Gen Sobue

A gene encoding a transmembrane protein is mutated in patients with diabetes mellitus and optic atrophy (Wolfram syndrome)

Wolfram syndrome (WFS; OMIM 222300) is an autosomal recessive neurodegenerative disorder defined by young-onset non-immune insulin-dependent diabetes mellitus and progressive optic atrophy. Linkage to markers on chromosome 4p was confirmed in five families. On the basis of meiotic recombinants and disease-associated haplotypes, the WFS gene was localized to a BAC/P1 contig of less than 250 kb. Mutations in a novel gene (WFS1) encoding a putative transmembrane protein were found in all affected individuals in six WFS families, and these mutations were associated with the disease phenotype. WFS1 appears to function in survival of islet ß-cells and neurons.

Testosterone Reduction Prevents Phenotypic Expression in a Transgenic Mouse Model of Spinal and Bulbar Muscular Atrophy

Spinal and bulbar muscular atrophy (SBMA) is a polyglutamine disease caused by the expansion of a CAG repeat in the androgen receptor (AR) gene. We generated a transgenic mouse model carrying a full-length AR containing 97 CAGs. Three of the five lines showed progressive muscular atrophy and weakness as well as diffuse nuclear staining and nuclear inclusions consisting of the mutant AR. These phenotypes were markedly pronounced in male transgenic mice, and dramatically rescued by castration. Female transgenic mice showed only a few manifestations that markedly deteriorated with testosterone administration. Nuclear translocation of the mutant AR by testosterone contributed to the phenotypic difference with gender and the effects of hormonal interventions. These results suggest the therapeutic potential of hormonal intervention for SBMA.

17-AAG, an Hsp90 inhibitor, ameliorates polyglutamine-mediated motor neuron degeneration

Heat-shock protein 90 (Hsp90) functions as part of a multichaperone complex that folds, activates and assembles its client proteins. Androgen receptor (AR), a pathogenic gene product in spinal and bulbar muscular atrophy (SBMA), is one of the Hsp90 client proteins. We examined the therapeutic effects of 17-allylamino-17-demethoxygeldanamycin (17-AAG), a potent Hsp90 inhibitor, and its ability to degrade polyglutamine-expanded mutant AR. Administration of 17-AAG markedly ameliorated motor impairments in the SBMA transgenic mouse model without detectable toxicity, by reducing amounts of monomeric and aggregated mutant AR. The mutant AR showed a higher affinity for Hsp90-p23 and preferentially formed an Hsp90 chaperone complex as compared to wild-type AR; mutant AR was preferentially degraded in the presence of 17-AAG in both cells and transgenic mice as compared to wild-type AR. 17-AAG also mildly induced Hsp70 and Hsp40. 17-AAG would thus provide a new therapeutic approach to SBMA and probably to other related neurodegenerative diseases.

A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Aβ

Through functional expression screening, we identified a gene, designated Humanin (HN) cDNA, which encodes a short polypeptide and abolishes death of neuronal cells caused by multiple different types of familial Alzheimers disease genes and by Aβ amyloid, without effect on death by Q79 or superoxide dismutase-1 mutants. Transfected HN cDNA was transcribed to the corresponding polypeptide and then was secreted into the cultured medium. The rescue action clearly depended on the primary structure of HN. This polypeptide would serve as a molecular clue for the development of new therapeutics for Alzheimers disease targeting neuroprotection.

Differential expression of inflammation- and apoptosis-related genes in spinal cords of a mutant SOD1 transgenic mouse model of familial amyotrophic lateral sclerosis.

