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A 23-year-old man experienced numbness in the perioral region and right arm, and right leg weakness on the second day after drinking a large amount of alcohol during foreign travel. His symptoms disappeared but then reappeared repetitively. Cerebral MRI performed on the third day after onset showed multiple white matter lesions; however, these lesions disappeared 26 days after onset. Neurological examination and nerve conduction studies revealed demyelinating polyneuropathy. Genetic testing for Charcot-Marie-Tooth disease, X-linked dominant 1 (CMTX1) due to GJB1 mutation was conducted based on the symptoms of transient central nervous system lesions and polyneuropathy exhibited by the patient and his mother. As a result, a c.530T>C (p.V177A) substitution in exon 2 of GJB1 was identified. CMTX1 patients should be advised to avoid excessive drinking because this could induce central nervous system lesions.

A 32-year-old woman showed transient central type facial nerve palsy and bulbar symptoms. Brain MRI revealed high intensity signals in the cerebral white matter, splenium of corpus callosum, and posterior limb of internal capsule. Two elder brothers of the patient had distal dominant peripheral neuropathies in four limbs. In this family, the point mutation of GJB1 gene, encoding connexin 32, was revealed and X-linked Charcot-Marie-Tooth disease (CMTX1) was diagnosed. The presented case was a heterozygote of this mutation. She showed severe transient central nervous system (CNS) symptoms and subclinical demyelinating peripheral neuropathy. The CNS symptoms and alterations of brain images were very similar among three siblings. There are many reports on male patients with CMTX1 who show associated CN symptoms, but female patients are very rare. There has been no previous report of a CMTX1 patient similar to the patient presented here. The trigger factors have been recognized at the onset of transient CN symptoms in these cases. The prevention of these factors is important for the management of such patients.

Recent advances in genetic analysis technology have enabled a surprising progress in genetic diagnosis in the field of neurological disease research. High-throughput molecular biology techniques, such as microarrays and next-generation sequencing, are the major contributors to this progress and to new discoveries. Charcot-Marie-Tooth disease (CMT), a known hereditary motor and sensory neuropathy, is clinically and genetically heterogeneous. Genetic studies have revealed at least 35 disease causing-genes responsible for Charcot-Marie-Tooth disease. Genetic studies have revealed that abnormalities in the following factors are the cause of inherited neuropathies: myelin components, transcription factors controlling myelination, myelin maintenance system, differentiation factors related to the peripheral nerve, neurofilaments, protein transfer system, mitochondrial proteins, DNA repair, RNA/protein synthesis, ion channels, and aminoacyl-tRNA synthetase. On the other hand concomitant with the increase in the number of genes that must be screened for mutations, the labor and reagent costs for molecular genetic testing have increased significantly. Therefore, new methodology for detecting gene mutations is required. Based on the recent progress in DNA analysis methods, resequencing microarray appears to be an economical and highly sensitive method for detecting mutations. We have been screening CMT patients for mutations using originally designed microarray DNA chips since 2007, thencehaving identified disease causing mutations in MPZ, GJB1, PMP22, EGR2, MFN2, NEFL, PRX, AARS, GARS, DNM2, and SETX genes in CMT patients.

Congenital cerebral hypomyelination includes a group of genetic disorders, such as Pelizaeus-Merzbacher disease (PMD), and is characterized by hypomyelination of the cerebral white matter. Until recently, no classification system was available for congenital hypomyelination disorders that are clinically and genetically excluded for PMD. However, the establishment of new disease entities with gene discoveries has generated a clinical need for a new classification and diagnostic criteria for this group of disorders. Here, we review the recent findings on congenital cerebral hypomyelination, which includes 11 diseases, with a novel disease classification and diagnostic criteria with flow charts.

