Akiko Iwaki

Heterozygous deletion of ITPR1, but not SUMF1 in spinocerebellar ataxia type 16

We have previously mapped autosomal dominant spinocerebellar ataxia (SCA) 16 to 3p26, overlapping with the locus of SCA15. Recently, partial deletions of ITPR1 and the neighbouring SUMF1 in the SCA15 and two additional families were reported. In the present study we determined the copy number of these genes by real time quantitative polymerase chain reaction (PCR) and found a heterozygous deletion of exons 1-48 of ITPR1, but not SUMF1 in SCA16. Breakpoint analysis revealed that the size of the deletion is 313,318 bp and the telomeric breakpoint is located in the middle of their intergenic region. Our data provide evidence that haploinsufficiency of ITPR1 alone causes SCA16 and SCA15.

Preferential expression of αB-crystallin in astrocytic elements of neuroectodermal tumors

Recently the authors have identified a major component of Rosenthal fibers as αBcrystallin, a major lens protein. In the current study the authors investigated the expression of αB‐crystallin in four cultured glioma cell lines and in 115 human neuroectodermal tumors. αB‐crystallin was expressed differentially by those glioma cell lines, but not by neuroblastoma cell lines. Northern blot analysis revealed two distinct messages for αB‐crystallin in C‐6, whereas only a single message in U‐373MG and G26‐24. In human surgical specimens positive immunostaining was frequently observed in the following brain tumors: pilocytic astrocytoma of the juvenile type, anaplastic astrocytoma, glioblastoma multiforme, and subependymal giant cell astrocytoma. The astrocytic elements of mixed oligoastrocytomas, glioblastomas with sarcomatous components, and gangliogliomas were likewise strongly stained. In contrast, little immunoreactivity was observed in ependymal and choroid plexus tumors. Thus, αB‐crystallin is mainly expressed by astrocytic tumors among neuroectodermal neoplasms, without regard to the presence of Rosenthal fibers. Cancer 68:2230–2240, 1991.

FALS with FUS mutation in Japan, with early onset, rapid progress and basophilic inclusion

Mutations in the fused in sarcoma (FUS, also known as translated in liposarcoma) gene have been recently discovered to be associated with familial amyotrophic lateral sclerosis (FALS) in African, European and American populations. In a Japanese family with FALS, we found the R521C FUS mutation, which has been reported to be found in various ethnic backgrounds. The family history revealed 23 patients with FALS among 46 family members, suggesting a 100% penetrance rate. They developed muscle weakness at an average age of 35.3 years, followed by dysarthria, dysphagia, spasticity and muscle atrophy. The average age of death was 37.2 years. Neuropathological examination of the index case revealed remarkable atrophy of the brainstem tegmentum characterized by cytoplasmic basophilic inclusion bodies in the neurons of the brainstem. We screened 40 FALS families in Japan and found 4 mutations (S513P, K510E, R514S, H517P) in exon 14 and 15 of FUS. Even in Asian races, FALS with FUS mutations may have the common characteristics of early onset, rapid progress and high penetrance rate, although in patients with the S513P mutation it was late-onset. Degeneration in multiple systems and cytoplasmic basophilic inclusion bodies were found in the autopsied cases.

αB-Crystallin in C6 glioma cells supports their survival in elevated extracellular K+: the implication of a protective role of αB-crystallin accumulation in reactive glia

Abstract It has been shown by immunohistochemical studies that αB-crystallin accumulates in the reactive and neoplastic glial cells in a variety of pathologic situations. However, the molecular mechanism for the induction of αB-crystallin in diseased brains is still unknown. Since any destructive brain lesions cause an abnormal elevation in the potassium (K+) concentration of the extracellular space, which disturbs the regulatory mechanism of glial cell volume, we investigated the influence of elevated extracellular K+ on the expression of αB-crystallin in glial cells. The treatment of rat C6 glioma cells with augmented K+ in the culture media induced an accumulation of αB-crystallin mRNA in a dose-dependent manner and an accumulation of the αB-crystallin as well. Furthermore, an overexpression of αB-crystallin in the C6 transformant transfected with a rat αB-crystallin cDNA conferred a resistant phenotype against the insult of elevated extracellular K+ on the glioma cells. Thus, αB-crystallin may contribute to the survival of reactive glia in the presence of a high extracellular K+ concentration.

