小坂 仁

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.

Background Conventional PCR-based direct sequencing of candidate genes for a family with X-linked leucoencephalopathy with unknown aetiology failed to identify any causative mutations. Objective To carry out exome sequencing of entire transcripts of the whole X chromosome to investigate a family with X linked leucoencephalopathy. Methods and results Next-generation sequencing of all the transcripts of the X chromosome, after liquid-based genome partitioning, was performed on one of the two affected male subjects (the proband) and an unaffected male subject (his brother). A nonsense mutation in MCT8 (c.1102A -> T (p. R368X)) was identified in the proband. Subsequent PCR-based direct sequencing of other family members confirmed the presence of this mutation, hemizygous in the other affected brother and heterozygous in the proband's mother and maternal grandmother. MCT8 mutations usually cause abnormal thyroid function in addition to neurological abnormalities, but this proband had normal thyroid function. Conclusion Single-lane exome next-generation sequencing is sufficient to fully analyse all the transcripts of the X chromosome. This method is particularly suitable for mutation screening of X-linked recessive disorders and can avoid biases in candidate gene choice.

We investigated seizure, intelligence quotient (IQ), and neurological outcomes including the process of motor function recovery after functional right hemispherectomy in 3 children with Rasmussen's encephalitis (RE). Before the procedure, they were unable to walk, nor sit without support due to progressive worsening of left hemiplegia and relentless epilepsia partialis continua (EPC) of the left extremities, which were refractory to antiepileptic drug and immunological treatment. After functional right hemispherectomy, EPC completely disappeared, although complete left hemiplegia was sustained. However, they recovered up to being able to walk independently with assistance devices, and to have an ordinary life with family support within 1.5 to 5 months through rehabilitation. At the same time, the interictal EEG improved on the unaffected side of hemisphere, exhibiting a posterior alpha rhythm. Their IQ also improved, and they were able to attend school. Early functional hemispherectomy should be considered before patients with RE are left in a serious condition due to progressive worsening of hemiplegia and seizures refractory to the available treatment.

We report acute encephalopathy in two cases with severe congenital hydrocephalus. Case 1 was a 23-month-old girl, born at of 36 weeks gestation and delivered by cesarean section due to congenital hydrocephalus. Magnetic resonance imaging (MRI) showed prominent ventricular dilation associated with hydrocephalus, Dandy Walker variant and cortical malformation. The blood test for toxoplasmosis, syphilis, varicella-zoster, rubella, cytomegalovirus, and herpes simplex virus (TORCH) complex and various metabolic tests of blood and urine specimens yielded unremarkable results. She was admitted to our hospital for respiratory failure with fever and her clinical course deteriorated, progressing to hemiconvulsion hemiplegia epilepsy syndrome. Case 2 was a 17-month-old boy, born by spontaneous vertex delivery at 39 weeks. Severe, asymmetrical ventricular dilation associated with hydrocephalus, cerebellar and brainstem hypoplasia, and punctuate calcifications of the thalamus, third and fourth ventricles, around the aqueduct, were observed on computed tomography (CT). The blood test for TORCH complex and various metabolic tests of blood and urine specimens yielded unremarkable results. He was admitted to our hospital for status epilepticus with fever and his clinical course progressed to hemorrhagic shock and encephalopathy syndrome. In patients with brain disorders, diagnosis and treatment are likely to be delayed and prognosis may thereby be worsened. When status epileptics or prolonged coma manifests even in patients with severe brain disorders, we must consider encephalopathy in the differential diagnosis. (C) 2010 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

【目的】意思疎通の困難な小児神経疾患の急性呼吸不全に対するMechanically Assisted Coughing(MAC)の有効性と安全性を明らかにする。【対象】日常でMACを使用していない意思疎通困難な神経疾患児のうち、平成22年2月から5月に急性呼吸不全に対してMACを使用した当院に入院した症例を対象とした。【方法】診療録からの後方視的検討。MAC導入3日以内にPaCO2が20mmHg以上改善、SpO2≧95%となる酸素必要量の減少、P/F比100以上改善、5日以内に無気肺消失を認めた症例を有効、喀出量が増えたが有効と判定できない症例を境界、それ以外を無効として検討した。【結果】10例11回の入院でMACが施行された(0.2-20.4歳、中央値1.8歳)。autoモードで陽圧:陰圧:休止=1:1:2秒、圧±20-30cmH2Oで5呼吸を3-10サイクル、一日1-4セット施行した。有効5回、無効3回、境界3回であった。気胸や不整脈のような合併症は生じなかった。【結論】MACは意思疎通の困難な児の急性呼吸不全にも有効な例があり、安全に施行できることが分かった。(著者抄録)

