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A R La Spada

Publications and source records attributed to A R La Spada.

17 recordsLinked to original sources
PubMed2004

Beta-synuclein gene alterations in dementia with Lewy bodies.

OBJECTIVE: To determine whether mutations in the genes for alpha-synuclein or beta-synuclein are responsible for dementia with Lewy bodies (DLB), a disorder closely related to Parkinson disease (PD). METHODS: The authors ascertained 33 sporadic cases of DLB and 10 kindreds segregating DLB. DNA samples from the 43 index cases were screened for alterations in the genes for alpha-synuclein and beta-synuclein, as alpha-synuclein alterations cause PD and beta-synuclein may modulate alpha-synuclein aggregation and neurotoxicity. RESULTS: Two amino acid alterations were identified in unrelated DLB index cases: a valine to methionine substitution at codon 70 (V70M) and a proline to histidine substitution at codon 123 (P123H), both in the beta-synuclein gene. These amino acid substitutions occur at conserved residues in highly conserved regions of the beta-synuclein protein. Screening of at least 660 chromosomes from control subjects matched to the patients' population groups failed to identify another V70M or P123H allele. Cosegregation analysis of an extended pedigree segregating the P123H beta-synuclein alteration suggested that it is a dominant trait with reduced penetrance or a risk factor polymorphism. Histopathology and immunohistochemistry analysis of index case brain sections revealed widespread Lewy body pathology and alpha-synuclein aggregation without evidence of beta-synuclein aggregation. CONCLUSION: Mutations in the beta-synuclein gene may predispose to DLB.

Aged↗
PubMed2003

Insights into the molecular basis of polyglutamine neurodegeneration from studies of a spinocerebellar ataxia type 7 mouse model.

Spinocerebellar ataxia type 7 (SCA7) is one member of a growing list of neurodegenerative disorders that are all caused by CAG repeat expansions that produce disease by encoding elongated polyglutamine tracts in a variety of apparently unrelated proteins. In this review, we provide an overview of our efforts to determine the molecular basis of polyglutamine neurotoxicity in SCA7 by modeling this polyglutamine repeat disorder in mice. We discuss how our SCA7 mouse model develops a phenotype that is reminiscent of the retinal and cerebellar disease pathology seen in human patients. All of these findings are considered in the context of numerous other models of polyglutamine disease pathology in mice and other organisms, together with various other in vitro and biochemical studies. We present the competing hypotheses of polyglutamine disease pathogenesis, and explain how our studies of SCA7 brainstem and retinal degeneration using this mouse model have yielded insights into possible mechanisms and pathways of polyglutamine disease pathology. In addition to illustrating how our SCA7 mouse model has allowed us to develop and advance notions of disease pathogenesis, we propose a model of polyglutamine molecular pathology that attempts to integrate the key observations in the field. We close by describing why our SCA7 mouse model should be useful for the next phase of polyglutamine disease research--the development of therapies, and predict that this stage of experimentation will continue to rely heavily on the mouse.

Ataxin-7↗
PubMed2001

Polyglutamine-expanded ataxin-7 antagonizes CRX function and induces cone-rod dystrophy in a mouse model of SCA7.

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant disorder caused by a CAG repeat expansion. To determine the mechanism of neurotoxicity, we produced transgenic mice and observed a cone-rod dystrophy. Nuclear inclusions were present, suggesting that the disease pathway involves the nucleus. When yeast two-hybrid assays indicated that cone-rod homeobox protein (CRX) interacts with ataxin-7, we performed further studies to assess this interaction. We found that ataxin-7 and CRX colocalize and coimmunoprecipitate. We observed that polyglutamine-expanded ataxin-7 can dramatically suppress CRX transactivation. In SCA7 transgenic mice, electrophoretic mobility shift assays indicated reduced CRX binding activity, while RT-PCR analysis detected reductions in CRX-regulated genes. Our results suggest that CRX transcription interference accounts for the retinal degeneration in SCA7 and thus may provide an explanation for how cell-type specificity is achieved in this polyglutamine repeat disease.

Age Factors↗
PubMed2001

Genomic organization, chromosome location, and expression analysis of mouse beta-synuclein, a candidate for involvement in neurodegeneration.

The synuclein family of proteins is a group of primarily brain-expressed polypeptides that show a high degree of amino acid conservation. alpha-Synuclein is the best known of the synuclein family, as it is a major component of the Lewy body, a cytoplasmic inclusion characteristic of Parkinson's disease as well as a variety of related neurodegenerative disorders. With the discovery that mutations in alpha-synuclein can cause Parkinson's disease, a potential role for the other synuclein family members in neurodegenerative disease is being considered. beta-Synuclein in particular may deserve special attention, as it is co-expressed with alpha-synuclein at presynaptic nerve terminals, is subject to phosphorylation by Ca(2+) calmodulin protein kinase II, appears important for neural plasticity, and forms aggregates in the brains of patients with Parkinson's disease and a related disorder. To facilitate study of beta-synuclein, we have cloned the mouse beta-synuclein gene (Sncb) and determined its genomic organization, size, and intron-exon structure. Using an interspecific backcross mapping panel from The Jackson Laboratory, we were then able to localize Sncb to chromosome 13 at the MGD 35.0 cM position. Like the human beta-synuclein gene, Sncb appears to consist of six exons separated by five introns. Unlike the human beta-synuclein gene, the mouse ortholog possesses a variant GC 5' splice donor sequence at the exon 4 - intron 4 boundary in a highly conserved splice junction consensus. Northern blot analysis and Western blot analysis both indicate that Sncb is highly expressed in the brain. Knowledge of the genomic organization and expression pattern of Sncb will allow functional studies of its potential role in neurodegeneration to commence in the mouse.

