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Publications (10 of 11) Show all publications
Tazelaar, G. H. .., Hop, P. J., Seelen, M., van Vugt, J. J. .., van Rheenen, W., Kool, L., . . . van Es, M. A. (2023). Whole genome sequencing analysis reveals post-zygotic mutation variability in monozygotic twins discordant for amyotrophic lateral sclerosis. Neurobiology of Aging, 122, 76-87
Open this publication in new window or tab >>Whole genome sequencing analysis reveals post-zygotic mutation variability in monozygotic twins discordant for amyotrophic lateral sclerosis
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2023 (English)In: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 122, p. 76-87Article in journal (Refereed) Published
Abstract [en]

Amyotrophic lateral sclerosis is a heterogeneous, fatal neurodegenerative disease, characterized by motor neuron loss and in 50% of cases also by cognitive and/or behavioral changes. Mendelian forms of ALS comprise approximately 10-15% of cases. The majority is however considered sporadic, but also with a high contribution of genetic risk factors. To explore the contribution of somatic mutations and/or epigenetic changes to disease risk, we performed whole genome sequencing and methylation analyses using samples from multiple tissues on a cohort of 26 monozygotic twins discordant for ALS, followed by in-depth validation and replication experiments. The results of these analyses implicate several mechanisms in ALS pathophysiology, which include a role for de novo mutations, defects in DNA damage repair and accelerated aging.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Amyotrophic Lateral Sclerosis, Genetic modifiers, Post-zygotic mutations, Repeat expansions
National Category
Neurology Neurosciences
Identifiers
urn:nbn:se:umu:diva-201947 (URN)10.1016/j.neurobiolaging.2022.11.010 (DOI)000906927400008 ()2-s2.0-85143864996 (Scopus ID)
Funder
The Swedish Brain Foundation, 2012-0262The Swedish Brain Foundation, 2012- 0305The Swedish Brain Foundation, 2013-0279The Swedish Brain Foundation, 2016-0303Swedish Research Council, 2012-3167Swedish Research Council, 2017-03100Knut and Alice Wallenberg Foundation, 2012.0091Knut and Alice Wallenberg Foundation, 2014.0305Swedish Association of Persons with Neurological DisabilitiesTorsten Söderbergs stiftelseRagnar Söderbergs stiftelseRegion VästerbottenKonung Gustaf V:s och Drottning Victorias Frimurarestiftelse
Available from: 2022-12-29 Created: 2022-12-29 Last updated: 2023-09-05Bibliographically approved
Müller, K., Oh, K.-W., Nordin, A., Panthi, S., Kim, S. H., Nordin, F., . . . Andersen, P. M. (2022). De novo mutations in SOD1 are a cause of ALS. Journal of Neurology, Neurosurgery and Psychiatry, 93, 201-206
Open this publication in new window or tab >>De novo mutations in SOD1 are a cause of ALS
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2022 (English)In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 93, p. 201-206Article in journal (Refereed) Published
Abstract [en]

Objective: The only identified cause of amyotrophic lateral sclerosis (ALS) are mutations in a number of genes found in familial cases but also in sporadic cases. De novo mutations occurring in a parental gonadal cell, in the zygote or postzygotic during embryonal development can result in an apparently sporadic/isolated case of ALS later in life. We searched for de novo mutations in SOD1 as a cause of ALS.

Methods: We analysed peripheral-blood exome, genome and Sanger sequencing to identify deleterious mutations in SOD1 in 4000 ALS patients from Germany, South Korea and Sweden. Parental kinship was confirmed using highly polymorphic microsatellite markers across the genome. Medical genealogical and clinical data were reviewed and compared with the literature.

Results: We identified four sporadic ALS cases with de novo mutations in SOD1. They aggregate in hot-spot codons earlier found mutated in familial cases. Their phenotypes match closely what has earlier been reported in familial cases with pathogenic mutations in SOD1. We also encountered familial cases where de novo mutational events in recent generations may have been involved.

