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Structural investigation of SOD1 aggregates in ALS: identification of prion strains using anti-peptide antibodies
Umeå University, Faculty of Medicine, Department of Medical Biosciences. (ALS-gruppen)
2018 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Strukturbestämning av SOD1 aggregat i ALS : identifiering av prionstammar med antipeptidantikroppar (Swedish)
Abstract [en]

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative syndrome characterized by progressive degeneration of motor neurons that result in muscle wasting. The symptoms advance gradually to paralysis and eventually death. Most patients suffer from sporadic ALS (sALS) but 10% report a familial predisposition. Mutations in the gene encoding super­oxide dismutase-1 (SOD1) were the first identified cause of ALS. The disease mecha­nism is debated but there is a consensus that mutations in this protein confer a cytotoxic gain of function. SOD1 aggregates in motor neurons are hallmarks of ALS both in patients and in transgenic mouse models expressing a mutated form of human SOD1 (hSOD1). Recently, our group showed that SOD1 aggregates are present also in sALS patients, thus indicating a broader involvement of this protein in ALS. Misfolding and aggregation of SOD1 are dif­ficult to study in vivo since aggregate concentration in the central nervous system (CNS) is exceedingly low. The aim of this thesis was to find a method circumventing this problem to investigate the hSOD1 aggregate structure, distribution and spread in ALS disease.

Many studies provide circumstantial evidence that the wild-type hSOD1 protein can be neurotoxic. We developed the first homozygous mouse model that highly overexpresses the wild-type enzyme. These mice developed an ALS-like syndrome and become terminally ill after around 370 days. Motor neuron loss and SOD1 aggregate accumulation in the CNS were observed. This lends further support to the hypothesis of a more general involve­ment of SOD1 in human disease.

A panel of polyclonal antibodies covering 90% of the SOD1 protein was developed by our laboratory. These antibodies were shown to be highly specific for misfolded SOD1. Aggre­gated hSOD1 was purified from the CNS of terminally ill hSOD1 mice. Disordered segments in aggregated hSOD1 could be identified with these antibodies. Two aggregate strains with different structural architectures, molecular properties, and growth kinetics, were found using this novel method. The strains, denoted A and B, were also associated with different disease progression. Aggregates formed in vitro were structurally different from these strains. The results gave rise to questions about aggregate development and possible prion-like spread. To investigate this, inoculations of purified strain A and B hSOD1 seeds was performed in lumbar spinal cords of 100-day old mice carrying a hSOD1G85R mutation. Mice seeded with A or B aggregates developed premature signs of ALS and became terminally ill 200 days earlier than mice inoculated with control preparation. Interestingly, a tem­plated spread of aggregates along the neuraxis was concomitantly observed, with strain A and B provoking the buildup of their respective hSOD1 aggregate structure. The phenotypes initiated by the A and B strains differed regarding progression rates, distribution, end-stage aggregate levels, and histopathology. To further establish the importance of hSOD1 aggregates in human disease, purification and inoculation of aggregate seeds from spinal cords of ALS patients and mice carrying the hSOD1G127X mutation were performed. Inoculation of both human and mouse seeds as described above, induced strain A aggregation and premature fatal ALS-like disease.

In conclusion, the data presented in this thesis provide a new, straightforward method for characterization of aggregate strains in ALS, and plausibly also in other neurodegen­erative diseases. Two different prion strains of hSOD1 aggregates were identified in mice that resulted in ALS-like disease. Emerging data suggest that prion-like growth and spread of hSOD1 aggregation could be the primary pathogenic mechanism not only in hSOD1 transgenic models, but also in human ALS.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2018. , p. 94
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1966
Keywords [en]
ALS, SOD1, prion, motor neuron disease, neurodegeneration, strain, seeding, protein aggregation, transgenic mice, peptide antibodies
National Category
Neurosciences Neurology
Research subject
Neurology
Identifiers
URN: urn:nbn:se:umu:diva-150911ISBN: 978-91-7601-907-8 (print)OAI: oai:DiVA.org:umu-150911DiVA, id: diva2:1239882
Public defence
2018-09-14, NUS 6A–L - Biomedicinhuset, Major Groove, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2018-08-22 Created: 2018-08-19 Last updated: 2018-08-24Bibliographically approved
List of papers
1. Expression of wild-type human superoxide dismutase-1 in mice causes amyotrophic lateral sclerosis
Open this publication in new window or tab >>Expression of wild-type human superoxide dismutase-1 in mice causes amyotrophic lateral sclerosis
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2013 (English)In: Human Molecular Genetics, ISSN 0964-6906, E-ISSN 1460-2083, Vol. 22, no 1, p. 51-60Article in journal (Refereed) Published
Abstract [en]

