Formation of advanced glycation end‐product‐modified superoxide dismutase‐1 (SOD1) is one of the mechanisms responsible for inclusions common to familial amyotrophic lateral sclerosis patients with SOD1 gene mutation,and transgenic mice expressing human SOD1 gene mutation

Neuronal Lewy body‐like hyaline inclusions (LBHI) and astrocytic hyaline inclusions (Ast‐HI) are morphological hallmarks of certain familial amyotrophic lateral sclerosis (FALS) patients with superoxide dismutase‐1 (SOD1) gene mutations, and transgenic mice expressing the human SOD1 gene mutation. The ultrastructure of inclusions in both diseases is identical: the essential common constituents are granule‐coated fibrils approximately 15– 25 nm in diameter and granular materials. Detailed immunohistochemical analyses have shown that the essential common protein of the inclusions in both diseases is an SOD1 protein. This finding, together with the immunoelectron microscopy finding that the abnormal granule‐coated fibrils comprising the inclusions are positive for SOD1, indicates that these granule‐coated fibrils containing SOD1 are important evidence for mutant SOD1‐linked disease in human and mouse. For im‐munoelectron microscopy, the granule‐coated fibrils are modified by advanced glycation endproducts (AGE) such as N^?‐carboxymethyl lysine, pyrraline and pentosidine (Maillard reaction). Based on the fact that AGE themselves are insoluble molecules with direct cytotoxic effects, the granule‐coated fibrils and granular materials are not digested by the lysosomal and ubiquitin systems. The neurons and astrocytes of the normal individuals and non‐transgenic mice show no significant immunoreactivity for AGE. Considered with the mutant‐SOD1 aggregation toxicity, a portion of the SOD1 comprising both types of the inclusion is modified by the AGE, and the formation of the AGE‐modified SOD1 (probably AGE‐modified mutant SOD1) is one of the mechanisms responsible for the aggregation (i.e. granule‐coated fibril formation).     

HtrA2/Omi‐immunoreactive intraneuronal inclusions in the anterior horn of patients with sporadic and Cu/Zn superoxide dismutase (SOD1) mutant amyotrophic lateral sclerosis

Y. Kawamoto, H. Ito, Y. Kobayashi, Y. Suzuki, I. Akiguchi, H. Fujimura, S. Sakoda, H. Kusaka, A. Hirano and R. Takahashi (2010) Neuropathology and Applied Neurobiology 36, 331–344
HtrA2/Omi‐immunoreactive intraneuronal inclusions in the anterior horn of patients with sporadic and Cu/Zn superoxide dismutase (SOD1) mutant amyotrophic lateral sclerosis Aims: HtrA2/Omi is a mitochondrial serine protease that promotes the apoptotic processes, but the relationship between HtrA2/Omi and amyotrophic lateral sclerosis (ALS) is still unknown. The purpose of the present study was to determine whether abnormal expression of HtrA2/Omi occurs in patients with ALS. Methods: We prepared autopsied spinal cord tissues from 7 control subjects, 11 patients with sporadic ALS (SALS) and 4 patients with Cu/Zn superoxide dismutase (SOD1)‐related familial ALS (FALS). We then performed immunohistochemical studies on HtrA2/Omi using formalin‐fixed, paraffin‐embedded sections from all of the cases. Results: In the control subjects, the anterior horn cells were mildly to moderately immunostained with HtrA2/Omi. In the patients with SALS, strong HtrA2/Omi immunoreactivity was found in some skein‐like inclusions and round hyaline inclusions as well as many spheroids, but Bunina bodies were immunonegative for HtrA2/Omi. In the patients with SOD1‐related FALS, Lewy body‐like hyaline inclusions were observed in three cases and conglomerate inclusions were observed in the remaining case, and both types of inclusions were intensely immunopositive for HtrA2/Omi. Conclusions: These results suggest that abnormal accumulations of HtrA2/Omi may occur in several types of motor neuronal inclusions in the anterior horn from SALS and SOD1‐linked FALS cases, and that HtrA2/Omi may be associated with the pathogenesis of both types of ALS.     