Conclusions:  De novo mutations are a cause of sporadic ALS and may also be underpinning smaller families with few affected ALS cases. It was not possible to ascertain if the origin of the de novo mutations was parental germline, zygotic or postzygotic during embryonal development. All ALS patients should be offered genetic counselling and genetic screening, the challenges of variant interpretation do not outweigh the potential benefits including earlier confirmed diagnosis and possible bespoken therapy.

Data availability statement: Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information.

Place, publisher, year, edition, pages
BMJ Publishing Group Ltd, 2022
Keywords
Psychiatry and Mental health, Clinical Neurology, Surgery
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-189488 (URN)10.1136/jnnp-2021-327520 (DOI)000722681900001 ()2-s2.0-85120353083 (Scopus ID)
Funder
Konung Gustaf V:s och Drottning Victorias FrimurarestiftelseSwedish Association of Persons with Neurological DisabilitiesKnut and Alice Wallenberg Foundation, 2012.0091, 2014.0305, 2020.0232The Swedish Brain Foundation, 2012-0262, 2012-0305, 2013-0279, 2016-0303, 2020-0353Swedish Research Council, 2012-3167, 2017-03100Region Västerbotten
Available from: 2021-11-12 Created: 2021-11-12 Last updated: 2023-03-24Bibliographically approved
van Rheenen, W., van der Spek, R. A. A., Bakker, M. K., van Vugt, J. J. F., Hop, P. J., Zwamborn, R. A. J., . . . Veldink, J. H. (2021). Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology. Nature Genetics, 53(12), 1636-1648
Open this publication in new window or tab >>Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology
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2021 (English)In: Nature Genetics, ISSN 1061-4036, E-ISSN 1546-1718, Vol. 53, no 12, p. 1636-1648Article in journal (Refereed) Published
Abstract [en]

A cross-ancestry genome-wide association meta-analysis of amyotrophic lateral sclerosis (ALS) including 29,612 patients with ALS and 122,656 controls identifies 15 risk loci with distinct genetic architectures and neuron-specific biology. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a lifetime risk of one in 350 people and an unmet need for disease-modifying therapies. We conducted a cross-ancestry genome-wide association study (GWAS) including 29,612 patients with ALS and 122,656 controls, which identified 15 risk loci. When combined with 8,953 individuals with whole-genome sequencing (6,538 patients, 2,415 controls) and a large cortex-derived expression quantitative trait locus (eQTL) dataset (MetaBrain), analyses revealed locus-specific genetic architectures in which we prioritized genes either through rare variants, short tandem repeats or regulatory effects. ALS-associated risk loci were shared with multiple traits within the neurodegenerative spectrum but with distinct enrichment patterns across brain regions and cell types. Of the environmental and lifestyle risk factors obtained from the literature, Mendelian randomization analyses indicated a causal role for high cholesterol levels. The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons.

Place, publisher, year, edition, pages
Nature Publishing Group, 2021
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-191609 (URN)10.1038/s41588-021-00973-1 (DOI)000727387900007 ()34873335 (PubMedID)2-s2.0-85122277130 (Scopus ID)
Available from: 2022-01-20 Created: 2022-01-20 Last updated: 2022-01-20Bibliographically approved
Rawcliffe, D. F. R., Österman, L., Nordin, A. & Holmberg, M. (2018). PTBP1 acts as a dominant repressor of the aberrant tissue-specific splicing of ISCU in hereditary myopathy with lactic acidosis. Molecular Genetics & Genomic Medicine, 6(6), 887-897
Open this publication in new window or tab >>PTBP1 acts as a dominant repressor of the aberrant tissue-specific splicing of ISCU in hereditary myopathy with lactic acidosis
2018 (English)In: Molecular Genetics & Genomic Medicine, ISSN 2324-9269, Vol. 6, no 6, p. 887-897Article in journal (Refereed) Published
Abstract [en]

Background: Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intron mutation in the iron-sulfur cluster assembly (ISCU) gene. The mutation results in aberrant splicing, where part of the intron is retained in the final mRNA transcript, giving rise to a truncated nonfunctional ISCU protein. Using an ISCU mini-gene system, we have previously shown that PTBP1 can act as a repressor of the mis-splicing of ISCU, where overexpression of PTBP1 resulted in a decrease of the incorrect splicing. In this study, we wanted to, in more detail, analyze the role of PTBP1 in the regulation of endogenous ISCU mis-splicing.