A 19-year-old university student with no personal or family history of neurologic disorders developed convulsions and was administered phenytoin. Two months later, he developed lower limb-dominant acute demyelinating polyneuropathy, from which he recovered within 2 months. At age 20, he rapidly developed visual disturbances and paraplegia from phenytoin intoxication. Cranial magnetic resonance imaging (MRI) revealed leukoencephalopathy with no evidence of thrombosis or vasoconstriction. Hyperhomocysteinemia, hypomethioninemia, low serum folate concentration, and an absence of megaloblastic anemia were consistent with the diagnosis of methylenetetrahydrofolate reductase (MTHFR) deficiency. A genomic DNA sequence analysis demonstrated compound heterozygosity for two missense mutations in the MTHFR gene, namely, [458G>T + 459C>T] (Gly149Val) and 358G>A (Ala116Thr), both of which are known pathogenic mutations. An absence of leukoencephalopathic changes on MRI scans performed 9 months previously strongly suggested that phenytoin intoxication caused acute leukoencephalopathy. Therefore, phenytoin may be an aggravating factor of remethylation defects in patients with MTHFR deficiency.

5,10-Methylenetetrahydrofolate reductase (MTHFR) deficiency is the most prevalent inborn error of folate metabolism, and has variable clinical manifestations from asymptomatic to severe psychomotor retardation, microcephalus and seizure. In untreated infantile cases, it predominantly affects the central nervous system, which is sometimes fatal. On the other hand, peripheral nerve involvement is uncommon. We present a severe infantile case of MTHFR deficiency that manifested unilateral phrenic nerve palsy with communicating hydrocephalus, developmental delay and died at 11 months of age. An enzymatic study confirmed MTHFR deficiency with residual activity of 0.75% of mean control values in cultured fibroblasts. Mutation analysis of the MTHFR gene revealed homozygous, tandem missense mutations c.[446G > T; 447C > T] in exon 3 of the MTHFR gene converting glycine to valine (Gly149Val). In MTHFR deficiency, betaine may improve the symptoms if started immediately after birth by reducing the level of serum homocysteine and increasing that of methionine. Our results show that we should be aware of possible inborn errors of folate metabolism such as MTHFR deficiency, in infants with unexplained developmental delay manifesting rapidly progressive polyneuropathy. (C) 2010 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

5歳女児。1病日に左足を引きずり歩行障害が出現し、時折静止できずに立位・座位困難となった。24病日頃より不眠が出現し、歩行障害のためずり這いをするようになった。構音障害、食事摂取量の低下、睡眠障害が次第に増悪し48病日に転院した。自己免疫性疾患の可能性を考え免疫療法を考慮した。54病日に1回目のステロイドパルス療法を施行し右上肢の舞踏病様運動と舌のジスキネジアが改善した。しかし、徐々に発語が消失し疎通性と自発性が低下し、68病日には疎通性が消失し痛み刺激に反応なく、体幹を前後左右に倒しては起き上がるという常同運動が出現した。75病日から免疫グロブリン療法を開始し、常同運動の著しい改善がみられ、疎通性も徐々に改善した。自立歩行も可能となり104病日に退院した。髄液抗NMDA受容体抗体が陽性であること、臨床経過とあわせて抗NMDA受容体脳炎と診断した。

Dravet syndrome (severe myoclonic epilepsy in infancy) is an epileptic syndrome with various types of seizures that begin in the first year of life and may result in intellectual impairment. Mutations of the SCN1A gene are the most prevalent genetic cause of Dravet syndrome. In this study, we report a 12-year-old girl with Dravet syndrome carrying an SCN1A mutation, c.2785Cdel (L929del fsX934). She had an episode of status epilepticus and persistent lethargy after 48h of acute febrile illness that was preceded by an annual flu vaccination. Low voltage activities detected by electroencephalogram and elevated neuron-specific enolase/interleukin-6 concentrations in the cerebrospinal fluid suggested acute encephalopathy. MRI showed abnormalities in the bilateral thalami, cerebellum and brainstem. These abnormalities were protracted over a month. The biochemical and MRI characteristics of this case are different from any known type of encephalopathy, and may suggest a vulnerability of neurons expressing mutant SCN1A in the brain. © Georg Thieme Verlag KG Stuttgart New York.

