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Tetsuo Ashizawa

Publications and source records attributed to Tetsuo Ashizawa.

At least 19 recordsLinked to original sources
PubMed2006

Genome-wide significance for a modifier of age at neurological onset in Huntington's disease at 6q23-24: the HD MAPS study.

BACKGROUND: Age at onset of Huntington's disease (HD) is correlated with the size of the abnormal CAG repeat expansion in the HD gene; however, several studies have indicated that other genetic factors also contribute to the variability in HD age at onset. To identify modifier genes, we recently reported a whole-genome scan in a sample of 629 affected sibling pairs from 295 pedigrees, in which six genomic regions provided suggestive evidence for quantitative trait loci (QTL), modifying age at onset in HD. METHODS: In order to test the replication of this finding, eighteen microsatellite markers, three from each of the six genomic regions, were genotyped in 102 newly recruited sibling pairs from 69 pedigrees, and data were analyzed, using a multipoint linkage variance component method, in the follow-up sample and the combined sample of 352 pedigrees with 753 sibling pairs. RESULTS: Suggestive evidence for linkage at 6q23-24 in the follow-up sample (LOD = 1.87, p = 0.002) increased to genome-wide significance for linkage in the combined sample (LOD = 4.05, p = 0.00001), while suggestive evidence for linkage was observed at 18q22, in both the follow-up sample (LOD = 0.79, p = 0.03) and the combined sample (LOD = 1.78, p = 0.002). Epistatic analysis indicated that there is no interaction between 6q23-24 and other loci. CONCLUSION: In this replication study, linkage for modifier of age at onset in HD was confirmed at 6q23-24. Evidence for linkage was also found at 18q22. The demonstration of statistically significant linkage to a potential modifier locus opens the path to location cloning of a gene capable of altering HD pathogenesis, which could provide a validated target for therapeutic development in the human patient.

Adolescent↗
PubMed2006

Collaborative analysis of alpha-synuclein gene promoter variability and Parkinson disease.

CONTEXT: Identification and replication of susceptibility genes for Parkinson disease at the population level have been hampered by small studies with potential biases. Alpha-synuclein (SNCA) has been one of the most promising susceptibility genes, but large-scale studies have been lacking. OBJECTIVE: To determine whether allele-length variability in the dinucleotide repeat sequence (REP1) of the SNCA gene promoter is associated with Parkinson disease susceptibility, whether SNCA promoter haplotypes are associated with Parkinson disease, and whether REP1 variability modifies age at onset. DESIGN, SETTING, AND PARTICIPANTS: We performed a collaborative analysis of individual-level data on SNCA REP1 and flanking markers in patients with Parkinson disease and controls. Study site recruitment, data collection, and analyses were performed between April 5, 2004, and December 31, 2005. Eighteen participating sites of a global genetics consortium provided clinical data. Genotyping was performed for SNCA REP1, -770, and -116 markers at individual sites; however, each site also provided 20 DNA samples for regenotyping centrally. MAIN OUTCOME MEASURES: Measures included estimations of Hardy-Weinberg equilibrium in controls; a test of heterogeneity; analyses for association of single variants or haplotypes; and survival analyses for age at onset. RESULTS: Of the 18 sites, 11 met stringent criteria for concordance with Hardy-Weinberg equilibrium and low genotyping error rate. These 11 sites provided complete data for 2692 cases and 2652 controls. There was no heterogeneity across studies (P>.60). The SNCA REP1 alleles differed in frequency for cases and controls (P<.001). Genotypes defined by the 263 base-pair allele were associated with Parkinson disease (odds ratio, 1.43; 95% confidence interval, 1.22-1.69; P<.001 for trend). Multilocus haplotypes differed in frequency for cases and controls (global score statistic, P<.001). Two-loci haplotypes were associated with Parkinson disease only when they included REP1 as one of the loci. However, genotypes defined by REP1 alleles did not modify age at onset (P = .55). CONCLUSION: This large-scale collaborative analysis demonstrates that SNCA REP1 allele-length variability is associated with an increased risk of Parkinson disease.