Amino Acid Sequence↗
PubMed2000

In vivo expansion of trinucleotide repeats yields plasmid and YAC constructs for targeting and transgenesis.

Production of mouse models of inherited neurodegenerative diseases is an important step towards understanding the mechanism of neurotoxicity and for testing potential therapies. We are interested in creating a mouse model for X-linked spinal and bulbar muscular atrophy (SBMA), a neuromuscular disorder caused by expansion of a CAG repeat within the androgen receptor (AR) gene. To permit generation of mice that will show a SBMA phenotype within their life span, we decided to obtain a yeast artificial chromosome (YAC) carrying the AR gene and introduce CAG repeat mutations numbering 100 or more triplets. SBMA patients with more than 70 CAGs have never been observed; therefore, we chose to expand a 59 CAG repeat tract in vivo in Escherichia coli. Although we set out to expand this repeat tract using a recombination paradigm involving two plasmid co-propagation, we did not observe large expansions. We were instead able to incrementally generate repeat tracts from 100 to 200 CAGs in a yeast integrating plasmid vector by taking advantage of replication instability. In the course of our experiments that yielded these CAG repeat tracts, we evaluated the role of repeat orientation, vector co-propagation, and recA function on the expansion process. We then used one of the yeast integrating vectors to successfully produce an AR YAC construct carrying 100 CAG repeats. AR YAC CAG100 will serve as a valuable reagent for the production of a SBMA mouse.

Blotting, Southern↗
PubMed2000

Late-onset SCA2: 33 CAG repeats are sufficient to cause disease.

SCA-2 is an autosomal dominant inherited disorder characterized by ataxia, slow saccades, and hyporeflexia. The authors evaluated a patient with a mild balance problem with a SCA-2 allele sized at 33 CAG repeats. The authors then ascertained her 91 year-old mother, who showed disease onset at age 86 with an SCA-2 allele of identical size. Their study indicates that 33 CAG repeats can be pathogenic at the SCA-2 locus, though such an allele may produce an extremely late onset and gradual rate of disease progression.

Aged↗
PubMed1998

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability.

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis -acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.

Age Factors↗
PubMed1998

Case of the month: August 1997--a 13 year old girl with progressive movement disorder.

A 13-year-old girl presented with a two year history of declining school performance, loss of coordination, and increased difficulty with sports. The family history was positive for Huntington's disease (HD). An MRI was suggestive for bilateral atrophy of the caudate. HD is autosomal dominant and the HD gene contains a polymorphic trinucleotide (CAG) repeat, which is expanded beyond 36 CAG repeats in HD. This patient had one normal-sized allele and one abnormally expanded allele with 68 CAG repeats, confirming the clinical diagnosis of HD. Juvenile onset of HD is uncommon, and is associated with unusually large CAG repeat numbers as was observed in this patient.

Adolescent↗
PubMed1997

Trinucleotide repeat instability: genetic features and molecular mechanisms.

Trinucleotide repeat expansions are an important cause of inherited neurodegenerative disease. The expanded repeats are unstable, changing in size when transmitted from parents to offspring (intergenerational instability, "meiotic instability") and often showing size variation within the tissues of an affected individual (somatic mosaicism, "mitotic instability"). Repeat instability is a clinically important phenomenon, as increasing repeat lengths correlate with an earlier age of onset and a more severe disease phenotype. The tendency of expanded trinucleotide repeats to increase in length during their transmission from parent to offspring in these diseases provides a molecular explanation for anticipation (increasing disease severity in successive affected generations). In this review, I explore the genetic and molecular basis of trinucleotide repeat instability. Studies of patients and families with trinucleotide repeat disorders have revealed a number of factors that determine the rate and magnitude of trinucleotide repeat change. Analysis of trinucleotide repeat instability in bacteria, yeast, and mice has yielded additional insights. Despite these advances, the pathways and mechanisms underlying trinucleotide repeat instability in humans remain largely unknown. There are many reasons to suspect that this uniquely human phenomenon will significantly impact upon our understanding of development, differentiation and neurobiology.

Animals↗
PubMed1996

Somatic stability of the expanded CAG trinucleotide repeat in X-linked spinal and bulbar muscular atrophy.