Familial amyotrophic lateral sclerosis (FALS)‐linked mutations in copper–zinc superoxide dismutase (SOD1) cause motor neuron death through one or more acquired toxic properties. We analyzed the molecular mechanism underlying motor neuron degeneration in the transgenic mouse model expressing the SOD1 gene with G93A mutation. Using cDNA microarray, the differentially expressed genes were identified in the spinal cords of G93A mice, 30 being elevated and seven decreased. cDNA microarray analysis to monitor gene expression during neurodegeneration revealed an up‐regulation of genes related to an inflammatory process, such as the tumor necrosis factor‐α (TNF‐α) gene, resulting from glial cell activation, together with the change in apoptosis‐related gene expression, such as caspase‐1. The increased expression of the inflammation‐ and apoptosis‐related genes occurred at 11 weeks of age in the presymptomatic stage prior to motor neuron death. These results suggest a mechanism of neurodegeneration that includes an inflammatory response as an important component. Thus, ALS has paralleled other neurodegenerative disorders, such as Alzheimers and prion diseases, in which the inflammatory process is believed to participate directly in neuronal death.

Leuprorelin rescues polyglutamine-dependent phenotypes in a transgenic mouse model of spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is an adult-onset motor neuron disease that affects males. It is caused by the expansion of a polyglutamine (polyQ) tract in androgen receptors. Female carriers are usually asymptomatic. No specific treatment has been established. Our transgenic mouse model carrying a full-length human androgen receptor with expanded polyQ has considerable gender-related motor impairment. This phenotype was abrogated by castration, which prevented nuclear translocation of mutant androgen receptors. We examined the effect of androgen-blockade drugs on our mouse model. Leuprorelin, a lutenizing hormone–releasing hormone (LHRH) agonist that reduces testosterone release from the testis, rescued motor dysfunction and nuclear accumulation of mutant androgen receptors in male transgenic mice. Moreover, leuprorelin treatment reversed the behavioral and histopathological phenotypes that were once caused by transient increases in serum testosterone. Flutamide, an androgen antagonist promoting nuclear translocation of androgen receptors, yielded no therapeutic effect. Leuprorelin thus seems to be a promising candidate for the treatment of SBMA.

Expression of mRNAs for neurotrophic factors (NGF, BDNF, NT-3, and GDNF) and their receptors (p75ngfr, TrkA, TrkB, and TrkC) in the adult human peripheral nervous system and nonneural tissues

The steady-state mRNA levels of the four neurotrophic factors of nerve growth factor (NGF), brain-dervied neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and glial cell line-derived neurotrophic factor (GDNF) and their receptors (p74ngfr, trkA, trkB and trkC) in the adult human peripheral nervous system (PNS) as well as nonneural tissues were examined using quantitative reverse transcription-polymerase chain reaction (RT-PCR). NGF and BDNF mRNA levels were high in the heart and spleen as well as in the dorsal root ganglia (DRG) and spinal cord, showing similar spatial expression patterns, while NT-3 mRNA levels were more pronounced in the liver and spleen. In contrast to these neurotrophins, GDNF mRNA expression occurred at the highest levels in the muscle, and it was also comparatively high in the spinal cord. p75ngfr mRNA was expressed extensively throughout the PNS tissues and in the spleen. The spatial expression patterns differed among trkA, and trkB and trkC mRNAs. trkA mRNA was greatly expressed in the DRG, sympathetic ganglia and spleen, while the trkB and trkC mRNA levels were high in the DRG, spinal cord and brain. The levels of trkB and trkC mRNAs with tyrosine kinase domain, compared to those with extracellular domain, were relatively high in the DRG, whereas they were low in the spinal cord and brain. The spatial patterns of the distributions of neurotrophic factors and their receptors mRNA levels in the adult human PNS and nonneural tissues are largely similar to those reported in other mammals, but these findings provide further, more specific, understanding relevant to the therapeutic approach to human diseases.

Gene expression profile of spinal motor neurons in sporadic amyotrophic lateral sclerosis.

