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S M Pulst

Publications and source records attributed to S M Pulst.

At least 37 records · Page 2Linked to original sources
PubMed2000

Ethical issues in DNA testing.

Molecular tests for single gene disorders have become the "gold standard," surpassing in sensitivity and specificity other ancillary tests such as imaging or neurophysiologic tests. Although direct technical problems are rare for DNA tests, few outcomes studies have been reported that examine sensitivity, specificity, and usage of tests outside the setting of academic medical centers. Ethical problems of DNA testing are mainly discussed in a theoretical framework and few published studies or case reports deal with real-life situations. Among neurologists, ethical dilemmas and attempts at their resolution are communicated mainly on a verbal basis, and even then relatively little follow-up is available. The potential use of information obtained through DNA testing by other family members, employers, insurance companies, and governmental agencies deserves scientific investigation and societal discussion. A major educational effort is needed to inform patients, providers, and third parties that the presence of a particular allele in an individual is only one piece in a complex puzzle of environmental and genetic interactions that may ultimately result in disease.

DNA↗
PubMed2000

Nuclear localization or inclusion body formation of ataxin-2 are not necessary for SCA2 pathogenesis in mouse or human.

Instability of CAG DNA trinucleotide repeats is the mutational mechanism for several neurodegenerative diseases resulting in the expansion of a polyglutamine (polyQ) tract. Proteins with long polyQ tracts have an increased tendency to aggregate, often as truncated fragments forming ubiquitinated intranuclear inclusion bodies. We examined whether similar features define spinocerebellar ataxia type 2 (SCA2) pathogenesis using cultured cells, human brains and transgenic mouse lines. In SCA2 brains, we found cytoplasmic, but not nuclear, microaggregates. Mice expressing ataxin-2 with Q58 showed progressive functional deficits accompanied by loss of the Purkinje cell dendritic arbor and finally loss of Purkinje cells. Despite similar functional deficits and anatomical changes observed in ataxin-1[Q80] transgenic lines, ataxin-2[Q58] remained cytoplasmic without detectable ubiquitination.

Animals↗
PubMed2000

Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.

Spinocerebellar ataxia type 10 (SCA10; MIM 603516; refs 1,2) is an autosomal dominant disorder characterized by cerebellar ataxia and seizures. The gene SCA10 maps to a 3.8-cM interval on human chromosome 22q13-qter (refs 1,2). Because several other SCA subtypes show trinucleotide repeat expansions, we examined microsatellites in this region. We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families. There was an inverse correlation between the expansion size, up to 22.5 kb larger than the normal allele, and the age of onset (r2=0.34, P=0.018). Analysis of 562 chromosomes from unaffected individuals of various ethnic origins (including 242 chromosomes from Mexican persons) showed a range of 10 to 22 ATTCT repeats with no evidence of expansions. Our data indicate that the new SCA10 intronic ATTCT pentanucleotide repeat in SCA10 patients is unstable and represents the largest microsatellite expansion found so far in the human genome.

Animals↗
PubMed2000

The ortholog of human ataxin-2 is essential for early embryonic patterning in C. elegans.

Ataxin-2, the gene product of the human spinocerebellar ataxia type 2 (SCA2) gene, is a protein of unknown function. Ataxin-2 interacts with ataxin-2-binding-protein 1 (A2BP1), a member of a novel family of putative RNA-binding proteins. Because the sequences of ataxin-2 and A2BP1 are evolutionarily conserved, we investigated functional aspects and expression pattern in the nematode Caenorhabditis elegans. Human ataxin-2 has 20.1% amino acid identity and 43.9% similarity to its C. elegans ortholog, designated ATX-2, that encodes a predicted 1026 aa protein. One of the worm orthologs of human A2BP1 is the numerator element FOX-1, with an overall 29.8% aa identity. We studied the expression pattern of atx-2 using the endogenous promotor coupled with a GFP expression vector. Atx-2 was widely expressed in the adult worm with strong expression in muscle and nervous tissue. It was also heavily expressed in the embryo. In order to elucidate the function of atx-2 and fox-1, we conducted RNA interference (RNAi) studies. The interfering dsRNA was introduced into larval L4 stage worms of the N2 strain by microinjection or soaking. DsRNA representing the full-length atx-2 gene resulted in arrested embryonic development in the offspring of all 58 microinjected worms. Nomarski imaging showed embryos in different stages of developmental arrest, indicating an essential role of atx-2 for early embryonic development. When fox-1 was targeted by RNAi, there was a marked reduction in the number of eggs per worm. The results presented here underline previous findings about the interaction of human ataxin-2 and A2BP1.

