Mio Ichiba

A gene-targeted mouse model for chorea-acanthocytosis

Chorea‐acanthocytosis (CHAC) is a hereditary neurodegenerative disorder with autosomal recessive transmission, in which selective degeneration of striatum has been reported in brain pathology. Clinically, CHAC shows Huntingtons disease‐like neuropsychiatric symptoms and red blood cell acanthocytosis. Recently, we identified the gene, CHAC, encoding a novel protein, chorein, in which a deletion mutation was found in Japanese families with CHAC. In the present study, we have identified the mouse CHAC cDNA sequence and the exon–intron structures of the gene and produced a CHAC model mouse introducing no. 60–61 exon deletion corresponding to a human disease mutation by a gene‐targeting technique. The mice began to show acanthocytosis and motor disturbance in old age. In behavioral observations, locomotor activity was significantly decreased and the contact time at social interaction test was decreased significantly in the model mice. In the brain pathology, many apoptotic cells were observed in the striatum of the mutant mice. In neurochemical determinations, the dopamine metabolite, homovanillic acid, concentration decreased significantly in the portion including the midbrain of the mutant mice. These findings are consistent with the human results reported elsewhere and indicate that the CHAC model mice showed a mild phenotype with late adult onset. The CHAC model mouse therefore provides a good model system to study the human disease.

Novel Pathogenic Mutations and Copy Number Variations in the VPS13A Gene in Patients With Chorea-Acanthocytosis

Chorea‐acanthocytosis (ChAc) is a rare autosomal recessive neurodegenerative disorder caused by loss of function mutations in the vacuolar protein sorting 13 homolog A (VPS13A) gene that encodes chorein. It is characterized by adult‐onset chorea, peripheral acanthocytes, and neuropsychiatric symptoms. In the present study, we performed a comprehensive mutation screen, including sequencing and copy number variation (CNV) analysis, of the VPS13A gene in ChAc patients. All 73 exons and flanking regions of VPS13A were sequenced in 35 patients diagnosed with ChAc. To detect CNVs, we also performed real‐time quantitative PCR and long‐range PCR analyses for the VPS13A gene on patients in whom only a single heterozygous mutation was detected. We identified 36 pathogenic mutations, 20 of which were previously unreported, including two novel CNVs. In addition, we investigated the expression of chorein in 16 patients by Western blotting of erythrocyte ghosts. This demonstrated the complete absence of chorein in patients with pathogenic mutations. This comprehensive screen provides an accurate and useful method for the molecular diagnosis of ChAc.

Mitochondrial DNA deletion mutations in patients with neuropsychiatric symptoms

It has been suggested that mitochondrial dysfunction is important in the pathogenesis of psychiatric disorders such as depression, schizophrenia and dementia. We report herein three adult patients exhibiting such psychiatric symptoms as the core manifestation, accompanied by various degrees of myopathic symptoms. Pathological findings in biopsied skeletal muscle were compatible with mitochondrial myopathy in all cases. Maternal inheritance was not apparent in all three cases; however, two patients were born to consanguineous parents. Mutation analysis on the mitochondrial DNA (mtDNA) and seven nuclear genes, in which pathogenic mutations are known to cause mtDNA deletions, was performed. MtDNA deletion mutations were identified in skeletal muscles of all patients. Neither pathogenic mutations nor copy number variation was identified among the nuclear genes. Although further studies are needed, the molecular pathways inducing mitochondrial abnormalities may be implicated in a variety of psychiatric conditions.

