QUANTITATIVE ANALYSIS OF MICROGLIAL CELLS IN THE DEGENERATING CEREBELLUM OF THE STAGGERER (RORAsg/sg) MUTANT MOUSE

Elevated levels of pro-inflammatory cytokines, such as IL-1ss and IL-6, have been detected in the cerebellum of Rora(sg/sg) mice during the first postnatal month of neurodegenerative process. This suggests the existence of a microglial reaction in the context of an inflammatory process that would be triggered by the massive neuronal loss. To test this hypothesis, we qualitatively and quantitatively studied the microglial cell population using lectin and nucleosidic diphosphatase labeling of the cerebellum of 30-day-old mice. The massive neuronal loss induces a 11.7-fold smaller size of the Rora(sg/sg) cerebellum compared to wild-types. We showed that the Rora(sg/sg) microglia population is exclusively composed of cells displaying the characteristic morphology of activated cells, with enlarged, heavily stained cell bodies and few thick processes, in contrast to microglial cells in the wild-type. The density of microglia is 2.7-fold higher in Rora(sg/sg) than wild-type mice (22444+/-5011 cells/mm(3) versus 8158+/-1584 cells/mm(3)), although the absolute number is 4-fold smaller. These results show that neurodegeneration in the Rora(sg/sg) cerebellum leads to persistance of microglial activation while in wild-type it disappears around P10.

Early-onset neurodegenerative disease of the cerebellum and motor axons

We describe a novel hereditary neurodegenerative disease of infancy affecting an Aboriginal family from northern Manitoba, Canada. The parents are nonconsanguineous, without a family history of neurodegenerative diseases. Four of 10 siblings (three males and one female) presented with neurologic abnormalities including arthrogryposis, seizures, and severe developmental delay shortly after birth. In two children, cerebellar atrophy and mild cerebral atrophy were documented on neuroimaging. Two children, a boy who died at age 40 months and a girl who died at age 22 months, underwent muscle biopsies at 3 weeks and 4 months of age, respectively. The biopsies revealed fiber-size variability in the boy, and grouped atrophy with fiber-type grouping in the girl. Two boys who died at ages 7.5 and 37 months underwent autopsies that indicated severe atrophy of the cerebellar hemispheres (especially the inferior lobules and vermis), hypomyelination of white-matter fascicles in the striatum, severe atrophy of corticospinal tracts in the brainstem and spinal cord, and atrophy of the anterior spinal roots. In the spinal cord, motor neuron cell bodies and the posterior columns were spared. This clinical entity likely represents a novel neurodegenerative disease of the cerebellum and long motor axons.

Differential effects of melatonin on hippocampal neurodegeneration in different aged accelerated senescence prone mouse-8

OBJECTIVES

A purpose of this study is to compare the differential effects of melatonin on hippocampal neurodegeneration in accelerated senescence prone mouse-8 (SAMP8) which is initiated treatment at different age.

METHODS

The 4-months old SAMP8 mice were injected subcutaneously with melatonin (1 mg/kg/day) for 4 months. Similar treatments were performed in the 7-months old mice. When the animals were complete 11-months old, a series of tests were performed. Y maze test and Eight-arm radial maze task were used to assess cognitive performance. Hippocampal pyramidal cells were estimated by Nissl's staining. By using Gomori's methenamine silver methods, the methenamine silver staining granules (MSSG) were observed in area CA1 of hippocampus. A computer-assisted morphometric study was carried out on the ultrastructure of perikaryal CA1 pyramidal cell mitochondria. The volume density (Vv), surface density (Sv), numerical density (Nv) and mean volume (V) of the mitochondria were calculated.

RESULTS

Melatonin treatment obviously reduced the deposition of MSSG and elevated hippocampal pyramidal cell number while improving the learning and memory deficits of SAMP8. The mice initiated treatment from 4-months old exhibited a greater response to melatonin supplementation than 7-months old mice. It also decreased mean volume (V) and significantly elevated the Sv and Nv of the mitochondria in hippocampal CA1 region. However, 7-months old mice showed little effects on it.

CONCLUSIONS

Our results indicate that the protective effects of melatonin on hippocampal neurodegeneration of SAMP8 are age dependent.