Golgi apparatus of the motor neurons in patients with amyotrophic lateral sclerosis and in mice models of amyotrophic lateral sclerosis

We examined the Golgi apparatus (GA) of motor neurons of patients with ALS and in mice models of ALS by immunohistological method using antiserum against MG160 and against components of the trans‐Golgi network (TGN46). The GA of half of the remaining spinal cord motor neurons of patients with sporadic ALS showed fragmentation, where the GA were dispersed or fragmented into numerous small, isolated elements. The GA of Betz cells in sporadic ALS were fragmented similar to that of anterior horn cells, and the GA of spinal cord motor neurons of those with familial ALS and of those with ALS with basophilic inclusions were fragmented or diminished. The GA in the majority of the motor neurons contained Bunina bodies, basophilic inclusions and superoxide dismutase 1 (SOD1)‐positive aggregates were fragmented. The motor neurons in transgenic mice expressing G93A mutation of the SOD1 gene showed the fragmentation of the GA months before the onset of paralysis. These findings suggest that the fragmentation of GA may be related to the neuronal degeneration in patients with ALS.     

Colocalization of Bunina bodies and TDP‐43 inclusions in a case of sporadic amyotrophic lateral sclerosis with Lewy body‐like hyaline inclusions

Sporadic amyotrophic lateral sclerosis (sALS) is characterized pathologically by loss of upper and lower motor neurons with occurrence of transactivation response DNA‐binding protein 43 kDa (TDP‐43)‐immunoreactive skein‐like and round hyaline inclusions. Lewy body‐like hyaline inclusions (LBHIs) are also found in a small proportion of sALS cases as well as in individuals with familial ALS with mutations in the Cu/Zu superoxide dismutase (SOD1) gene. LBHIs in sALS are immunopositive for TDP‐43, but not for SOD1. The occurrence of Bunina bodies (BBs) is another key pathological feature of sALS. BBs are immunonegative for TDP‐43 but immunopositive for cystatin C, transferrin, peripherin and sortilin‐related receptor CNS expressed 2 (SorCS2). Despite differences between BBs and TDP‐43 inclusions in terms of protein constituents and ultrastructure, the two inclusions are known to be linked. We recently encountered a case of sALS of 10 months duration in which many round hyaline inclusions, LBHIs and BBs were found in the anterior horn cells of the spinal cord. Our immunohistochemical and ultrastructural examinations revealed the presence of BBs within the skein‐like and round hyaline inclusions, and in the LBHIs. Colocalization of BB‐related proteins (cystatin C, transferrin and SorCS2) and TDP‐43 was also confirmed in the halo of LBHIs as well as in the marginal portion of the skein‐like and round hyaline inclusions. These findings suggest that there is some relationship between BBs and TDP‐43‐immunoreactive inclusions in terms of their formation processes.     

Amyotrophic lateral sclerosis: recent insights from transgenic animal models with SOD1 mutations]

Mutations in Cu/Zn superoxide dismutase (SOD1) have been linked to some familial cases of amyotrophic lateral sclerosis (ALS). In order to reproduce the different degree of toxicity to the mutant protein by mutations, we generated new transgenic mice with two mutations from which the progression of the disease in human family is rapid (L84V) or extremely slow (H46R). By comparing the two transgenic mice with different SOD1 mutations, we demonstrate that the time course and the first symptoms in these mice were likely to human SOD1-mediated familial ALS. In addition, we report here that rats that express a human SOD1 transgene with two different ALS-associated mutations (G93A and H46R) develop striking motor neuron degeneration and paralysis. The larger size of this rat model as compared with the ALS mice will facilitate studies involving manipulations of spinal fluid (implantation of intrathecal catheters for chronic therapeutic studies; CSF sampling) and spinal cord (e.g., direct administration of viral- and cell-mediated therapies). Using this rat model we showed that intrathecal administration of the hepatocyte growth factor attenuates motoneuron death and prolongs the duration of the disease of transgenic rats.     

Histological Evidence of Protein Aggregation in Mutant SOD1 Transgenic Mice and in Amyotrophic Lateral Sclerosis Neural Tissues

