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Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), is an autosomal dominant neurodegenerative disease. This disorder is caused by polyglutamine (polyQ)-containing mutant ataxin-3, which tends to misfold and aggregate in neuron cells. We previously demonstrated a protective function of carbonic anhydrase 8 (CA8) in MJD disease models and a decreased glycolytic activity associated with down-regulated CA8 in a human osteosarcoma (OS) cell model. Given that a reduction in body weight accompanied by gait and balance instability was observed in MJD patients and transgenic (Tg) mice, in this study, we aimed to examine whether metabolic defects are associated with MJD and whether CA8 expression is involved in metabolic dysfunction in MJD. Our data first showed that glucose uptake ability decreases in cells harboring mutant ataxin-3, but increases in cells overexpressing CA8. In addition, the expressions of glucose transporter 3 (GLUT3) and phosphofructokinase-1 (PFK1) were significantly decreased in the presence of mutant ataxin-3. Consistently, immunohistochemistry (IHC) showed that GLUT3 was less expressed in cerebella of aged MJD Tg mice, indicating that the dysfunction of GLUT3 may be associated with late-stage disease. On the other hand, transient down-regulation of CA8 revealed decreased expressions of GLUT3 and PFK1 in HEK293 cells harboring wild-type (WT) ataxin-3, but no further reduction of GLUT3 and PFK1 expressions were observed in HEK293 cells harboring mutant ataxin-3. Moreover, immunoprecipitation (IP) and immunofluorescence (IF) demonstrated that interactions exist between ataxin-3, CA8 and GLUT3 in MJD cellular and Tg models. These lines of evidence suggest that CA8 plays an important role in glucose metabolism and has different impacts on cells with or without mutant ataxin-3. Interestingly, the decreased relative abundance of Firmicutes/Bacteroidetes (F/B) ratio in the feces of aged MJD Tg mice coincided with weight loss and metabolic dysfunction in MJD. Taken together, our results are the first to demonstrate the effects of CA8 on glucose metabolism and its involvement in the metabolic defects in MJD disease. Further investigations will be required to clarify the underlying mechanisms for the metabolic defects associated with MJD.

Machado-Joseph disease (MJD)/Spinocerebellar ataxia type 3 (SCA3) is an inherited neurodegenerative disease that can lead to a regression of motor coordination and muscle control in the extremities. It is known that expansion of CAG repeats encodes abnormally long polyQ in mutant ataxin-3, the disease protein. It is also noted that mutant ataxin-3 interacts with 1,4,5-trisphosphate receptor type 1 (IP3R1) and induces abnormal Ca2+ release. Previously, we have shown a significant increase in the expression of carbonic anhydrase VIII (CA8) in SK-N-SH-MJD78 cells, which are human neuroblastoma cells overexpressing mutant ataxin-3 with 78 glutamine repeats. In the current study, we showed the presence of significantly increased CA8 expression in MJD mouse cerebellum in either early or late disease stage, with a gradual decrease in CA8 expression as the MJD mice naturally aged. By immunofluorescence and immunoprecipitation analysis, we also found that CA8 co-localized and interacted with mutant ataxin-3 in SK-N-SH-MJD78 cells harboring overexpressed CA8 (SK-MJD78-CA8). In addition, we found that SK-MJD78-CA8 cells, as well as cerebellar granule neurons (CGNs) of MJD transgenic (Tg) mouse with overexpressed CA8, were more resistant to reactive oxygen species (ROS) stress than the control cells. Importantly, overexpression of CA8 in SK-MJD78-CA8 cells and in MJD CGNs rescued abnormal Ca2+ release and caused an increase in cell survival. In summary, we demonstrate the protective function of CA8 in MJD disease models and speculate that the declining expression of CA8 following an initial increased expression may be related to the late onset phenomenon of MJD.