CAG repeat disorder models and human neuropathology: similarities and differences

CAG repeat diseases are hereditary neurodegenerative disorders caused by expansion of a polyglutamine tract in each respective disease protein. They include at least nine disorders, including Huntington's disease (HD), dentatorubral pallidoluysian atrophy (DRPLA), spinal and bulbar muscular atrophy (SBMA), and the spinocerebellar ataxias SCA1, SCA2, SCA3 (also known as Machado-Joseph disease), SCA6, SCA7, and SCA17. It is thought that a gain of toxic function resulting from the protein mutation plays important and common roles in the pathogenesis of these diseases. Recent studies have disclosed that, in addition to the presence of clinical phenotypes and conventional neuropathology in each disease, human brains affected by CAG repeat diseases share several polyglutamine-related changes in their neuronal nuclei and cytoplasm including the formation of intranuclear inclusions. Although these novel pathologic changes also show a distribution pattern characteristic to each disease, they are generally present beyond the lesion distribution of neuronal loss, suggesting that neurons are affected much more widely than has been recognized previously. Various mouse models of CAG repeat diseases have revealed that CAG repeat lengths, which are responsible for polyglutamine diseases in humans, are not sufficient for creating the conditions characteristic of each disease in mice. Although high expression of mutant proteins in mice results in the successful generation of polyglutamine-related changes in the brain, there are still some differences from human pathology in the lesion distribution or cell types that are affected. In addition, no model has yet successfully reproduced the specific neuronal loss observed in humans. Although there are no models that fully represent the neuropathologic changes present in humans, the data obtained have provided evidence that clinical onset is not clearly associated with neuronal cell death, but depends on intranuclear accumulation of mutant proteins in neurons.

Corticobasal syndrome and primary progressive aphasia as manifestations of LRRK2 gene mutations

BACKGROUND

Mutations in the LRRK2 gene are an important cause of familial and nonfamilial parkinsonism. Despite pleomorphic pathology, LRRK2 mutations are believed to manifest clinically as typical Parkinson disease (PD). However, most genetic screens have been limited to PD clinic populations.

OBJECTIVE

To clinically characterize LRRK2 mutations in cases recruited from a spectrum of neurodegenerative diseases.

METHODS

We screened for the common G2019S mutation and several additional previously reported LRRK2 mutations in 434 individuals. A total of 254 patients recruited from neurodegenerative disease clinics and 180 neurodegenerative disease autopsy cases from the University of Pennsylvania brain bank were evaluated.

RESULTS

Eight cases were found to harbor a LRRK2 mutation. Among patients with a mutation, two presented with cognitive deficits leading to clinical diagnoses of corticobasal syndrome and primary progressive aphasia.

CONCLUSION

The clinical presentation of LRRK2-associated neurodegenerative disease may be more heterogeneous than previously assumed.

MLC1 is associated with the dystrophin-glycoprotein complex at astrocytic endfeet

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a progressive cerebral white matter disease with onset in childhood, caused by mutations in the MLC1 gene. MLC1 is a protein with unknown function that is mainly expressed in the brain in astrocytic endfeet at the blood–brain and cerebrospinal fluid–brain barriers. It shares its localization at astrocytic endfeet with the dystrophin-associated glycoprotein complex (DGC). The objective of the present study was to investigate the possible association of MLC1 with the DGC. To test this hypothesis, (co)-localization of DGC-proteins and MLC1 was analyzed by immunohistochemical stainings in gliotic brain tissue from a patient with multiple sclerosis, in glioblastoma tissue and in brain tissue from an MLC patient. In control tissue, a direct protein interaction was tested by immunoprecipitation. Results revealed that MLC1 is co-localized with DGC-proteins in gliotic brain tissue. We demonstrated that both MLC1 and aquaporin-4, a member of the DGC, were redistributed in glioblastoma cells. In MLC brain tissue, we showed absence of MLC1 and altered expression of several DGC-proteins. We demonstrated a direct protein interaction between MLC1 and Kir4.1. From these results we conclude that MLC1 is associated with the DGC at astrocytic endfeet.

Hypomyelination with atrophy of the basal ganglia and cerebellum: Follow-up and pathology

BACKGROUND AND OBJECTIVE

Hypomyelination with atrophy of the basal ganglia and cerebellum is a recently defined disorder. Only a few patients have been described. We report on 11 additional patients and new MRI findings and provide histopathologic confirmation of the MRI interpretation.

METHODS

We reviewed the patients' clinical history and present findings. We scored the MRI abnormalities. The histopathology of one patient was re-examined.

