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Hoorntje ET, Bollen IA, Barge-Schaapveld DQ, van Tienen FH, Te Meerman GJ, Jansweijer JA, van Essen AJ, Volders PG, Constantinescu AA, van den Akker PC, van Spaendonck-Zwarts KY, Oldenburg RA, Marcelis CL, van der Smagt JJ, Hennekam EA, Vink A, Bootsma M, Aten E, Wilde AA, van den Wijngaard A, Broers JL, Jongbloed JD, van der Velden J, van den Berg MP, van Tintelen JP. Lamin A/C-Related Cardiac Disease: Late Onset With a Variable and Mild Phenotype in a Large Cohort of Patients With the Lamin A/C p.(Arg331Gln) Founder Mutation. ACTA ACUST UNITED AC 2018; 10:CIRCGENETICS.116.001631. [PMID: 28790152 DOI: 10.1161/circgenetics.116.001631] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Accepted: 05/08/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND Interpretation of missense variants can be especially difficult when the variant is also found in control populations. This is what we encountered for the LMNA c.992G>A (p.(Arg331Gln)) variant. Therefore, to evaluate the effect of this variant, we combined an evaluation of clinical data with functional experiments and morphological studies. METHODS AND RESULTS Clinical data of 23 probands and 35 family members carrying this variant were retrospectively collected. A time-to-event analysis was performed to compare the course of the disease with carriers of other LMNA mutations. Myocardial biopsies were studied with electron microscopy and by measuring force development of the sarcomeres. Morphology of the nuclear envelope was assessed with immunofluorescence on cultured fibroblasts. The phenotype in probands and family members was characterized by atrioventricular conduction disturbances (61% and 44%, respectively), supraventricular arrhythmias (69% and 52%, respectively), and dilated cardiomyopathy (74% and 14%, respectively). LMNA p.(Arg331Gln) carriers had a significantly better outcome regarding the composite end point (malignant ventricular arrhythmias, end-stage heart failure, or death) compared with carriers of other pathogenic LMNA mutations. A shared haplotype of 1 Mb around LMNA suggested a common founder. The combined logarithm of the odds score was 3.46. Force development in membrane-permeabilized cardiomyocytes was reduced because of decreased myofibril density. Structural nuclear LMNA-associated envelope abnormalities, that is, blebs, were confirmed by electron microscopy and immunofluorescence microscopy. CONCLUSIONS Clinical, morphological, functional, haplotype, and segregation data all indicate that LMNA p.(Arg331Gln) is a pathogenic founder mutation with a phenotype reminiscent of other LMNA mutations but with a more benign course.
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Affiliation(s)
| | - Ilse A Bollen
- For the author affiliations, please see the Appendix
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Aryan Vink
- For the author affiliations, please see the Appendix
| | | | - Emmelien Aten
- For the author affiliations, please see the Appendix
| | | | | | - Jos L Broers
- For the author affiliations, please see the Appendix
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Theunissen TEJ, Gerards M, Hellebrekers DMEI, van Tienen FH, Kamps R, Sallevelt SCEH, Hartog ENMMD, Scholte HR, Verdijk RM, Schoonderwoerd K, de Coo IFM, Szklarczyk R, Smeets HJM. Selection and Characterization of Palmitic Acid Responsive Patients with an OXPHOS Complex I Defect. Front Mol Neurosci 2017; 10:336. [PMID: 29093663 PMCID: PMC5651253 DOI: 10.3389/fnmol.2017.00336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/03/2017] [Indexed: 12/19/2022] Open
Abstract
Mitochondrial disorders are genetically and clinically heterogeneous, mainly affecting high energy-demanding organs due to impaired oxidative phosphorylation (OXPHOS). Currently, effective treatments for OXPHOS defects, with complex I deficiency being the most prevalent, are not available. Yet, clinical practice has shown that some complex I deficient patients benefit from a high-fat or ketogenic diet, but it is unclear how these therapeutic diets influence mitochondrial function and more importantly, which complex I patients could benefit from such treatment. Dietary studies in a complex I deficient patient with exercise intolerance showed increased muscle endurance on a high-fat diet compared to a high-carbohydrate diet. We performed whole-exome sequencing to characterize the genetic defect. A pathogenic homozygous p.G212V missense mutation was identified in the TMEM126B gene, encoding an early assembly factor of complex I. A complementation study in fibroblasts confirmed