Showing papers by "Guy A. Rouleau published in 2000"
245 citations
TL;DR: It is reported that PABP2 is detected in filamentous nuclear inclusions, which are the pathological hallmark of OPMD, and the inclusions were labeled with antibodies directed against ubiquitin and the subunits of the proteasome and contained a form of P ABP2 that was more resistant to salt extraction than the protein dispersed in the nucleoplasm.
Abstract: Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disease characterized by progressive eyelid drooping, swallowing difficulties and proximal limb weakness. The autosomal dominant form of the disease is caused by short (GCG)8–13 expansions in the PABP2 gene. This gene encodes the poly(A) binding protein 2 (PABP2), an abundant nuclear protein that binds with high affinity to nascent poly(A) tails, stimulating their extension and controlling their length. I nt his work we report that PABP2 is detected in filamentous nuclear inclusions, which are the pathological hallmark of OPMD. Using both immunoelectron microscopy and fluorescence confocal microscopy, the OPMD-specific nuclear inclusions appeared decorated by anti-PABP2 antibodies. In addition, the inclusions were labeled with antibodies directed against ubiquitin and the subunits of the proteasome and contained a form of PABP2 that was more resistant to salt extraction than the protein dispersed in the nucleoplasm. This suggests that the polyalanine expansions in PABP2 induce a misfolding and aggregation of the protein into insoluble inclusions, similarly to events in neurodegenerative diseases caused by CAG/polyglutamine expansions. No significant differences were observed in the steady-state poly(A) tail length in OPMD and normal myoblasts. However, the nuclear inclusions were shown to sequester poly(A) RNA. This raises the possibility that in OPMD the polyalanine expansions in the PABP2 protein may interfere with the cellular traffic of poly(A) RNA.
229 citations
TL;DR: This result implicates RAI1 as a possible contributor to SCA2 neurodegeneration and raises the possibility that other CAG-containing proteins may play a role in the pathogenesis of other polyglutamine disorders.
Abstract: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant disorder caused by the expansion of a polymorphic (CAG)(n) tract, which is translated into an expanded polyglutamine tract in the ataxin-2 protein. Although repeat length and age at disease onset are inversely related, approximately 50% of the age at onset variance in SCA2 remains unexplained. Other familial factors have been proposed to account for at least part of this remaining variance in the polyglutamine dis-orders. The ability of polyglutamine tracts to interact with each other, as well as the presence of intra-nuclear inclusions in other polyglutamine disorders, led us to hypothesize that other CAG-containing proteins may interact with expanded ataxin-2 and affect the rate of protein accumulation, and thus influence age at onset. To test this hypothesis, we used step-wise multiple linear regression to examine 10 CAG-containing genes for possible influences on SCA2 age at onset. One locus, RAI1, contributed an additional 4.1% of the variance in SCA2 age at onset after accounting for the effect of the SCA2 expanded repeat. This locus was further studied in SCA3/Machado-Joseph disease (MJD), but did not have an effect on SCA3/MJD age at onset. This result implicates RAI1 as a possible contributor to SCA2 neurodegeneration and raises the possibility that other CAG-containing proteins may play a role in the pathogenesis of other polyglutamine disorders.
91 citations
TL;DR: It is proposed that transcriptional or translational frameshifts occurring within expanded CAG tracts result in the production and accumulation of polyalanine-containing mutant proteins and it is hypothesized that these alanine polymers deposit in cells forming INIs and may contribute to nuclear toxicity.
Abstract: Machado-Joseph disease (MJD) is one of several disorders caused by the expansion of a coding CAG repeat (exp-CAG). The presence of intranuclear inclusions (INIs) in patients and cellular models of exp-CAG-associated diseases has lead to a nuclear toxicity model. Similar INIs are found in oculopharyngeal muscular dystrophy, which is caused by a short expansion of an alanine-encoding GCG repeat. Here we propose that transcriptional or translational frameshifts occurring within expanded CAG tracts result in the production and accumulation of polyalanine-containing mutant proteins. We hypothesize that these alanine polymers deposit in cells forming INIs and may contribute to nuclear toxicity. We show evidence that supports our hypothesis in lymphoblast cells from MJD patients, as well as in pontine neurons of MJD brain and in in vitro cell culture models of the disease. We also provide evidence that alanine polymers alone are harmful to cells and predict that a similar pathogenic mechanism may occur in the other CAG repeat disorders.