RESULTS

The patients' early psychomotor development was normal or delayed, followed by increasing extrapyramidal movement abnormalities, ataxia, and spasticity. Mental capacities were variably affected. MRI showed hypomyelination with, on follow-up, evidence of further myelin loss and variable white matter atrophy. The putamen was small or, more often, absent; the head of the caudate nucleus was decreased in size. In contrast, the thalamus and globus pallidus remained normal. Cerebellar atrophy was invariably present. Histopathology confirmed the myelin deficiency, probably related to both lack of deposition and low-grade further loss. The degeneration of putamen was subtotal. The cerebellar cortex was affected, particularly the granular layer.

CONCLUSION

Hypomyelination with atrophy of the basal ganglia and cerebellum is a syndrome diagnosed by distinctive MRI findings. Histopathology confirms hypomyelination, low-grade further myelin loss, subtotal degeneration of the putamen, and cerebellar cortical atrophy. All known patients are sporadic, and the mode of inheritance is unclear.

Huntington's disease--like 2 is associated with CUG repeat-containing RNA foci

OBJECTIVE

Huntington's disease-like 2 (HDL2) is caused by a CAG/CTG expansion mutation on chromosome 16q24.3. The repeat falls, in the CTG orientation, within a variably spliced exon of junctophilin-3 (JPH3). The existence of a JPH3 splice variant with the CTG repeat in 3' untranslated region suggested that transcripts containing an expanded CUG repeat could play a role in the pathogenesis of HDL2, similar to the proposed pathogenic role of expanded CUG repeats in myotonic dystrophy type 1 (DM1). The goal of this study, therefore, was to test the plausibility of an RNA gain-of-function component in the pathogenesis of HDL2.

METHODS

The presence and composition of RNA foci in frontal cortex from HDL2, Huntington's disease, DM1, and control brains were investigated by in situ hybridization and immunohistochemistry. An untranslatable JPH3 transcript containing either a normal or an expanded CUG repeat was engineered and expressed in human embryonic kidney 293 and HT22 cells to further test the toxic RNA hypothesis. The formation of RNA foci and the extent of cell death were quantified.

RESULTS

RNA foci resembling DM1 foci were detected in neurons in HDL2 cortex and other brain regions. Similar to DM1, the foci colocalize with muscleblind-like protein 1, and nuclear muscleblind-like protein 1 in HDL2 cortical neurons is decreased relative to controls. In cell experiments, expression of a JPH3 transcript with an expanded CUG repeat resulted in the formation of RNA foci that colocalized with muscleblind-like protein 1 and in cell toxicity.

INTERPRETATION

These results imply that RNA toxicity may contribute to the pathogenesis of HDL2.

Neuropathologic heterogeneity in HDDD1: a familial frontotemporal lobar degeneration with ubiquitin-positive inclusions and progranulin mutation

Hereditary dysphasic disinhibition dementia (HDDD) describes a familial disorder characterized by personality changes, and language and memory deficits. The neuropathology includes frontotemporal lobar atrophy, neuronal loss and gliosis and, in most cases, abundant Abeta plaques and neurofibrillary tangles (NFTs). A Pick/Alzheimer's spectrum was proposed for the original family (HDDD1). Here we report the clinicopathologic case of an HDDD1 individual using modern immunohistochemical methods, contemporary neuropathologic diagnostic criteria to distinguish different frontotemporal lobar degenerations (FTLDs), and progranulin (PRGN) mutation analysis. Clinical onset was at age 62 years with personality changes and disinhibition, followed by nonfluent dysphasia, and memory loss that progressed to muteness and total dependence with death at age 84 years. There was severe generalized brain atrophy (weight=570 g). Histopathology showed superficial microvacuolation, marked neuronal loss, gliosis, and ubiquitin-positive, tau-negative cytoplasmic and intranuclear neuronal inclusions in frontal, temporal, and parietal cortices. There were also frequent neuritic plaques and NFTs in parietal and occipital cortices. The case met neuropathologic criteria for both FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and Alzheimer disease (Braak NFT stage V). We discovered a novel pathogenic PGRN mutation c.5913 A>G (IVS6-2 A>G) segregating with FTLD-U in this kindred. In conclusion, HDDD1 is an FTLD-U caused by a PGRN mutation and is neuropathologically heterogeneous with Alzheimer disease as a common comorbidity.