The mechanisms leading to neurodegeneration in ALS (amyotrophic lateral sclerosis) are not well understood, but cytosolic protein aggregates appear to be common in sporadic and familial ALS as well as transgenic mouse models expressing mutant Cu/Zn superoxide dismutase (SOD1). In this study, we systematically evaluated the presence of these aggregates in three different mouse models (G93A, G85R, and G37R SOD1) and compared these aggregates to those seen in cases of sporadic and familial ALS. Inclusions and loss of motor neurons were observed in spinal cords of all of these three mutant transgenic lines. Since a copper-mediated toxicity hypothesis has been proposed to explain the cytotoxic gain-of-function of mutant SOD1, we sought to determine the involvement of the copper chaperone for SOD1 (CCS) in the formation of protein aggregates. Although all aggregates contained CCS, SOD1 was not uniformly found in the inclusions. Similarly, CCS-positive skein-like inclusions were rarely seen in ALS neurons. These studies do not provide strong evidence for a causal role of CCS in aggregate formation, but they do suggest that protein aggregation is a common event in all animal models of the disease. Selected proteins, such as the glutamate transporter GLT-1, were not typically observed within the inclusions. Most inclusions were positively stained with antibodies recognizing ubiquitin, proteasome, Hsc70 in transgenic lines, and some Hsc70-positive inclusions were detected in sporadic ALS cases. Overall, these observations suggest that inclusions might be sequestered into ubiquitin-proteasome pathway and some chaperone proteins such as Hsc70 may be involved in formation and/or degradation of these inclusions.     

Nonoxidative protein glycation is implicated in familial amyotrophic lateral sclerosis with superoxide dismutase-1 mutation

To assess a role for oxidative stress in the pathogenesis of amyotrophic lateral sclerosis (ALS), we analyzed the immunohistochemical localization of 8-hydroxy-2′-deoxyguanosine (OHdG) as a nucleic acid oxidation product, acrolein-protein adduct and 4-hydroxy-2-nonenal (HNE)-protein adduct as lipid peroxidation products, N ^ɛ-carboxymethyl-lysine (CML) as a lipid peroxidation or protein glycoxidation product, pentosidine as a protein glycoxidation product, and imidazolone and pyrraline as nonoxidative protein glycation products in the spinal cord of three familial ALS patients with superoxide dismutase-1 (SOD1) A4V mutation, six sporadic ALS patients, and six age-matched control individuals. The spinal cord sections of the control cases did not show any distinct immunoreactivities for these examined products. In the familial ALS cases, intense immunoreactivities for pyrraline and CML were confined to the characteristic Lewy body-like hyaline inclusions, and imidazolone immunoreactivity was located in the cytoplasm of the residual motor neurons. No significant immunoreactivities for other examined products were detected in the familial ALS spinal cords. In the sporadic ALS cases, intense immunoreactivities for pentosidine, CML and HNE-protein adduct were seen in the cytoplasm of the degenerated motor neurons, and OHdG immunoreactivity was located in the cell nuclei of the residual neurons and glial cells. The present results indicate that oxidative reactions are involved in the disease processes of sporadic ALS, while there is no evidence for increased oxidative damage except for CML deposition in the familial ALS spinal cords. Furthermore, it is likely that the accumulation of pyrraline and imidazolone supports a nonoxidative mechanism in SOD1-related motor neuron degeneration. Received: 18 August 1999 / Revised, accepted: 17 November 1999     

Astrocytic hyaline inclusions contain advanced glycation endproducts in familial amyotrophic lateral sclerosis with superoxide dismutase 1 gene mutation: immunohistochemical and immunoelectron microscopical analyses

To clarify the neuropathological significance of the deposition of N ^ɛ -carboxymethyl lysine (CML), an advanced glycation endproduct, in astrocytic hyaline inclusions in familial amyotrophic lateral sclerosis (FALS), autopsy specimens from five members of two different families who had the superoxide dismutase 1 (SOD1) gene mutations were analysed. Immunohistochemically, most of the neuronal and astrocytic hyaline inclusions were intensely stained by the antibody against CML. The distributions and intensities of the immunoreactivities for CML and SOD1 were similar in the inclusions in both cell types. Immunoelectron microscopy showed that both inclusions consisted of CML-positive granule-coated fibrils and granular materials. No significant CML or SOD1 immunoreactivity was observed in the neurons and astrocytes of the normal control subjects. Our results suggest that astrocytic hyaline inclusions contain CML and SOD1 in FALS patients with SOD1 gene mutations, and that the formation of CML-modified protein (probably CML-modified SOD1) is related to the cell degeneration. Received: 3 July 1998 / Revised, accepted: 21 September 1998     

Presence of Cu/Zn superoxide dismutase (SOD) immunoreactivity in neuronal hyaline inclusions in spinal cords from mice carrying a transgene for Gly93Ala mutant human Cu/Zn SOD