The causative pathomechanism of sporadic amyotrophic lateral sclerosis (ALS) is not clearly understood. Using microarray technology combined with laser‐captured microdissection, gene expression profiles of degenerating spinal motor neurons isolated from autopsied patients with sporadic ALS were examined. Gene expression was quantitatively assessed by real‐time reverse transcription polymerase chain reaction and in situ hybridization. Spinal motor neurons showed a distinct gene expression profile from the whole spinal ventral horn. Three percent of genes examined were downregulated, and 1% were upregulated in motor neurons. Downregulated genes included those associated with cytoskeleton/axonal transport, transcription, and cell surface antigens/receptors, such as dynactin, microtubule‐associated proteins, and early growth response 3 (EGR3). In contrast, cell death–associated genes were mostly upregulated. Promoters for cell death pathway, death receptor 5, cyclins A1 and C, and caspases‐1, ‐3, and ‐9, were upregulated, whereas cell death inhibitors, acetyl‐CoA transporter, and NF‐κB were also upregulated. Moreover, neuroprotective neurotrophic factors such as ciliary neurotrophic factor (CNTF), Hepatocyte growth factor (HGF), and glial cell line–derived neurotrophic factor were upregulated. Inflammation‐related genes, such as those belonging to the cytokine family, were not, however, significantly upregulated in either motor neurons or ventral horns. The motor neuron–specific gene expression profile in sporadic ALS can provide direct information on the genes leading to neurodegeneration and neuronal death and are helpful for developing new therapeutic strategies. Ann Neurol 2005;57:236–251

Familial transthyretin-type amyloid polyneuropathy in Japan: Clinical and genetic heterogeneity

Familial amyloid polyneuropathy (FAP) was once considered a disease peculiar to endemic areas, but it is now recognized not to be a rare disease among hereditary neuropathic disorders in Japan. FAP in Japan, the majority of which is caused by transthyretin (TTR)-related amyloid deposition, shows a wide spectrum of clinical pictures. This variability can be explained on the basis of the many causative gene mutations of TTR, but even in the same TTR type of FAP, the clinical phenotypes seem to vary in different kindreds or individuals. Especially in the case of the Val30Met TTR type, the sex ratio and the age at onset are considerably different between patients in endemic foci and those in nonendemic areas. It is also noteworthy that serious cardiac amyloidosis is commonly seen in patients with FAP of the non-Val30Met TTR type. In addition to TTR gene mutation, unknown factors may play an important role in the development of FAP. At present, liver transplantation is the only life-saving treatment, but this therapy is always associated with great stress for the patient and the donor, particularly in living-related transplantation. Less invasive treatments for this disease are required.

Mutations in COQ2 in familial and sporadic multiple-system atrophy the multiple-system atrophy research collaboration

BACKGROUND Multiple-system atrophy is an intractable neurodegenerative disease characterized by autonomic failure in addition to various combinations of parkinsonism, cerebellar ataxia, and pyramidal dysfunction. Although multiple-system atrophy is widely considered to be a nongenetic disorder, we previously identified multiplex families with this disease, which indicates the involvement of genetic components. METHODS In combination with linkage analysis, we performed whole-genome sequencing of a sample obtained from a member of a multiplex family in whom multiple-system atrophy had been diagnosed on autopsy. We also performed mutational analysis of samples from members of five other multiplex families and from a Japanese series (363 patients and two sets of controls, one of 520 persons and one of 2383 persons), a European series (223 patients and 315 controls), and a North American series (172 patients and 294 controls). On the basis of these analyses, we used a yeast complementation assay and measured enzyme activity of parahydroxybenzoate-polyprenyl transferase. This enzyme is encoded by the gene COQ2 and is essential for the biosynthesis of coenzyme Q10. Levels of coenzyme Q10 in lymphoblastoid cells and brain tissue were measured on high-performance liquid chromatography. RESULTS We identified a homozygous mutation (M78V-V343A/M78V-V343A) and compound heterozygous mutations (R337X/V343A) in COQ2 in two multiplex families. Furthermore, we found that a common variant (V343A) and multiple rare variants in COQ2, all of which are functionally impaired, are associated with sporadic multiple-system atrophy. The V343A variant was exclusively observed in the Japanese population. CONCLUSIONS Functionally impaired variants of COQ2 were associated with an increased risk of multiple-system atrophy in multiplex families and patients with sporadic disease, providing evidence of a role of impaired COQ2 activities in the pathogenesis of this disease. (Funded by the Japan Society for the Promotion of Science and others.).