A novel splice site mutation in the Cockayne syndrome group A gene in two siblings with Cockayne syndrome

Cockayne syndrome (CS) is mainly caused by mutations in the Cockayne syndrome group A or B (CSA or CSB) genes which are required for a sub-pathway of nucleotide excision repair entitled transcription coupled repair. Approximately 20% of the CS patients have mutations in CSA, which encodes a 44 kDa tryptophane (Trp, W) and aspartic acid (Asp, D) amino acids (WD) repeat protein. Up to now, nine different CSA mutations have been identified. We examined two Somali siblings 9 and 12 years old with clinical features typical of CS including skin photosensitivity, progressive ataxia, spasticity, hearing loss, central and peripheral demyelination and intracranial calcifications. Molecular analysis showed a novel splice acceptor site mutation, a G to A transition in the -1 position of intervening sequence 6 (g.IVS6-1G>A), in the CSA (excision repair cross-complementing 8 (ERCC8)) gene. IVS6-1G>A results in a new 28 amino acid C-terminus and premature termination of the CSA protein (G184DFs28X). A review of the CSA protein and the 10 known CSA mutations is also presented.

Fragile X-associated tremor/ataxia syndrome--an older face of the fragile X gene

BACKGROUND

A 76-year-old man presented with an 8-year history of balance problems and a 2-year history of short-term memory loss. He had also been experiencing long-term problems with impotence and episodes of urinary incontinence, and had been managed for hypertension for 25 years. His medical history was otherwise unremarkable. Three of his grandchildren had been diagnosed with fragile X syndrome.

INVESTIGATIONS

Neurological examination, cognitive and neuropsychological testing, nerve conduction studies, MRI, and genetic testing.

DIAGNOSIS

Fragile X-associated tremor/ataxia syndrome (FXTAS) resulting from a premutation (CGG repeat) expansion of the FMR1 gene.

MANAGEMENT

Explanation of the genetic ramifications of premutation carrier status for the FMR1 gene, and symptomatic treatment for the clinical difficulties experienced by the patient.

Spinocerebellar ataxia type 17 is caused by mutations in the TATA-box binding protein

The spinocerebellar ataxia type 17 (SCA17) is characterized by cerebellar ataxia, dementia, and involuntary movements, including chorea and dystonia. In addition, psychiatric symptoms, pyramidal signs, and rigidity are common. MRI shows variable atrophy of the cerebrum, brainstem, and cerebellum. The autosomal dominantly inherited progressive neurodegenerative disorder is caused by an expanded CAA/CAG repeat coding for glutamine. Alleles of the normal range carry 25 to 42 glutamine residues, disease causing alleles 43 to 63. Alleles with 43 to 48 glutamine codons may be associated with incomplete penetrance. The mean age of onset is about 30 years for individuals with full-penetrance alleles, but ranges from three to 55 years.

wasted away, a Drosophila mutation in triosephosphate isomerase, causes paralysis, neurodegeneration, and early death

To identify genes required for maintaining neuronal viability, we screened our collection of Drosophila temperature-sensitive paralytic mutants for those exhibiting shortened lifespan and neurodegeneration. Here, we describe the characterization of wasted away (wstd), a recessive, hypomorphic mutation that causes progressive motor impairment, vacuolar neuropathology, and severely reduced lifespan. We demonstrate that the affected gene encodes the glycolytic enzyme, triosephosphate isomerase (Tpi). Mutations causing Tpi deficiency in humans are also characterized by progressive neurological dysfunction, neurodegeneration, and early death. In Tpi-deficient flies and humans, a decrease in ATP levels did not appear to cause the observed phenotypes because ATP levels remained normal. We also found no genetic evidence that the mutant Drosophila Tpi was misfolded or involved in aberrant protein-protein associations. Instead, we favor the hypothesis that mutations in Tpi lead to an accumulation of methylglyoxal and the consequent enhanced production of advanced glycation end products, which are ultimately responsible for the death and dysfunction of Tpi-deficient neurons. Our results highlight an essential protective role of Tpi and support the idea that advanced glycation end products may also contribute to pathogenesis of other neurological disorders.

Polyglutamine disease: Recent advances in the neuropathology of dentatorubral-pallidoluysian atrophy

Polyglutamine diseases are hereditary neurodegenerative disorders that are caused by the expansion of a CAG repeat in the causative genes. They comprise at least nine disorders, including DRPLA, HD, and Machado-Joseph disease. Initially, the discovery of neuronal intranuclear inclusions (NIIs) in human brains and in a murine model of HD provided a plausible hypothesis that the expression of expanded polyglutamine stretches leads to NII formation, resulting in neuronal cell death in selective brain regions characteristic to each disease. Recent studies, however, suggest that nuclear dysfunction, especially transcriptional abnormalities caused by the diffuse intranuclear accumulation of mutant proteins, plays a pivotal role in the development and progression of clinical symptoms. Polyglutamine diseases have a similarity with neuronal storage disease, and this pathological process might become a target for the establishment of an effective therapy for these diseases.