Despite advances in discovery of deafness genes, clinical application still entails difficulties because of the genetic heterogeneity of deafness. In order to establish strategy for clinical application, we reviewed the genes responsible for hearing loss patients in Japan (Usami S et al; Acta Otolaryngol 128: 446-454, 2008), and discussed diagnostic strategy for mutation screening based on a mutation/gene database (Abe S et al; Genet Test 11: 333-340, 2007). Our series of mutation screenings has revealed that mutations in GJB2, SLC26A4, and CDH23, and the 1555A>G mutation in the mitochondrial 12S rRNA, were the major causes of hearing loss in Japanese patients. Interestingly, spectrums of GJB2, SLC26A4, and CDH23 mutations found in the Japanese population were quite different from those reported in populations with European ancestry. Our simultaneous screening of the multiple deafness mutations was based on the mutation spectrum of a corresponding population. The multicenter trial for this assay using an Invader panel revealed that approximately 40% of congenital hearing loss subjects could be diagnosed. This assay will enable us to detect deafness mutations in an efficient and practical manner in the clinical platform.

CMTX1, the second most common type of inherited hereditary motor and sensory neuropathy (HMSN), is associated with mutations of the gene for the gap junction protein connexin 32 (Cx32). In this condition, central conduction velocity is known to be delayed, presumably because mutated Cx32 is expressed in oligodendrocytes. A 45-year-old man presented with a 5-year history of progressive gait disturbance due to leg muscle weakness. The family history revealed that the mother had also progressive gait disturbance in her early 40s, and the younger sister could not walk faster than before at the age of 41. On neurological assessment, the patient exhibited pes cavus, distal muscle atrophy and weakness, and absence of the knee and ankle jerks. Touch sensation was impaired in the both feet. Motor and sensory nerve conduction velocities were reduced to 30-36 m/s with mild temporal dispersion. Sural nerve biopsy revealed diffuse loss of large myelinated fibers with the remaining large and intermediate nerve fibers being frequently surrounded by a thin myelin sheath. Onion bulb formation was only occasional and mild in degree. His hearing acuity was normal on pure-tone audiometry, but BAEP test demonstrated prolonged central conduction time (-I wave 1.8 milliseconds, I-V wave 6.4 milliseconds). The BAEP findings prompted us to choose Cx32 gene to analyze first to find a novel mutation of two (A and T) base pairs deletion at codons 277 and 278 (Met93fs). Thus, the present case indicates that Cx32 gene mutation should be targeted first in case of HMSN with abnormal BAEP.

We report a patient of Charcot-Marie-Tooth disease (CMT) accompanied by transient splenium abnormality in brain MRI. A 34-year-old man suffered from chronic progressive unsteadiness and sensory disturbance of all limbs. Neurological examination showed muscle weakness and atrophy in the distal extremities with pes cavus, mild sensory disturbance of four extremities and generalized decreased reflexes. The nerve conduction study described the presence of sensory-motor polyneuropathy. We could not investigate his GJB1 gene. However, we suspected that he was X-linked CMT (CMTX), because his electrophysiological findings showed intermediate slowing of MCV, and auditory brain-stem response (ABR) demonstrated central conduction slowing. Brain MRI revealed the abnormal high signal intensity in the splenium of the corpus callosum on T2-weighted image. This lesion diminished two months later without any treatment. Recently, there had been reported transient splenium abnormality in CMTX cases, and there were clinical similarities between the cases of these reports and our case. We considered that the pathophysiology of this case was the disruption of gap junction communications expressed between oligodendrocyte and astrocytes induced by connexin 32 (Cx32) mutations. Furthermore, the transient functional disturbance of astrocytes would be another pathophysiologic mechanism of splenium abnormality.

The acute coronary syndrome, consisting of myocardial infarction and unstable angina, is the most important manifestation of coronary disease and is characterized by atherosclerotic plaque disruption and coronary thrombosis. In the coronary vessel wall, this process contains abnormalities of extracellular matrix, fibrinolytic system, endothelial function, and, possibly, vascular inflammation. Potentially thousands of genes are relevant to this apparently complex disease. Although many risk factors are intercorrelated, raising the possibility of a higher level of genetic control by a small number of master genes that control fundamental physiological systems. Such genes are likely to be relevant to the combined processes of plaque instability and coronary thrombosis.

