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Mitochondrial dysfunctions in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL).

ABSTRACT: Several inherited human diseases have been linked to mitochondrial aminoacyl-tRNA synthetases (mtARSs). Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a leukodystrophy caused by mutations in the DARS2 gene which encodes mitochondrial aspartyl-tRNA synthetase. As mitochondrial ARSs are key components of the mitochondrial translation apparatus, we investigated the effects of DARS2 mutations on mitochondrial functions and mitochondrial morphology in an LBSL patient. In fibroblasts from the patient with LBSL, biosynthesis of respiratory chain complex proteins encoded by mitochondrial DNA was decreased, while those encoded by nuclear DNA were not. Cellular oxygen consumption rates and respiratory control ratio were decreased in the LBSL patient; in addition, fragmentation of mitochondria was increased, while their tubular elongation and interconnectivity were decreased. Taken together, these findings suggest that DARS2 mutations impair translations of mitochondrial DNA-encoded respiratory chain complex proteins, consequently causing dysfunction of cellular respiration and impediment of mitochondrial dynamics, which highlights the role of mtARSs in the maintenance of normal mitochondrial bioenergetics and dynamics.

SUBMITTER: Lin TK

PROVIDER: S-EPMC6822708 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Mitochondrial dysfunctions in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL).

Lin Tsu-Kung TK Chang Yung-Yee YY Lin Hung-Yu HY Liou Chia-Wei CW Wang Pei-Wen PW Chuang Jiin-Haur JH Chen Shang-Der SD Chuang Yao-Chung YC Huang Sheng-Teng ST Hsu Te-Yao TY Peng Cheng-Huei CH Lan Min-Yu MY

PloS one 20191031 10

Several inherited human diseases have been linked to mitochondrial aminoacyl-tRNA synthetases (mtARSs). Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a leukodystrophy caused by mutations in the DARS2 gene which encodes mitochondrial aspartyl-tRNA synthetase. As mitochondrial ARSs are key components of the mitochondrial translation apparatus, we investigated the effects of DARS2 mutations on mitochondrial functions and mitochondrial morphology in a ...[more]

PMID: 31671122

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Project description:BackgroundLBSL is a mitochondrial disorder caused by mutations in the mitochondrial aspartyl-tRNA synthetase gene DARS2, resulting in a distinctive pattern on brain magnetic resonance imaging (MRI) and spectroscopy. Clinical presentation varies from severe infantile to chronic, slowly progressive neuronal deterioration in adolescents or adults. Most individuals with LBSL are compound heterozygous for one splicing defect in an intron 2 mutational hotspot and a second defect that could be a missense, non-sense, or splice site mutation or deletion resulting in decreased expression of the full-length protein.AimTo present a new family with two affected members with LBSL and report a novel DARS2 mutation.ResultsAn 8-year-old boy (Patient 1) was referred due to headaches and abnormal MRI, suggestive of LBSL. Genetic testing revealed a previously reported c.492 + 2 T > C mutation in the DARS2 gene. Sanger sequencing uncovered a novel variant c.228-17C > G in the intron 2 hotspot. Family studies found the same genetic changes in an asymptomatic 4-year-old younger brother (Patient 2), who was found on follow-up to have an abnormal MRI. mRNA extracted from patients' fibroblasts showed that the c.228-17C > G mutation caused skipping of exon 3 resulting in lower DARS2 mRNA level. Complete absence of DARS2 protein was also found in both patients.SummaryWe present a new family with two children affected with LBSL and describe a novel mutation in the DARS2 intron 2 hotspot. Despite findings of extensive white matter disease in the brain and spine, the proband in this family presented only with headaches, while the younger sibling, who also had extensive white matter changes, was asymptomatic. Our in-vitro results confirmed skipping of exon 3 in patients and family members carrying the intron 2 variant, which is consistent with previous reported mutations in intron 2 hotspots. DARS2 mRNA and protein levels were also reduced in both patients, further supporting the pathogenicity of the novel variant.

Project description:BackgroundEarly infratentorial and focal spinal cord lesions on magnetic resonance imaging (MRI) are associated with a higher risk of long-term disability in patients with multiple sclerosis (MS). The role of diffuse spinal cord lesions remains less understood. The purpose of this study was to evaluate focal and especially diffuse spinal cord lesions in patients with early relapsing-remitting MS and their association with intracranial lesion topography, global and regional brain volume, and spinal cord volume.MethodsWe investigated 58 MS patients with short disease duration (< 5 years) from a large academic MS center and 58 healthy controls matched for age and sex. Brain, spinal cord, and intracranial lesion volumes were compared among patients with- and without diffuse spinal cord lesions and controls. Binary logistic regression models were used to analyse the association between the volume and topology of intracranial lesions and the presence of focal and diffuse spinal cord lesions.ResultsWe found spinal cord involvement in 75% of the patients (43/58), including diffuse changes in 41.4% (24/58). Patients with diffuse spinal cord changes exhibited higher volumes of brainstem lesion volume (p = 0.008). The presence of at least one brainstem lesion was associated with a higher probability of the presence of diffuse spinal cord lesions (odds ratio 47.1; 95% confidence interval 6.9-321.6 p < 0.001) as opposed to focal spinal cord lesions (odds ratio 0.22; p = 0.320). Patients with diffuse spinal cord lesions had a lower thalamus volume compared to patients without diffuse spinal cord lesions (p = 0.007) or healthy controls (p = 0.002).ConclusionsDiffuse spinal cord lesions are associated with the presence of brainstem lesions and with a lower volume of the thalamus. This association was not found in patients with focal spinal cord lesions. If confirmed, thalamic atrophy in patients with diffuse lesions could increase our knowledge on the worse prognosis in patients with infratentorial and SC lesions.