Hypomyelination with hypogonadotropic hypogonadism and hypodontia (4H syndrome) is a rare disease, characterized by both central and peripheral hypomyelination. We describe a 21-year-old male with mildly progressive ataxia, mental retardation, pituitary hypogonadotropic hypogonadism, delayed dentition, and cataract. Brain magnetic resonance imaging showed hypomyelinated white matter, cerebellar atrophy, and a thin corpus callosum. The literature suggests that abnormal findings upon sural nerve biopsy may indicate peripheral hypomyelination, even in the absence of clinically and physiologically evident peripheral neuropathy. A sural nerve biopsy of this patient was normal, and this finding is further discussed. Taken together with previous reports, this case suggests that 4H syndrome can be regarded as a spectrum disorder, the cardinal signs of which may be central hypomyelination, ataxia, hypogonadotropic hypogonadism, and hypodontia. (C) 2010 Elsevier B.V. All rights reserved.

P>Purpose: De novo STXBP1 mutations have been found in individuals with early infantile epileptic encephalopathy with suppression-burst pattern (EIEE). Our aim was to delineate the clinical spectrum of subjects with STXBP1 mutations, and to examine their biologic aspects. Methods: STXBP1 was analyzed in 29 and 54 cases of cryptogenic EIEE and West syndrome, respectively, as a second cohort. RNA splicing was analyzed in lymphoblastoid cells from a subject harboring a c.663 + 5G > A mutation. Expression of STXBP1 protein with missense mutations was examined in neuroblastoma2A cells. Results: A total of seven novel STXBP1 mutations were found in nine EIEE cases, but not in West syndrome. The mutations include two frameshift mutations, three nonsense mutations, a splicing mutation, and a recurrent missense mutation in three unrelated cases. Including our previous data, 10 of 14 individuals (71%) with STXBP1 aberrations had the onset of spasms after 1 month, suggesting relatively later onset of epileptic spasms. Nonsense-mediated mRNA decay associated with abnormal splicing was demonstrated. Transient expression revealed that STXBP1 proteins with missense mutations resulted in degradation in neuroblastoma2A cells. Discussion: Collectively, STXBP1 aberrations can account for about one-third individuals with EIEE (14 of 43). These genetic and biologic data clearly showed that haploinsufficiency of STXBP1 is the important cause for cryptogenic EIEE.

We present the case of a 26 year-old man who developed normally until he began having difficulty walking at age 12. He subsequently became unable to stand at 15 years old and exhibited mental regression and generalized tonic convulsions by age 20. Magnetic resonance imaging revealed incomplete myelination of cerebral white matter, which resembled that of Pelizaeus-Merzbacher disease. By sequencing the proteolipid protein 1 (PLP1) gene, we found a novel mutation (c.352_353delAG (p.Glyl30fs)) in the latter half of exon 3 (exon 3B) that is spliced out in the DM20 isoform. Exon 3B mutations are known to cause a mild phenotype since they do not disturb DM20 production. Mutations that truncate PLP1 correlate with a mild phenotype by activating the nonsense-mediated decay mechanism that specifically detects and degrades mRNAs containing a premature termination codon. This attenuates the production of toxic mutant PLP1. The very mild presentation in the present case seems to be derived from the unique nature of the mutation, which preserves DM20 production and decreases mutant PLP1. (C) 2009 Elsevier B.V. All rights reserved.

Plectin is a cytoskeletal linker protein which has a long central rod and N- and C-terminal globular domains. Mutations in the gene encoding plectin (PLEC) cause two distinct autosomal recessive subtypes of epidermolysis bullosa: EB simplex (EBS) with muscular dystrophy (EBS-MD), and EBS with pyloric atresia (EBS-PA). Previous studies have demonstrated that loss of full-length plectin with residual expression of the rodless isoform leads to EBS-MD, whereas complete loss or marked attenuation of expression of full-length and rodless plectin underlies the more severe EBS-PA phenotype. However, muscular dystrophy has never been identified in EBS-PA, not even in the severe form of the disease. Here, we report the first case of EBS associated with both pyloric atresia and muscular dystrophy. Both of the premature termination codon-causing mutations of the proband are located within exon 32, the last exon of PLEC. Immunofluorescence and immunoblot analysis of skin samples and cultured fibroblasts from the proband revealed truncated plectin protein expression in low amounts. This study demonstrates that plectin deficiency can indeed lead to both muscular dystrophy and pyloric atresia in an individual EBS patient. (C) 2010 Wiley-Liss, Inc.