Adult↗
PubMed2006

MBNL1 and CUGBP1 modify expanded CUG-induced toxicity in a Drosophila model of myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by a CTG expansion in the 3' UTR of the dystrophia myotonica protein kinase (DMPK) gene. It has been hypothesized that the pathogenesis in DM1 is triggered by a toxic gain of function of the expanded DMPK RNA. This expanded RNA is retained in nuclear foci where it sequesters and induces alterations in the levels of RNA-binding proteins (RNA-BP). To model DM1 and study the implication of RNA-BP in CUG-induced toxicity, we have generated a Drosophila DM1 model expressing a non-coding mRNA containing 480 interrupted CUG repeats; i.e. [(CUG)20CUCGA]24. This (iCUG)480 transcript accumulates in nuclear foci and its expression leads to muscle wasting and degeneration in Drosophila. We also report that altering the levels of two RNA-BP known to be involved in DM1 pathogenesis, MBNL1 and CUGBP1, modify the (iCUG)480 degenerative phenotypes. Expanded CUG-induced toxicity in Drosophila is suppressed when MBNL1 expression levels are increased, and enhanced when MBNL1 levels are reduced. In addition, (iCUG)480 also causes a decrease in the levels of soluble MBNL1 that is sequestered in the CUG-containing nuclear foci. In contrast, increasing the levels of CUGBP1 worsens (iCUG)480-induced degeneration even though CUGBP1 distribution is not altered by the expression of the expanded triplet repeat. Our data supports a mechanism for DM1 pathogenesis in which decreased levels of MBNL and increased levels of CUGBP mediate the RNA-induced toxicity observed in DM1. Perhaps more importantly, they also provide proof of the principle that CUG-induced muscle toxicity can be suppressed.

Animals↗
PubMed2006

Ataxin 10 induces neuritogenesis via interaction with G-protein beta2 subunit.

Spinocerebellar ataxia type 10 (SCA10) is a dominantly inherited disorder caused by an intronic ATTCT pentanucleotide repeat expansion. The ATXN10 gene encodes a novel protein, ataxin 10, known previously as E46L, which is widely expressed in the brain. Ataxin 10 deficiency has been shown recently to cause increased apoptosis in primary cerebellar cultures, thus implicated in SCA10 pathogenesis. The biologic functions of ataxin 10 remain largely unknown. By using yeast-two-hybrid screening of a human brain cDNA library, we identified the G-protein beta2 subunit (Gbeta2) as an ataxin 10 binding partner, and the interaction was confirmed by coimmunoprecipitation and colocalization in mammalian cells in culture. Overexpression of ataxin 10 in PC12 cells induced neurite extension and enhanced neuronal differentiation induced by nerve growth factor (NGF). Moreover, coexpression of ataxin 10 and Gbeta2 potently activated the Ras-MAP kinase-Elk-1 cascade. Dominant negative Ras or inhibitor of MEK-1/2 (U0126) aborted this activation, and blocked morphologic changes, whereas inhibition of TrkA receptor by K252a had no effects. Our data suggest that the ataxin 10-Gbeta2 interaction represents a novel mechanism for inducing neuritogenesis in PC12 cells by activating the Ras-MAP kinase-Elk-1 cascade.

Animals↗
PubMed2005

Interruptions in the expanded ATTCT repeat of spinocerebellar ataxia type 10: repeat purity as a disease modifier?

Spinocerebellar ataxia type 10 (SCA10) is one of numerous genetic disorders that result from simple repeat expansions. SCA10 is caused by expansion of an intronic ATTCT pentanucleotide repeat tract. It is clinically characterized by progressive ataxia, seizures, and anticipation, which can vary within and between families. We report two SCA10 families showing distinct frequencies of seizures and correlations of repeat length with age at onset. One family displayed uninterrupted ATTCT expansions, whereas the other showed multiple interruptions of the repeat by nonconsensus repeat units, which differed both in the length and/or sequence of the repeat unit. Disease-causing microsatellite expansions have been assumed to be composed of uninterrupted pure repeats. Our findings for SCA10 challenge this convention and suggest that the purity of the expanded repeat element may be a disease modifier.

Age of Onset↗
PubMed2005

A rare truncating mutation in ADH1C (G78Stop) shows significant association with Parkinson disease in a large international sample.