Myoclonic epilepsy with ragged-red fibers (MERRF) is a maternally inherited mitochondrial neuromuscular disease. We previously reported a significant decrease of mRNA and protein levels of nuclear DNA-encoded carbonic anhydrase VIII (CA8) in MERRF cybrids harboring A8344G mutation in mitochondrial DNA (mtDNA). In this study, we established a reporter construct of luciferase gene-carrying hCA8 promoter containing several putative transcription factor-binding sites, including GC-box, AP-2 and TATA-binding element in the 5'flanking region of the hCA8 gene. Using a series of mutated hCA8 promoter constructs, we demonstrated that a proximal GC-box, recognized by Sp1 and other Sp family members, may be a key cis-element functioning at the promoter. Additionally, a significant increase of the hCA8 promoter activity was observed in the wild-type and mutant cybrids with over-expression of eGFP-Sp1, but no detectable increase in the CA8 protein expression. In contrast, over-expression of Flag-Sp1 and Flag-Sp4 significantly increased the hCA8 promoter activity as well as endogenous CA8 protein expression in neuron-like HEK-293 T cells. However, down-regulation of Sp1, but not Sp4, in 293 T cells revealed a significant reduction of CA8 expression, suggesting that Sp1 is a predominant transcription factor for regulation of CA8 activity. Furthermore, our data indicate that chromatin structure may be involved in the expression of hCA8 gene in MERRF cybrids. Taken together, these results suggest that Sp1 transactivates hCA8 gene through the proximal GC box element in the promoter region. The key modulator-responsive factor to the mtDNA mutation and how it may affect nuclear hCA8 gene transcription need further investigations.

Mitochondrial DNA (mtDNA) mutations are associated with a large number of neuromuscular diseases. Myoclonus epilepsy with ragged-red fibers (MERRF) syndrome is a mitochondrial disease inherited through the maternal lineage. The most common mutation in MERRF syndrome, the A8344G mutation of mtDNA, is associated with severe defects in mitochondrial protein synthesis, which impair the assembly and function of the respiratory chain. We have previously shown that there is a decreased level of heat shock protein 27 (HSP27) in lymphoblastoid cells derived from a MERRF patient and in cytoplasmic hybrids (cybrids) harboring the A8344G mutation of mtDNA. In the present study, we found a dramatic decrease in the level of phosphorylated HSP27 (p-HSP27) in the mutant cybrids. Even though the steady-state level of p-HSP27 was reduced in the mutant cybrids, normal phosphorylation and dephosphorylation were observed upon exposure to stress, indicating normal kinase and phosphatase activities. To explore the roles that p-HSP27 may play, transfection experiments with HSP27 mutants, in which three specific serines were replaced with alanine or aspartic acid, showed that the phosphomimicking HSP27 desensitized mutant cybrids to apoptotic stress induced by staurosporine (STS). After heat shock stress, p-HSP27 was found to enter the nucleus immediately, and with a prolonged interval of recovery, p-HSP27 returned to the cytoplasm in wild-type cybrids but not in mutant cybrids. The translocation of p-HSP27 was correlated with cell viability, as shown by the increased number of apoptotic cells after p-HSP27 returned to the cytoplasm. In summary, our results demonstrate that p-HSP27 provides significant protection when cells are exposed to different stresses in the cell model of MERRF syndrome. Therapeutic agents targeting anomalous HSP27 phosphorylation might represent a potential treatment for mitochondrial diseases.

Mitochondrial DNA (mtDNA) mutations are responsible for human neuromuscular diseases caused by mitochondrial dysfunction. Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a maternally inherited mitochondrial encephalomyopathy with various syndromes involving both muscular and nervous systems. The most common mutation in MERRF syndrome, A8344G mutation in mtDNA, has been associated with severe defects in protein synthesis. This defect impairs assembly of complexes in electron transport chain and results in decreased respiratory function of mitochondria. In this study, we showed a significant decrease of the heat shock protein 27 (Hsp27) in lymphoblastoid cells derived from a MERRF patient and in cybrid cells harboring MERRF A8344G mutation. However, normal cytoplasmic distributions of Hsp27 and normal heat shock responses were observed in both wild type and mutant cybrids. Furthermore, overexpression of wild type Hsp27 in mutant MERRF cybrids significantly decreased cell death under staurosporine (STS) treatment, suggesting a protective function of Hsp27 in cells harboring the A8344G mutation of mtDNA. Meanwhile, reverse transcriptase PCR showed no difference in the mRNA level between normal and mutant cybrids, indicating that alterations may occur at the protein level. Evidenced by the decreased levels of Hsp27 upon treatment with proteasome inhibitor, starvation and rapamycin and the accumulation of Hsp27 upon lysosomal inhibitor treatment; Hsp27 may be degraded by the autophagic pathway. In addition, the increased formation of LC3-II and autophagosomes was found in MERRF cybrids under the basal condition, indicating a constitutively-activated autophagic pathway. It may explain, at least partially, the faster turnover of Hsp27 in MERRF cybrids. This study provides information for us to understand that Hsp27 is degraded through the autophagic pathway and that Hsp27 may have a protective role in MERRF cells. Regulating Hsp27 and the autophagic pathway might help develop therapeutic solutions for treatment of MERRF syndrome in the future.