Clinical and molecular genetic assessment of a chorea-acanthocytosis pedigree

BACKGROUND Chorea-acanthocytosis (ChAc) is an autosomal recessive hereditary disease characterized by neurodegeneration in the striatum and acanthocytosis that is caused by mutations in the VPS13A gene. There are only few reports that studied clinical status of the obligate carriers of ChAc. Clinical courses with follow-up neuroradiological and neuropsychological evaluations in individuals with ChAc have been rarely reported. METHODS We followed an index patient with ChAc and evaluated the clinical features of the pedigree members. Genetic analyses of VPS13A and genes responsible for other neuroacanthocytotic and neurodegenerative diseases were performed. CONCLUSIONS The index patient was homozygous for a 3889C>T nonsense mutation in the VPS13A gene and presented with a typical ChAc phenotype. Neuropsychological evaluation with brain imaging in the patient over 3 years revealed atrophy and a decrease in blood flow at the basal ganglia and frontal lobe, and impairment in cognitive function reflecting frontal lobe dysfunction in progressive manners. Four out of five heterozygous mutation carriers in the pedigree showed signs or symptoms potentially attributable to a heterozygous VPS13A mutation.

Familial Semantic Dementia with P301L Mutation in the Tau Gene

Background/Aims: Semantic dementia (SD) is a clinical subclassification of frontotemporal lobar degeneration. Patients with ‘pure SD’ present with semantic memory impairment preceding the frontal symptoms, and there have been no reports of familial cases. Methods: We evaluated the clinical features of, and performed neuropsychological examinations on, the proband and two affected family members. Then we performed neuroimaging and genetic analysis of MAPT and other dementia-related genes in the proband. Results: All three cases had semantic memory impairment with loss of word meanings as the primary early symptom. We diagnosed all cases as pure SD and identified a P301L mutation in the MAPT gene of the proband. Conclusion: Although the P301L mutation identified here has been previously described as pathogenic for frontotemporal dementia with parkinsonism-17 (FTDP-17), the proband and his two affected relatives showed different clinical symptoms from those of typical FTDP-17 cases who carry the P301L mutation. Pathologically, pure SD usually shows a TAR DNA-binding protein proteinopathy, but the molecular understanding of SD is not well established. Although our cases were clinically pure SD, the proband has a tau gene mutation, which would lead to tauopathy. These findings suggest that reconsideration of the molecular understanding of SD is warranted.

Adult-type metachromatic leukodystrophy with compound heterozygous ARSA mutations: A case report and phenotypic comparison with a previously reported case

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by a deficiency of arylsulfatase A. MLD is a heterogeneous disease with variable age at onset and variable clinical features. We evaluated a 33‐year‐old female patient who developed manifestations of disinhibitory behavior. She was diagnosed with MLD by genetic analysis, which revealed compound heterozygous ARSA missense mutations (p.G99D and p.T409I). The same combination of mutations was previously reported in a Japanese patient with similar symptoms. We performed additional, detailed neuropsychological tests with functional imaging on the current patient that demonstrated frontal lobe dysfunction. These results indicate that the mutations have important implications for genotype–phenotype correlation in MLD.

A new phenotype of chorea-acanthocytosis with dilated cardiomyopathy and myopathy

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Different Clinical Phenotypes in Siblings with a Presenilin-1 P264L Mutation

Background: Mutations in the presenilin-1 gene (PSEN1) have been identified in autosomal dominant early-onset cases of Alzheimer’s disease (AD). Aims: To investigate different clinical phenotypes of siblings possessing the same heterozygous P264L mutation in the PSEN1 gene. Methods: We evaluated clinical features, neuroimaging results, and neuropsychological examinations. The PSEN1 gene and other dementia-related gene mutations were screened. Results: We clinically diagnosed the proband as atypical AD with frontotemporal dementia features and diagnosed the elder brother of the proband as typical AD, based on neuropsychological symptoms and a brain imaging examination including amyloid imaging data. A heterozygous P264L mutation in the PSEN1 gene was identified in both siblings. Conclusion: This study is one of few reports of AD siblings possessing the same mutation but exhibiting different clinical phenotypes in a Japanese family possessing a P264L mutation in the PSEN1 gene. The current results suggest that unknown modifiers, including both genetic and epigenetic factors, may alter the pathological and clinical phenotypes of a genetically predetermined disease.

Comprehensive analysis of the genes responsible for neuroacanthocytosis in mood disorder and schizophrenia.