BACKGROUND: Alcohol dehydrogenases (ADHs) may be involved in the pathogenesis of neurodegenerative disorders because of their multiple roles in detoxification pathways and retinoic acid synthesis. In a previous study, significant association of an ADH class IV allele with Parkinson disease (PD) was found in a Swedish sample. PATIENTS: The previously associated single-nucleotide polymorphism plus 12 further polymorphisms in the ADH cluster on human chromosome 4q23 were screened for association in an extension of the original sample that now included 123 Swedish PD patients and 127 geographically matched control subjects. A rare nonsense single-nucleotide polymorphism in ADH1C (G78stop, rs283413) was identified in 3 of these patients but in no controls. To obtain sufficient power to detect a possible association of this rare variant with disease, we screened a large international sample of 1076 PD patients of European ancestry and 940 matched controls. RESULTS: The previously identified association with an ADH class IV allele remained significant (P<.02) in the extended Swedish study. Furthermore, in the international collaboration, the G78stop mutation in ADH1C was found in 22 (2.0%) of the PD patients but only in 6 controls (0.6%). This association was statistically significant (chi(2)(1) = 7.5; 2-sided P = .007; odds ratio, 3.25 [95% confidence interval, 1.31-8.05]). In addition, the G78stop mutation was identified in 4 (10.0%) of 40 Caucasian index cases with PD with mainly hereditary forms of the disorder. CONCLUSION: Findings presented herein provide further evidence for mutations in genes encoding ADHs as genetic risk factors for PD.

Adult↗
PubMed2005

Recent progress in spinocerebellar ataxia type-10 (SCA10).

Spinocerebellar ataxia type 10 (SCA10) is a dominantly inherited ataxia caused by expansion of ATTCT pentanucleotide repeat in intron 9 of a novel gene, E46L, on chromosome 22q13.3. SCA10 is a complex neurodegenerative condition. Initial studies characterized SCA10 as pure cerebellar ataxia associated with seizures. Recent identification of new SCA10 families revealed more diverse phenotypes, including polyneuropathy, pyramidal signs, cognitive and neuropsychiatric impairment. Moreover, several families manifest with ataxia without seizures. Thus a complete clinical spectrum is emerging. Progress has also been made in understanding the molecular and genetic mechanisms of pathogenesis. The length of expanded ATTCT repeats is variable in different tissues and highly unstable during paternal transmission, revealing complex genetic and pathogenetic processes. Under torsional stress, ATTCT repeats form unpaired DNA structure and may serve as an erroneous DNA replication origin, potentially contributing to repeat instability and aberrant cell cycle entry. E46L is a cytoplasmic protein with unknown function. Reduced expression of E46L in primary neuronal cultures from cerebellum and cortex by small interfering RNAs (siRNAs) caused increased apoptosis, raising the possibility that reduced expression of E46L might also play an important role in SCA10 pathogenesis.

Animals↗
PubMed2004

Chemotherapeutic deletion of CTG repeats in lymphoblast cells from DM1 patients.

Myotonic dystrophy type 1 (DM1) is caused by the expansion of a (CTG).(CAG) repeat in the DMPK gene on chromosome 19q13.3. At least 17 neurological diseases have similar genetic mutations, the expansion of DNA repeats. In most of these disorders, the disease severity is related to the length of the repeat expansion, and in DM1 the expanded repeat undergoes further elongation in somatic and germline tissues. At present, in this class of diseases, no therapeutic approach exists to prevent or slow the repeat expansion and thereby reduce disease severity or delay disease onset. We present initial results testing the hypothesis that repeat deletion may be mediated by various chemotherapeutic agents. Three lymphoblast cell lines derived from two DM1 patients treated with either ethylmethanesulfonate (EMS), mitomycin C, mitoxantrone or doxorubicin, at therapeutic concentrations, accumulated deletions following treatment. Treatment with EMS frequently prevented the repeat expansion observed during growth in culture. A significant reduction of CTG repeat length by 100-350 (CTG).(CAG) repeats often occurred in the cell population following treatment with these drugs. Potential mechanisms of drug-induced deletion are presented.

Alleles↗
PubMed2004

Spinocerebellar ataxia type 8: molecular genetic comparisons and haplotype analysis of 37 families with ataxia.

