Transcriptomic profiling of TK2 deficient human skeletal muscle suggests a role for the p53 signalling pathway and identifies growth and differentiation factor-15 as a potential novel biomarker for mitochondrial myopathies

BACKGROUND: Mutations in the gene encoding thymidine kinase 2 (TK2) result in the myopathic form of mitochondrial DNA depletion syndrome which is a mitochondrial encephalomyopathy presenting in children. In order to unveil some of the mechanisms involved in this pathology and to identify potential biomarkers and therapeutic targets we have investigated the gene expression profile of human skeletal muscle deficient for TK2 using cDNA microarrays. RESULTS: We have analysed the whole transcriptome of skeletal muscle from patients with TK2 mutations and compared it to normal muscle and to muscle from patients with other mitochondrial myopathies. We have identified a set of over 700 genes which are differentially expressed in TK2 deficient muscle. Bioinformatics analysis reveals important changes in muscle metabolism, in particular, in glucose and glycogen utilisation, and activation of the starvation response which affects aminoacid and lipid metabolism. We have identified those transcriptional regulators which are likely to be responsible for the observed changes in gene expression. CONCLUSION: Our data point towards the tumor suppressor p53 as the regulator at the centre of a network of genes which are responsible for a coordinated response to TK2 mutations which involves inflammation, activation of muscle cell death by apoptosis and induction of growth and differentiation factor 15 (GDF-15) in muscle and serum. We propose that GDF-15 may represent a potential novel biomarker for mitochondrial dysfunction although further studies are required

Etanercept-Induced Myelopathy in a Pediatric Case of Blau Syndrome

Blau syndrome is a rare autoinflammatory disorder within the group of pediatric granulomatous diseases. Mutations in nucleotide-binding oligomerization domain 2 (NOD2/CARD15) are responsible for this condition, which has an autosomal dominant pattern of inheritance and variable expressivity. The clinical picture includes arthritis, uveitis, skin rash, and granulomatous inflammation. Central nervous system involvement is seldom reported, although some isolated cases of seizures, neurosensorial hearing loss, and transient cranial nerve palsy have been described. Treatment consists of nonsteroidal anti-inflammatory drugs, corticosteroids, and immunosuppressive agents, among which anti-tumor-necrosis-factor-alpha (TNF-α) biologic agents, such as etanercept, play an important role. Among the major adverse effects of TNF-α inhibitors, demyelinating disease, multiple sclerosis, and acute transverse myelitis have been reported in adults. We describe a case of pediatric Blau syndrome affected by etanercept-induced myelopathy, manifesting as a clinical syndrome of transverse myelitis. The patient experienced rapid recovery after etanercept was discontinued. To our knowledge, this is the first such case reported in the literature and, possibly, the one with the latest onset, following 8 years of treatment. We discuss the etiopathogenic mechanisms of this reaction and possible explanations for the imaging findings

Prognostic value of X-chromosome inactivation in symptomatic female carriers of dystrophinopathy

<p>Abstract</p> <p>Background</p> <p>Between 8% and 22% of female carriers of <it>DMD</it> mutations exhibit clinical symptoms of variable severity. Development of symptoms in <it>DMD</it> mutation carriers without chromosomal rearrangements has been attributed to skewed X-chromosome inactivation (XCI) favouring predominant expression of the <it>DMD</it> mutant allele. However the prognostic use of XCI analysis is controversial. We aimed to evaluate the correlation between X-chromosome inactivation and development of clinical symptoms in a series of symptomatic female carriers of dystrophinopathy.</p> <p>Methods</p> <p>We reviewed the clinical, pathological and genetic features of twenty-four symptomatic carriers covering a wide spectrum of clinical phenotypes. <it>DMD</it> gene analysis was performed using MLPA and whole gene sequencing in blood DNA and muscle cDNA. Blood and muscle DNA was used for X-chromosome inactivation (XCI) analysis thought the <it>AR</it> methylation assay in symptomatic carriers and their female relatives, asymptomatic carriers as well as non-carrier females.</p> <p>Results</p> <p>Symptomatic carriers exhibited 49.2% more skewed XCI profiles than asymptomatic carriers. The extent of XCI skewing in blood tended to increase in line with the severity of muscle symptoms. Skewed XCI patterns were found in at least one first-degree female relative in 78.6% of symptomatic carrier families. No mutations altering XCI in the <it>XIST</it> gene promoter were found.</p> <p>Conclusions</p> <p>Skewed XCI is in many cases familial inherited. The extent of XCI skewing is related to phenotype severity. However, the assessment of XCI by means of the <it>AR</it> methylation assay has a poor prognostic value, probably because the methylation status of the <it>AR</it> gene in muscle may not reflect in all cases the methylation status of the <it>DMD</it> gene.</p