65 citations
TL;DR: The results do not support the role of either of these genes in increasing susceptibility to schizophrenia or in modulating its phenotype in the studied population.
52 citations
TL;DR: It is concluded that a large genomic deletion in GCH1 may account for some “mutation‐negative” patients with dominantly inherited DRD.
Abstract: Although it is assumed that most patients with autosomal dominant dopa-responsive dystonia (DRD) have a GTP cyclohydrolase I dysfunction, conventional genomic DNA sequencing of the gene (GCH1) coding for this enzyme fails to reveal any mutations in about 40% of DRD patients, which makes molecular genetic diagnosis difficult. We found a large heterozygous GCH1 deletion, which cannot be detected by the usual genomic DNA sequence analysis, in a three-generation DRD family and conclude that a large genomic deletion in GCH1 may account for some "mutation-negative" patients with dominantly inherited DRD.
50 citations
TL;DR: OPMD among Bukhara Jews is the result of a shared, historically distinct, PABP2 (GCG)9 mutation that likely arose or was introduced in this population at the time they first settled in BukHara and Samarkand during the 13th or 14th centuries.
Abstract: Objective: To determine whether all cases of oculopharyngeal muscular dystrophy (OPMD) among Bukhara Jews share the same founder mutation. Background: Autosomal dominant OPMD is caused by a (GCG) 8–13 repeat expansion in the polyadenylation binding protein 2 ( PABP2 ) gene. The disease has a worldwide distribution but is particularly prevalent in Bukhara Jews and in French Canadians, in whom it was introduced by three sisters in 1648. Methods: We established the size of the PABP2 mutation in 23 Bukhara Jewish patients belonging to eight unrelated families. In all families, we constructed haplotypes for the carrying chromosomes composed of the alleles for eight chromosome 14q polymorphic markers. Results: All patients share a (GCG) 9 PABP2 mutation and a four-marker haplotype. Furthermore, a shared intron single nucleotide polymorphism (SNP) in the PABP2 gene 2.6Kb from the mutation was not observed in 22 families with (GCG) 9 mutations from nine different countries. The smaller size of the chromosomal region in linkage disequilibrium around the mutation in Bukhara Jews, as compared with French Canadians, suggests a founder effect that occurred more than 350 years ago. Based on the Luria–Delbruck corrected “genetic clock,” we estimate that the mutation appeared or was introduced once in the Bukhara Jewish population between ad 872 and 1512 (mean, ad 1243). Conclusion: OPMD among Bukhara Jews is the result of a shared, historically distinct, PABP2 (GCG) 9 mutation that likely arose or was introduced in this population at the time they first settled in Bukhara and Samarkand during the 13th or 14th centuries.
46 citations
TL;DR: It is found that expression of mutated PABP2 protein is sufficient for its accumulation as intranuclear inclusions in muscle fibers.
Abstract: Oculopharyngeal muscular dystrophy is caused by expansion of a (GCG)n trinucleotide repeat in the poly(A) binding protein 2 (PABP2) gene. The pathological hallmark of oculopharyngeal muscular dystrophy is the accumulation of intranuclear inclusions in muscle fibers. To test whether the polyalanine expansion of PABP2 directly leads to the formation of the nuclear aggregates, both normal and expanded PABP2 cDNAs were expressed in COS-7 cells. We find that expression of mutated PABP2 protein is sufficient for its accumulation as intranuclear inclusions.
40 citations
TL;DR: This is the first report of coexistence of dominant and recessive families with the D90A Cu,Zn SOD mutation within the same country.