We reported elsewhere that an untranslated CTG expansion causes the dominantly inherited neurodegenerative disorder spinocerebellar ataxia type 8 (SCA8). SCA8 shows a complex inheritance pattern with extremes of incomplete penetrance, in which often only one or two affected individuals are found in a given family. SCA8 expansions have also been found in control chromosomes, indicating that separate genetic or environmental factors increase disease penetrance among SCA8-expansion-carrying patients with ataxia. We describe the molecular genetic features and disease penetrance of 37 different families with SCA8 ataxia from the United States, Canada, Japan, and Mexico. Haplotype analysis using 17 STR markers spanning an approximately 1-Mb region was performed on the families with ataxia, on a group of expansion carriers in the general population, and on psychiatric patients, to clarify the genetic basis of the reduced penetrance and to investigate whether CTG expansions among different populations share a common ancestral background. Two major ancestrally related haplotypes (A and A') were found among white families with ataxia, normal controls, and patients with major psychosis, indicating a common ancestral origin of both pathogenic and nonpathogenic SCA8 expansions among whites. Two additional and distinct haplotypes were found among a group of Japanese families with ataxia (haplotype B) and a Mexican family with ataxia (haplotype C). Our finding that SCA8 expansions on three independently arising haplotypes are found among patients with ataxia and cosegregate with ataxia when multiple family members are affected further supports the direct role of the CTG expansion in disease pathogenesis.

Case-Control Studies↗
PubMed2004

Somatic and germline instability of the ATTCT repeat in spinocerebellar ataxia type 10.

Spinocerebellar ataxia type 10 (SCA10) is an autosomal dominant disorder characterized by ataxia, seizures, and anticipation. It is caused by an expanded ATTCT pentanucleotide repeat in intron 9 of a novel gene, designated "SCA10." The ATTCT expansion in SCA10 represents a novel class of microsatellite repeat and is one of the largest found to cause human diseases. The expanded ATTCT repeat is unstably transmitted from generation to generation, and an inverse correlation has been observed between size of repeat and age at onset. In this multifamily study, we investigated the intergenerational instability, somatic and germline mosaicism, and age-dependent repeat-size changes of the expanded ATTCT repeat. Our results showed that (1) the expanded ATTCT repeats are highly unstable when paternally transmitted, whereas maternal transmission resulted in significantly smaller changes in repeat size; (2) blood leukocytes, lymphoblastoid cells, buccal cells, and sperm have a variable degree of mosaicism in ATTCT expansion; (3) the length of the expanded repeat was not observed to change in individuals over a 5-year period; and (4) clinically determined anticipation is sometimes associated with intergenerational contraction rather than expansion of the ATTCT repeat.

Age Distribution↗
PubMed2004

Huntington's Disease-like 2 (HDL2) in North America and Japan.

Huntington's Disease-like 2 (HDL2) is a progressive, autosomal dominant, neurodegenerative disorder with marked clinical and pathological similarities to Huntington's disease (HD). The causal mutation is a CTG/CAG expansion mutation on chromosome 16q24.3, in a variably spliced exon of junctophilin-3. The frequency of HDL2 was determined in nine independent series of patients referred for HD testing or selected for the presence of an HD-like phenotype in North America or Japan. The repeat length, ancestry, and age of onset of all North American HDL2 cases were determined. The results show that HDL2 is very rare, with a frequency of 0 to 15% among patients in the nine case series with an HD-like presentation who do not have the HD mutation. HDL2 is predominantly, and perhaps exclusively, found in individuals of African ancestry. Repeat expansions ranged from 44 to 57 triplets, with length instability in maternal transmission detected in a repeat of r2=0.29, p=0.0098). The results further support the evidence that the repeat expansion at the chromosome 16q24.3 locus is the direct cause of HDL2 and provide preliminary guidelines for the genetic testing of patients with an HD-like phenotype.

Adult↗
PubMed2004

Friedreich ataxia in carriers of unstable borderline GAA triplet-repeat alleles.

Friedreich ataxia patients are homozygous for expanded GAA triplet-repeats containing 66 to 1,700 triplets. We report two patients with delayed-onset, hyperreflexia and gradually progressive disease. Both were heterozygous for large expansions and also carried alleles with 44 and 66 triplet-repeats, respectively. Due to somatic instability, 15% (GAA-44) and 75% (GAA-66) of cells contained alleles with >/=66 triplet-repeats, constituting a plausible mechanism for their mild phenotype. A sibling with a stable GAA-37 allele and a large expansion was clinically normal. Instability of borderline alleles confers a risk for Friedreich ataxia, and the range of pathogenic alleles is broader than previously recognized.

Alleles↗
PubMed2004

Minocycline in Huntington's disease: a pilot study.