Introduction: Connexin26, a gap junction protein that spreads in the inner ear, is thought to be mainly responsible for nonsyndromic hereditary deafness. In the Caucasian population, 30delG is the most frequent mutation. 233delC is the most frequent, however, in the Japanese population. We studied 233delC mutations with restriction enzyme Apa I., Subjects: Subjects were 61 patients visiting the hospital between March 1997 and October 1999 suspected of hereditary deafness. All gave written informed consent for participation., Methods: Genomic DNA was extracted from peripheral blood cells and amplified by polymerase chain reaction (PCR) using 1 set of primers targeting the connexin26 gene (nucleotide--36 to 256). After ethanol precipitation, the PCR product was digested by restriction enzyme Apa I and analyzed through agarose gel electrophoresis. The wild gene is digested by Apa I and appeared to be shorter than the original PCR product, i.e., judged to be normal., Results: Three patients had 233delC mutations--1 homozygous and 2 heterozygous. These mutant alleles were confirmed to have 233delC mutations by direct sequence., Conclusions: In targeting the mutation 233delC of the connexin 26 gene, restriction enzyme Apa I appears to be the most useful and economic method.

We report a 59-year-old man with X-linked Charcot-Marie-Tooth (CMT) disease and a new point mutation in the connexin32 gene. The patient first noticed mild gait disturbance five years previously. On admission, he exhibited muscle atrophy and weakness in the distal part of both legs, mild muscle atrophy of both hands without weakness, and a minimal reduction of touch sensation in the right dorsal foot. Nerve conduction velocity of the peripheral nerves was diffusely reduced. Electromyography exhibited high-amplitude, long-duration, polyphasic motor unit potentials in the muscles of the extremities. Fibrillation potential and positive sharp wave were present in the affected muscles. Cerebrospinal fluid protein was slightly elevated. The polyneuropathy did not respond to high-dose corticosteroid treatment, and showed very slow progression. His parents were not consanguineous. His father and two sons were healthy, but similar illness (more severe) was suspected in his younger brother. Gene analysis (Southern hybridization) did not reveal any duplication or deletion in the CMT 1 A-REP region. However, a novel mutation (Thr191Ala) was detected in the connexin32. Although more than 160 mutations in the connexin 32 gene have been identified worldwide, approximately ten mutations have so far been reported in Japan. In comparison with X-linked CMT patients with other connexin32 mutations, the present case was characterized by late onset and mild neurological manifestation. Gene analysis provides a useful tool for diagnosing cases with slowly progressive, motor dominant polyneuropathy of unknown origin.

Hereditary motor and sensory neuropathy type 1 (HMSN1) is the most common, but genetically heterogenous demyelinating peripheral neuropathy. HMSN1A is caused in most cases by a 1.5-Mb tandem duplication in chromosome 17p11.2. Hereditary neuropathy with liability to pressure palsies is caused by the reciprocal deletion of the 1.5-Mb HMSN1A region. The peripheral myelin protein22 (PMP-22) gene is located within the HMSN1A region and has a point mutation in non-duplicated HMSN1A patients. HMSN1B patients have a mutation in the protein zero (P0) gene located on chromosome 1q22-23 Point mutation in PMP-22 or P0 is also reported in patients with Dejerine-Sottas disease. In X-linked HMSN1 patients (HMSNX1) a mutation occurs in the connexin 32 gene located on chromosome Xq13. The morphological phenotype is different among the genotypes of HMSN1.

Charcot-Marie-Tooth neuropathy (CMT) is the most common inherited peripheral neuropathy. CMT is classified into type types on the basis of pathological and electrophysiological findings: type 1(CMT1), characterized by decreased nerve conduction velocities and by "onion bulb" formation: type 2(CMT2), in which nerve conduction velocities are normal and "onion bulb" formations are rarely seen. CMT1 loci map to chromosome 17 (CMT1A), chromosome 1(CMT1B), another unknown autosome (CMT1C) and the X chromosome (CMTX). Recent work has identified the gene products corresponding to CMT1A, CMT1B and CMTX as peripheral myelin protein-22(PMP22), Po and connexin 32, respectively. Dejerine-Sottas disease has been identified as being caused by the mutation of PMP-22 or Po gene.