Animals↗
PubMed2000

Parkin is associated with actin filaments in neuronal and nonneural cells.

Inactivating mutations of the gene encoding parkin are responsible for autosomal recessive juvenile parkinsonism (AR-JP). However, little information is known about the function and distribution of parkin. We generated antibodies to two different peptides of parkin. By Western blot analysis and immunohistochemistry, we found that parkin is a 50-kd protein that is expressed in neuronal processes and cytoplasm of selected neurons in the basal ganglia, midbrain, cerebellum, and cerebral cortex. Unlike ubiquitin and alpha-synuclein, parkin labeling was not found in Lewy bodies of four sporadic Parkinson disease brains. Parkin was colocalized with actin filaments but not with microtubules in COS1 kidney cells and nerve growth factor-induced PC12 neurons. These results point to the importance of the cytoskeleton and associated proteins in neurodegeneration.

Actin Cytoskeleton↗
PubMed1999

Familial multisystem degeneration with parkinsonism associated with the 11778 mitochondrial DNA mutation.

OBJECTIVE: To investigate a family with maternally inherited, adult-onset multisystem degeneration including prominent parkinsonism to determine whether clinical features can result from a mitochondrial DNA (mtDNA) mutation. The parkinsonism was levodopa responsive and was associated with the loss of pigmented neurons in the substantia nigra in at least one patient. BACKGROUND: Mitochondrial dysfunction is hypothesized to play a role in late-onset neurodegenerative diseases including PD and AD. Mitochondrial genetic mutations are hypothesized to account for these defects, but attempts to identify specific mtDNA mutations have been inconclusive. METHODS: Clinical examinations, DNA sequencing, and restriction digestion and biochemical analyses were performed. RESULTS: Maternal relatives harbor a G-to-A missense mutation, heteroplasmic in some patients, at nucleotide position 11778 of the mitochondrial ND4 gene of complex I that converts a highly conserved arginine to a histidine. Sequencing of the entire mitochondrial genome in an affected family member reveals no other mutations likely to be pathogenic. This mutation has been identified previously only in families with Leber's hereditary optic neuropathy-a disorder also linked to complex I dysfunction but usually limited clinically to optic atrophy. CONCLUSIONS: These data reveal previously unsuspected clinical heterogeneity of the G11778A mutation, and suggest that an inherited mtDNA mutation can contribute to the development of adult-onset parkinsonism and multisystem degeneration.

Base Sequence↗
PubMed1999

Genetic linkage analysis.

Genetic linkage analysis is a powerful tool to detect the chromosomal location of disease genes. It is based on the observation that genes that reside physically close on a chromosome remain linked during meiosis. For most neurologic diseases for which the underlying biochemical defect was not known, the identification of the chromosomal location of the disease gene was the first step in its eventual isolation. By now, genes that have been isolated in this way include examples from all types of neurologic diseases, from neurodegenerative diseases such as Alzheimer, Parkinson, or ataxias, to diseases of ion channels leading to periodic paralysis or hemiplegic migraine, to tumor syndromes such as neurofibromatosis types 1 and 2.

Base Sequence↗
PubMed1999

Expression of ataxin-2 in brains from normal individuals and patients with Alzheimer's disease and spinocerebellar ataxia 2.

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. The SCA2 gene product, ataxin-2, is a basic protein with two domains (Sm1 and Sm2) implicated in RNA splicing and protein interaction. However, the wild-type function of ataxin-2 is yet to be determined. To help clarify the function of ataxin-2, we produced antibodies to three antigenic peptides of ataxin-2 and analyzed the expression pattern of ataxin-2 in normal and SCA2 adult brains and cerebellum at different developmental stages. These studies revealed that (1) both wild-type and mutant forms of ataxin-2 were synthesized; (2) the wild-type ataxin-2 was localized in the cytoplasm in specific neuronal groups with strong labeling of Purkinje cells; (3) the level of ataxin-2 increased with age in Purkinje cells of normal individuals; and (4) ataxin-2-like immunoreactivity in SCA2 brain tissues was more intense than in normal brain tissues, and intranuclear ubiquitinated inclusions were not seen in SCA2 brain tissues.