Methods: Overexpression and knockdown of PTBP1 was performed in myoblasts from two HML patients and a healthy control. Quantification of ISCU mis-splicing was done by qRTPCR. Biotinylated ISCU RNA, representing wildtype and mutant intron sequence, was used in a pull-down assay with nuclear extracts from myoblasts. Levels of PTBP1 in human cell lines and mice tissues were analyzed by qRTPCR and western blot.

Results: PTBP1 overexpression in HML patient myoblasts resulted in a substantial decrease of ISCU mis-splicing while knockdown of PTBP1 resulted in a drastic increase. The effect could be observed in both patient and control myoblasts. We could also show that PTBP1 interacts with both the mutant and wild-type ISCU intron sequence, but with a higher affinity to the mutant sequence. Furthermore, low levels of PTBP1 among examined mouse tissues correlated with high levels of incorrect splicing of ISCU.

Conclusion: Our results show that PTBP1 acts as a dominant repressor of ISCU mis-splicing. We also show an inverse correlation between the levels of PTBP1 and ISCU mis-splicing, suggesting that the high level of mis-splicing in the skeletal muscle is primarily due to the low levels of PTBP1.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
alternative splicing, hereditary myopathy, ISCU, PTBP1
National Category
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-153102 (URN)10.1002/mgg3.413 (DOI)000454205500003 ()30209894 (PubMedID)2-s2.0-85053400372 (Scopus ID)
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2019-01-14Bibliographically approved
Nordin, A., Akimoto, C., Wuolikainen, A., Alstermark, H., Forsberg, K., Baumann, P., . . . Andersen, P. M. (2017). Sequence variations in C9orf72 downstream of the hexanucleotide repeat region and its effect on repeat-primed PCR interpretation: a large multinational screening study. Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 18(3-4), 256-264
Open this publication in new window or tab >>Sequence variations in C9orf72 downstream of the hexanucleotide repeat region and its effect on repeat-primed PCR interpretation: a large multinational screening study
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2017 (English)In: Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, ISSN 2167-8421, E-ISSN 2167-9223, Vol. 18, no 3-4, p. 256-264Article in journal (Refereed) Published
Abstract [en]

A large GGGGCC-repeat expansion mutation (HREM) in C9orf72 is the most common known cause of ALS and FTD in European populations. Sequence variations immediately downstream of the HREM region have previously been observed and have been suggested to be one reason for difficulties in interpreting RP-PCR data. Our objective was to determine the properties of these sequence variations with regard to prevalence, the range of variation, and effect on disease prognosis. We screened a multi-national cohort (n = 6981) for the HREM and samples with deviant RP-PCR curves were identified. The deviant samples were subsequently sequenced to determine sequence alteration. Our results show that in the USA and European cohorts (n = 6508) 10.7% carried the HREM and 3% had a sequence variant, while no HREM or sequence variants were observed in the Japanese cohort (n = 473). Sequence variations were more common on HREM alleles; however, certain population specific variants were associated with a non-expanded allele. In conclusion, we identified 38 different sequence variants, most located within the first 50 bp downstream of the HREM region. Furthermore, the presence of an HREM was found to be coupled to a lower age of onset and a shorter disease survival, while sequence variation did not have any correlation with these parameters.

Keywords
ALS, C9orf72, FTD, RP-PCR interpretation, variants
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-134981 (URN)10.1080/21678421.2016.1262423 (DOI)000400792800012 ()27936955 (PubMedID)2-s2.0-85003794482 (Scopus ID)
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2023-03-23Bibliographically approved
Nordin, A., Akimoto, C., Wuolikainen, A., Alstermark, H., Jonsson, P., Birve, A., . . . Andersen, P. M. (2015). Extensive size variability of the GGGGCC expansion in C9orf72 in both neuronal and non-neuronal tissues in 18 patients with ALS or FTD. Human Molecular Genetics, 24(11), 3133-3142
Open this publication in new window or tab >>Extensive size variability of the GGGGCC expansion in C9orf72 in both neuronal and non-neuronal tissues in 18 patients with ALS or FTD
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2015 (English)In: Human Molecular Genetics, ISSN 0964-6906, E-ISSN 1460-2083, Vol. 24, no 11, p. 3133-3142Article in journal (Refereed) Published
Abstract [en]

