Chung-Yee Yuo

The effect of hydroxyurea in spinal muscular atrophy cells and patients

BACKGROUND Spinal muscular atrophy (SMA) is a degenerative motor neuron disease caused by homozygous mutations of the survival motor neuron 1 (SMN1) gene. Effective treatment for SMA is unavailable at present. The aim of this study was to investigate the effect of hydroxyurea (HU) in SMA cells and patients. MATERIALS AND METHODS Fifteen SMA lymphoid and three fibroblast cell lines, 2 from SMA patients and 1 control, were treated with HU at different concentrations, and 33 patients (types II, III) randomized into three groups on different HU dosage, 20, 30, 40 mg/kg/day, were treated for 8 weeks and followed up for another drug-free 8 weeks. The effect of HU on SMN2 gene expression and clinical manifestations was evaluated. RESULTS After treatment, in vitro, full-length mRNA level and gems number increased significantly, and hnRNP A1 protein decreased. In vivo, there were slight increases in muscle strength scores at 4 weeks and full-length SMN mRNA at 8 weeks in 30 mg/kg/day subgroup. CONCLUSIONS Treating with HU enhanced SMN2 gene expression in SMA cells and showed slight trend towards improvement in some clinical outcome measures in SMA patients which suggests HU may be safe to use in SMA patients but larger randomized, placebo-controlled, double-blind trials are needed to further investigate its efficacy.

Detecting Epstein-Barr virus DNA from peripheral blood mononuclear cells in adult patients with systemic lupus erythematosus in Taiwan

Epstein-Barr virus (EBV) has been found by many serology studies to be associated with systemic lupus erythematosus (SLE). However, the results of DNA studies have been conflicting. Therefore, instead of antibody to EBV, we studied the association between EBV DNA and SLE. In this case-control study in Taiwan, we enrolled 87 SLE patients and 174 age- and sex-matched controls. Peripheral blood mononuclear cells of SLE patients and matched controls were tested for EBV DNA by polymerase chain reaction (PCR) and Southern blot. Of the 87 SLE patients, 71 (81.6%) were found to be positive for EBV DNA, while 85 (48.9%) of the 174 controls (odds ratio 4.64, 95% confidence interval 2.50–8.62, P<0.0001) were positive. While the EBV DNA-positive rate did not decline with age in SLE patients (P>0.05), it did decline with age in controls (P<0.05). Furthermore, based on a real-time quantitative PCR study, we have found a significant difference between EBV viral load in SLE and controls (P=0.008). Therefore, in our molecular study of DNA level, we found evidence for the association of EBV infection and SLE, suggesting that EBV contributes, if not to the development of SLE, then to disease perpetuation.

5‐(N‐ethyl‐N‐isopropyl)‐amiloride enhances SMN2 exon 7 inclusion and protein expression in spinal muscular atrophy cells

Spinal muscular atrophy (SMA) is a common inherited neuromuscular disorder caused by homozygous loss of function of the survival motor neuron 1 (SMN1) gene. All SMA patients carry at least one copy of a nearly identical SMN2 gene. However, a critical nucleotide change in SMN2 results in alternative splicing and exclusion of exon 7 in the majority of SMN2 messenger RNA (mRNA), thus producing a low level of functional SMN protein. Increasing SMN protein production by promoting SMN2 exon 7 inclusion could be a therapeutic approach for SMA. It has been shown that cellular pH microenvironment can modulate pre‐mRNA alternative splicing in vivo. In this study, we tested whether inhibitors of the Na+/H+ exchanger can modulate the exon 7 splicing of SMN2 mRNA

The viral death protein Apoptin interacts with Hippi, the protein interactor of Huntingtin-interacting protein 1.

Apoptin, a chicken anemia virus-encoded protein, induces apoptosis in human tumor cells but not in normal cells. The tumor-specific activity of Apoptin is correlated with its nuclear localization in tumor cells. In an attempt to elucidate the molecular mechanism of Apoptin-induced apoptosis, we identified human Hippi, the protein interactor and apoptosis co-mediator of Huntingtin interacting protein 1, as one of the Apoptin-associated proteins by yeast two-hybrid screen. We also demonstrated that Hippi could interact with Apoptin both in vitro and in human cells. Furthermore, subcellular localization studies showed that Hippi and Apoptin perfectly colocalized in the cytoplasm of normal human HEL cells, whereas in cancerous HeLa cells most Apoptin and Hippi were located separately in the nucleus and cytoplasm and, thus, showed only a modest colocalization. Mapping studies indicate that Hippi binds within the self-multimerization domain of Apoptin, and Apoptin binds to the C-terminal half of Hippi, including its death effector domain-like motif. Our results suggest that the Apoptin-Hippi interaction may play a role in the suppression of apoptosis in normal cells.