A common cause of amyotrophic lateral sclerosis (ALS) is mutations in the gene encoding superoxide dismutase-1. There is evolving circumstantial evidence that the wild-type protein can also be neurotoxic and that it may more generally be involved in the pathogenesis of ALS. To test this proposition more directly, we generated mice that express wild-type human superoxide dismutase-1 at a rate close to that of mutant superoxide dismutase-1 in the commonly studied G93A transgenic model. These mice developed an ALS-like syndrome and became terminally ill after around 370 days. The loss of spinal ventral neurons was similar to that in the G93A and other mutant superoxide dismutase-1 models, and large amounts of aggregated superoxide dismutase-1 were found in spinal cords, but also in the brain. The findings show that wild-type human superoxide dismutase-1 has the ability to cause ALS in mice, and they support the hypothesis of a more general involvement of the protein in the disease in humans.

National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-63578 (URN)10.1093/hmg/dds399 (DOI)000312643400004 ()23026746 (PubMedID)
Available from: 2013-01-03 Created: 2013-01-03 Last updated: 2018-08-19Bibliographically approved
2. Structural and kinetic analysis of protein-aggregate strains in vivo using binary epitope mapping
Open this publication in new window or tab >>Structural and kinetic analysis of protein-aggregate strains in vivo using binary epitope mapping
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2015 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 112, no 14, p. 4489-4494Article in journal (Refereed) Published
Abstract [en]

Despite considerable progress in uncovering the molecular details of protein aggregation in vitro, the cause and mechanism of protein-aggregation disease remain poorly understood. One reason is that the amount of pathological aggregates in neural tissue is exceedingly low, precluding examination by conventional approaches. We present here a method for determination of the structure and quantity of aggregates in small tissue samples, circumventing the above problem. The method is based on binary epitope mapping using anti-peptide antibodies. We assessed the usefulness and versatility of the method in mice modeling the neurodegenerative disease amyotrophic lateral sclerosis, which accumulate intracellular aggregates of superoxide dismutase-1. Two strains of aggregates were identified with different structural architectures, molecular properties, and growth kinetics. Both were different from superoxide dismutase-1 aggregates generated in vitro under a variety of conditions. The strains, which seem kinetically under fragmentation control, are associated with different disease progressions, complying with and adding detail to the growing evidence that seeding, infectivity, and strain dependence are unifying principles of neurodegenerative disease.

Place, publisher, year, edition, pages
National Academy of Sciences, 2015
Keywords
protein aggregation, neurodegeneration, strain, amyotrophic lateral sclerosis, transgenic mice
National Category
Pharmacology and Toxicology Medical Bioscience
Identifiers
urn:nbn:se:umu:diva-103147 (URN)10.1073/pnas.1419228112 (DOI)000352287800075 ()25802384 (PubMedID)
Available from: 2015-05-28 Created: 2015-05-18 Last updated: 2018-08-19Bibliographically approved
3. Two superoxide dismutase prion strains transmit amyotrophic lateral sclerosis-like disease
Open this publication in new window or tab >>Two superoxide dismutase prion strains transmit amyotrophic lateral sclerosis-like disease
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2016 (English)In: Journal of Clinical Investigation, ISSN 0021-9738, E-ISSN 1558-8238, Vol. 126, no 6, p. 2249-2253Article in journal (Refereed) Published
Abstract [en]