A GGGGCC-repeat expansion in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) among Caucasians. However, little is known about the variability of the GGGGCC expansion in different tissues and whether this correlates with the observed phenotype. Here, we used Southern blotting to estimate the size of hexanucleotide expansions in C9orf72 in neural and non-neural tissues from 18 autopsied ALS and FTD patients with repeat expansion in blood. Digitalization of the Southern blot images allowed comparison of repeat number, smear distribution and expansion band intensity between tissues and between patients. We found marked intra-individual variation of repeat number between tissues, whereas there was less variation within each tissue group. In two patients, the size variation between tissues was extreme, with repeat numbers below 100 in all studied non-neural tissues, whereas expansions in neural tissues were 20-40 times greater and in the same size range observed in neural tissues of the other 16 patients. The expansion pattern in different tissues could not distinguish between diagnostic groups and no correlation was found between expansion size in frontal lobe and occurrence of cognitive impairment. In ALS patients, a less number of repeats in the cerebellum and parietal lobe correlated with earlier age of onset and a larger number of repeats in the parietal lobe correlated with a more rapid progression. In 43 other individuals without repeat expansion in blood, we find that repeat sizes up to 15 are stable, as no size variation between blood, brain and spinal cord was found.

National Category
Medical Genetics Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-103256 (URN)10.1093/hmg/ddv064 (DOI)000355674000011 ()25712133 (PubMedID)2-s2.0-84930747272 (Scopus ID)
Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2023-03-23Bibliographically approved
Akimoto, C., Volk, A. E., van Blitterswijk, M., Van den Broeck, M., Leblond, C. S., Lumbroso, S., . . . Kubisch, C. (2014). A blinded international study on the reliability of genetic testing for GGGGCC-repeat expansions in C9orf72 reveals marked differences in results among 14 laboratories. Journal of Medical Genetics, 51(6), 419-424
Open this publication in new window or tab >>A blinded international study on the reliability of genetic testing for GGGGCC-repeat expansions in C9orf72 reveals marked differences in results among 14 laboratories
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2014 (English)In: Journal of Medical Genetics, ISSN 0022-2593, E-ISSN 1468-6244, Vol. 51, no 6, p. 419-424Article in journal (Refereed) Published
Abstract [en]

Background The GGGGCC-repeat expansion in C9orf72 is the most frequent mutation found in patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Most of the studies on C9orf72 have relied on repeat-primed PCR (RP-PCR) methods for detection of the expansions. To investigate the inherent limitations of this technique, we compared methods and results of 14 laboratories. Methods The 14 laboratories genotyped DNA from 78 individuals (diagnosed with ALS or FTD) in a blinded fashion. Eleven laboratories used a combination of amplicon-length analysis and RP-PCR, whereas three laboratories used RP-PCR alone; Southern blotting techniques were used as a reference. Results Using PCR-based techniques, 5 of the 14 laboratories got results in full accordance with the Southern blotting results. Only 50 of the 78 DNA samples got the same genotype result in all 14 laboratories. There was a high degree of false positive and false negative results, and at least one sample could not be genotyped at all in 9 of the 14 laboratories. The mean sensitivity of a combination of amplicon-length analysis and RP-PCR was 95.0% (73.9-100%), and the mean specificity was 98.0% (87.5-100%). Overall, a sensitivity and specificity of more than 95% was observed in only seven laboratories. Conclusions Because of the wide range seen in genotyping results, we recommend using a combination of amplicon-length analysis and RP-PCR as a minimum in a research setting. We propose that Southern blotting techniques should be the gold standard, and be made obligatory in a clinical diagnostic setting.

