Search

Background Spinocerebellar ataxia type 17 (SCA17) involves the expression of a CAG/CAA expansion mutation in the gene encoding TATA-box binding protein (TBP), a general transcription initiation factor. The spectrum of SCA17 clinical presentation is broad. Methods We screened for triplet expansion in the TBP gene in Taiwanese Parkinson's disease (PD), Alzheimer's disease (AD) and atypical parkinsonism and investigated the functional implication of expanded alleles using lymphoblastoid cells as a model. Results A total of 6 mildly expanded alleles (44–46) were identified in patients group. The frequency of the individuals carrying expanded alleles in PD (3/602 [0.5%]), AD (2/245 [0.8%]) and atypical parkinsonism (1/44 [2.3%]) is not significant as compared to that in the control subjects (0/644 [0.0%]). In lymphoblastoid cells, HSPA5, HSPA8 and HSPB1 expression levels in cells with expanded TBP were significantly lower than that of the control cells. Although not significantly, the levels of PARK7 protein isoforms 6.1 and 6.4 are notably increased in SCA17 lymphoblastoid cells. Treatment of TBH ( tert -butyl hydroperoxide) significantly increases cell death in the cells with mildly expanded TBP. Conclusions Our findings expand the spectrum of SCA17 phenotype and may contribute to our understanding of the disease.

Trinucleotide repeat (TNR) expansion in the gene for TATA binding protein (TBP) has recently been described as causal for spinocerebellar ataxia type 17. The normal number of repeats has been considered to be 42 or less. An intermediate range with reduced penetrance has been assumed to be 43-47 CAA/CAG repeats. We examined this gene in 30 patients with autosomal-dominant cerebellar ataxia (ADCA), 35 patients with sporadic ataxia, 11 patients with Huntington's disease (HD), 351 patients with idiopathic Parkinson's disease (PD), 105 patients with Alzheimer's disease (AD), and 291 controls with no history of neurodegenerative disease. Three patients (one with sporadic PD and two with AD) carrying more than 42 TNRs in the TBP gene were identified. This reveals that the phenotype associated with CAG/CAA expansion in the TBP gene may be heterogeneous.

Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant inherited disorder characterized by degeneration of spinocerebellar tracts and selected brainstem neurons owing to the expansion of a CAG repeat of the human TATA-binding protein (hTBP) gene. To gain insight into the pathogenesis of this hTBP mutation, we generated transgenic mice with the mutant hTBP gene driven by the Purkinje specific protein (Pcp2/L7) gene promoter. Mice with the expanded hTBP allele developed ataxia within 2-5 months. Behavioral analysis of L7-hTBP transgenic mice showed reduced fall latency in a rotarod assay. Purkinje cell degeneration was identified by immunostaining of calbindin and IP3R1. Reactive gliosis and neuroinflammation occurred in the transgenic cerebellum, accompanied by up-regulation of GFAP and Iba1. The L7-hTBP transgenic mice were thus confirmed to recapitulate the SCA17 phenotype and were used as a disease model to explore the potential of granulocyte-colony stimulating factor in SCA17 treatment. Our results suggest that granulocyte-colony stimulating factor has a neuroprotective effect in these transgenic mice, ameliorating their neurological and behavioral deficits. These data indicate that the expression of the mutant hTBP in Purkinje cells is sufficient to produce cell degeneration and an ataxia phenotype, and constitutes a good model for better analysis of the neurodegeneration in SCA17.

Background Miyoshi distal myopathy (MM) and limb girdle muscular dystrophy type 2B (LGMD2B) were found to map to the same mutant gene encoding for dysferlin on chromosome 2p13. Most reported cases were large inbred kindreds whose members demonstrated both MM and LGMD2B phenotypes. Objective To investigate the clinical, neurophysiological, histopathological, and genetic features in 4 patients with MM from 2 unrelated Chinese families demonstrating linkage to the dysferlin locus. Results All patients were characterized by early adult onset, preferential atrophy, and weakness of calf muscles, marked elevation of serum creatine kinase levels, and absence of dysferlin staining. Magnetic resonance imaging showed fatty and fibrotic tissue signals in the affected muscles. Genetic analysis revealed novel compound heterozygous mutations, 1310+1G to A and GGG to GTC transition at nucleotide 1650 ( G426V ) in one family and another novel compound heterozygous mutation, a deletion of C at nucleotide 477 and a CCG to CTG transition at nucleotide 6576 (P2068L), in the other family. Conclusion Miyoshi distal myopathy in these 2 Chinese families demonstrated a homogenous phenotype and compound heterozygous mutations. Among the 4 mutations, 3 were novel mutations that, to our knowledge, have not been reported previously.