Mutations in COA7 cause spinocerebellar ataxia with axonal neuropathy.

Several genes related to mitochondrial functions have been identified as causative genes of neuropathy or ataxia. Cytochrome c oxidase assembly factor 7 (COA7) may have a role in assembling mitochondrial respiratory chain complexes that function in oxidative phosphorylation. Here we identified four unrelated patients with recessive mutations in COA7 among a Japanese case series of 1396 patients with Charcot-Marie-Tooth disease (CMT) or other inherited peripheral neuropathies, including complex forms of CMT. We also found that all four patients had characteristic neurological features of peripheral neuropathy and ataxia with cerebellar atrophy, and some patients showed leukoencephalopathy or spinal cord atrophy on MRI scans. Validated mutations were located at highly conserved residues among different species and segregated with the disease in each family. Nerve conduction studies showed axonal sensorimotor neuropathy. Sural nerve biopsies showed chronic axonal degeneration with a marked loss of large and medium myelinated fibres. An immunohistochemical assay with an anti-COA7 antibody in the sural nerve from the control patient showed the positive expression of COA7 in the cytoplasm of Schwann cells. We also observed mildly elevated serum creatine kinase levels in all patients and the presence of a few ragged-red fibres and some cytochrome c oxidase-negative fibres in a muscle biopsy obtained from one patient, which was suggestive of subclinical mitochondrial myopathy. Mitochondrial respiratory chain enzyme assay in skin fibroblasts from the three patients showed a definitive decrease in complex I or complex IV. Immunocytochemical analysis of subcellular localization in HeLa cells indicated that mutant COA7 proteins as well as wild-type COA7 were localized in mitochondria, which suggests that mutant COA7 does not affect the mitochondrial recruitment and may affect the stability or localization of COA7 interaction partners in the mitochondria. In addition, Drosophila COA7 (dCOA7) knockdown models showed rough eye phenotype, reduced lifespan, impaired locomotive ability and shortened synaptic branches of motor neurons. Our results suggest that loss-of-function COA7 mutation is responsible for the phenotype of the presented patients, and this new entity of disease would be referred to as spinocerebellar ataxia with axonal neuropathy type 3.

Peripheral nerve pathology at fixed stage in spinal muscular atrophy with respiratory distress type 1.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is characterized by severe respiratory failure due to diaphragmatic paralysis and distal muscular weakness in early infancy. After an initial decline in respiratory state and motor function until 1-2years of age, residual capabilities reach a plateau. We report the peripheral neuropathological findings of a patient with SMARD1 at 1year and 1month of age, when his muscle strength and respiratory symptoms had deteriorated and then stabilized for several months. Peripheral nerve biopsy revealed severely progressed axonal degeneration. This finding suggests the rapid progression of peripheral axonal neuropathy in SMARD1 that leads to its characteristic clinical course of respiratory failure and paralysis in the early infantile period.

Potential utility of cinacalcet as a treatment for CDC73-related primary hyperparathyroidism: a case report.

We report a Japanese pedigree with familial primary hyperparathyroidism due to a CDC73 mutation. To our knowledge, this is the first report of cinacalcet as a treatment for CDC73-related primary hyperparathyroidism. The proband had severe psychomotor retardation and received laryngotracheal separation surgery. At 19 yr of age, he developed acute pancreatitis. Hypercalcemia (12.2-13.8 mg/dL), elevated levels of intact PTH (86-160 pg/mL), and a tumor detected upon neck ultrasonography led to the diagnosis of primary hyperparathyroidism. Family history and biochemical examinations revealed that three family members (the proband's mother, elder brother, and maternal grandfather) had primary hyperparathyroidism. We identified a novel heterozygous mutation, c.240delT, p.Glu81Lysfs*28, in the CDC73 gene in three affected family members, excluding the proband's elder brother who refused genetic testing. Parathyroidectomy for the proband was considered as high-risk, because the tumor was located close to the tracheostomy orifice. After receiving approval from the institutional review board and obtaining the consent, we initiated cinacalcet treatment. At 22 yr of age, treatment with 100 mg of cinacalcet maintained serum calcium levels below 11.0 mg/dL with no apparent side effects. Our report presents the potential efficacy of cinacalcet as a treatment for CDC73-related primary hyperparathyroidism, in particularly inoperative cases.

Increased number of Hassall's corpuscles in myasthenia gravis patients with thymic hyperplasia.