Minocycline is a caspase inhibitor, decreases inducible nitric oxide synthase (iNOS), and has been shown to delay disease progression in the mouse model R6/2 of Huntington's disease (HD). This safety and tolerability study included 30 patients with HD who were given minocycline over a 6-month period and underwent assessments every 2 months with laboratory studies, the Abnormal Involuntary Movements Scale, the Unified Huntington's Disease Rating Scale, and the Mini-Mental State Examination. Minocycline was well tolerated during this study period and no serious adverse events were noted.

Adult↗
PubMed2004

Detection of large pathogenic expansions in FRDA1, SCA10, and SCA12 genes using a simple fluorescent repeat-primed PCR assay.

At least 18 human genetic diseases are caused by expansion of short tandem repeats. Here we describe a successful application of a fluorescent PCR method for the detection of expanded repeats in FRDA1, SCA10, and SCA12 genes. Although this test cannot give a precise estimate of the size of the expansion, it is robust, reliable, and inexpensive, and can be used to screen large series of patients. It proved useful for confirming the presence of large expansions in the Friedreich ataxia gene following an ambiguous result of long-range PCR, as well as rapid pre-screening for large repeat expansions associated with Friedreich ataxia and SCA10 and the shorter repeat expansions associated with SCA12.

Case-Control Studies↗
PubMed2003

Haplotype analysis of the ETM2 locus in familial essential tremor.

The objective of this study was to analyze a sample of unrelated individuals with autosomal dominant essential tremor (ET) for a genetic association with loci in a candidate region (ETM2) on chromosome 2p24.1 that harbors a disease gene for ET. ET is a common movement disorder that is genetically linked to ETM2 in four large families. It is unknown whether this candidate locus is associated with dominantly inherited ET in other individuals. Based on information from previous genetic linkage studies, a linkage disequilibrium study was designed to compare individuals with a family history of ET (n=45) with normal controls (n=70). Three unreported dinucleotide polymorphic loci (etm1240, etm1231, and etm1234) were identified on a physical map of the ETM2 interval in a region of no recombination. The study sample was tested for allele frequency differences by the CLUMP program and haplotypes were analyzed by the FASTEHPLUS program. The allele frequencies were significantly different between ET cases and the control samples for the loci etm1231 (P< or =0.0419) and etm1234 (P<0.0001). A haplotype formed by the loci etm1231 and etm1234 occurred with a frequency of 29% in cases (n=45) and 9% in a white newborn sample (P<0.0001, n=35). The haplotype was not found in normal individuals older than 60 years without tremor (P=0.0063, n=35). This study provides evidence that an ancestral haplotype on chromosome 2p24.1 segregates with the ET disease phenotype in individuals with a family history of the disorder and will facilitate the search for a causative gene.

Aged↗
PubMed2003

Unpaired structures in SCA10 (ATTCT)n.(AGAAT)n repeats.

A number of human hereditary diseases have been associated with the instability of DNA repeats in the genome. Recently, spinocerebellar ataxia type 10 has been associated with expansion of the pentanucleotide repeat (ATTCT)(n).(AGAAT)(n) from a normal range of ten to 22 to as many as 4500 copies. The structural properties of this repeat cloned in circular plasmids were studied by a variety of methods. Two-dimensional gel electrophoresis and atomic force microscopy detected local DNA unpairing in supercoiled plasmids. Chemical probing analysis indicated that, at moderate superhelical densities, the (ATTCT)(n).(AGAAT)(n) repeat forms an unpaired region, which further extends into adjacent A+T-rich flanking sequences at higher superhelical densities. The superhelical energy required to initiate duplex unpairing is essentially length-independent from eight to 46 repeats. In plasmids containing five repeats, minimal unpairing of (ATTCT)(5).(AGAAT)(5) occurred while 2D gel analysis and chemical probing indicate greater unpairing in A+T-rich sequences in other regions of the plasmid. The observed experimental results are consistent with a statistical mechanical, computational analysis of these supercoiled plasmids. For plasmids containing 29 repeats, which is just above the normal human size range, flanked by an A+T-rich sequence, atomic force microscopy detected the formation of a locally condensed structure at high superhelical densities. However, even at high superhelical densities, DNA strands within the presumably compact A+T-rich region were accessible to small chemicals and oligonucleotide hybridization. Thus, DNA strands in this "collapsed structure" remain unpaired and accessible for interaction with other molecules. The unpaired DNA structure functioned as an aberrant replication origin, in that it supported complete plasmid replication in a HeLa cell extract. A model is proposed in which unscheduled or aberrant DNA replication is a critical step in the expansion mutation.

Base Composition↗