Prognostic value of X-chromosome inactivation in symptomatic female carriers of dystrophinopathy

Background: Between 8% and 22% of female carriers of DMD mutations exhibit clinical symptoms of variable severity. Development of symptoms in DMD mutation carriers without chromosomal rearrangements has been attributed to skewed X-chromosome inactivation (XCI) favouring predominant expression of the DMD mutant allele. However the prognostic use of XCI analysis is controversial. We aimed to evaluate the correlation between X-chromosome inactivation and development of clinical symptoms in a series of symptomatic female carriers of dystrophinopathy. Methods: We reviewed the clinical, pathological and genetic features of twenty-four symptomatic carriers covering a wide spectrum of clinical phenotypes. DMD gene analysis was performed using MLPA and whole gene sequencing in blood DNA and muscle cDNA. Blood and muscle DNA was used for X-chromosome inactivation (XCI) analysis thought the AR methylation assay in symptomatic carriers and their female relatives, asymptomatic carriers as well as non-carrier females. Results: Symptomatic carriers exhibited 49.2% more skewed XCI profiles than asymptomatic carriers. The extent of XCI skewing in blood tended to increase in line with the severity of muscle symptoms. Skewed XCI patterns were found in at least one first-degree female relative in 78.6% of symptomatic carrier families. No mutations altering XCI in the XIST gene promoter were found. Conclusions: Skewed XCI is in many cases familial inherited. The extent of XCI skewing is related to phenotype severity. However, the assessment of XCI by means of the AR methylation assay has a poor prognostic value, probably because the methylation status of the AR gene in muscle may not reflect in all cases the methylation status of the DMD gene

Transcriptomic profiling of TK2 deficient human skeletal muscle suggests a role for the p53 signalling pathway and identifies growth and differentiation factor-15 as a potential novel biomarker for mitochondrial myopathies

BACKGROUND: Mutations in the gene encoding thymidine kinase 2 (TK2) result in the myopathic form of mitochondrial DNA depletion syndrome which is a mitochondrial encephalomyopathy presenting in children. In order to unveil some of the mechanisms involved in this pathology and to identify potential biomarkers and therapeutic targets we have investigated the gene expression profile of human skeletal muscle deficient for TK2 using cDNA microarrays. RESULTS: We have analysed the whole transcriptome of skeletal muscle from patients with TK2 mutations and compared it to normal muscle and to muscle from patients with other mitochondrial myopathies. We have identified a set of over 700 genes which are differentially expressed in TK2 deficient muscle. Bioinformatics analysis reveals important changes in muscle metabolism, in particular, in glucose and glycogen utilisation, and activation of the starvation response which affects aminoacid and lipid metabolism. We have identified those transcriptional regulators which are likely to be responsible for the observed changes in gene expression. CONCLUSION: Our data point towards the tumor suppressor p53 as the regulator at the centre of a network of genes which are responsible for a coordinated response to TK2 mutations which involves inflammation, activation of muscle cell death by apoptosis and induction of growth and differentiation factor 15 (GDF-15) in muscle and serum. We propose that GDF-15 may represent a potential novel biomarker for mitochondrial dysfunction although further studies are required

Transcriptomic profiling of TK2 deficient human skeletal muscle suggests a role for the p53 signalling pathway and identifies growth and differentiation factor-15 as a potential novel biomarker for mitochondrial myopathies

BACKGROUND: Mutations in the gene encoding thymidine kinase 2 (TK2) result in the myopathic form of mitochondrial DNA depletion syndrome which is a mitochondrial encephalomyopathy presenting in children. In order to unveil some of the mechanisms involved in this pathology and to identify potential biomarkers and therapeutic targets we have investigated the gene expression profile of human skeletal muscle deficient for TK2 using cDNA microarrays. RESULTS: We have analysed the whole transcriptome of skeletal muscle from patients with TK2 mutations and compared it to normal muscle and to muscle from patients with other mitochondrial myopathies. We have identified a set of over 700 genes which are differentially expressed in TK2 deficient muscle. Bioinformatics analysis reveals important changes in muscle metabolism, in particular, in glucose and glycogen utilisation, and activation of the starvation response which affects aminoacid and lipid metabolism. We have identified those transcriptional regulators which are likely to be responsible for the observed changes in gene expression. CONCLUSION: Our data point towards the tumor suppressor p53 as the regulator at the centre of a network of genes which are responsible for a coordinated response to TK2 mutations which involves inflammation, activation of muscle cell death by apoptosis and induction of growth and differentiation factor 15 (GDF-15) in muscle and serum. We propose that GDF-15 may represent a potential novel biomarker for mitochondrial dysfunction although further studies are required