Huntington's disease: seeing the pathogenic process through a genetic lens

Thirteen years ago, the culmination of genetic rather than biochemical strategies resulted in the identification of the root cause of Huntington's disease: an expanded CAG trinucleotide repeat that leads to an elongated polyglutamine tract in the huntingtin protein. Since then, biochemical and cell biological attempts to elucidate pathogenesis have largely focused on N-terminal polyglutamine-containing huntingtin fragments. However, continued application of genetic strategies has suggested that the disease process is, in fact, triggered by the presence of expanded polyglutamine in intact huntingtin. An increased emphasis on the earliest presymptomatic stages of the disease, facilitated by incorporating genetic lessons from human patients into the search for biochemical targets, could provide a route to a rational treatment to prevent or slow the onset of this devastating neurodegenerative disorder.

p53-Mediated Apoptosis, Neuroglobin Overexpression, and Globin Deposits in a Patient With Hereditary Ferritinopathy

The apoptotic death of putaminal neurons and glia in a patient with hereditary ferritinopathy is studied immunohistochemically with antibodies to p53, activated caspase-3, PUMA, BAX, cytochrome c, and inducible nitric oxide synthase. In addition to the overexpression of ferritin and the iron accumulations assumed to result from the genetically incompetent ferritin molecule, additional contributions to the iron, heme, and hyaline deposits in this disease are sought with antibodies to 2 recently discovered globins in humans, neuroglobin and cytoglobin. The "pathognomonic" swollen to vacuolated nuclei are immunoreactive for both p53 and activated caspase-3, indicating the intervention of the p53-mediated apoptotic pathway. The immunohistochemical demonstration of neuroglobin in the swollen nuclei and both globins in the hyaline deposits highlights the potential pathogenic importance of 2 other iron-containing proteins in this disease that is largely restricted to brain. Hereditary ferritinopathy is the first human disease in which abnormalities in these heme-containing proteins are demonstrated.

The role of mitochondria in inherited neurodegenerative diseases

In the past decade, the genetic causes underlying familial forms of many neurodegenerative disorders, such as Huntington's disease, Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, Friedreich ataxia, hereditary spastic paraplegia, dominant optic atrophy, Charcot-Marie-Tooth type 2A, neuropathy ataxia and retinitis pigmentosa, and Leber's hereditary optic atrophy have been elucidated. However, the common pathogenic mechanisms of neuronal death are still largely unknown. Recently, mitochondrial dysfunction has emerged as a potential 'lowest common denominator' linking these disorders. In this review, we discuss the body of evidence supporting the role of mitochondria in the pathogenesis of hereditary neurodegenerative diseases. We summarize the principal features of genetic diseases caused by abnormalities of mitochondrial proteins encoded by the mitochondrial or the nuclear genomes. We then address genetic diseases where mutant proteins are localized in multiple cell compartments, including mitochondria and where mitochondrial defects are likely to be directly caused by the mutant proteins. Finally, we describe examples of neurodegenerative disorders where mitochondrial dysfunction may be 'secondary' and probably concomitant with degenerative events in other cell organelles, but may still play an important role in the neuronal decay. Understanding the contribution of mitochondrial dysfunction to neurodegeneration and its pathophysiological basis will significantly impact our ability to develop more effective therapies for neurodegenerative diseases.

The spectrum of clinical disease caused by the A467T and W748S POLG mutations: a study of 26 cases