Accumulation of αB-crystallin in brains of patients with Alexander's disease is not due to an abnormality of the 5′-flanking and coding sequence of the genomic DNA

alpha B-Crystallin is a major protein component of Rosenthal fibers, which massively accumulate in the brains of patients suffering from Alexanders disease. To examine whether or not accumulation of alpha B-crystallin is due to any abnormality of the gene structures, we determined the sequence of the alpha B-crystallin gene in two cases of pathologically confirmed Alexanders disease. Direct sequencing of the promoter and coding regions of the alpha B-crystallin gene in patients revealed them to have a normal sequence. Northern blotting showed a single alpha B-crystallin mRNA species expressed in the Alexanders disease brain.

The contactin 4 gene locus at 3p26 is a candidate gene of SCA16

Objective: To identify of the gene responsible for the onset of spinocerebellar ataxia type 16 (SCA16). Methods: We reanalyzed the linkage of the original Japanese pedigree using updated information, including three additional subjects. We then screened all exons located in the critical region. Results: We reassigned the locus of SCA16 to 3p26.2-pter (maximum logarithm-of-odds score = 5.177) and identified only one point mutation (4,256C→T) in the 3′ untranslated region of the contactin 4 gene (CNTN4) on chromosome 3p26.2-26.3, which cosegregated with the disease. This mutation was not detected in 520 control subjects; moreover, we revised the phenotype of SCA16 from pure to complicated SCA. Conclusion: The contactin 4 gene (CNTN4) is associated with cerebellar degeneration in spinocerebellar ataxia type 16. Additional studies are necessary to prove 4,256C→T to be a causative mutation.

Comprehensive behavioral study of mGluR3 knockout mice: Implication in schizophrenia related endophenotypes

BackgroundWe previously performed systematic association studies of glutamate receptor gene family members with schizophrenia, and found positive associations of polymorphisms in the GRM3 (a gene of metabotropic glutamate receptor 3: mGluR3) with the disorder. Physiological roles of GRM3 in brain functions and its functional roles in the pathogenesis of schizophrenia remain to be resolved.ResultsWe generated mGluR3 knockout (KO) mice and conducted comprehensive behavioral analyses. KO mice showed hyperactivity in the open field, light/dark transition, and 24-hour home cage monitoring tests, impaired reference memory for stressful events in the Porsolt forced swim test, impaired contextual memory in cued and contextual fear conditioning test, and impaired working memory in the T-Maze forced alternation task test. Hyperactivity and impaired working memory are known as endophenotypes of schizophrenia. We examined long-term synaptic plasticity by assessing long-term potentiation (LTP) in the CA1 region in the hippocampi of KO and wild-type (WT) mice. We observed no differences in the amplitude of LTP between the two genotypes, suggesting that mGluR3 is not essential for LTP in the CA1 region of the mouse hippocampus. As hyperactivity is typically associated with increased dopaminergic transmission, we performed in vivo microdialysis measurements of extracellular dopamine in the nucleus accumbens of KO and WT mice. We observed enhancements in the methamphetamine (MAP)-induced release of dopamine in KO mice.ConclusionsThese results demonstrate that a disturbance in the glutamate-dopamine interaction may be involved in the pathophysiology of schizophrenia-like behavior, such as hyperactivity in mGluR3 KO mice.

Comprehensive behavioural study of GluR4 knockout mice: implication in cognitive function

Fast excitatory transmission in the mammalian central nervous system is mediated by AMPA‐type glutamate receptors. The tetrameric AMPA receptor complexes are composed of four subunits, GluR1–4. The GluR4 subunit is highly expressed in the cerebellum and the early postnatal hippocampus and is thought to be involved in synaptic plasticity and the development of functional neural circuitry through the recruitment of other AMPA receptor subunits. Previously, we reported an association of the human GluR4 gene (GRIA4) with schizophrenia. To examine the role of the GluR4 subunit in the higher brain function, we generated GluR4 knockout mice and conducted electrophysiological and behavioural analyses. The mutant mice showed normal long‐term potentiation (LTP) in the CA1 region of the hippocampus. The GluR4 knockout mice showed mildly improved spatial working memory in the T‐maze test. Although the retention of spatial reference memory was intact in the mutant mice, the acquisition of spatial reference memory was impaired in the Barnes circular maze test. The GluR4 knockout mice showed impaired prepulse inhibition. These results suggest the involvement of the GluR4 subunit in cognitive function.