Expansion of trinucleotide repeats has now been associated with eight inherited diseases: X-linked spinal and bulbar muscular atrophy, two fragile X syndromes, myotonic dystrophy, Huntington's disease, spinocerebellar ataxia type I, dentatorubral pallidoluysian atrophy and Machado-Joseph disease. It has been shown that these expanded DNA repeats are unstable in number when transmitted from parents to offspring ("meiotic instability"), while somatic variation in repeat number has also been found in the fragile X syndrome and myotonic dystrophy. Moderate meiotic instability has been demonstrated in X-linked spinal and bulbar muscular atrophy (SBMA, Kennedy's disease). In order to determine if the expanded CAG repeat in SBMA also shows somatic instability, we compared different tissues from two patients with SBMA. We then examined the in vitro stability of the CAG repeat expansion by analyzing fibroblast cell cultures. Length comparison of expanded CAG repeats from all these materials clearly demonstrates that the CAG trinucleotide repeat in SBMA does not exhibit somatic variation.

Cells, Cultured↗
PubMed1994

Trinucleotide repeat expansion in neurological disease.

Expansion of trinucleotide repeats is now recognized as a major cause of neurological disease. At least seven disorders result from trinucleotide repeat expansion: X-linked spinal and bulbar muscular atrophy (SBMA), two fragile X syndromes of mental retardation (FRAXA and FRAXE), myotonic dystrophy, Huntington's disease, spinocerebellar ataxia type 1 (SCA1), and dentatorubral-pallidoluysian atrophy (DRPLA). The expanded trinucleotide repeats are unstable, and the phenomenon of anticipation, i.e., worsening of disease phenotype over successive generations, correlates with increasing expansion size. In this review, we compare the clinical and molecular features of the trinucleotide repeat diseases, which may be classified into two types. Fragile X and myotonic dystrophy are multisystem disorders usually associated with large expansions of untranslated repeats, while the four neurodegenerative disorders, SBMA, Huntington's disease, SCA1, and DRPLA, are caused by smaller expansions of CAG repeats within the protein coding portion of the gene. CAG repeats encode polyglutamine tracts. Polyglutamine tract expansion thus appears to be a common mechanism of inherited neurodegenerative disease. Although polyglutamine tract lengthening presumably has a toxic gain of function effect in the CAG trinucleotide repeat disorders, the basis of this neuronal toxicity remains unknown.

Humans↗
PubMed1994

Decrease in androgen binding and effect of androgen treatment in a case of X-linked bulbospinal neuronopathy.

X-linked recessive bulbospinal neuronopathy is a motoneuron disorder to be distinguished from amyotrophic lateral sclerosis, Effective treatment is not known. Patients with X-linked recessive bulbospinal neuronopathy may show gynecomastia and testicular atrophy, and a mutation in the androgen receptor gene has been found associated with the disease. Intermediate steps leading from the androgen receptor abnormality to the clinical syndrome have not yet been elucidated. Therefore, binding of androgen ([3H]dihydrotestosterone) to its specific receptor by genital skin fibroblasts cultured from a patient with X-linked recessive bulbospinal neuronopathy and confirmed androgen receptor mutation was studied. Markedly decreased binding capacity was found. We treated the patient for 6 months with nandrolone-decanoate. No effect on his neuromuscular status was observed during 2 years of follow-up.

Anabolic Agents↗
PubMed1992

Meiotic stability and genotype-phenotype correlation of the trinucleotide repeat in X-linked spinal and bulbar muscular atrophy.

Expansion of the trinucleotide repeat (CAG)n in the first exon of the androgen receptor gene is associated with a rare motor neuron disorder, X-linked spinal and bulbar muscular atrophy. We have found that expanded (CAG)n alleles undergo alteration in length when transmitted from parent to offspring. Of 45 meioses examined, 12 (27%) demonstrated a change in CAG repeat number. Both expansions and contractions were observed, although their magnitude was small. There was a greater rate of instability in male meiosis than in female meiosis. We also found evidence for a correlation between disease severity and CAG repeat length, but other factors seem to contribute to the phenotypic variability in this disorder.

Base Sequence↗
PubMed1991

Androgen receptor gene mutations in X-linked spinal and bulbar muscular atrophy.

X-linked spinal and bulbar muscular atrophy (Kennedy's disease) is an adult-onset form of motorneuron disease which may be associated with signs of androgen insensitivity. We have now investigated whether the androgen receptor gene on the proximal long arm of the X chromosome is a candidate gene for this disease. In patient samples we found androgen receptor gene mutations with increased size of a polymorphic tandem CAG repeat in the coding region. These amplified repeats were absolutely associated with the disease, being present in 35 unrelated patients and none of 75 controls. They segregated with the disease in 15 families, with no recombination in 61 meioses (the maximum log likelihood ratio (lod score) is 13.2 at a recombination rate of 0). The association is unlikely to be due to linkage disequilibrium, because 11 different disease alleles were observed. We conclude that enlargement of the CAG repeat in the androgen receptor gene is probably the cause of this disorder.

Base Sequence↗