Background: 1p36 deletion syndrome is one of the most common subtelomeric deletion syndromes, characterized by moderate to severe mental retardation, characteristic facial appearance, hypotonia, obesity, and seizures. The clinical features often overlap with those of Prader-Willi syndrome (PWS). To elucidate the phenotype-genotype correlation in 1p36 deletion syndrome, two cases involving a PWS-like phenotype were analyzed on molecular cytogenetics. Methods: Two patients presenting with the PWS-like phenotype but having negative results for PWS underwent fluorescence in situ hybridization (FISH). The size of the chromosome 1p36 deletions was characterized using probes of BAC clones based on the University of California, Santa Cruz (UCSC) Genome Browser. Results: PWS was excluded on FISH and methylation-specific polymerase chain reaction. Subsequent FISH using the probe D1Z2 showed deletion of the 1p36.3 region, confirming the diagnosis of 1p36 deletion syndrome. Further analysis characterized the 1p36 deletions as being located between 4.17 and 4.36 Mb in patient 1 and between 4.89 and 6.09 Mb in patient 2. Conclusion: Patients with 1p36 deletion syndrome exhibit a PWS-like phenotype and are therefore probably underdiagnosed. The possible involvement of the terminal 4 Mb region of chromosome 1p36 in the PWS-like phenotype is hypothesized.

Mutations in the gap junction protein gamma-2 gene, GJC2, cause a central hypomyelinating disorder; Pelizaeus-Merzbacher-like disease (PMLD; MIM311601). Using a homozygosity mapping and positional candidate gene approach, we identified a homozygous mutation (c.-167A>G) within the GJC2 promoter at a potent SOX10 binding site in a patient with mild PMLD. Functionally, this mutation completely abolished the SOX10 binding and attenuated GJC2 promoter activity. These findings suggest not only that the SOX10-to-GJC2 transcriptional dysregulation is a cause of PMLD, but also that GJC2 may be in part responsible for the central hypomyelination caused by SOX10 mutations. ANN NEUROL 2010;68:250-254

Mutations involving the voltage-gated sodium channel alpha(I) gene SCN1A are major genetic causes of childhood epileptic disorders, as typified by Dravet syndrome. Here we investigated the upstream regions of the SCN1A 5' noncoding exons and found two major regions with promoter activity. These two major promoters were simultaneously active in various brain regions and in most neurons. Using multiplex ligation-dependent probe amplification (MLPA) assays with probes for the 5' noncoding exons, their upstream regions, and all coding exons of SCN1A, we investigated 130 epileptic patients who did not show any SCN1A mutations by sequence analysis of all coding exons and exon intron boundaries. Among 71 Dravet syndrome patients, we found two patients with heterozygous microdeletions removing the 5' noncoding exons and regions with promoter activity but not affecting the coding exons. We also identified four patients with deletions/duplication in the coding region. One patient with symptomatic focal epilepsy also showed a deletion in the coding region. This study provides the first case of microdeletion limited to the SCN1A 5' promoter region with the coding sequence preserved, and indicates the critical involvement of this upstream region in the molecular pathology of Dravet syndrome. Hum Mutat 31:820-829, 2010. (C) 2010 Wiley-Liss, Inc.

Purpose: Rasmussen's encephalitis (RE) is a progressive and catastrophic epileptic disorder caused by chronic localized encephalitis. We performed a nationwide survey of RE to assess the clinical picture, treatment effect, and prognosis of Japanese RE patients. Subjects & methods: The subjects were 27 patients (male:1 2; female: IS) from 13 medical facilities. All of them satisfied the clinical and neuroimaging criteria for RE, including 14 pathologically proven cases. Results: They were divided into the childhood-onset rapidly progressive type (CORP, n = 19), and late-onset slowly progressive type (LOSP, n = 8). The mean age at epilepsy onset was 4 years and 4 months in CORP, and 16 years in LOSP. The mean period between the onset age of epilepsy and development of frequent seizures was 1 year and 4 months in the former, and 3 years and 4 months in the latter. The immunomodulatory treatment including high-dose steroid (n = 14) and high-dose intravenous immunoglobulin therapies (IVIgG, n = 12) achieved more than a 50% reduction in the seizure frequency in 5 (36%) and 4 (33%) patients, respectively. Eight and seven patients underwent focal cortical resection and functional hemispherectomy, leading to significant improvement in 5 of the 8 patients and excellent seizure control in all 7 patients, respectively. Conclusion: Although the high-dose steroid and IVIG therapies may have alleviated the exacerbation of seizures in those with RE, they could not halt the disease progression. Functional hemispherectomy is still the only curative therapy for RE, despite the fact that the early introduction of this procedure remains controversial. (C) 2009 Elsevier B.V. All rights reserved.