that the p.G212V mutation caused the complex I deficiency. The mechanism turned out to be an incomplete assembly of the peripheral arm of complex I, leading to a decrease in the amount of mature complex I. The patient clinically improved on a high-fat diet, which was supported by the 25% increase in maximal OXPHOS capacity in TMEM126B defective fibroblast by the saturated fatty acid palmitic acid, whereas oleic acid did not have any effect in those fibroblasts. Fibroblasts of other patients with a characterized complex I gene defect were tested in the same way. Patient fibroblasts with complex I defects in NDUFS7 and NDUFAF5 responded to palmitic acid, whereas ACAD9, NDUFA12, and NDUFV2 defects were non-responding. Although the data are too limited to draw a definite conclusion on the mechanism, there is a tendency that protein defects involved in early assembly complexes, improve with palmitic acid, whereas proteins defects involved in late assembly, do not. Our data show at a clinical and biochemical level that a high fat diet can be beneficial for complex I patients and that our cell line assay will be an easy tool for the selection of patients, who might potentially benefit from this therapeutic diet.
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Affiliation(s)
- Tom E J Theunissen
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands.,Department of Genetics and Cell Biology, School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Mike Gerards
- Maastricht Centre for Systems Biology, Maastricht University, Maastricht, Netherlands
| | | | - Florence H van Tienen
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Rick Kamps
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Suzanne C E H Sallevelt
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands
| | | | - Hans R Scholte
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, Netherlands
| | - Robert M Verdijk
- Department of Pathology, Erasmus Medical Center, Rotterdam, Netherlands
| | - Kees Schoonderwoerd
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, Netherlands
| | | | - Radek Szklarczyk
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Hubert J M Smeets
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, Netherlands.,Department of Genetics and Cell Biology, School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, Netherlands.,Maastricht Centre for Systems Biology, Maastricht University, Maastricht, Netherlands
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van Tienen FH, Lindsey PJ, van der Kallen CJ, Smeets HJ. Prolonged Nrf1 overexpression triggers adipocyte inflammation and insulin resistance. J Cell Biochem 2011; 111:1575-85. [PMID: 21053274 DOI: 10.1002/jcb.22889] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Adipose tissue is currently being recognized as an important endocrine organ, carrying defects in a number of metabolic diseases. Mitochondria play a key role in normal adipose tissue function and mitochondrial alterations can result in pathology, like lipodystrophy or type 2 diabetes. Although Pgc1α is regarded as the main regulator of mitochondrial function, downstream Nrf1 is the key regulator of mitochondrial biogenesis. Nrf1 is also involved in a wide range of other processes, including proliferation, innate immune response, and apoptosis. To determine transcriptional targets of Nrf1, 3T3-L1 preadipocytes were transfected with either pNrf1 or a control vector. Two days post-confluence, 3T3-L1 preadipocytes were allowed to differentiate. At day 8 of differentiation, Nrf1 overexpressing cells had an increased mtDNA copy number and reduced lipid content. This was not associated with an increased ATP production rate per cell. Using global gene expression analysis, we observed that Nrf1 overexpression stimulated cell proliferation, apoptosis, and cytokine expression. In addition, prolonged Nrf1 induced an adipokine expression profile of insulin resistant adipocytes. Nrf1 has a wide range of transcriptional targets, stimulators as well as inhibitors of adipose tissue functioning. Therefore, post-transcriptional regulation of Nrf1, or stimulating specific Nrf1 targets may be a more suitable approach for stimulating mitochondrial biogenesis and treating adipose tissue defects, instead of directly stimulating Nrf1 expression. In addition, our results show that short-term effects can drastically differ from long-term effects.
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Affiliation(s)
- Florence H van Tienen
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, The Netherlands
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