Transcribed pseudogene ψPPM1K generates endogenous siRNA to suppress oncogenic cell growth in hepatocellular carcinoma

Pseudogenes, especially those that are transcribed, may not be mere genomic fossils, but their biological significance remains unclear. Postulating that in the human genome, as in animal models, pseudogenes may function as gene regulators through generation of endo-siRNAs (esiRNAs), antisense RNAs or RNA decoys, we performed bioinformatic and subsequent experimental tests to explore esiRNA-mediated mechanisms of pseudogene involvement in oncogenesis. A genome-wide survey revealed a partial retrotranscript pseudogene ψPPM1K containing inverted repeats capable of folding into hairpin structures that can be processed into two esiRNAs; these esiRNAs potentially target many cellular genes, including NEK8. In 41 paired surgical specimens, we found significantly reduced expression of two predicted ψPPM1K-specific esiRNAs, and the cognate gene PPM1K, in hepatocellular carcinoma compared with matched non-tumour tissues, whereas the expression of target gene NEK8 was increased in tumours. Additionally, NEK8 and PPM1K were downregulated in stably transfected ψPPM1K-overexpressing cells, but not in cells transfected with an esiRNA1-deletion mutant of ψPPM1K. Furthermore, expression of NEK8 in ψPPM1K-transfected cells demonstrated that NEK8 can counteract the growth inhibitory effects of ψPPM1K. These findings indicate that a transcribed pseudogene can exert tumour-suppressor activity independent of its parental gene by generation of esiRNAs that regulate human cell growth.

ALPK1 genetic regulation and risk in relation to gout

BACKGROUND The present study investigated whether single nucleotide polymorphisms (SNPs) in the alpha-protein kinase 1 (ALPK1) gene are associated with gout in aboriginal and Han Chinese Taiwanese. METHODS A total of 1351 aborigines from the community (511 cases and 840 controls) and 511 Han people from hospital (104 cases and 407 controls) were recruited. SNPs in potentially functional regions of the 38 genes within 4q25 were identified and genotypes determined by direct sequencing. Quantitation of blood ALPK1 mRNA expression levels and luciferase assay of gout-associated rs231253 pGL3-SNP constructs cotransfected with hsa-miR-519e were examined. RESULTS We found that ALPK1 gene was the most determinant of gout. Three SNPs of rs11726117 M861T [C], rs231247 [G] and rs231253 [G] were most associated with gout risk [odd ratios (OR) ≥1.44, P ≤ 3.78 × 10(-6)) in aborigines. A replication set using Han people had risk at rs11726117 and rs231247 (OR ≥1.72, P ≤ 4.08 × 10(-3)). From pooled analysis (Breslow-Day test, P > 0.33) assuming an additive model, each increasing copy of the risk allele of rs11726117 [C], rs231247 [G] and rs231253 [G] showed significantly elevated OR for gout ≥1.42 (P ≥ 1.53 × 10(-6)). Consistently, the composite homozygous of linked 3 SNPs (versus wild-type, OR = 1.83, P = 8.21 × 10(-4)) had strong associations with ALPK1 mRNA expression. Luciferase showed reduced hybridization between hsa-miR-519e and construct carrying gout-associated rs231253 [G] than the wild-type [C] (P = 6.19 × 10(-4)). CONCLUSIONS Our study found that a newly identified ALPK1 gene can effectively interfere with microRNA target recognition and modulates the mRNA expression; and the varying distribution of the implicated SNPs among cases and controls in the two studied populations suggests a significant role in gout susceptibility.

A novel FKRP gene mutation in a Taiwanese patient with limb-girdle muscular dystrophy 2I

