The Common miRNA Signatures Associated with Mitochondrial Dysfunction in Different Muscular Dystrophies

Secondary mitochondrial damage in skeletal muscles is a common feature of different neuromuscular disorders, which fall outside the mitochondrial cytopathies. The common cause of mitochondrial dysfunction and structural changes in skeletal muscle tissue remains to be discovered. Although they are associated with different clinical, genetic, and pathologic backgrounds, the pathomechanisms underlying neuromuscular disorders might be attributed to the complex interaction and cross talk between mitochondria and the associated miRNAs. This study aimed to identify the common miRNA signatures that are associated with mitochondrial damage in different muscular dystrophies (MDs; Duchenne muscular dystrophy, megaconial congenital muscular dystrophy, Ullrich congenital muscular dystrophy, and α-dystroglycanopathy). The miRNome profiles of skeletal muscle biopsies acquired from four different MD groups and control individuals were analyzed by miRNA microarray. We identified 17 common up-regulated miRNAs in all of the tested MD groups. A specific bioinformatics approach identified 10 of these miRNAs to be specifically related to the mitochondrial pathways. Six miRNAs, miR-134-5p, miR-199a-5p, miR-382-5p, miR-409-3p, miR-497-5p, and miR-708-5p, were associated with the top four mitochondrial pathways and were thus selected as priority candidates for further validation by quantitative real-time PCR analysis. We demonstrate, for the first time, common up-regulated miRNAs that are associated with mitochondrial damage in different MD groups, therefore contributing to the pathophysiology. Our findings may open a new gate toward therapeutics.

Establishment of primary myoblast cell cultures from cryopreserved skeletal muscle biopsies to serve as a tool in related research & development studies

BACKGROUND

Primary myoblast cell cultures display the phenotypic characteristics and genetic defects of the donor tissue and represent an in vitro model system reflecting the disease pathology. They have been generated only from freshly harvested tissue biopsies. Here, we describe a novel technique to establish myoblast cell cultures from cryopreserved skeletal muscle biopsy tissues that are useful for diagnostic and research purposes.

METHODS AND RESULTS

This protocol was performed on seven gradually frozen muscle biopsy specimens from various neuromuscular disorders that were stored in dimethylsulfoxide (DMSO)-supplemented freezing media at -80 °C for up to one year. After storage for varying periods of time, primary myoblast cultures were successfully established from all cryopreserved biopsy tissues without any chromosomal abnormality. Desmin immunoreactivity confirmed that the cell cultures contained >90% pure myoblasts. The myoblasts differentiated into multinucleated myotubes successfully. Furthermore, there were no statistically significant differences in cell viability, metabolic activity, population doubling time, and myocyte enhancer factor 2 (MEF2C) expression between cell cultures established from freshly harvested and one year-stored frozen tissue specimens.

CONCLUSIONS

This protocol opens up new horizons for basic research and the pre-clinical studies of novel therapies by using cryopreserved skeletal muscle biopsies stored under suitable conditions in tissue banks.

The altered expression of perineuronal net elements during neural differentiation

Background

Perineuronal nets (PNNs), which are localized around neurons during development, are specialized forms of neural extracellular matrix with neuroprotective and plasticity-regulating roles. Hyaluronan and proteoglycan link protein 1 (HAPLN1), tenascin-R (TNR) and aggrecan (ACAN) are key elements of PNNs. In diseases characterized by neuritogenesis defects, the expression of these proteins is known to be downregulated, suggesting that PNNs may have a role in neural differentiation.

Methods

In this study, the mRNA and protein levels of HAPLN1, TNR and ACAN were determined and compared at specific time points of neural differentiation. We used PC12 cells as the in vitro model because they reflect this developmental process.

Results

On day 7, the HAPLN1 mRNA level showed a 2.9-fold increase compared to the non-differentiated state. However, the cellular HAPLN1 protein level showed a decrease, indicating that the protein may have roles in neural differentiation, and may be secreted during the early period of differentiation. By contrast, TNR mRNA and protein levels remained unchanged, and the amount of cellular ACAN protein showed a 3.7-fold increase at day 7. These results suggest that ACAN may be secreted after day 7, possibly due to its large amount of post-translational modifications.

Conclusions

Our results provide preliminary data on the expression of PNN elements during neural differentiation. Further investigations will be performed on the role of these elements in neurological disease models.

Transcript levels of plastin 3 and neuritin 1 modifier genes in spinal muscular atrophy siblings

BACKGROUND

In single gene disorders, patients with the same genotype may have variations in severity. One of the main factors affecting disease severity is modifier genes. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by degeneration of alpha motor neurons. Plastin 3 (PLS3) is a phenotypic modifier of SMA, and neuritin 1 (NRN1) has also been suggested as a possible modifier gene. The aim of the present study was therefore to analyze PLS3 and NRN1 expression in SMA siblings in four families.

