Spinocerebellar ataxia type-1 and spinobulbar muscular atrophy gene products interact with glyceraldehyde-3-phosphate dehydrogenase.

Spinocerebellar ataxia type1 (SCA1) is one of several neurodegenerative disorders caused by expansions of translated CAG trinucleotide repeats which code for polyglutamine in the respective proteins. Most hypotheses about the molecular defect in these disorders suggest a gain of function, which may involve interactions with other proteins via the expanded polyglutamine tract. In this study we used ataxin-1, the SCA1 gene product, as a bait in the yeast two-hybrid system and identified the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase as an ataxin-1 interacting protein. In addition, the yeast two hybrid data demonstrate that wild type and mutant ataxin-1 form homo and heterodimers. Physical interaction between GAPDH and ataxin-1 was also demonstrated in vitro. To investigate if GAPDH might interact with other glutamine repeat-containing proteins involved in neurodegenerative disorders, we tested its binding to the androgen receptor which is mutated in spinobulbar muscular atrophy. The androgen receptor interacts with GAPDH both in the yeast two-hybrid system and in vitro. The binding of both ataxin-1 and the androgen receptor to GAPDH does not vary with the length of the polyglutamine tract. While provocative, these findings do not address the selective neuronal loss in each of these disorders in light of the wide expression patterns of GAPDH and the respective polyglutamine containing proteins. Nonetheless, such interactions may increase the susceptibility of specific neurons to a variety of insults and initiate degeneration.

SCA1 transgenic mice: a model for neurodegeneration caused by an expanded CAG trinucleotide repeat.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant inherited disorder characterized by degeneration of cerebellar Purkinje cells, spinocerebellar tracts, and selective brainstem neurons owing to the expansion of an unstable CAG trinucleotide repeat. To gain insight into the pathogenesis of the SCA1 mutation and the intergenerational stability of trinucleotide repeats in mice, we have generated transgenic mice expressing the human SCA1 gene with either a normal or an expanded CAG tract. Both transgenes were stable in parent to offspring transmissions. While all six transgenic lines expressing the unexpanded human SCA1 allele had normal Purkinje cells, transgenic animals from five of six lines with the expanded SCA1 allele developed ataxia and Purkinje cell degeneration. These data indicate that expanded CAG repeats expressed in Purkinje cells are sufficient to produce degeneration and ataxia and demonstrate that a mouse model can be established for neurodegeneration caused by CAG repeat expansions.

Molecular and clinical correlations in spinocerebellar ataxia type 3 and Machado-Joseph disease.

The autosomal dominant spinocerebellar ataxias are clinically and genetically a heterogeneous group of neurodegenerative disorders. Genetic studies have classified some of these disorders based on the mapping of their respective genes. The gene for Machado-Joseph disease, one type of spinocerebellar ataxia, has been mapped to the long arm of chromosome 14q24.3-ter. The gene for another spinocerebellar ataxia, which is clinically distinct from Machado-Joseph disease, has been also localized to the same region on 14q and has been named type 3 spinocerebellar ataxia. Recently, expansions of a CAG trinucleotide repeat in a novel gene on chromosome 14q32.1 were shown in 11 patients affected with Machado-Joseph disease. In this study, we analyzed the DNA samples from 103 individuals representing 42 independent families with dominantly inherited ataxia to determine whether any had the Machado-Joseph disease mutation. The Machado-Joseph disease CAG expansion was detected in 5 of these 42 families. Sixteen affected individuals displayed a normal allele containing 14 to 31 CAG repeats and an expanded allele ranging between 66 and 79 CAG repeats. Seven asymptomatic individuals showed an allele ranging between 67 and 80 CAG repeats. Two of these families had a phenotype consistent with Machado-Joseph disease while the other 3 had clinical features of type 3 spinocerebellar ataxia. These data suggest that a single locus at 14q32.1 is responsible for two forms of spinocerebellar ataxia, spinocerebellar ataxia type 3 and Machado-Joseph disease, and that this locus may account for approximately 11% of this group of dominantly inherited ataxias.

The human collagenase-3 (CLG3) gene is located on chromosome 11q22.3 clustered to other members of the matrix metalloproteinase gene family.

The gene coding for human collagenase-3 (CLG3), a recently described matrix metalloproteinase produced by breast carcinomas, has been localized by fluorescence in situ hybridization on chromosome 11q22.3. Physical mapping of an isolated YAC clone containing CLG3 has revealed that this gene is tightly linked to those encoding other matrix metalloproteinases, including fibroblast collagenase (CLG1), stromelysin-1 (STMY1), and stromelysin-2 (STMY2). Further mapping of this region using pulsed-field gel electrophoresis has shown that the CLG3 gene is localized to the telomeric side of the matrix metalloproteinase cluster, the relative order of the loci being centromere-STMY2-CLG1-STMY1-CLG3-telomere.

Clinical, neuropathologic, and genetic studies of a large spinocerebellar ataxia type 1 (SCA1) kindred: (CAG)n expansion and early premonitory signs and symptoms.