This investigation deals with the immunocytochemical localization of Cu/Zn superoxide dismutase (SOD) in the spinal cord neurons of transgenic mice that overexpress Gly93Ala mutant human Cu/Zn SOD and demonstrate clinicopathological features similar to human amyotrophic lateral sclerosis (ALS) with Cu/Zn SOD mutation. At low magnification of light microscopy, the gray and white matter of the spinal cord of Gly93Ala mice showed more intense Cu/Zn SOD immunoreactivity than that of control mice. At higher magnification, the cytoplasm of control mice neurons displayed a distinct staining for Cu/Zn SOD, whereas the surrounding neuropil was only weakly stained. In contrast, the intensity of Cu/ Zn SOD immunoreactivity in the cytoplasm of the majority of Gly93Ala mice neurons was similar to that in the neuropil. Almost all neuronal hyaline inclusions (NHIs) of Gly93Ala mice were positively immunostained by antibodies to Cu/Zn SOD, ubiquitin and phosphorylated neurofilament protein (NFP), the intensities of which were much higher in the NHIs than in the surrounding cytoplasm. In control mice, significant Cu/Zn SOD precipitation was not observed to be limited to any particular region of the neuronal cytoplasm. Intracytoplasmic vacuoles in the neuronal soma and processes of Gly93Ala mice were not stained by any of these antibodies. These results indicate that Cu/Zn SOD colocalizes with ubiquitin and phosphorylated NFP in NHIs of mice expressing mutant Cu/Zn SOD; similar findings have been shown for Lewy body-like inclusions of familial ALS patients with Cu/Zn SOD mutation. Moreover, our results point to the possibility that Cu/Zn SOD mutation may have a role in the abnormal Cu/Zn SOD accumulation in the NHIs, in association with motor neuron degeneration. Received:16 July 1997 / Revised, accepted: 25 September 1997     

Advanced glycation endproducts are deposited in neuronal hyaline inclusions: a study on familial amyotrophic lateral sclerosis with superoxide dismutase-1 mutation

To determine the role of advanced glycation endproducts (AGE) in the pathogenesis of familial amyotrophic lateral sclerosis (ALS) with superoxide dismutase-1 (SOD1) mutation, we investigated the immunohistochemical localization of N(epsilon)-carboxymethyl-lysine (CML), one of the major AGE structures, in spinal cords from three familial ALS patients with a heterozygous Ala to Val substitution at codon 4 in the gene for SOD1. Neuronal hyaline inclusions (NHIs), the abnormal structures seen in some of the remaining lower motor neurons of familial ALS patients with SOD1 mutation, were intensely stained by a monoclonal antibody specific for CML in contrast to the only weakly stained cytoplasm. Immunoelectron microscopy depicted the CML determinants restricted to the granule-associated thick linear structures that mainly compose the NHIs. The NHIs were also recognized by antibodies to SOD1, phosphorylated neurofilament protein and ubiquitin. No focal collection of either CML or SOD1 was found in neurons of the control individuals. Our results indicate that CML is a component of the NHIs of familial ALS patients with SOD1 mutation, and suggest that the CML formation may be mediated by protein glycoxidation or lipid peroxidation in the presence of oxidative stress from mutant SOD1, in association with motor neuron degeneration.     

Phosphorylated Smad2/3 immunoreactivity in sporadic and familial amyotrophic lateral sclerosis and its mouse model

Phosphorylated Smad2/3 (pSmad2/3), the central mediators of transforming growth factor (TGF)-beta signaling, were recently identified in tau-positive inclusions in certain neurodegenerative disorders. To clarify whether the localization of pSmad2/3 is altered in amyotrophic lateral sclerosis (ALS), we immunohistochemically examined spinal cords from sporadic ALS (SALS), from familial ALS (FALS) patients with the A4V mutation in their Cu/Zn superoxide dismutase (SOD1) gene, and from G93A mutant SOD1 transgenic (mSOD1 Tg) mice. In control spinal cords, pSmad2/3 immunoreactivity was observed exclusively in neuronal and glial nuclei. In SALS and FALS patients the nuclei showed increased immunoreactivity for pSmad2/3. Noticeably, round hyaline inclusions (RHIs) and skein-like inclusions of SALS patients were immunoreactive for pSmad2/3. Double immunofluorescence staining for pSmad2/3 and transactive response-DNA-binding protein (TDP)-43 revealed co-localization of these proteins within RHIs. In contrast, Bunina bodies in SALS and Lewy body-like hyaline inclusions (LBHIs) in FALS were devoid of labeling for pSmad2/3. Similarly, in the mSOD1 Tg mice pSmad2/3 immunoreactivity was increased in the nuclei, while LBHIs were not labeled. These findings suggest increased TGF-beta-Smad signaling in SALS, FALS, and mSOD1 Tg mice, as well as impaired TGF-beta signal transduction in RHI-bearing neurons of SALS patients, presumably at the step of pSmad2/3 translocation into the nucleus. The pathomechanisms, including the process of inclusion development, appears to be different between SALS and mSOD1-related FALS or Tg mice.     