National Category
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-91059 (URN)10.1136/jmedgenet-2014-102360 (DOI)000336841300009 ()2-s2.0-84901475610 (Scopus ID)
Available from: 2014-07-11 Created: 2014-07-10 Last updated: 2023-03-23Bibliographically approved
Nordin, A., Larsson, E. & Holmberg, M. (2012). The defective splicing caused by the ISCU intron mutation in patients with myopathy with lactic acidosis is repressed by PTBP1 but can be de-repressed by IGF2BP1. Human Mutation, 33(3), 467-470
Open this publication in new window or tab >>The defective splicing caused by the ISCU intron mutation in patients with myopathy with lactic acidosis is repressed by PTBP1 but can be de-repressed by IGF2BP1
2012 (English)In: Human Mutation, ISSN 1059-7794, E-ISSN 1098-1004, Vol. 33, no 3, p. 467-470Article in journal (Refereed) Published
Abstract [en]

Hereditary myopathy with lactic acidosis (HML) is caused by an intron mutation in the iron-sulfur cluster assembly gene ISCU which leads to the activation of cryptic splice sites and the retention of part of intron 4. This incorrect splicing is more pronounced in muscle than in other tissues, resulting in a muscle-specific phenotype. In this study, we identified five nuclear factors that interact with the sequence harboring the mutation and analyzed their effect on the splicing of the ISCU gene. The identification revealed three splicing factors, SFRS14, RBM39 and PTBP1, and two additional RNA binding factors, matrin 3 (MATR3) and IGF2BP1. IGF2BP1 showed a preference for the mutant sequence, whereas the other factors showed similar affinity for both sequences. PTBP1 was found to repress the defective splicing of ISCU, resulting in a drastic loss of mutant transcripts. In contrast, IGF2BP1 and RBM39 shifted the splicing ratio toward the incorrect splice form.

Keywords
ISCU;hereditary myopathy;alternative splicing;PTBP1
National Category
Basic Medicine
Identifiers
urn:nbn:se:umu:diva-50593 (URN)10.1002/humu.22002 (DOI)2-s2.0-84857045747 (Scopus ID)
Available from: 2012-01-02 Created: 2011-12-14 Last updated: 2023-03-23Bibliographically approved
Nordin, A. (2011). Genetic and functional studies of hereditary myopathy with lactic acidosis. (Doctoral dissertation). Umeå: Umeå Universitet
Open this publication in new window or tab >>Genetic and functional studies of hereditary myopathy with lactic acidosis
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Genetiska och funktionella studier av hereditär myopati med laktacidos
Abstract [en]

Hereditary myopathy with lactic acidosis (HML, OMIM#255125) is an autosomal recessive disorder which originates from Västerbotten and Ångermanland in the Northern part of Sweden. HML is characterized by severe exercise intolerance which manifests with tachycardia, dyspnea, muscle pain, cramps, elevated lactate and pyruvate levels, weakness and myoglobinuria. The symptoms arise from malfunction of the energy metabolism in skeletal muscles with defects in several important enzymes involved in the TCA cycle and the electron transport chain. All affected proteins contain iron-sulfur (Fe-S) clusters, which led to the suggestion that the disease was caused by malfunctions in either the transportation, assembly or processing of Fe-S clusters.

The aim of my thesis was to identify the disease causing gene of HML and to investigate the underlying disease-mechanisms. In paper I we identified a disease-critical region on chromosome 12; a region containing 16 genes. One of the genes coded for the Fe-S cluster assembly protein ISCU and an intronic base pair substitution (g.7044G>C) was identified in the last intron of this gene. The mutation gave rise to the insertion of intron sequence into the mRNA, leading to a protein containing 15 abberant amino acids and a premature stop. In paper II we investigated why a mutation in an evolutionary well conserved protein with a very important cellular role, which in addition is expressed in almost all tissues, gives rise to a muscle-restricted phenotype. Semi-quantitative RT-PCR analysis showed that the mutant transcript constituted almost 80% of total ISCU mRNA in muscle, while in both heart and liver the normal splice form was dominant. We could also show that, in mice, complete absence of Iscu protein was coupled with early embryonic death, further emphasizing the importance of the protein in all tissues. These data strongly suggested that tissue-specific splicing was the main mechanism responsible for the muscle-specific phenotype of HML. In paper III the splicing mechanisms that give rise to the mutant ISCU transcript was further investigated. We identified three proteins; PTBP1, IGF2BP1 and RBM39, that could bind to the region containing the mutation and could affect the splicing pattern of ISCU in an in vitro system. PTBP1 repressed the inclusion of the intronic sequence, while IGF2BP1 and RBM39 repressed the total ISCU mRNA level though the effect was more pronounced for the normal transcript. Moreover, IGF2BP1 and RBM39 were also able to reverse the effect of PTBP1. IGF2BP1, though not a splicing factor, had higher affinity for the mutant sequence. This suggested that the mutation enables IGF2BP1 binding, thereby preventing the PTBP1 induced repression seen in the normal case.

