Akihito Suenaga

Mutations of the Notch3 Gene in Non-Caucasian Patients with Suspected CADASIL Syndrome

The Notch3 gene has been recently identified as a causative gene for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). To investigate the genetic contribution of Notch mutations in familial cases with vascular leukoencephalopathy, we screened 13 patients from 11 unrelated families, which were selected on the basis of magnetic resonance imaging findings and positive family history. We identified three different missense mutations in 5 patients from 4 families. Two (Arg90Cys and Arg133Cys) are the same as previously reported in Caucasian patients, the other (Cys174Phe) is a novel mutation causing a loss of a cysteine in epidermal-growth-factor-like repeats of Notch3. These data indicate that the CADASIL Notch3 mutations were found in approximately 35% of familial cases with leukoencephalopathy, suggesting genetic heterogeneity of the disease.

Successful application of pentoxifylline in the treatment of HTLV-I associated myelopathy

Fifteen patients with human T-cell lymphotropic virus type-I (HTLV-I)-associated myelopathy (HAM) were treated in an uncontrolled preliminary trial by oral administration of pentoxifylline (PTX). Motor function, neurological evaluation, immunological markers and parameters were evaluated after four weeks. In 13 of the 15 patients, motor disability, especially spasticity, improved substantially. PTX suppressed spontaneous proliferation of peripheral blood mononuclear cells in 14 of the 15 patients at four weeks. No adverse effect was observed. We concluded that PTX may be a safe and beneficial agent for the treatment of HAM.

Molecular and clinical analyses of Japanese patients with carbamoylphosphate synthetase 1 (CPS1) deficiency.

AbstractCarbamoylphosphate synthetase I deficiency (CPS1D) is a urea-cycle disorder characterized by episodes of life-threatening hyperammonemia. Correct diagnosis is crucial for patient management, but is difficult to make from clinical presentation and conventional laboratory tests alone. Enzymatic or genetic diagnoses have also been hampered by difficult access to the appropriate organ and the large size of the gene (38 exons). In this study, in order to address this diagnostic dilemma, we performed the largest mutational and clinical analyses of this disorder to date in Japan. Mutations in CPS1 were identified in 16 of 18 patients with a clinical diagnosis of CPS1D. In total, 25 different mutations were identified, of which 19 were novel. Interestingly, in contrast to previous reports suggesting an extremely diverse mutational spectrum, 31.8% of the mutations identified in Japanese were common to more than one family. We also identified two common polymorphisms that might be useful for simple linkage analysis in prenatal diagnosis. The accumulated clinical data will also help to reveal the clinical presentation of this rare disorder in Japan.

Specificity of ω-conotoxin MVIIC-binding and -blocking calcium channel antibodies in Lambert-Eaton myasthenic syndrome

Abstract An immunoprecipitation assay was used to measure ω-conotoxin MVIIC (P/Q-type) binding and blocking calcium channel antibodies in 67 patients with Lambert-Eaton myasthenic syndrome (LEMS) and in a large control population. We first showed the presence of ω-conotoxin MVIIC-blocking antibody in LEMS patients. Binding antibodies were detected in 55 of 67 (82.1%) LEMS patients and in 2 of 296 (0.7%) controls. In contrast, blocking antibodies were positive in 14 of 67 (20.9%) LEMS patients and 8 of 171 (4.7%) controls. No LEMS patient had negative binding antibodies and positive blocking antibodies. The immunoprecipitation assay detected no antibodies against the whole P/Q-type calcium channel in either the paraneoplastic cerebellar degeneration or the amyotrophic lateral sclerosis sera. Neither the ω-conotoxin MVIIC-binding nor the -blocking calcium channel antibodies were correlated with clinical severity across the individuals, but longitudinal studies of some LEMS patients showed an inverse relation between binding antibody titre and disease severity. We concluded that the 125I-ω-conotoxin MVIIC assay for anti-P/Q-type voltage-gated calcium channel antibodies is highly specific for LEMS and that this sensitive binding antibody assay could be more valuable than the blocking antibody assay in the diagnosis of LEMS.

'Split tolerance' induction by intrathymic injection of acetylcholine receptor in a rat model of autoimmune myasthenia gravis; implications for the design of specific immunotherapies.

Experimental autoimmune myasthenia gravis (EAMG) in the Lewis rat, induced by a single injection of acetylcholine receptor (AChR) protein, is a model used to study human myasthenia gravis (MG), The production of anti‐AChR antibodies In the animal model and human MG is T cell‐dependent, and AChR‐specific T cells have been considered as a potential target for specific immunotherapy. Intrathymic injection of antigens induces antigen‐specific tolerance in several T cell‐mediated autoimmune models. We examined the effect of intrathymic injection of AChR on T cell responses and the production of antibodies to AChR in EAMG rats. Primed lymph node cells from rats receiving intrathymic injection of AChR exhibited reduced proliferation to AChR with marked suppression of interferon‐gamma (IFN‐γ) secretion in the antigen‐stimulated culture, compared with those of rats injected with PBS. However, neither anti‐Narke AChR nor anti‐rat AChR antibody production was suppressed or enhanced in intrathymically AChR‐injected animals compared with that of animals injected intrathymically with PBS or perithymically with AChR. This ‘split tolerance’ may be attributable to the suppression of type‐1 T helper cells (Th1). Our results suggest that the suppression of Th1 function alone may not be sufficient for the prevention of antibody‐mediated autoimmune diseases.

Seronegative myasthenia gravis associated with atonic urinary bladder and accommodative insufficiency

We report a 20-year-old female with generalized myasthenia gravis (MG) who developed atonic urinary bladder and accommodative insufficiency. Although her sera did not contain antibodies to either nicotinic acetylcholine receptor (AChR) or voltage-gated calcium channels, a positive intravenous edrophonium test and a waning phenomenon on electromyographic studies indicated a diagnosis of seronegative MG. Myasthenic symptoms as well as urinary incontinence and impaired near vision disappeared with slight sequelae after corticosteroid therapy and total removal of the hyperplastic thymus. These symptoms recurred during a tapering course of corticosteroids, and improved again with an increased dose. Therefore, in this patient, the neuromuscular transmission of muscarinic type of AChR in the smooth muscles was also affected. This patient provides insight into the mechanisms by which some smooth muscles are involved in MG.

Homozygosity and linkage disequilibrium mapping of autosomal recessive distal myopathy (Nonaka distal myopathy)

AbstractAutosomal recessive distal myopathy or Nonaka distal myopathy (NM) is characterized by its unique distribution of muscular weakness and wasting. The patients present with spared quadriceps muscles even in a late stage of the disease. The hamstring and tibialis anterior muscles are affected severely in early adulthood. We have localized the NM gene to the region between markers D9S319 and D9S276 on chromosome 9 by linkage analysis. To further refine the localization of the NM gene, we conducted homozygosity and linkage disequilibrium analysis for 14 patients from 11 NM families using 18 polymorphic markers. All of the patients from consanguineous NM families were found to be homozygous for six markers located within the region between markers D9S2178 and D9S1859. We also provided evidence for significant allelic associations between the NM region and five marker loci. Examination of the haplotype analysis identified a predominant ancestral haplotype comprising the associated alleles 199-160-154-109 (marker order: D9S2179-D9S2180-D9S2181-D9S1804), present in 60% of NM chromosomes and in 0% of parent chromosomes. On the basis of the data obtained in this study, the majority of NM chromosomes were derived from a single ancestral founder, and the NM gene is probably located within the 1.5-Mb region between markers D9S2178 and D9S1791.