The thymus is implicated as an organ that contributes to autoimmunity in myasthenia gravis (MG) patients. Hassall's corpuscles (HCs) are assumed to represent the terminally differentiated stage of medullary thymic epithelial cells (mTECs). By using multicolor immunohistofluorescence analysis, we examined HCs in thymuses that were therapeutically excised from MG (+) and MG (-) patients. We found that the number of HCs per unit area of the thymic medulla was significantly elevated in the thymuses of MG (+) patients with thymic hyperplasia. CCL21 expression increased in the hyperplastic MG thymuses. We speculate that the altered differentiation of mTECs is associated with the thymic hyperplasia and the onset of MG.

Genotype-phenotype correlations in alternating hemiplegia of childhood.

OBJECTIVE: Clinical severity of alternating hemiplegia of childhood (AHC) is extremely variable. To investigate genotype-phenotype correlations in AHC, we analyzed the clinical information and ATP1A3 mutations in patients with AHC. METHODS: Thirty-five Japanese patients who were clinically diagnosed with AHC participated in this study. ATP1A3 mutations were analyzed using Sanger sequencing. Detailed clinical information was collected from family members of patients with AHC and clinicians responsible for their care. RESULTS: Gene analysis revealed 33 patients with de novo heterozygous missense mutations of ATP1A3: Glu815Lys in 12 cases (36%), Asp801Asn in 10 cases (30%), and other missense mutations in 11 cases. Clinical information was compared among the Glu815Lys, Asp801Asn, and other mutation groups. Statistical analysis revealed significant differences in the history of neonatal onset, gross motor level, status epilepticus, and respiratory paralysis in the Glu815Lys group compared with the other groups. In addition, 8 patients who did not receive flunarizine had severe motor deteriorations. CONCLUSIONS: The Glu815Lys genotype appears to be associated with the most severe AHC phenotype. Although AHC is not generally seen as a progressive disorder, it should be considered a disorder that deteriorates abruptly or in a stepwise fashion, particularly in patients with the Glu815Lys mutation.

Identification of ATP1A3 mutations by exome sequencing as the cause of alternating hemiplegia of childhood in Japanese patients.

BACKGROUND: Alternating hemiplegia of childhood (AHC) is a rare disorder characterized by transient repeated attacks of paresis and cognitive impairment. Recent studies from the U.S. and Europe have described ATP1A3 mutations in AHC. However, the genotype-phenotype relationship remains unclear. The purpose of this study was to identify the genetic abnormality in a Japanese cohort of AHC using exome analysis. PRINCIPAL FINDINGS: A total of 712,558 genetic single nucleotide variations in 8 patients with sporadic AHC were found. After a series of exclusions, mutations of three genes were regarded as candidate causes of AHC. Each patient harbored a heterozygous missense mutation of ATP1A3, which included G755C, E815K, C927Y and D801N. All mutations were at highly conserved amino acid residues and deduced to affect ATPase activity of the corresponding ATP pump, the product of ATP1A3. They were de novo mutations and not identified in 96 healthy volunteers. Using Sanger sequencing, E815K was found in two other sporadic cases of AHC. In this study, E815K was found in 5 of 10 patients (50%), a prevalence higher than that reported in two recent studies [19 of 82 (23%) and 7 of 24 (29%)]. Furthermore, the clinical data of the affected individuals indicated that E815K resulted in a severer phenotype compared with other ATP1A3 mutations. INTERPRETATION: Heterozygous de novo mutations of ATP1A3 were identified in all Japanese patients with AHC examined in this study, confirming that ATP1A3 mutation is the cause of AHC.

5,10-Methylenetetrahydrofolate reductase deficiency with progressive polyneuropathy in an infant.

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 11months 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.

Dysbindin, syncoilin, and beta-synemin mRNA levels in dystrophic muscles.

Progressive muscular dystrophies are genetic diseases with various modes of transmission. Duchenne muscular dystrophy (DMD) is caused by the defect of dystrophin, and Fukuyama congenital muscular dystrophy (FCMD) is caused by an abnormal fukutin gene leading to the glycosylation defect of alpha-dystroglycan. Dystrobrevin is one member of the dystrophin glycoprotein complex and its binding partners include dysbindin, syncoilin, and beta-synemin (desmuslin). Dysbindin is reported to be upregulated at the protein level in mdx mouse muscles, and syncoilin protein is also reported to be upregulated in biopsied muscles with neuromuscular disorders. In the present study we measured mRNA levels of dysbindin, syncoilin, and beta-synemin in biopsied muscles with DMD and FCMD. Upregulation of human dysbindin mRNA was observed in DMD muscles in comparison with normal muscles (p < .05). The differences in human syncoilin and beta-synemin mRNA ratios between DMD and normal muscles were not statistically significant, although upregulation tendency of human syncoilin mRNA was noted in DMD muscles (.05 < p < .1). Furthermore, the differences of human dysbindin, syncoilin, and beta-synemin mRNA ratios between FCMD and normal muscles were not statistically significant. These data provide insight into the pathophysiology of these muscular dystrophies.