In conclusion, we have determined the genetic cause of HML, identifying a base pair substitution in the last intron of the ISCU gene that gives rise to abnormally spliced transcript. The muscle-specific phenotype was also analyzed and tissue-specific splicing was identified as the main disease-mechanism. Furthermore, nuclear factors with ability to affect the splicing pattern of the mutant ISCU gene were identified. This work has thoroughly investigated the fundamental disease mechanisms, thus providing deeper understanding for this hereditary myopathy.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2011. p. 39
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1454
Keywords
Hereditary myopathy with lactic acidosis, ISCU, intron mutation, mouse model, tissue-specific splicing
National Category
Medical Genetics
Research subject
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-50592 (URN)978-91-7459-308-2 (ISBN)
Public defence
2012-01-27, Sal B, By 1D 9 tr, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2012-01-05 Created: 2011-12-14 Last updated: 2018-06-08Bibliographically approved
Nordin, A., Larsson, E., Thornell, L.-E. & Holmberg, M. (2011). Tissue-specific splicing of ISCU results in a skeletal muscle phenotype in myopathy with lactic acidosis, while complete loss of ISCU results in early embryonic death in mice. Human Genetics, 129(4), 371-378
Open this publication in new window or tab >>Tissue-specific splicing of ISCU results in a skeletal muscle phenotype in myopathy with lactic acidosis, while complete loss of ISCU results in early embryonic death in mice
2011 (English)In: Human Genetics, ISSN 0340-6717, E-ISSN 1432-1203, Vol. 129, no 4, p. 371-378Article in journal (Refereed) Published
Abstract [en]

Hereditary myopathy with lactic acidosis (HML) is caused by an intron mutation in the iron-sulphur cluster assembly gene (ISCU) leading to incorporation of intron sequence into the mRNA. This results in a deficiency of Fe-S cluster proteins, affecting the TCA cycle and the respiratory chain. The proteins involved in the Fe-S machinery are evolutionary conserved and shown to be fundamental in all organisms examined. ISCU is expressed at high levels in numerous tissues in mammals, including high metabolic tissues like the heart, suggesting that a drastic mutation in the ISCU gene would be damaging to all energy-demanding organs. In spite of this, the symptoms in patients with HML are restricted to skeletal muscle, and it has been proposed that splicing events may contribute to the muscle specificity. In this study we confirm that a striking difference in the splicing pattern of mutant ISCU exists between different tissues. The highest level of incorrectly spliced ISCU mRNA was found in skeletal muscle, while the normal splice form predominated in patient heart. The splicing differences were also reflected at a functional level, where loss of Fe-S cluster carrying enzymes and accumulation of iron were present in muscle, but absent in other tissues. We also show that complete loss of ISCU in mice results in early embryonic death. The mice data confirm a fundamental role for ISCU in mammals and further support tissue-specific splicing as the major mechanism limiting the phenotype to skeletal muscle in HML.

Keywords
iron-sulfur proteins; succinate-dehydrogenase; paroxysmal myoglobinuria; deficiency; exercise; clusters; mutation; mitochondria; metabolism; maturation
National Category
Medical Genetics
Research subject
Medicine
Identifiers
urn:nbn:se:umu:diva-40798 (URN)10.1007/s00439-010-0931-3 (DOI)000289275200002 ()21165651 (PubMedID)2-s2.0-79953832566 (Scopus ID)
Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2023-03-24Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7703-647x

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