Familial amyotrophic lateral sclerosis and Cu/Zn superoxide dismutase mutation

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that involves mainly the motor neuron system. Five to 10 percent of the ALS cases are familial; most others are sporadic. Several mutations in the superoxide dismutase-1 (SOD1) gene have recently been shown to be associated with about 20% of familial ALS patients. The reduced enzyme activity of many mutant SOD1 points to the possibility that a loss-of-function effect of the mutant enzyme is responsible for the pathogenesis of the disease. However, this conflicts with the autosomal dominant inheritance of SOD1 mutation-associated ALS and the normal SOD1 activity in homozygous patients in a SOD1-linked ALS family. Current biochemical investigations have provided evidence that mutant SOD1 may catalyze the peroxynitrite-mediated nitration of protein tyrosine residues, release copper and zinc ions, facilitate apoptosis of neurons and have enhanced peroxidase activity. Immunocytochemical studies demonstrated the presence of intense SOD1 immunoreactivity in Lewy body-like inclusions, which are characteristic features of a certain form of familial ALS with posterior column involvement, in the lower motor neurons of patients in ALS families with different SOD1 mutations. More recently, strains of transgenic mice expressing mutant SOD1 have been established. These mice clinicopathologically develop a motor neuron disease mimicking human ALS with the exception of pronounced intraneuronal vacuolar degeneration. The overexpression of wild-type SOD1 in mice has failed to give rise to the disease. Only one transgene for mutant SOD1 is enough to cause motor neuron degeneration and the severity of clinical course correlates with the transgene copy number. These observations in SOD1-linked familial ALS and its transgenic mouse model suggest a novel neurotoxic function of mutant SOD1.     

Apoptosis‐Inducing Factor and Cyclophilin A Cotranslocate to the Motor Neuronal Nuclei in Amyotrophic Lateral Sclerosis Model Mice

Aims: Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease whose mechanism is not understood. Recently, it was reported that apoptosis‐inducing factor (AIF) was involved in motor neuronal cell death in ALS model mice, and AIF‐induced neuronal cell death by interacting with cyclophilin A (CypA). However, it is unknown whether the CypA and AIF‐complex induces chromatinolysis in ALS. Therefore, in the present study, we investigated the process of motor neuron degeneration as the disease progresses and to determine whether the CypA‐AIF complex would play a role in inducing motor neuronal cell death in mutant superoxide dismutase 1 (SOD1)^G93A ALS model mice. Methodology: We prepared the nuclear fractions of spinal cords and demonstrated the nuclear translocation of CypA with AIF in SOD1^G93A mice by immunoprecipitation. The localization of CypA and AIF in the spinal cords was assessed by immunohistochemistry. Results: In the spinal cords of SOD1^G93A mice, the expressions of CypA and AIF were detected in the motor neurons, and CypA and AIF cotranslocated to the motor neuronal nuclei with CypA. Furthermore, the expression of CypA was detected in GFAP‐positive astrocytes, but not in CD11b‐positive microglial cells. On the other hand, these findings were not detected in the spinal cords of wild‐type mice. Conclusions: From these results, we suggest that CypA and AIF may play cooperative and pivotal roles in motor neuronal death in the murine ALS model.     