Abstract: The Cu,Zn superoxide dismutase (Cu,Zn SOD) mutations described in amyotrophic lateral sclerosis (ALS) have, for the most part, a dominant influence . However, while a few cases with a heterozygous D90A mutation have been described in different countries, D90A has been recently proven to be recessively inherited with a common founder effect in Scandinavia. We screened French ALS families for Cu,Zn SOD mutations. The presence of the D90A allele was found in two index-cases, and their families were subsequently studied. In the first family the ALS patients were homozygotes for D90A, while in the second, all ALS patients were heterozygotes. In both families the disease was found to initially involve the lower limbs with slower progression than in sporadic cases, and frequent atypical signs such as paresthesia and urgency of micturition. We determined the D90A allele frequency in controls (n = 200) and sporadic ALS patients (n = 408). No D90A allele was found. This is the first report of coexistence of dominant and recessive families with the D90A Cu,Zn SOD mutation within the same country.
36 citations
TL;DR: The variability in position of the deletions and the observation of a new chromosomal rearrangement in the NF2 gene underscore the importance of FISH analysis in the molecular diagnosis of NF2.
23 citations
TL;DR: To define the critical region for HED, detailed haplotypes were constructed with new pericentromeric polymorphic markers and it was confirmed that the HED locus maps centromeric to D13S1832.1.
Abstract: Hidrotic ectodermal dysplasia (HED) or Clouston syndrome is a rare autosomal dominant disorder characterized by nail dystrophy, alopecia and palmoplantar hyperkeratosis, which maps to chromosome 13q11-q12.1. We confirmed linkage of HED to this region in a large French family. To define the critical region for HED, detailed haplotypes were constructed with new pericentromeric polymorphic markers. A recombination event in the family indicates that the HED locus maps centromeric to D13S1832. Our French family does not share a common haplotype with other pedigrees previously published (particularly French-Canadian), indicating that the mutations in these families are likely to be of different origin.
TL;DR: Because decreased PECT activity in FA occurs in brain regions having no, or only modest, morphologic damage, this may represent a systemic change consequent to the frataxin gene defect, and therapeutic intervention in FA designed to increase synthesis of membrane phospholipids may warrant further investigation.
Abstract: Much evidence, derived from biochemical studies of both blood and autopsied brain, has suggested that phospholipid metabolism is abnormal in patients with Friedreich's ataxia (FA), a disorder characterized by severe neuronal loss in the spinal cord and lower brain stem with no, or only modest, damage in other brain regions. To establish the cause of our recent finding of reduced brain levels of phospholipids in FA, we assayed activities of 10 phospholipid-metabolizing enzymes in the autopsied cerebellar cortex of patients with the disorder and, for comparison, in a group of patients with spinocerebellar ataxia type 1 (SCA-1), a disease characterized, unlike FA, by marked neuronal loss in the cerebellar cortex. Enzyme activities were also measured in four brain areas which are relatively unaffected morphologically in both FA and SCA-1. We found that ethanolamine kinase activity was increased in multiple brain regions of patients with FA (increased 31%-137%) and, more modestly, in SCA-1 (increased 39%-60%), suggesting a nonspecific enhancement of phosphoethanolamine production in both disorders. In contrast, the activity of phosphoethanolamine cytidylyltransferase (PECT), the rate-limiting enzyme of phosphatidylethanolamine synthesis, was significantly and markedly decreased by 35%-78% in the cerebellar, frontal, and occipital cortices of patients with FA but was normal in SCA-1. Reduced PECT activity in FA may explain the lower brain levels of phosphatidylethanolamine in the disorder. Moreover, because decreased PECT activity in FA occurs in brain regions having no, or only modest, morphologic damage, this may represent a systemic change consequent to the frataxin gene defect. Our data also suggest that therapeutic intervention in FA designed to increase synthesis of membrane phospholipids may warrant further investigation.
TL;DR: The results suggest that the loci investigated have no major role in the genetic predisposition to bipolar disorder, and are likely to have a small proportion of the total genetic variability.
TL;DR: A BAC/PAC-based contig map of the HED (hidrotic ectodermal dysplasia) or Clouston syndrome gene has been mapped to the pericentromeric region of chromosome 13 (13q11) to a 2.4-cM intervals, providing the basis for genomic sequencing and gene identification in the ED2 critical region.