts with relative preservation of neuronal cell populations in olivary and dentate nuclei. In contrast, patients with the m.8344A>G mutation or recessive POLG mutations showed extensive and global neuronal cell loss in all 3 olivary-cerebellum areas examined. Molecular analysis of mutated mtDNA heteroplasmy levels revealed that neuronal cell loss occurred independently of the level of mutated mtDNA present within surviving neurons. High levels of neuronal respiratory chain deficiency, particularly of complex I, were detected in surviving cells; levels of deficiency were greater in regions with extensive cell loss. We found a relationship between respiratory deficiency and neuronal cell density, indicating that neuronal cell death correlates with respiratory deficiency. These findings highlight the vulnerability of the olivary-cerebellum to mtDNA defects.
Brain, 2012
Neuropathological findings in mitochondrial DNA disease vary and are often dependent on the type ... more Neuropathological findings in mitochondrial DNA disease vary and are often dependent on the type of mitochondrial DNA defect. Many reports document neuronal cell loss, demyelination, gliosis and necrotic lesions in post-mortem material. However, previous studies highlight vascular abnormalities in patients harbouring mitochondrial DNA defects, particularly in those with the m.3243A>G mutation in whom stroke-like events are part of the mitochondrial encephalopathy lactic acidosis and stroke-like episodes syndrome. We investigated microangiopathic changes in the cerebellum of 16 genetically and clinically well-defined patients. Respiratory chain deficiency, high levels of mutated mitochondrial DNA and increased mitochondrial mass were present within the smooth muscle cells and endothelial cells comprising the vessel wall in patients. These changes were not limited to those harbouring the m.3243A>G mutation frequently associated with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes, but were documented in patients harbouring m.8344A>G and autosomal recessive polymerase (DNA directed), gamma (POLG) mutations. In 8 of the 16 patients, multiple ischaemic-like lesions occurred in the cerebellar cortex suggestive of vascular smooth muscle cell dysfunction. Indeed, changes in vascular smooth muscle and endothelium distribution and cell size are indicative of vascular cell loss. We found evidence of blood-brain barrier breakdown characterized by plasma protein extravasation following fibrinogen and IgG immunohistochemistry. Reduced immunofluorescence was also observed using markers for endothelial tight junctions providing further evidence in support of blood-brain barrier breakdown. Understanding the structural and functional changes occurring in central nervous system microvessels in patients harbouring mitochondrial DNA defects will provide an important insight into mechanisms of neurodegeneration in mitochondrial DNA disease. Since therapeutic strategies targeting the central nervous system are limited, modulating vascular function presents an exciting opportunity to lessen the burden of disease in these patients.
Brain, 2012
Defects in the mitochondrial DNA replication enzyme, polymerase , are an important cause of mitoc... more Defects in the mitochondrial DNA replication enzyme, polymerase , are an important cause of mitochondrial disease with $25% of all adult diagnoses attributed to mutations in the POLG gene. Peripheral neuronopathy is often part of the clinical syndrome and can represent the most disabling feature. In spite of this, the molecular mechanisms underlying the neuronopathy remain to be elucidated and treatment strategies are limited. In the present study, we use a combined approach comprising clinical, electrophysiological, neuropathological and molecular genetic investigations to unravel the mechanisms underpinning peripheral neuronopathy in autosomal recessive polymerase -related disease. Electrophysiological assessments documented a dorsal root ganglionopathy in all 11 cases. Of the 11 cases, eight also showed changes consistent with motor fibre loss. Detailed neuropathological investigation of two patients confirmed the electrophysiological findings, revealing atrophy of posterior columns and striking neuronal cell loss from the dorsal root ganglia, which was accompanied by severe mitochondrial biochemical abnormalities involving respiratory chain complexes I and IV due to clonally-expanded mitochondrial DNA deletions and a significant reduction in mitochondrial DNA copy number in affected neurons. We propose that the respiratory chain defects, secondary to mitochondrial DNA deletion and depletion, are likely to be responsible for pathology observed in the dorsal root ganglion and the sensory ganglionopathy documented electrophysiologically. Abbreviations: CNPase = 2 0 ,3 0 cyclic nucleotide 3 0 phosphodiesterase; COX = cytochrome c oxidase; POLG = polymerase
Archives of Neurology, 2012
To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain pro... more To explore the relationship between α-synuclein pathology and mitochondrial respiratory chain protein levels within single substantia nigra neurons. We examined α-synuclein and mitochondrial protein expression in substantia nigra neurons of 8 patients with dementia with Lewy bodies, 5 patients with Parkinson disease, and 8 control subjects. Protein expression was determined using immunocytochemistry followed by densometric analysis. We examined single substantia nigra neurons from 5 patients with idiopathic Parkinson disease (mean age, 81.2 years), 8 patients with dementia with Lewy bodies (mean age, 75 years), and 8 neurologically and pathologically normal control subjects (mean age, 74.5 years). The control cases showed minimal Lewy body pathology and cell loss. Patients with dementia with Lewy bodies and idiopathic Parkinson disease fulfilled the clinical and neuropathologic criteria for these diseases. Our results showed that mitochondrial density is the same in nigral neurons with and without α-synuclein pathology. However, there are significantly higher levels of the respiratory chain subunits in neurons containing α-synuclein pathology. The finding of increased levels of respiratory chain complex subunits within neurons containing α-synuclein does not support a direct association between mitochondrial respiratory chain dysfunction and the formation of α-synuclein pathology.