A de novo 9q33.3-q34.11 microdeletion involving STX8P1 has been found in one of four individuals (group A) with early-onset West syndrome, severe hypomyelination, poor visual attention, and developmental delay. Although haploinsufficiency of STXBP1 was involved in early infantile epileptic encephalopathy in a previous different cohort study (group B), no mutations of SIXBP1 were found in two of the remaining three subjects of group A (one was unavailable), We assumed that another gene within the deletion might contribute to the phenotype of group A. SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebratish, turned out to be deleted. In two subjects, an in-frame 3 bp deletion and a 6 bp duplication in SHAN1 were found at the initial nucleation site of the alpha/beta spectrin heterodimer. SPTAN1 was further screened in six unrelated individuals with WS and hypomyelination, but no mutations were found. Recombinant mutant (mut) and wild-type (WT) alpha-II spectrin could assemble heterodimers with beta-II spectrin, but alpha-II (mut)/beta-II spectrin heterodimers were thermolabile compared with the alpha-II (WT)/beta-II heterodimers. Transient expression in mouse cortical neurons revealed aggregation of alpha-II (mut)/beta-II and alpha-II (mut)/beta-III spectrin heterodimers, which was also observed in lymphoblastoid cells from two subjects with in-frame mutations. Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold. These findings suggest that pathological aggregation of alpha/beta spectrin heterodimers and abnormal AIS integrity resulting from SPTAN1 mutations were involved in pathogenesis of infantile epilepsy.

Deficiency of 4-aminobutyrate aminotransferase (GABA-T) is a rare disorder of GABA catabolism, with only a single sibship reported. We report on a third case, a Japanese female infant with severe psychomotor retardation and recurrent episodic lethargy with intractable seizures, with the diagnosis facilitated by proton magnetic resonance (MR) spectroscopy ((1)H-MRS). Neuroimaging was performed at the first episode of lethargy. For (1)H-MRS, locations were placed in the semioval center and the basal ganglia. Quantification of metabolite concentrations were derived using the LCModel. We confirmed the diagnosis subsequently by enzyme and molecular studies, which involved direct DNA sequence analysis and the development of a novel multiplex ligation-dependent probe amplification test. (1)H-MRS analysis revealed an elevated GABA concentration in the basal ganglia (2.9 mmol/l). Based on the results of quantitative (1)H-MRS and clinical findings, GABA-T deficiency was suspected and confirmed in cultured lymphoblasts. Molecular studies of the GABA-T gene revealed compound heterozygosity for a deletion of one exon and a missense mutation, 275G > A, which was not detected in 210 control chromosomes. Our results suggest that excessive prenatal GABA exposure in the central nervous system (CNS) was responsible for the clinical manifestations of GABA transaminase deficiency. Our findings suggest the dual nature of GABA as an excitatory molecule early in life, followed by a functional switch to an inhibitory species later in development. Furthermore, quantitative (1)H-MRS appears to be a useful, noninvasive tool for detecting inborn errors of GABA metabolism in the CNS.