Adult↗
PubMed1999

Mapping of a new autosomal dominant spinocerebellar ataxia to chromosome 22.

The autosomal dominant cerebellar ataxias (ADCAs) are a clinically and genetically heterogeneous group of disorders. The clinical symptoms include cerebellar dysfunction and associated signs from dysfunction in other parts of the nervous system. So far, five spinocerebellar ataxia (SCA) genes have been identified: SCA1, SCA2, SCA3, SCA6, and SCA7. Loci for SCA4 and SCA5 have been mapped. However, approximately one-third of SCAs have remained unassigned. We have identified a Mexican American pedigree that segregates a new form of ataxia clinically characterized by gait and limb ataxia, dysarthria, and nystagmus. Two individuals have seizures. After excluding all known genetic loci for linkage, we performed a genomewide search and identified linkage to a 15-cM region on chromosome 22q13. A maximum LOD score of 4.3 (recombination fraction 0) was obtained for D22S928 and D22S1161. This distinct form of ataxia has been designated "SCA10." Anticipation was observed in the available parent-child pairs, suggesting that trinucleotide-repeat expansion may be the mutagenic mechanism.

Adolescent↗
PubMed1998

Genomic structure of the human gene for spinocerebellar ataxia type 2 (SCA2) on chromosome 12q24.1.

Spinocerebellar ataxia type 2 (SCA2) is a member of a group of neurodegenerative diseases that are caused by instability of a DNA CAG repeat. We report the genomic structure of the SCA2 gene. Its 25 exons, encompassing approximately 130 kb of genomic DNA, were mapped onto the physical map of the region. Exonic sizes varied from 37 to 890 bp, and intronic sizes ranged from 323 bp to more than 15 kb. The CAG repeat was contained in the 5' coding region of the gene in exon 1. Determination of the splice junction sequences indicated the presence of only one deviation from the GT-AG rule at the donor splice site of intron 9, which contained a GC instead of a GT dinucleotide. Exon 10, immediately downstream from this rare splice donor site, was alternatively spliced. Alternative splicing does not affect the reading frame and is predicted to encode an isoform containing 70 amino acids less.

Alternative Splicing↗
PubMed1998

Oculomotor phenotypes in autosomal dominant ataxias.

OBJECTIVE: To quantify the oculomotor features of the common spinocerebellar ataxia (SCA) syndromes. SETTING: University ataxia clinic. PATIENTS: Twenty probands with documented SCA mutations. METHODS: Electro-oculographic recordings of saccadic, smooth pursuit, optokinetic, vestibular, and visual-vestibular eye movements. RESULTS: Distinct phenotype and genotype patterns were identified with modest overlap between patterns. Slowing of saccade peak velocities occurred only in SCA1 and SCA2, being present in 100% of patients with SCA2. Impaired vestibulo-ocular reflex gain occurred with SCA3 only. Patients with SCA6 had prominent deficits in smooth tracking but normal saccade velocities and vestibuloocular reflex gain. CONCLUSIONS: The oculomotor findings are consistent with pure cerebellar involvement in SCA6, pontine involvement in SCA1 and SCA2, and vestibular nerve or nuclei involvement in SCA3. These phenotypes can be useful for clinical diagnosis and for investigating the mechanism of system specificity with the SCA syndromes.

Adult↗
PubMed1998

Neurofibromatosis 2 tumour suppressor schwannomin interacts with betaII-spectrin.

NF2 is the most commonly mutated gene in benign tumours of the human nervous system. The NF2 protein, called schwannomin or merlin, is absent in virtually all schwannomas, and many meningiomas and ependymomas. Using the yeast two-hybrid system, we identified betaII-spectrin (also known as fodrin) as a schwannomin-binding protein. Interaction occurred between the carboxy-terminal domain of schwannomin isoform 2 and the ankyrin-binding region of betaII-spectrin. Isoform 1 of schwannomin, in contrast, interacted weakly with betaII-spectrin, presumably because of its strong self-interaction. Thus, alternative splicing of NF2 may regulate betaII-spectrin binding. Schwannomin co-immunoprecipitated with betaII-spectrin at physiological concentrations. The two proteins interacted in vitro and co-localized in several target tissues and in STS26T cells. Three naturally occurring NF2 missense mutations showed reduced, but not absent, betaII-spectrin binding, suggesting an explanation for the milder phenotypes seen in patients with missense mutations. STS26T cells treated with NF2 antisense oligonucleotides showed alterations of the actin cytoskeleton. Schwannomin itself lacks the actin binding sites found in ezrin, radixin and moesin, suggesting that signalling to the actin cytoskeleton occurs via actin-binding sites on betaII-spectrin. Thus, schwannomin is a tumour suppressor directly involved in actin-cytoskeleton organization, which suggests that alterations in the cytoskeleton are an early event in the pathogenesis of some tumour types.