Limb-girdle muscular dystrophy (LGMD) is a group of hereditary muscle diseases with preferential involvement of the shoulder and pelvic girdle muscles, but with no pathognomonic features as in facioscapulohumeral and congenital muscular dystrophies. We report 18-year-old female with progressive shoulder and pelvic muscle weakness. She had marked restrictive pulmonary dysfunction. Echocardiogram showed mild decrease in ejection fraction of 52% (normal: >55%). She was first seen in our hospital at age 2 years with progressive proximal muscle weakness and elevated creatine kinase (CK) level to 15,290 IU/L, with what clinically and pathologically appeared to be steroid-responsive inflammatory myopathy. She responded dramatically to steroid therapy. Progressive proximal muscle weakness began again at age 8 years. Serum CK was 14,910 IU/L. She was wheelchair-bound by age 12. Muscle biopsy showed dystrophic changes without inflammation with reduced immunoreactivity to an antibody against sugar chain (VIA4-1) of alpha-dystroglycan. On laminin overlay assay, there was a nearly complete loss of laminin-binding activity to alpha-dystroglycan. Genetic analysis of fukutin-related protein (FKRP) gene revealed a novel compound heterozygous mutation of c.823C>T (p.R275C) and c.948delC, confirming the diagnosis of LGMD2I, the first reported case in East Asia.

Hydrogen peroxide decreases the survival rate of HeLa cells with stable knockdown of survival motor neuron protein.

The mutations of survival motor neuron (SMN) gene result in spinal muscular atrophy (SMA), a common neurodegenerative disease. Some of the motor neurons undergoing cell death is the predominant characteristic in SMA pathology. However, the viability and sensitivity to stresses of other cell types also need to be determined. In this article, we established HeLa stable cell line with inducible SMN knockdown to study its viability and sensitivity to oxidative stress. SMN knockdown in the HeLa stable cell line was induced by doxycycline. The proliferative and survival rates of SMN knockdown cells with or without hydrogen peroxide (H2O2) treatment were determined. Our results showed that the proliferative rate of SMN knockdown cells decreased only slightly compared with that of the cells without doxycycline treatment. In contrast, after H2O2 reached certain concentrations, the survival rate of SMN knockdown cells decreased significantly. Our data indicate that SMN knockdown alone is not critical to cell viability. However, when SMN knockdown cells are under stress, such as oxidative stress, their survival rate may significantly decrease. Our results will be helpful to prevent the detrimental effect caused by the cell death of non‐motor neurons under stress in SMA patients. In addition, the cell model we established can be used to study the mechanism and screen drugs to prevent the detrimental effects in cases of SMA disease.

Novel LMNA Mutation in a Taiwanese Family with Autosomal Dominant Emery-Dreifuss Muscular Dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by early-onset contractures, slowly progressive weakness, and muscle wasting in humeroperoneal muscles, and adult-onset cardiomyopathy with conduction block. We analyzed blood samples from an EDMD family, including a mother and two daughters, and found a novel mutation in codon 520 in exon 9 of the lamin A/C (LMNA) gene, resulting in a substitution of tryptophan (W) by glycine (G) in all three patients. The mother died after a stroke-like episode at the age of 43. The elder sister received pacemaker implantation, which improved symptoms of exercise intolerance and dizziness. These cases illustrate the necessity of correct diagnosis, evaluation, and follow-up of cardiac problems due to the wide clinical spectrum and high prevalence of cardiac conduction block in patients with autosomal dominant EDMD.

High Expression Level of Tra2-β1 Is Responsible for Increased SMN2 Exon 7 Inclusion in the Testis of SMA Mice

Spinal muscular atrophy (SMA) is an inherited neuromuscular disease caused by deletion or mutation of SMN1 gene. All SMA patients carry a nearly identical SMN2 gene, which produces low level of SMN protein due to mRNA exon 7 exclusion. Previously, we found that the testis of SMA mice (smn−/− SMN2) expresses high level of SMN2 full-length mRNA, indicating a testis-specific mechanism for SMN2 exon 7 inclusion. To elucidate the underlying mechanism, we established primary cultures of testis cells from SMA mice and analyzed them for SMN2 exon 7 splicing. We found that primary testis cells after a 2-hour culture still expressed high level of SMN2 full-length mRNA, but the level decreased after longer cultures. We then compared the protein levels of relevant splicing factors, and found that the level of Tra2-β1 also decreased during testis cell culture, correlated with SMN2 full-length mRNA downregulation. In addition, the testis of SMA mice expressed the highest level of Tra2-β1 among the many tissues examined. Furthermore, overexpression of Tra2-β1, but not ASF/SF2, increased SMN2 minigene exon 7 inclusion in primary testis cells and spinal cord neurons, whereas knockdown of Tra2-β1 decreased SMN2 exon 7 inclusion in primary testis cells of SMA mice. Therefore, our results indicate that high expression level of Tra2-β1 is responsible for increased SMN2 exon 7 inclusion in the testis of SMA mice. This study also suggests that the expression level of Tra2-β1 may be a modifying factor of SMA disease and a potential target for SMA treatment.