Objective: The mechanism underlying the development of neuropsychiatric symptoms such as unconsciousness, abnormal behavior, delirium, hallucinations, and convulsions in influenza has not been thoroughly investigated. The relationship between drug administration and neuropsychiatric symptoms during influenza is also poorly understood. This study is the first pharmacoepidemiologic study focused on investigating the relationship between drug administration and neuropsychiatric symptoms.<br>Design: Cohort study<br>Methods: Study subjects were patients under 18 years old who had influenza during the 2006/07 season. We prepared two kinds of questionnaires for doctor and for patient's family, and carried out the survey between January and March, 2007. Using data from 9,389 patients, we analyzed the relationship between neuropsychiatric symptoms, such as delirium, unconsciousness and convulsion, and drug administration of acetaminophen and oseltamivir.<br>Results: Analysis of the relationship between delirium and drug administration provided hazard ratios of 1.55(p=0.061)for acetaminophen and 1.51(p=0.084)for oseltamivir. These hazard ratios, which were adjusted for risk factors by multivariate analysis of the proportional hazard model, showed an increasing tendency of delirium after administration of each drug. In patients who received oseltamivir, a high incidence of delirium was observed between 6 and 12 hours after onset of fever. Furthermore, delirium was found to develop in a shorter time following oseltamivir use than it did after acetaminophen use. There was no relationship between unconsciousness and acetaminophen administration, as demonstrated by a hazard ratio of 1.06(p=0.839). The incidence of unconsciousness increased significantly with oseltamivir use with a hazard ratio of 1.79(p=0.0389), and unconsciousness was found to occur in a short time after oseltamivir use.<br>Conclusion: The results obtained from this study suggest that there are increased risks of delirium and unconsciousness with drug administration. Further pharmacoepidemiologic studies for hypothesis testing are required to study the relationship between abnormal behavior and drug administration.

1歳男児。発達の遅れがみられ先天性異常が疑われた。末梢血、骨髄検査で泡沫細胞が認められ、ムコリピドーシスを疑い精査したが診断確定に至らなかった。明らかな外表奇形はみられなかったが巨舌を認め、吸気時喘鳴を聴取した。軽度の陥没呼吸がみられ腹部は全体に硬く軽度膨満がみられた。神経学的には追視ならびに固視はみられたが発語は認めなかった。驚愕反射は明らかに亢進し、姿勢はfrog postureをとり、筋トーヌスは低下していた。痙性は認めたが固縮はなく、自発運動はほぼ消失し下肢に尖足拘縮を認めた。上腕二頭筋・三頭筋反射・膝蓋腱反射及びアキレス腱反射は両側亢進し、Babinski反射は陽性であった。AST/ALT軽度高値を認めライソゾーム病が疑われた。頭部MRIで髄鞘化遅延に加え、視床の異常信号を認め、β-ガラクトシダーゼ酵素活性測定を行いGM1ガングリオシドーシスと診断した。

Local axonal degeneration is a common pathological feature of peripheral neuropathies and neurodegenerative disorders of the central nervous system, including Alzheimer&apos;s disease, Parkinson&apos;s disease, and stroke; however, the underlying molecular mechanism is not known. Here, we analyzed the gracile axonal dystrophy (gad) mouse, which displays the dying-back-type of axonal degeneration in sensory neurons, to find the molecules involved in the mechanism of axonal degeneration. The gad mouse is analogous to a null mutant of ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1). UCH-L1 is a deubiquitinating enzyme expressed at high levels in neurons, as well as testis and ovary. In addition, we recently discovered a new function of UCH-L1-namely to bind to and stabilize mono-ubiquitin in neurons, and found that the level of mono-ubiquitin was decreased in neurons, especially in axons of the sciatic nerve, in gad mice. The low level of ubiquitin suggests that the target proteins of the ubiquitin proteasome system are not sufficiently ubiquitinated and thus degraded in the gad mouse; therefore, these proteins may be the key molecules involved in axonal degeneration. To identify molecules involved in axonal degeneration in gad mice, we compared protein expression in sciatic nerves between gad and wild-type mice at 2 and 12 weeks old, using two-dimensional difference gel electrophoresis. As a result, we found age-dependent accumulation of several proteins, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and 14-3-3, in gad mice compared with wild-type mice. Histochemical analyses demonstrated that GAPDH and 14-3-3 were localized throughout axons in both gad and wild-type mice, but GAPDH accumulated in the axons of gad mice. Recently, it has been suggested that a wide range of neurodegenerative diseases are characterized by the accumulation of intracellular and extracellular protein aggregates, and it has been reported that oxidative stress causes the aggregation of GAPDH. Furthermore, histochemical analysis demonstrated that sulfonated GAPDH, a sensor of oxidative stress that elicits cellular dysfunction, was expressed in the axons of gad mice, and 4-hydroxy-2-nonenal, a major marker of oxidative stress, was also only detected in gad mice. Our findings suggest that GAPDH may participate in a process of the dying-back-type of axonal degeneration in gad mice and may provide valuable insight into the mechanisms of axonal degeneration. (C) 2008 Elsevier Ltd. All rights reserved.