We report the clinical, neuropathologic, and genetic studies of a large kindred (family M-ADCA1) with autosomal dominant spinocerebellar ataxia type 1 (SCA1), ascertained in 41 members, with clinical data available in twenty-two. The mean age of onset was 36.3 +/- 6.2 years (ages, 26 to 52), the mean duration of the disease was 15.8 +/- 6.5 years (range, 10 to 28 years), and the mean age at death was 54.1 +/- 9.5 years (ages, 39 to 72). Premonitory signs and symptoms appeared earlier than the usual onset symptoms in many of the clinically unaffected patients who inherited the mutated SCA1 gene. Anticipation was present when we compared the seventh and eighth generations. A more severe course of the disease occurred in offspring of affected males. Neuropathologic examination, performed on three patients, showed the usual findings of SCA1; Golgi and immunocytochemistry studies suggested primary damage of the Purkinje cells. We analyzed the CAG-repeat mutation responsible for the SCA1 phenotype in a total of 41 family members. There was expansion in 19 subjects (10 clinically affected, seven with early signs and symptoms, and two asymptomatic individuals), and all showed heterozygosity, with one allele between 41 and 59 repeats (SCA1 mutation) and the other in the range of 6 to 39 repeats (normal range). The clinical analysis of "at risk" patients with the SCA1 mutation showed that minor signs and symptoms begin before full clinical diagnosis, and these premonitory manifestations can herald full development of SCA1 by years.

Chemiluminescent detection of blotted PCR products (CB-PCR) of two CAG dynamic mutations (Huntington's disease and spinocerebellar ataxia type 1).

We have used a non-isotopic PCR assay based on the chemiluminescent detection of blotted PCR products (CB-PCR) for two dynamic mutation diseases (Huntington's disease and spinocerebellar ataxia type 1). This gives an accurate sizing of alleles and permits a rapid analysis of at risk persons. The system involves PCR of the samples, separation of alleles on polyacrylamide gels, Southern blotting, and hybridisation with specific primers 3' labelled with fluorescein (F1)-dUTP as probes. CB-PCR retains the isotopic sensitivity for accurate allele determination, avoids isotopic manipulation, and provides the advantages of safety, long term storage of probes, and recycling of hybridisation solutions.

Prenatal diagnosis of Werdnig-Hoffmann disease: DNA analysis of a mummified umbilical cord using closely linked microsatellite markers.

We present a case of prenatal diagnosis of Werdnig-Hoffmann disease, the most severe type of spinal muscular atrophy (SMA). DNA obtained from a mummified umbilical cord of a decreased affected brother of the index case was analysed with four closely linked microsatellite markers [EF1/2a and EF13/14 (D5S125), MAP1B, and JK53CA (D5S112)], flanking the SMA gene, on chromosome 5q11.2-13.3. The fetus was diagnosed as homozygous for the deleterious SMA gene.

Mapping of the human Zn-alpha 2-glycoprotein gene (AZGP1) to chromosome 7q22 by in situ hybridization.

The gene coding for Zn-alpha 2-glycoprotein (AZGP1), a human protein with a high degree of similarity to class I major histocompatibility complex (MHC) antigens, was mapped by fluorescent in situ hybridization to chromosome 7q22, a common breakpoint in myelodysplastic syndromes. Since classical MHC genes map on chromosome 6, this assignment indicates that besides duplication of the putative common ancestor gene, transposition events to different chromosomes have also been involved in the evolutionary diversification of this gene family.

Presymptomatic analysis of spinocerebellar ataxia type 1 (SCA1) via the expansion of the SCA1 CAG-repeat in a large pedigree displaying anticipation and parental male bias.

Autosomal dominant cerebellar ataxia type 1 (ADCA1) is a clinical and genetic heterogeneous neurodegenerative disorder which leads to progressive cerebellar ataxia. One defective gene responsible for the disease was first localised to 6p (SCA1, spinocerebellar ataxia type 1) and the mutation has been more recently characterised. We have analysed the CAG-repeat mutation responsible for the SCA1 phenotype in a large Spanish kindred with 41 affected members, in which positive linkage with D6S89 was previously shown. All (10) clinically affected members analysed were heterozygous with one disease allele being between 41 to 57 CAG repeats, and the other in the normal range, from 6 to 39 repeats. Nine clinically unaffected individuals who were between the ages of 18 and 40, were found to have expansions of the CAG repeat (41 to 59), and 22 other 'at risk' individuals were found to have inherited the SCA1 gene with copies of the CAG repeat in the normal range. We have also observed that affected fathers passed on the mutated SCA1 gene with larger increases in the number of CAG repeats than affected mothers did. In one case a decrease in the number of CAG repeats (51 to 50) was detected in the transmission from the affected mother, and in two cases no change was observed in the transmission of a 41 allele repeat by a mother. As in the other disorders in which knowledge of the mutation has been obtained, analysis of the repeat expansion dramatically changes diagnosis of SCA1.