Reduced expression of sarcospan in muscles of Fukuyama congenital muscular dystrophy.

Expression profiles of sarcospan in muscles with muscular dystrophies are scarcely reported. To examine this, we studied five Fukuyama congenital muscular dystrophy (FCMD) muscles, five Duchenne muscular dystrophy (DMD) muscles, five disease control and five normal control muscles. Immunoblot showed reactions of sarcospan markedly decreased in FCMD and DMD muscle extracts. Immunohistochemistry of FCMD muscles showed that most large diameter myofibers expressed sarcospan discontinuously at their surface membranes. Immature small diameter FCMD myofibers usually did not express sarcospan. Immunoreactivity of sarcospan in DMD muscles was similarly reduced. With regard to dystroglycans and sarcoglycans, immunohistochemistry of FCMD muscles showed selective deficiency of glycosylated alpha-dystroglycan, together with reduced expression of beta-dystroglycan and alpha-, beta-, gamma-, delta-sarcoglycans. Although the expression of glycosylated alpha-dystroglycan was lost, scattered FCMD myofibers showed positive immunoreaction with an antibody against the core protein of alpha-dystroglycan. The group mean ratios of sarcospan mRNA copy number versus GAPDH mRNA copy number by real-time RT-PCR showed that the ratios between FCMD and normal control groups were not significantly different (P>0.1 by the two-tailed t test). This study implied either O-linked glycosylation defects of alpha-dystroglycan in the Golgi apparatus of FCMD muscles may lead to decreased expression of sarcoglycan and sarcospan molecules, or selective deficiency of glycosylated alpha-dystroglycan due to impaired glycosylation in FCMD muscles may affect the molecular integrity of the basal lamina of myofibers. This, in turn, leads to decreased expression of sarcoglycans, and finally of sarcospan at the FCMD myofiber surfaces.

Screening of the early growth response 2 gene in Japanese patients with Charcot-Marie-Tooth disease type 1.

Charcot-Marie-Tooth disease type 1 (CMT1) is a heterogeneous disorder. Most CMT1 patients are associated with a duplication of 17p11.2-p12 (CMT1A duplication), but a small number of patients have mutations of peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), connexin 32 (Cx32) and early growth response 2 (EGR2) genes. In our previous study, we identified the responsible mutations in 72 of 128 Japanese CMT1 patients as CMT1A duplication in 40, PMP22 mutation in 6, MPZ mutation in 12 and Cx32 mutation in 14 patients. A total of 56 Japanese CMT1 patients with no identified mutations were screened for EGR2 mutation by denaturing gradient gel electrophoresis (DGGE). We detected a heterozygous Asp383Tyr mutation of EGR2 in one patient with severe CMT1, Dejerine-Sottas syndrome. EGR2 mutation is rare cause of CMT1 in Japan as in other nations. We were unable to identify the responsible mutation in 55 of 128 CMT1 patients and need further analysis to identify their candidate genes.

Infantile spongiform leukoencephalopathy: clinical and neuropathologic findings.

A 10-month-old male with spongy leukoencephalopathy is presented. Neurologic manifestations included feeding difficulties, horizontal nystagmus, and spasticity at 5 months of age. His head circumference was within the normal range. Radiologic examination demonstrated a diffuse white matter disorder. There was no detectable biochemical abnormality. He followed a neurologically progressive course. Neuropathologic findings revealed characteristic vacuolar changes in the white matter located immediately under the cortex with spongy alterations of the entire subcortical white matter, including intense astrocytic gliosis and marked vascular hyperplasia. Tissue of the matrix was destroyed in the deep white matter to form cystic areas of degeneration. White matter myelin development was severely disturbed compared with that of a normal infant of the same age. Cortical neuronal cells were preserved and did not reveal any specific abnormalities. Electron microscopic examination revealed that each vacuole in the white matter was covered by several layers of myelin structures, and intralamellar splits of white matter myelin were observed. These neuropathologic findings are also observed in some known inherent metabolic disorders. The present patient, however, did not demonstrate any metabolic abnormalities. These findings suggested a new genetic disorder of myelin metabolism.