Actins↗
PubMed1998

[Neurofibromatosis versus schwannomatosis].

Neurofibromatosis Type 1 and 2 (NF1 und NF2) are different forms of neurofibromatosis, well defined both clinically and genetically. In absence of typical clinical features of NF1 (café-au-lait-spots, cutaneous neurofibromas, Lisch-nodules) or NF2 (vestibular schwanoma) clinical classification is often not possible. Neurofibromas are more common in NF1 and schwannomas are typical for NF2, but pathological histology does not provide sufficient evidence for diagnosis. We describe 14 patients who presented with the clinical picture of multiple spinal tumours. Detailed family history, exact clinical examination including an ophthalmological examination led to the diagnosis of NF2 in four cases. Mutation analysis confirmed the diagnosis of NF2 in one case by identification of a 163 base pair deletion in the NF2 transcript. To investigate the expression of schwannomin and neurofibromin we stained tumour paraffin sections of six patients with antibodies against peptides of the NF1 and the NF2 protein. Based on preserved immunoreactivities we were able to exclude diagnosis of NF1 in three and NF2 in two cases. In four patients the clinical symptoms could confirm the diagnosis of schwannomatosis. Combining the results of clinical, neurogenetical and immunohistochemical examinations we could diagnose NF1 or NF2 in ten patients in total. Immunoreactivity led to the suggestion of NF2 in two patients; the other two patients whose tumours were not stained so far, could as yet not be classified for NF.

Adult↗
PubMed1998

Analysis of the dynamic mutation in the SCA7 gene shows marked parental effects on CAG repeat transmission.

The gene for spinocerebellar ataxia 7 (SCA7) includes a transcribed, translated CAG tract that is expanded in SCA7 patients. We have determined expansions in 73 individuals from 17 SCA7 kindreds and compared them with repeat lengths of 180 unaffected individuals. Subjects with abnormal expansions comprise 59 clinically affected individuals and 14 at-risk currently unaffected individuals predicted to carry the mutation by haplotype analysis. For expanded alleles, CAG repeat length correlates with disease progression and severity and correlates inversely with age of onset. Increased repeat lengths are seen in generational transmission of the disease allele, consistent with the pattern of clinical anticipation seen in these kindreds. Repeat lengths in expanded alleles show somatic mosaicism in leukocyte DNA, suggesting that these alleles are unstable within individuals as well as between generations. Although dynamic repeat expansions from paternal transmissions are greater than those from maternal transmissions, maternal transmission of disease is more common, suggesting germline or embryonic effects of the repeat expansion.

Adolescent↗
PubMed1998

The mouse SCA2 gene: cDNA sequence, alternative splicing and protein expression.

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. Sequence analysis revealed that SCA2 is a novel gene of unknown function. In order to provide insights into the molecular mechanisms of pathogenesis of SCA2 and to identify conserved domains, we isolated and characterized the mouse homolog of the SCA2 gene. Sequence and amino acid analysis revealed 89% identity at the nucleotide and 91% identity at the amino acid level. However, there was no extended polyglutamine tract in the mouse SCA2 cDNA, suggesting that the normal function of SCA2 is not dependent on this domain. Northern blot analysis of different mouse tissues indicated that the mouse SCA2 gene was expressed in most tissues, but at varying levels. Alternative splicing seen in human SCA2 was conserved in the mouse. By northern blot analysis, SCA2 was expressed during embryogenesis as early as day 8 of gestation (E8). Immunohistochemical staining using affinity-purified antibodies demonstrated that ataxin 2 was expressed in the cytoplasm of Purkinje cells as well as in other neurons of the CNS.

Alternative Splicing↗