METHODS

The study group consisted of four SMA families with seven with discordant phenotype and two affected siblings. Total RNA was isolated from whole blood. PLS3 and NRN1 expression was analyzed on quantitative real-time polymerase chain reaction.

RESULTS

In family 1 only NRN1 expression was increased in the mildly affected sister. In family 2 only PLS3 had a modifier effect. Family 3, which had type III siblings with identical clinical phenotypes, had similar PLS3 expression between the siblings but no NRN1 expression. In family 4, neither PLS3 nor NRN1 had any correlation with severity.

CONCLUSION

On analysis of the expression of NRN1 in SMA patients for the first time, NRN1 could be a potential modifier gene. PLS3 expression does not always modify SMA phenotype. In patients with no modifier effect of known genes, genome sequencing and transcriptome analysis are promising for the identification of novel modifiers and understanding of SMA pathophysiology.

Carboxylic acid derivatives of histone deacetylase inhibitors induce full length SMN2 transcripts: a promising target for spinal muscular atrophy therapeutics

INTRODUCTION

Proximal spinal muscular atrophy (SMA) is a common autosomal recessively inherited neuromuscular disorder. It is caused by homozygous absence of the survival motor neuron 1 (SMN1) gene. SMN2, which modulates the severity of the disease, represents a major target for therapy. The aim of this study was to investigate whether SMN2 expression can be increased by caffeic acid, chlorogenic acid and curcumin, which are designed by modifications of the carboxylic acid class of histone deacetylase (HDAC) inhibitors.

MATERIAL AND METHODS

Using quantitative real-time PCR, we analysed the levels of full-length SMN2 and Δ7SMN2 mRNA. We performed LDH cytotoxicity assay to analyse whether SMN2 activating concentrations of caffeic acid, chlorogenic acid and curcumin were cytotoxic to fibroblasts.

RESULTS

We found that caffeic acid and curcumin were more efficient than chlorogenic acid and increased full-length SMN2 mRNA levels 1.5 and 1.7-fold, respectively. Δ7SMN2 mRNA levels were measured to investigate alternative splicing of exon 7. We also found that cytotoxicity was not observed at SMN2 activating concentrations.

CONCLUSIONS

Our data suggest that carboxylic acid derivatives including phenolic structure and symmetry could be a good candidate for SMA treatment.

The relationship between vitamin D receptor gene polymorphisms and bone density, osteocalcin level and growth in adolescents

BACKGROUND/OBJECTIVE

The relationship between vitamin D receptor gene polymorphisms and bone density, osteocalcin and growth was investigated.

SUBJECTS

Eighty eight adolescents aged between 8-15, with no history of illness influencing the level of bone parameters, were examined in our study.

METHODS

Areal BMD for lumbar spine (L1-4) was assessed by dual energy X-ray absorptiometry (DEXA). Height and weight were measured on the day of the DEXA scans. Serum osteocalcin level was determined by using ELISA method. DNA was extracted from white blood cells, amplified by the polymerase chain reaction (PCR) and the polymorphic sites were analyzed by using ApaI, TaqI and FokI restriction enzymes.

RESULTS

The most frequent genotypes were FF (% 54.6), Aa (% 53.4) and Tt (% 48.8). No significant relationship was found between VDR genotypes and areal BMD, osteocalcin level or growth in either sex. But there was a strong tendency for a higher BMD at the lumbar spine of TT and AA genotypes compared to tt and Aa genotypes. The children with TT genotype were taller and heavier than the children with tt genotype

CONCLUSION

Our results suggest that VDR gene TaqI polymorphism may be associated with body weight and bone mass, but more studies with larger groups should be conducted.

Polymorphisms of vitamin D receptor gene in Turkish familial psoriasis patients

Psoriasis is characterized by hyperproliferation and abnormal differentiation of keratinocytes, and inflammation. 1,25-Dihydroxyvitamin D3, which is used for the treatment of psoriasis, binds to vitamin D receptor (VDR) and modulates gene transcription. We analyzed VDR gene FokI, ApaI and TaqI polymorphisms in 51 Turkish familial psoriasis patients (psoriasis vulgaris and psoriatic arthritis) and 100 healthy subjects, and evaluated the correlation between VDR genotypes and calcipotriol response. We found that the TT genotype was significantly more frequent in the patients than in the controls (51 vs. 35%: P < or = 0.05). The frequency of the T allele in patients was also significantly higher than that in the controls (73.5 vs. 59.5%: P < or = 0.025). In psoriatic arthritis patients, T allele frequency was even higher (91.7%: P < or = 0.05). With regard to response to calcipotriol treatment, in nonresponsive patients TT genotype and T allele frequencies were higher than they were in the controls (63.6 vs. 35%: P < or = 0.025, 81.8 vs. 59.5%: P < or = 0.01, respectively). In conclusion, we show that VDR gene TaqI polymorphism is associated with familial psoriasis in the Turkish population. We also demonstrate that VDR gene polymorphisms may play a role in partial resistance to calcipotriol therapy.