Machado–Joseph disease is an autosomal dominant spinocerebellar degeneration caused by the expansion of a polyglutamine tract within the gene product, ataxin-3. We have previously shown that increased oxidative stress and decreased expression of Hsp27 may be contributory factors to the disease progression. In this study, we utilized neuroblastoma SK-N-SH cells stably transfected with full-length expanded ataxin-3 to further investigate the mechanism(s) resulting in the decreased expression of Hsp27. Results from 35 S-methionine pulse-chase labeling and protein degradation assays revealed that decreased Hsp27 in mutant MJD cells is due to defects in protein synthesis. Our results further demonstrated that Hsp27 degradation is independent of the proteasome degradation pathway. In addition, we showed that overexpression of Hsp27 desensitizes mutant MJD cells to apoptotic stress. Taken together, these findings provide the first evidence that expanded ataxin-3 interferes with Hsp27 synthesis, which may contribute to the impairment of the cells’ ability to respond to stresses and trigger the progression of this late-onset disease.

Machado-Joseph disease/Spinocerebellar ataxia type 3 is an autosomal dominant neurodegenerative disease caused by polyglutamine-expanded ataxin-3. In this study, COS7-MJD26-GFP and COS7-MJD78-GFP cells, which were stably transfected with GFP-tagged full-length MJD gene with either 26 or 78 glutamine repeat, were used to demonstrate that both protein and mRNA levels of bcl-2 are decreased in the presence of expanded ataxin-3. However, the promoter activity in COS7-MJD78-GFP cells is much higher than that in COS7-MJD26-GFP, suggesting that the decrease of bcl-2 expression may be due to defects in mRNA stability. Therefore, 5,6-dichloro-benzimidazole 1-β- d -ribofuranoside, an adenosine analogue to inhibit mRNA synthesis, was used to estimate the bcl-2 mRNA degradation rate. Our results demonstrated that bcl-2 mRNA decay in COS7-MJD78-GFP cells is about 3.5-fold faster than that in COS7-MJD26-GFP. Our study provides evidence, for the first time, that dysfunction of mRNA stability resulted from the presence of mutant ataxin-3.

Objective – Machado–Joseph disease (MJD)/spinocerebellar ataxia type 3 is an autosomal dominant spinocerebellar degeneration, for which there is no effective treatment. Patients and methods – This study involved the clinical response of lamotrigine (LTG) on six MJD patients with early truncal ataxia and the effect of LTG on the alteration of ataxin-3 expression in the transformed MJD lymphoblastoid cells. Result – LTG medication was found, on the basis of single leg standing test tandem gait index, to effectively improve gait balance, but did not prove to be effective in the withdrawal period. In Western blot analysis of ataxin-3 in MJD lymphoblastoid cells, extracellular application of LTG, while leaving the normal level of ataxin-3 intact, decreased the expression of mutant ataxin-3 in a dose-related manner. Conclusion – Our results indicated that LTG may have significant benefits in relief of gait disturbance in MJD patients with early ataxia, and may be related to the decreased expression of mutant ataxin-3.

Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant spinocerebellar degeneration characterized by a wide range of clinical manifestations. In this review, we discuss the role(s) that heat shock protein 27 (HSP27) may play in the cell death process of spinocerebellar ataxia type 3.