Clinical, pathologic and molecular genetic studies of Japanese HMSN patients were reported. Among 26 HMSN I probands tested, the PMP22 gene region was duplicated in 18 (69%). A proband of HNPP, whose PMP22 gene region was deleted, was described. A proband with HMSN I was found to have a mutant allele that caused a substitution of arginine for glycine at amino acid 93 of PMP22. The mutation was located in the transmembrane portion of PMP22. The patient's sural nerve showed decrease of large myelinated fibers and frequent segmental demyelination and remyelination. A family with HMSN IB was found to have a mutant allele that caused a substitution of histidine for arginine at amino acid 98 of Po. The mutation was located in the extracellular domain of Po. The sural nerve from a proband showed uncompaction of major dense lines, wide-spaced major dense lines, and thin myelin sheath relative to axon size. One family of HMSN X with a mutant allele that caused a substitution of leucine for serine at amino acid 26 of Cx32 was found. The mutation was located in the fist transmembrane portion of Cx32. A variety of genetic abnormalities, probably underlying pathologic changes of the peripheral nerve, found among Caucasians were also noticed among Japanese.

A 28-year-old man had complaints of muscle weakness in both his legs and fingers. Moderate degrees of symmetrical atrophy adn weakness of the bilateral lower limbs, moderate degree of muscle atrophy was also noticed distal to the lower one third of the upper thigh. A moderate degree of weakness of the anterior tibial, extensor digitorum and peroneus muscles was also noted. Pes cavus deformity was evident bilaterally. Knee jerk was normal, and Achilles tendon reflex was absent without pathologic reflexes. He could not walk on his heels. Vibratory sensation was severely decreased in the toes, and both touch and pain sensations were slightly decreased on the dorsum of the feet. The median motor nerve conduction velocity was 28.9 m/sec with a prolonged distal latency. An amplitude of M-wave evoked by electrical stimulation of the median nerve 1 mV. No M-wave was obtained from stimulation of the tibial nerve, and no sensory nerve action potentials were elicited from electrical stimulation of the median and sural nerves. Histologic studies of the biopsied sural nerve revealed the occasional presence of internodes with a thin myelin sheath and a decrease in the density of large myelinated fibers. Small and atypical onion-bulbs were occasionally observed by electron microscopy. Based on the neurological examination and nerve conduction study of the family members, a sister, mother and grandmother of the proband were found to be mildly affected without any disability in their daily activities. However, the father and an uncle on the mother's side of the proband were normal. Therefore, we concluded clinically that this family had HMSN type I with autosomal dominant inheritance or X-linked HMSN. In the studies of fluorescence in situ hybridization and restriction fragment length polymorphism of the genomic DNA of the proband, a DNA duplication in chromosome 17p11.2-12 was not observed. A single-strand conformational polymorphism analysis of the genomic DNA encoding connexin32 (Cx32) revealed the abnormal band different from that of the control. A sequence analysis of the genomic DNA obtained by use of the polymerase chain reaction was also performed. It revealed that there was a mutant allele, a cytosine to thymine substitution of the nucleotide position 140, which caused a substitution of leucine for serine at amino acid position 26. The proband's mother was heterozygous for the mutant allele and the normal allele. This type of Cx32 mutation was different from any type of Cx32 mutation reported in the literature. The mutation in this family is located in the first transmembrane portion of Cx32, and may alter the function of Cx32 protein, as well as lead to the functional and structural abnormalities of the myelin sheath at the nodes of Ranvier and Schmidt-Lanterman's incisures, where Cx32 is present. This is the first Japanese X-linked HMSN family showing a new type of mutation of Cx32 gene with clinical findings and a histologic evaluation of the sural nerve.