Neuroacanthocytosis syndromes are mainly comprised of two diseases: chorea-acanthocytosis (ChAc) and McLeod syndrome (MLS). There is a high incidence of psychiatric disorders such as mood disorder and schizophrenia among neuroacanthocytosis patients. We hypothesized that neuroacanthocytosis-related-genes might be associated with susceptibility to these psychiatric disorders. We performed a comprehensive mutation screen of VPS13A and XK, the gene responsible for ChAc and MLS, respectively, in 85 mood disorder subjects and XK in 86 schizophrenia subjects and compared the variants to 100 or more control alleles. We also performed copy number variation (CNV) analysis in 72 mood disorder subjects and 86 schizophrenia subjects. We identified three non-synonymous, two synonymous and six intron variants in mood disorder subjects and a novel GAT triplet repeat polymorphism in VPS13A. By CNV analysis, we identified a heterozygous exon 60-61 deletion in VPS13A in one mood disorder subject. We identified one non-synonymous and one intron variant in mood disorder and schizophrenia subjects, respectively, in XK. The presence of a pathogenic mutation or a potentially functional variant in mood disorder or schizophrenia subjects suggests that neuroacanthocytosis-related-genes might be involved in the pathogenesis of these psychiatric disorders.

Chorea-acanthocytosis with upper motor neuron degeneration and 3419_3420 delCA and 3970_3973 delAGTC VPS13A mutations.

Chorea-acanthocytosis (ChAc) is caused by loss of function mutations of VPS13A gene encoding the large disease protein named chorein [8, 10]. However, McLeod syndrome, Huntington’s disease-like 2, and pantothenate kinase-associated neurodegeneration also present with choreic movements and acanthocytosis. To our knowledge, only five autopsy cases of genetically proven ChAc have been reported [1, 6, 7, 9, 11]. Here, we report an autopsy case of ChAc with upper motor neuron degeneration and with novel VPS13A mutations. A Japanese man developed generalized tonic-clonic seizure at age of 35. At age of 37, he presented with postural instability due to lapse of knees, self-mutilation, orofacial dyskinesia with tongue-biting, involuntary vocalization, and pill-rolling tremor in the left hand. Blood smear showed that 30% of erythrocytes were acanthocytes after 5 min of incubation in normal saline (normal, less than 1%) [5]. Neurological examination showed that deep tendon reflexes in all limbs were absent. Brain CT and MRI revealed mild atrophy of the bilateral caudate nuclei. Genetic analysis revealed no expansion of CAG repeats in the genes of Huntington’s disease and dentatorubral-pallidoluysian atrophy. Expression of Kell antigen of erythrocytes was normal. At age of 42, he was bound to a wheelchair and gradually unable to move his left upper and lower extremities. At age of 47, congestive heart failure became apparent and he died suddenly. Postmortem examination revealed severe degeneration of the neostriatum (Fig. 1a, b). Moderate neuronal loss was found in the substantia nigra pars reticulata and mild in the spinal anterior horn. These findings were consistent with histopathological features of ChAc [12]. Furthermore, neuronal loss in the motor cortex with pyramidal tract degeneration, more severe on the right side, was evident (Fig. 1c–i). No Bunina bodies or TDP-43-positive inclusions were noted in the upper and lower motor neurons. Genetic analysis revealed two novel heterozygous mutations in exon 32 (c.3419_3420 delCA) and exon 35 (c.3970_3973 delAGTC) of the VPS13A gene (Fig. 2). Both mutations, which lead to premature stop codon further downstream resulting in truncated chorein, are considered to be pathogenic. Although epilepsy has been well recognized in patients with ChAc [2], the cortical degeneration in our case is not due to epilepsy, because of the absence of neuronal loss or gliosis in the medial temporal lobe. Moreover, no Bunina bodies or TDP-43-immunoreactive inclusions were noted in our case. Therefore, complication of neurodegenerative diseases causing bilateral pyramidal tract degeneration, such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration with motor neuron disease, appeared to be excluded. Although the inheritance of ChAc is widely known as autosomal recessive, single heterozygous VPS13A Y. Miki (&) F. Mori K. Wakabayashi Department of Neuropathology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki 036-8562, Japan e-mail: yasuomiki@hotmail.com