Hirschsprung disease (HSCR), or congenital intestinal aganglionosis, is a relatively common disorder characterized by the absence of ganglion cells in the nerve plexuses of the lower digestive tract, resulting in intestinal obstruction in neonates. Mutations in genes of the RET receptor tyrosine kinase and endothelin receptor B (EDNRB) signaling pathways have been shown to be associated in HSCR patients. In this study, we collected genomic DNA samples from 55 HSCR patients in central Taiwan and analyzed the coding regions of the RET and EDNRB genes by PCR amplification and DNA sequencing. In the 55 patients, an A to G transition was detected in two (identical twin brothers). The mutation was at the end of RET exon 19 at codon 1062 (Y1062C), a reported critical site for the signaling pathways. Single nucleotide polymorphisms (SNP) in exons 2, 7, 11, 13, and 15 of RET and exon 4 of EDNRB in the HSCR patients or controls were detected. The differences between patients and controls in allele distribution of the five RET polymorphic sites were statistically significant. The most frequent genotype encompassing exons 2 and 13 SNPs (the polymorphic sites with the highest percentage of heterozygotes) was AA/GG in patients, which was different from the AG/GT in the normal controls. Transmission disequilibrium was observed in exons 2, 7, and 13, indicating nonrandom association of the susceptibility alleles with the disease in the patients. This study represents the first comprehensive genetic analysis of HSCR disease in Taiwan.

Objective – To identify various subtypes of spinocerebellar ataxias (SCAs) among autosomal dominant cerebellar ataxia (ADCA) patients referred to our research center, SCA1, SCA2, SCA3/MJD (Machado–Joseph disease), SCA6, SCA7, SCA8 and SCA12 loci were assessed for expansion of trinucleotide repeats. Patients and methods – A total of 211 ADCA patients, including 202 patients with dominantly inherited ataxia from 81 Taiwanese families and nine patients with sporadic ataxia, were included in this study and subjected to polymerase chain reaction (PCR) analysis. The amplified products of all loci were analyzed on both 3% agarose gels and 6% denaturing urea-polyacrylamide gels. PCR-based Southern blots were also applied for the detection of SCA7 locus. Results – The SCA1 mutation was detected in six affected individuals from one family (1.2%) with expanded alleles of 50–53 CAG repeats. Fourteen individuals from nine families (11%) had a CAG trinucleotide repeat expansion at the SCA2 locus, while affected SCA2 alleles have 34–49 CAG repeats. The SCA3/MJD CAG trinucleotide repeat expansion in 60 affected individuals from 26 families (32%) was expanded to 71–85 CAG repeats. As for the SCA7 locus, there were two affected individuals from one family (1.2%) possessed 41 and 100 CAG repeats, respectively. However, we did not detect expansion in the SCA6, SCA8 and SCA12 loci in any patient. Conclusions – The SCA3/MJD CAG expansion was the most frequent mutation among the SCA patients. The relative prevalence of SCA3/MJD in Taiwan was higher than that of SCA2, SCA1 and SCA7.

Spinocerebellar ataxia (SCA) type 7 is an autosomal dominant disorder characterized by neural loss, mainly in the cerebellum and regions of the brainstem and particularly the inferior olivary complex. This neurodegeneration disease is associated with expansion of unstable CAG repeats within the 5'-translated region of the SCA7 gene, located on chromosome 3p. We conducted a local survey of the normal population and candidate patients for the analysis of the CAG repeats in the SCA7 gene. The distributions of the CAG repeat units of SCA7 gene in the normal population in Taiwan were established in this study by using the radioactive genomic polymerase chain reaction (PCR). The normal range of CAG repeats is from 6 to 17 repeats, with the more common being around 8-13 repeats. The range is narrower than that reported for other ethnic groups (7-35 CAGs). Meanwhile, by the use of a combination of PCR and Southern blot analysis, one SCA7 family was identified and is reported here. A marked instability of the CAG repeat number during transmission from father to son (41 vs. 100) was observed in the SCA7 family. Clinical anticipation is significant in this family including an infantile case, who was found to have nystagmus from the age of 1 month. To date, the SCA7 mutation has been detected in one of 73 families with autosomal dominant cerebellar ataxia phenotypes, which is about 1.4% of the ataxia families referred to us, compared to 1.4% SCA1, 9.6% SCA2, and 27.3% SCA3/Machado-Joseph disease in our collection. In addition, we demonstrate that the PCR-based Southern blot analysis, with the advantages of sensitivity of PCR and specificity of Southern blot, is a reliable diagnostic method for SCA7 mutation screening. The molecular analysis technique makes possible the quick and accurate diagnosis of SCA7 patients and in the future will hopefully be applied to prenatal screening for SCA7 families.

Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar degeneration characterized by cerebellar ataxia and pyramidal signs associated in varying degrees with a dystonic-rigid extrapyramidal syndrome or peripheral amyotrophy. Unstable CAG trinucleotide repeat expansion in the MJD gene on the long arm of chromosome 14 has been identified as the pathological mutation for MJD. While investigating the distribution of CAG repeat lengths of the MJD gene in Taiwan's population, we have identified 18 MJD-affected patients and 12 at-risk individuals in seven families. In addition, we have analyzed the range of CAG repeat lengths in 96 control individuals. The CAG repeat number ranged from 13 to 44 in the controls and 72-85 in the affected and at-risk individuals. Our results indicated that the CAG repeat number was inversely correlated with the age of onset. The differences in CAG repeat length between parent and child and between siblings are greater with paternal transmission than maternal transmission. Our data show a tendency towards the phenomenon of anticipation in the MJD families but do not support unidirectional expansion of CAG repeats during transmission. We also demonstrated that PCR amplification of the CAG repeats in the MJD gene from villous DNA was possible and might prove useful as a diagnostic tool for affected families in the future.

Adenosine dialdehyde (AdOx) is an indirect methyltransferase inhibitor broadly used in cell culture to accumulate methyl-accepting proteins in hypomethylated states for in vitro protein methylation analyses. In this study we included a translation inhibitor, cycloheximide, in the AdOx treatment of HeLa cells. The methyl-accepting proteins disappeared in the double treatment, indicating that they were most likely newly synthesized in the AdOx incubation period. AdOx treatment could also be used in combination with in vivo methylation, another technique frequently used to study protein methylation. AdOx treatment prior to in vivo methylation accumulated methyl-accepting proteins for the labeling reaction. The continued presence of AdOx in the in vivo labeling period decreased the methylation of the majority of in vivo methyl-accepting polypeptides. The level and pattern of the in vivo methylated polypeptides did not change after a 12-h chase, supporting the notion that the methylated polypeptide as well as the methyl groups on the modified polypeptides are stable. On the other hand, methylarginine-specific antibodies detected limited but consistent reduction of the methylarginine-containing proteins in AdOx-treated samples compared to the untreated ones. Thus, AdOx treatment probably only blocked a small fraction of stable protein methylation. Overall, it is likely that base-stable methylation are formed soon after the synthesis of the polypeptide and remain stable after the modification.

Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar degeneration characterized by a wide range of clinical manifestations. An unstable CAG trinucleotide repeat expansion in MJD gene on long arm of chromosome 14 has been identified as the pathologic mutation of MJD and apoptosis was previously shown to be responsible for the neuronal cell death of the disease. In this study, we utilized human neuronal SK-N-SH cells stably transfected with HA-tagged full-length MJD with 78 polyglutamine repeats to examine the effects of polyglutamine expansion on neuronal cell survival in the early stage of disease. Various pro-apoptotic agents were used to assess the tolerance of the mutant cells and to compare the differences between cells with and without mutant ataxin-3. Concentration- and time-dependent experiments showed that the increase in staurosporine-induced cell death was more pronounced and accelerated in cells containing expanded ataxin-3 via MTS assays. Interestingly, under basal conditions, Western blot and immunocytochemical analyses showed a significant decrease of Bcl-2 protein expression and an increase of cytochrome c in cells containing expanded ataxin-3 when compared with those of the parental cells. The same reduction of Bcl-2 was further confirmed in fibroblast cells with mutant ataxin-3. In addition, exogenous expression of Bcl-2 desensitized SK-N-SH-MJD78 cells to poly-Q toxicity. These results indicated that mitochondrial-mediated cell death plays a role in the pathogenesis of MJD. In our cellular model, full-length expanded ataxin-3 that leads to neurodegenerative disorders significantly impaired the expression of Bcl-2 protein, which may be, at least in part, responsible for the weak tolerance to polyglutamine toxicity at the early stage of disease and ultimately resulted in an increase of stress-induced cell death upon apoptotic stress.