We studied 26 patients belonging to 20 families with a disorder caused by mutations in the POLG gene. The patients were homozygous for 1399 G/A or 2243 G/C (giving the amino acid changes A467T and W748S, respectively) or compound heterozygotes for these two mutations. Irrespective of genotype, the patients exhibited a progressive neurological disorder usually starting in their teens and characterized by epilepsy, headache, ataxia, neuropathy, myoclonus and late onset ophthalmoplegia. However, major differences in survival were seen depending on genotype, with compound heterozygotes having a significantly shorter survival time than patients homozygous either for the A467T or W748S (P = 0.006). Epilepsy occurred in 22 of the 26 patients and in the majority of these there was an occipital EEG focus. Episodes of both generalized and focal motor status epilepticus were common and highly resistant to treatment, even with generalized anaesthesia. Status epilepticus was the recorded cause of death in 9 of 11 patients. Liver failure was the sole cause of death in two patients and evolved terminally in six others, all but one of whom were being treated with sodium valproate. Two patients underwent liver transplantation, but only one survived. Delayed psychomotor development and subsequent cognitive decline also occurs. This study demonstrates the clinical spectrum of a disorder that combines features of Alpers' syndrome and a later onset mitochondrial spinocerebellar ataxia with epilepsy and headache. Patients with this disorder are at high risk of death from status epilepticus and from liver failure, if exposed to sodium valproate. Each mutation appears capable of producing a disorder that is recessively inherited, although we also find evidence in one patient suggesting that heterozygotes may manifest. Compound heterozygotes have a significantly more severe phenotype raising the possibility of a dominant negative effect.

In situ stem cell therapy: novel targets, familiar challenges

Tissue engineering approaches for expanding, differentiating and engrafting embryonic or adult stem cells have significant potential for tissue repair but harnessing endogenous stem cell populations offers numerous advantages over these approaches. There has been rapid basic biological progress in the identification of stem cell niches throughout the body and the molecular factors that regulate their function. These niches represent novel therapeutic targets and efforts to use them involve the familiar challenges of delivering molecular medicines in vivo. Here we review recent progress in the use of genes, proteins and small molecules for in situ stem cell control and manipulation, with a focus on using stem cells of the central nervous system for neuroregeneration.

MRI of a family with leukoencephalypathy with vanishing white matter

Leukoencephalopathy with vanishing white matter (VWM) is a newly described entity with characteristic MRI features. We report the cranial MRI findings in three sisters with slowly progressive neurological deterioration. The MRI showed symmetrical diffuse abnormalities of cerebral white matter with hypointensity on FLAIR images. The diagnosis of leukoencephalopathy with VWM was made on the basis of genetic analysis.

Dynamic regulation of molecular chaperone gene expression in polyglutamine disease

Expanded polyglutamine disease proteins cause adult-onset progressive neurodegeneration. Constitutive overexpression of the Hsp70 molecular chaperone is capable of suppressing polyglutamine neurodegeneration. We showed that endogenous Hsp70 expression was induced, at both transcriptional and translational levels, in Drosophila models of polyglutamine disease. Soon after the endogenous Hsp70 induction reached a maximum level at larval stage, its expression declined progressively with age. We further showed that cellular heat shock response remained intact in aged flies, indicating the decline of Hsp70 levels observed in polyglutamine-expressing flies is not due to normal ageing. In contrast to the well-documented polyglutamine suppression caused by constitutive Hsp70 overexpression, no suppression of degeneration was observed when inducible copies of hsp70 transgenes were instead coexpressed. This supports a transcriptional dysregulation of endogenous hsp70 gene induction in polyglutamine flies. Altogether, we propose that transcriptional malfunctioning of molecular chaperone gene expression contributes to the late-onset and progressive nature of polyglutamine toxicity.

Canine spongiform leukoencephalomyelopathy is associated with a missense mutation in cytochrome b

Two families of dogs (Australian cattle dogs and Shetland sheepdogs) with an inherited "spongiform leukoencephalomyelopathy" were identified, with widespread vacuolation of white matter of the brain and spinal cord. Affected dogs of both breeds developed tremors at 2-9 weeks of age followed by progressive neurological worsening with ataxia, paresis, paralysis, spasticity, and cranial nerve dysfunction. The modes of inheritance of both families were most likely maternal. The cerebrospinal fluid (CSF) analysis showed elevated ratio of 3-OH butyrate to acetoacetic acid. Mitochondrial DNA sequencing showed a G to A transition at 14,474 nt (G14474A, GenBank accession no. NC002008 ) that results in an amino acid change of valine-98 to methionine (V98M) of mitochondrial encoded cytochrome b. Western blot analysis showed increased levels of core I and core II but decreased level of cytochrome c1 of the complex III and cytochrome c oxidase of the complex IV of the respiratory chain.

Histology of hereditary neuralgic amyotrophy

We report the findings in five muscle and three sural nerve biopsies, and in one postmortem plexus specimen, from six patients with hereditary neuralgic amyotrophy (HNA). We found that the sensory nerves are definitely involved in HNA despite the mainly motor symptoms, and that lesions in nerves and muscles are more widespread throughout the peripheral nervous system than clinically presumed, but, simultaneously, very focally affect isolated fascicles within individual nerves.