Project description:BACKGROUND:KARS encodes lysyl- transfer ribonucleic acid (tRNA) synthetase, which catalyzes the aminoacylation of tRNA-Lys in the cytoplasm and mitochondria. Eleven families/sporadic patients and 16 different mutations in KARS have been reported to date. The associated clinical phenotype is heterogeneous ranging from early onset encephalopathy to isolated peripheral neuropathy or nonsyndromic hearing impairment. Recently additional presentations including leukoencephalopathy as predominant cerebral involvement or cardiomyopathy, isolated or associated with muscular and cerebral involvement, have been reported. A progressive Leukoencephalopathy with brainstem and spinal cord calcifications was previously described in a singleton patient and in two siblings, without the identification of the genetic cause. We reported here about a new severe phenotype associated with biallelic KARS mutations and sharing some common points with the other already reported phenotypes, but with a distinct clinical and neuroimaging picture. Review of KARS mutant patients published to date will be also discussed. RESULTS:Herein, we report the clinical, biochemical and molecular findings of 2 unreported Italian patients affected by developmental delay, acquired microcephaly, spastic tetraparesis, epilepsy, sensory-neural hypoacusia, visual impairment, microcytic hypochromic anaemia and signs of hepatic dysfunction. MRI pattern in our patients was characterized by progressive diffuse leukoencephalopathy and calcifications extending in cerebral, brainstem and cerebellar white matter, with spinal cord involvement. Genetic analysis performed on these 2 patients and in one subject previously described with similar MRI pattern revealed the presence of biallelic mutations in KARS in all 3 subjects. CONCLUSIONS:With our report we define the molecular basis of the previously described Leukoencephalopathy with Brainstem and Spinal cord Calcification widening the spectrum of KARS related disorders, particularly in childhood onset disease suggestive for mitochondrial impairment. The review of previous cases does not suggest a strict and univocal genotype/phenotype correlation for this highly heterogeneous entity. Moreover, our cases confirm the usefulness of search for common brain and spine MR imaging pattern and of broad genetic screening, in syndromes clinically resembling mitochondrial disorders in spite of normal biochemical assay.

Project description:The spinal cord after injury shows altered transcription in numerous genes. We tested in a pilot study whether the nucleus raphé magnus, a descending serotonergic brainstem region whose stimulation improves recovery after incomplete spinal cord injury (SCI), can influence these transcriptional changes. Rats received 2 h of low-frequency electrical stimulation in the raphé magnus 3 days after an impact contusion at segment T8. Comparison groups lacked injuries or activated stimulators or both. Immediately following stimulation, spinal cords were extracted, their RNA transcriptome sequenced, and differential gene expression quantified. Confirming many previous studies, injury primarily increased inflammatory and immune transcripts and decreased those related to lipid and cholesterol synthesis and neuronal signaling. Stimulation plus injury, contrasted with injury alone, caused significant changes in 43 transcripts (39 increases, 4 decreases), all protein-coding. Injury itself decreased only four of these 43 transcripts, all reversed by stimulation, and increased none of them. The non-specific 5-HT7 receptor antagonist pimozide reversed 25 of the 43 changes. Stimulation in intact rats principally caused decreases in transcripts related to oxidative phosphorylation, none of which were altered by stimulation in injury. Gene ontology (biological process) annotations comparing stimulation with either no stimulation or pimozide treatment in injured rats highlighted defense responses to lipopolysaccharides and microorganisms, and also erythrocyte development and oxygen transport (possibly yielding cellular oxidant detoxification). Connectivity maps of human orthologous genes generated in the CLUE database of perturbagen-response transcriptional signatures showed that drug classes whose effects in injured rats most closely resembled stimulation without pimozide include peroxisome proliferator-activated receptor agonists and angiotensin receptor blockers, which are reportedly beneficial in SCI. Thus the initial transcriptional response of the injured spinal cord to raphé magnus stimulation is upregulation of genes that in various ways are mostly protective, some probably located in recently arrived myeloid cells.

Dataset Information

Mitochondrial dysfunctions in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL).

Publications

Mitochondrial dysfunctions in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL).

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