Background: Machado-Joseph disease is the most frequent dominant ataxia worldwide. Despite its frequency and presence in many populations, only 2 founder mutations have been suggested to explain its current geographic distribution.Objectives: To trace back in history the main mutational events in Machado-Joseph disease, we aimed to assess ancestral haplotypes and population backgrounds, to date the mutations, and to trace the routes and time of introduction of the founder haplotypes in different populations.Design, Setting, and Participants: We studied 264 families with Machado-Joseph disease from 20 different populations. Six intragenic single-nucleotide polymorphisms were used to determine ancestral mutational events; 4 flanking short tandem repeats were used to construct extended haplotypes and measure accumulation of genetic diversity over time within each lineage.Results: The worldwide-spread lineage, TTACAC, had its highest diversity in the Japanese population, where we identified the ancestral short tandem repeat-based haplotype. Accumulated variability suggested a postneolithic mutation, about5774 +/- 1116 years old, with more recent introductions in North America, Germany, France, Portugal, and Brazil. As to the second mutational event, in the GTGGCA lineage, only 7 families ( of 71 families) did not have Portuguese ancestry, although gene diversity was again smaller in Portuguese families (0.44) than in non-Portuguese families (0.93).Conclusions: The worldwide-spread mutation may have first occurred in Asia and later been diffused throughout Europe, with a founder effect accounting for its high prevalence in Portugal; the other Machado-Joseph disease lineage is more recent, about 1416 +/- 434 years old, and its dispersion may be explained mainly by recent Portuguese emigration.

Machado–Joseph disease (MJD)/spinocerebellar ataxia type 3 is an autosomal dominant spinocerebellar degeneration characterized by a wide range of clinical manifestations. Unstable CAG trinucleotide repeat expansion in the MJD gene has been identified as the pathologic mutation of MJD. In this study, human SK-N-SH neuroblastoma cells stably transfected with full-length MJD with 78 CAG repeats were established. Compared with the parental cells, cells expressing mutant ataxin-3 displayed normal morphology for over 80 generations. Less than 1% of the transfected cells contained nuclear aggregates under basal conditions, indicating that this cellular model represented an early disease stage. While t-butyl hydroperoxide (TBH) was used to assess the oxidative tolerance of cells, the results demonstrated that the transfected cells were more susceptible to low concentrations of TBH than the parental cells. Most interestingly, from 2D gel electrophoresis analysis, we identified that the expression of heat shock protein 27 (HSP27), known as a suppressor of poly(Q)-mediated cell death, dramatically decreased in SK-N-SH cells stably transfected with full-length mutant MJD. The same reduction of HSP27 was further confirmed in lymphoblastoid cells from MJD patients. Our results demonstrated that both neuronal and non-neuronal cells with expanded full-length ataxin-3 revealed reduced protein expression of HSP27. We propose that the reduction of HSP27 in the early stage of the disease plays an important role during cell death process in MJD.

The molecular mechanism of neuritogenesis has been extensively studied but remains unclear. In this study, we identified Mob2 protein which plays a significant role in promoting neurite formation in Neuro2A (N2A) cells. Our results showed that Mob2 was expressed in developing N2A cells. To study whether Mob2 was involved in neurite formation, we downregulated Mob2 expression using RNA interference and found that neurite formation decreased in low serum induced N2A cells. In addition, we found that overexpression of Mob2 promoted neurite formation in N2A cells. Furthermore, downregulation of Mob2 expression altered the rearrangement of the actin cytoskeleton and decreased the expression of phosphorylated Moesin. Together, these results provide information on the role of Mob2 in mediating neurite formation.