Amyotrophic lateral sclerosis (ALS) is an adult-onset degeneration of motor neurons that is commonly caused by mutations in the gene encoding superoxide dismutase 1 (SOD1). Both patients and Tg mice expressing mutant human SOD1 (hSOD1) develop aggregates of unknown importance. In Tg mice, 2 different strains of hSOD1 aggregates (denoted A and B) can arise; however, the role of these aggregates in disease pathogenesis has not been fully characterized. Here, minute amounts of strain A and B hSOD1 aggregate seeds that were prepared by centrifugation through a density cushion were inoculated into lumbar spinal cords of 100-day-old mice carrying a human SOD1 Tg. Mice seeded with A or B aggregates developed premature signs of ALS and became terminally ill after approximately 100 days, which is 200 days earlier than for mice that had not been inoculated or were given a control preparation. Concomitantly, exponentially growing strain A and B hSOD1 aggregations propagated rostrally throughout the spinal cord and brainstem. The phenotypes provoked by the A and B strains differed regarding progression rates, distribution, end-stage aggregate levels, and histopathology. Together, our data indicate that the aggregate strains are prions that transmit a templated, spreading aggregation of hSOD1, resulting in a fatal ALS-like disease.

National Category
Medical Bioscience Neurosciences
Identifiers
urn:nbn:se:umu:diva-122554 (URN)10.1172/JCI84360 (DOI)000377027500021 ()27140399 (PubMedID)
Available from: 2016-07-25 Created: 2016-06-20 Last updated: 2019-09-12Bibliographically approved
4. Mutant superoxide dismutase aggregates from human spinal cord transmit amyotrophic lateral sclerosis
Open this publication in new window or tab >>Mutant superoxide dismutase aggregates from human spinal cord transmit amyotrophic lateral sclerosis
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2018 (English)In: Acta Neuropathologica, ISSN 0001-6322, E-ISSN 1432-0533, Vol. 136, no 6, p. 939-953Article in journal (Refereed) Published
Abstract [en]

Motor neurons containing aggregates of superoxide dismutase 1 (SOD1) are hallmarks of amyotrophic lateral sclerosis (ALS) caused by mutations in the gene encoding SOD1. We have previously reported that two strains of mutant human (h) SOD1 aggregates (denoted A and B) can arise in hSOD1-transgenic models for ALS and that inoculation of such aggregates into the lumbar spinal cord of mice results in rostrally spreading, templated hSOD1 aggregation and premature fatal ALS-like disease. Here, we explored whether mutant hSOD1 aggregates with prion-like properties also exist in human ALS. Aggregate seeds were prepared from spinal cords from an ALS patient carrying the hSOD1G127Gfs*7 truncation mutation and from mice transgenic for the same mutation. To separate from mono-, di- or any oligomeric hSOD1 species, the seed preparation protocol included ultracentrifugation through a density cushion. The core structure of hSOD1G127Gfs*7 aggregates present in mice was strain A-like. Inoculation of the patient- or mouse-derived seeds into lumbar spinal cord of adult hSOD1-expressing mice induced strain A aggregation propagating along the neuraxis and premature fatal ALS-like disease (p < 0.0001). Inoculation of human or murine control seeds had no effect. The potencies of the ALS patient-derived seed preparations were high and disease was initiated in the transgenic mice by levels of hSOD1G127Gfs*7 aggregates much lower than those found in the motor system of patients carrying the mutation. The results suggest that prion-like growth and spread of hSOD1 aggregation could be the primary pathogenic mechanism, not only in hSOD1 transgenic rodent models, but also in human ALS.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Superoxide dismutase, prion-like, aggregation, propagation, motor neuron disease
National Category
Neurosciences
Research subject
Neurology; Pathology
Identifiers
urn:nbn:se:umu:diva-150909 (URN)10.1007/s00401-018-1915-y (DOI)000451952700008 ()30284034 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationTorsten Söderbergs stiftelseThe Swedish Brain FoundationThe Kempe FoundationsVästerbotten County Council
Note

Originally included in thesis in manuscript form.

Available from: 2018-08-18 Created: 2018-08-18 Last updated: 2019-09-12Bibliographically approved

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