An autopsy case of sporadic amyotrophic lateral sclerosis associated with the I113T SOD1 mutation

A 64‐year‐old man noticed weakness in his arms and dyspnea upon exertion. Four months later he was admitted to our hospital, where muscle atrophy and hyperactive deep tendon reflexes in the arms were observed upon examination. A needle electromyograph study revealed acute and chronic denervation in the extremities, and he was diagnosed as having amyotrophic lateral sclerosis (ALS). Seven months after onset of the disease, he died of respiratory failure. Neuropathologically, neuronal cell loss was observed in the motor cortex, hypoglossal nuclei, cervical and lumbar anterior horns and Clarke's nuclei. Some of the remaining neurons contained neurofilamentous conglomerate inclusions (CIs). A small number of Lewy body‐like hyaline inclusions (LBHIs) were also observed. No the Bunina bodies, skein‐like inclusions or basophilic inclusions were detectable. Tract degeneration was moderate in the dorsal and ventral spinocerebellar tracts, mild in the pyramidal tract, but not discerned in the posterior column. Immunohistochemical examinations revealed that the CIs were strongly positive for phosphorylated neurofilament and moderately positive for ubiquitin and Cu/Zn superoxide dismutase 1 (SOD1). Moreover, a number of phosphorylated tau protein‐positive globose neurofibrillary tangles (NFTs) and threads were observed in the periaqueductal gray matter, oculomotor nuclei and trochlear nuclei. Although the family history was negative for neuromuscular diseases, the neuropathological findings indicated features of familial ALS with a SOD1 mutation. In fact, DNA analysis of frozen‐brain tissue revealed the presence of the I113T SOD1 mutation. This case represents the first one of this mutation in a patient who showed CIs as well as LBHIs in the motor neurons at the same time, in addition to the NFTs in the mesencephalic tegmentum.     

Mice lacking cytosolic copper/zinc superoxide dismutase display a distinctive motor axonopathy.

OBJECTIVE: To characterize the motor neuron dysfunction in two models by performing physiologic and morphometric studies. BACKGROUND: Mutations in the gene encoding cytosolic superoxide dismutase 1 (SOD1) account for 25% of familial ALS (FALS). Transgenes with these mutations produce a pattern of lower motor neuron degeneration similar to that seen in patients with FALS. In contrast, mice lacking SOD1 develop subtle motor symptoms by approximately 6 months of age. METHODS: Physiologic measurements, including motor conduction and motor unit estimation, were analyzed in normal mice, mice bearing the human transgene for FALS (mFALS mice), and knockout mice deficient in SOD1 (SOD1-KO). In addition, morphometric analysis was performed on the spinal cords of SOD1-KO and normal mice. RESULTS: In mFALS mice, the motor unit number in the distal hind limb declined before behavioral abnormalities appeared, and motor unit size increased. Compound motor action potential amplitude and distal motor latency remained normal until later in the disease. In SOD1-KO mice, motor unit numbers were reduced early but declined slowly with age. In contrast with the mFALS mice, SOD1-KO mice demonstrated only a modest increase in motor unit size. Morphometric analysis of the spinal cords from normal and SOD1-KO mice showed no significant differences in the number and size of motor neurons. CONCLUSIONS: The physiologic abnormalities in mFALS mice resemble those in human ALS. SOD1-deficient mice exhibit a qualitatively different pattern of motor unit remodeling that suggests that axonal sprouting and reinnervation of denervated muscle fibers are functionally impaired in the absence of SOD1.     

The neuronal Golgi apparatus is fragmented in transgenic mice expressing a mutant human SOD1, but not in mice expressing the human NF-H gene

Fragmentation of the Golgi apparatus (GA) of motor neurons was first described in sporadic amyotrophic lateral sclerosis (ALS) and later confirmed in transgenic mice expressing the G93A mutation of the gene encoding the enzyme Cu,Zn superoxide dismutase (SOD1(G93A)) found in some cases of familial ALS. In these transgenic mice, however, the fragmentation of the neuronal GA was associated with cytoplasmic and mitochondrial vacuoles not seen in ALS. The present new series of transgenic mice expressing 14-17 trans gene copies of SOD1(G93A), compared to 25 copies in the mice we studied previously, showed consistent fragmentation of the GA of spinal cord motor neurons, axonal swellings, Lewy-like body inclusions in neurons and glia, but none of the cytoplasmic or mitochondrial vacuoles originally reported. Thus, this animal model recapitulates the clinical and most neuropathological findings of sporadic ALS. Neurofilaments (NF) accumulate in axons and, less often, in neuronal perikarya in most cases of sporadic ALS and they have been implicated in its pathogenesis. In order to investigate whether fragmentation of the neuronal GA also occurs in association with accumulation of perikaryal NFs, we studied the organelle in transgenic mice expressing the heavy subunit of human neurofilaments (NF-H) which developed a motor neuronopathy resembling ALS. The neuronal GA of mice expressing NF-H, however, was intact despite massive accumulation of NFs in both perikarya and axons of motor neurons. In contrast, in transgenic mice expressing SOD1(G93A), the GA was fragmented despite the absence of accumulation of perikaryal NFs. These findings suggest that, in transgenic mice with neuronopathies caused by the expression of mutant SOD1(G93A) or the human NF-H, the GA and the perikaryal NFs are independently involved in the pathogenesis. The evidence suggests that the GA plays a central role in the pathogenesis of the vast majority of sporadic ALS and in FALS with SOD1 mutations.     