An autopsied case of sporadic adult-onset amyotrophic lateral sclerosis with FUS-positive basophilic inclusions.

Basophilic inclusions (BIs), which are characterized by their staining properties of being weakly argyrophilic, reactive with Nissl staining, and immunohistochemically negative for tau and transactive response (TAR) DNA‐binding protein 43 (TDP‐43), have been identified in patients with juvenile‐onset amyotrophic lateral sclerosis (ALS) and adult‐onset atypical ALS with ophthalmoplegia, autonomic dysfunction, cerebellar ataxia, or a frontal lobe syndrome. Mutations in the fused in sarcoma gene (FUS) have been reported in cases of familial and sporadic ALS, and FUS immunoreactivity has been demonstrated in basophilic inclusion body disease (BIBD), neuronal intermediate filament inclusion disease (NIFID), and atypical frontotemporal lobar degeneration with ubiquitin‐positive and tau‐negative inclusions (aFTLD‐U). In the present study, we immunohistochemically and ultrastructurally studied an autopsy case of sporadic adult‐onset ALS with numerous BIs. The patient presented with the classical clinical course of ALS since 75 years of age and died at age 79. Postmortem examination revealed that both Betz cells in the motor cortex and motor neurons in the spinal cord were affected. The substantia nigra was spared. Notably, BIs were frequently observed in the motor neurons of the anterior horns, the inferior olivary nuclei, and the basal nuclei of Meynert. BIs were immunopositive for p62, LC3, and FUS, but immunonegative for tau, TDP‐43, and neurofilament. Ultrastructurally, BIs consisted of filamentous or granular structures associated with degenerated organelles with no limiting membrane. There were no Bunina bodies, skein‐like inclusions, or Lewy‐like inclusions. All exons and exon/intron boundaries of the FUS gene were sequenced but no mutations were identified.

Autopsy case of autosomal recessive hereditary spastic paraplegia with reference to the muscular pathology

An autopsied case of autosomal recessive hereditary spastic paraplegia with severe neurogenic muscular atrophy is described herein. This patient, a 16‐year‐old woman, presented with gait disturbance. She developed progressive spastic paralysis of the upper and lower limbs and mental deterioration. She became bedridden at approximately 40 years of age. Dysarthria worsened at 45 years of age. She died of pneumonia at 50 years of age. Her younger sister has shown similar clinical symptoms and became bedridden at 37 years of age. Their parents were second cousins. Autopsy revealed a severely atrophic brain, weighing 720 g. The cerebral cortex was thin, and the white matter was extremely reduced in volume. Microscopically, neuronal loss and variable astrogliosis with diffuse spongy changes were evident at the cerebral cortex, thalamic nuclei, basal ganglia and hippocampus. The remaining neurons were atrophied with heavy deposition of lipofuscin. In the spinal cord, the pyramidal tracts as well as the dorsal spinocerebellar tracts were degenerated. In addition, marked loss of the anterior horn cells was seen. Severe neuronal loss of the nucleus gracilis was also detected. In contrast, only mild degeneration of the ventral spinocerebellar tracts and fasciulus cuneatus in the spinal cord were observed. In the frozen sections of skeletal muscle, severe neurogenic atrophy and fatty infiltration were evident. In addition, several rimmed vacuoles were observed in the atrophic fibers, and cytochrome coxidase‐deficient fibers were present in part. Reduced nicoti‐namide adenine dinucleotide (NADH)‐tetrazolium reductase reaction revealed abnormal accumulation of mitochondria around the center of the non‐atrophic muscle fibers. It is suggested that an analysis of mitochondrial function of Japanese autosomal recessive hereditary spastic hemiplegia may provide additional information to clarify the pathogenesis.