Acta neuropathologica communications, 2016
Dementia with Lewy bodies (DLB) patients frequently experience well formed recurrent complex visu... more Dementia with Lewy bodies (DLB) patients frequently experience well formed recurrent complex visual hallucinations (RCVH). This is associated with reduced blood flow or hypometabolism on imaging of the primary visual cortex. To understand these associations in DLB we used pathological and biochemical analysis of the primary visual cortex to identify changes that could underpin RCVH. Alpha-synuclein or neurofibrillary tangle pathology in primary visual cortex was essentially absent. Neurone density or volume within the primary visual cortex in DLB was also unchanged using unbiased stereology. Microarray analysis, however, demonstrated changes in neuropeptide gene expression and other markers, indicating altered GABAergic neuronal function. Calcium binding protein and GAD65/67 immunohistochemistry showed preserved interneurone populations indicating possible interneurone dysfunction. This was demonstrated by loss of post synaptic GABA receptor markers including gephyrin, GABARAP, and ...
Neuropathology and Applied Neurobiology, 2016
Scientific reports, 2016
CLARITY enables immunofluorescent labelling and imaging of large volumes of tissue to provide a b... more CLARITY enables immunofluorescent labelling and imaging of large volumes of tissue to provide a better insight into the three dimensional relationship between cellular morphology and spatial interactions between different cell types. In the current study, we optimise passive CLARITY and immunofluorescent labelling of neurons and mitochondrial proteins in mouse and human brain tissues to gain further insights into mechanisms of neurodegeneration occurring in mitochondrial disease. This is the first study to utilise human cerebellum fixed in paraformaldehyde and cryoprotected in conjunction with formalin-fixed tissues opening up further avenues for use of archived tissue. We optimised hydrogel-embedding and passive clearance of lipids from both mouse (n = 5) and human (n = 9) cerebellum as well as developing an immunofluorescent protocol that consistently labels different neuronal domains as well as blood vessels. In addition to visualising large structures, we were able to visualise ...
Neuropharmacology, Jan 27, 2015
Increasingly in the realm of neurological disorders, particularly those involving neurodegenerati... more Increasingly in the realm of neurological disorders, particularly those involving neurodegeneration, mitochondrial dysfunction is emerging at the core of their pathogenic processes. Most of these diseases still lack effective treatment and are hampered by a shortfall in the development of novel medicines. Clearly new targets that translate well to the clinic are required. Physiological parameters in the form of neuronal network activity are increasingly being used as a therapeutic screening approach in drug development and disorders with mitochondrial dysfunction generally display neuronal network activity disturbance. However research directly linking the disturbances in neuronal network activity with mitochondrial dysfunction is only just starting to emerge. This review will summarize the breadth of knowledge linking neuronal network activity to mitochondrial dysfunction in neurodegenerative diseases and suggest potential avenues for exploration in respect to future drug development.
Annals of neurology, Jan 18, 2015
To determine the prevalence and progression of epilepsy in adult patients with mitochondrial dise... more To determine the prevalence and progression of epilepsy in adult patients with mitochondrial disease. We prospectively recruited a cohort of 182 consecutive adult patients attending a specialized mitochondrial disease clinic in Newcastle upon Tyne between Jan 1(st) 2005 and Jan 1(st) 2008. We then followed this cohort over a 7 year period, recording primary outcome measures of occurrence of first seizure, status epilepticus, stroke-like episode, and death. The overall prevalence of epilepsy in the cohort was 23.1%. The mean age of epilepsy onset was 29.4 years. The prevalence varied widely between genotypes, with several genotypes having no cases of epilepsy, a prevalence of 34.9% in the most common genotype (m.3243A>G mutation), and 92.3% in the m.8344A>G mutation. Among the cohort as a whole, focal seizures, with or without progression to bilateral convulsive seizures, was the most common seizure type. Conversely, all of the patients with the m.8344A>G mutation and epilep...
Neuropathology and applied neurobiology, Jan 4, 2015
Cerebellar ataxia is common in patients with mitochondrial disease and despite previous neuropath... more Cerebellar ataxia is common in patients with mitochondrial disease and despite previous neuropathological investigations demonstrating vulnerability of the olivocerebellar pathway in patients with mitochondrial disease, the exact neurodegenerative mechanisms are still not clear. We use quantitative quadruple immunofluorescence to enable precise quantification of mitochondrial respiratory chain protein expression in Purkinje cell bodies and their synaptic terminals in the dentate nucleus. We investigated NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 13 protein expression in twelve clinically and genetically-defined patients with mitochondrial disease and ataxia and ten age-matched controls. Molecular genetic analysis was performed to determine heteroplasmy levels of mutated mitochondrial DNA levels in Purkinje cell bodies and inhibitory synapses. Our data reveal that complex I deficiency is present in both Purkinje cell bodies and their inhibitory synapses which surround...