Histological evidence of redox system breakdown caused by superoxide dismutase 1 (SOD1) aggregation is common to SOD1-mutated motor neurons in humans and animal models

Living cells produce reactive oxygen species (ROSs). To protect themselves from these ROSs, the cells have developed both an antioxidant system containing superoxide dismutase 1 (SOD1) and a redox system including peroxiredoxin2 (Prx2, thioredoxin peroxidase) and glutathione peroxidase1 (GPx1): SOD1 converts superoxide radicals into hydrogen peroxide (H₂O₂), and H₂O₂ is then converted into harmless water (H₂O) and oxygen (O₂) by Prx2 and GPx1 that directly regulate the redox system. To clarify the biological significance of the interaction of the redox system (Prx2/GPx1) with SOD1 in SOD1-mutated motor neurons in vivo, we produced an affinity-purified rabbit antibody against Prx2 and investigated the immunohistochemical localization of Prx2 and GPx1 in neuronal Lewy body-like hyaline inclusions (LBHIs) in the spinal cords of familial amyotrophic lateral sclerosis (FALS) patients with a two-base pair deletion at codon 126 and an AlaVal substitution at codon 4 in the SOD1 gene, as well as in transgenic rats expressing human SOD1 with H46R and G93A mutations. The LBHIs in motor neurons from the SOD1-mutated FALS patients and transgenic rats showed identical immunoreactivities for Prx2 and GPx1: the reaction product deposits with the antibodies against Prx2 and GPx1 were localized in the LBHIs. In addition, the localizations of the immunoreactivities for SOD1 and Prx2/GPx1 were similar in the inclusions: the co-aggregation of Prx2/GPx1 with SOD1 in neuronal LBHIs in mutant SOD1-related FALS patients and transgenic rats was evident. Based on the fact that Prx2/GPx1 directly regulates the redox system, such co-aggregation of Prx2/GPx1 with SOD1 in neuronal LBHIs may lead to the breakdown of the redox system itself, thereby amplifying the mutant SOD1-mediated toxicity in mutant SOD1-linked FALS patients and transgenic rats expressing human mutant SOD1.     

ALS pathogenesis: Recent insights from genetics and mouse models

For the vast majority of cases of amyotrophic lateral sclerosis (ALS) the etiology remains unknown. After the discovery of missense mutations in the gene coding for the Cu/Zn superoxide dismutase 1 (SOD1) in subsets of familial ALS, several transgenic mouse lines have been generated with various forms of SOD1 mutants overexpressed at different levels. Studies with these mice yielded complex results with multiple targets of damage in disease including mitochondria, proteasomes, and secretory pathways. Many unexpected discoveries were made. For instance, the toxicity of mutant SOD1 seems unrelated to copper-mediated catalysis but rather to formation of misfolded SOD1 species and aggregates. Transgenic studies revealed a potential role of wtSOD1 in exacerbating mutant SOD1-mediated disease. Another key finding came from chimeric mouse studies and from Cre-lox mediated gene deletion experiments which have highlighted the importance of non-neuronal cells in the disease progression. Involvement of cytoskeletal components in ALS pathogenesis is supported by several mouse models of motor neuron disease with neurofilament abnormalities and with genetic defects in microtubule-based transport. Recently, the generation of new animal models of ALS has been made possible with the discovery of ALS-linked mutations in other genes encoding for alsin, dynactin, senataxin, VAPB, TDP-43 and FUS. Following the discovery of mutations in the TARDBP gene linked to ALS, there have been some reports of transgenic mice with high level overexpression of WT or mutant forms of TDP-43 under strong gene promoters. However, these TDP-43 transgenic mice do not exhibit all pathological features the human ALS disease. Here, we will describe these new TDP-43 transgenic mice and discuss their validity as animal models of human ALS.