ALS Research Journal News - August/September 2012

This summary includes some of the most recent advances in ALS research. If you would like certain news items featured, or have questions, please contact researchgrants@alsa-national.org.

Quick Summary: This month brings progress in understanding genetic influences on age of onset and survival in ALS, greater detail on the epidemiology and clinical features of C9ORF72, and progress on understanding the cell biology of TDP-43, plus multiple other papers of interest.

Feature News Story Axonal Guidance Gene Modifies Age of Onset and Survival in ALS

Cellular, Molecular, and Genetic Research

• Age of Onset Locus Discovered on Chromosome one (1)
• C9ORF72 Round-up
• VCP Round-up
• Ubiquilin and FTD
• Calcium Channel Linked to Normal Shuttling of TDP-43
• Autophagy Activators Mitigate TDP-43 Proteinopathy
• TDP-43 Mislocalization Linked to Decline in RNA Editing Enzyme
• Acetylcholine Receptor Mutations Increase ALS Risk

Clinical Research and Drug Development

• Pooled Analysis Indicates No Effect on ALS Risk from NSAID Use
• Patient-Derived iPS Cells for ALS Drug Screening
• Challenges of Neural Stem Cell Replacement Therapy
• TDP-43 as a Plasma Biomarker

Reviews

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Feature New Story

Axonal Guidance Gene Modifies Age of Onset and Survival in ALS

A gene involved in axonal guidance modifies age of onset and survival in ALS, according to a new study. The gene, called EPHA4, encodes a receptor in the ephrin axonal guidance system, which helps guide spinal motor neurons to their targets during development and regrowth. The international team making the discovery was led by Wim Robberecht, M.D., of University Hospital in Leuven, Belgium.

The researchers found that blocking expression of the zebrafish or mouse versions of the gene protected motor neurons in both animal models from the harmful effects of mutant SOD1. In SOD1 rats, the pharmacological blockade of the receptor delayed disease onset and prolonged survival. In addition, both genetic and pharmacologic reduction of receptor signaling mitigated phenotypic abnormalities in the TDP-43 mutant mouse model of ALS. Reduction of signaling also improved the phenotype of a fish model of spinal muscular atrophy, suggesting that “the ephrin system may be a generic determinant of vulnerability of neurons to degeneration,” the authors stated.

The importance of the gene for ALS in humans was confirmed through a genetic association study in almost 3000 ALS patients. Lower expression of EPHA4 was associated with later disease onset and longer survival. Two previously unknown EPHA4 gene variants were identified, one of which reduced gene expression and the other reduced signaling capacity of the receptor.

Van Hoecke A, Schoonaert L, Lemmens R, Timmers M, Staats KA, Laird AS, Peeters E, Philips T, Goris A, Dubois B, Andersen PM, Al-Chalabi A, Thijs V, Turnley AM, van Vught PW, Veldink JH, Hardiman O, Van Den Bosch L, Gonzalez-Perez P, Van Damme P, Brown RH Jr, van den Berg LH, Robberecht W. EPHA4 is a disease modifier of amyotrophic lateral sclerosis in animal models and in humans. Nat Med. 2012 Aug 26. doi: 10.1038/nm.2901. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22922411

Cellular, Molecular, and Genetic Research

Age of Onset Locus Discovered on Chromosome One (1)
An international consortium of researchers convened by and funded in part by The ALS Association has identified a region on chromosome 1 that strongly influences the age of onset of ALS. The study examined DNA from over 4000 ALS patients and 5000 controls of Caucasian origin from centers in the United States and Europe, including Belgium, France, the Netherlands, Ireland, Italy, Sweden, and the United Kingdom. The study was conducted by The International Consortium on Amyotrophic Lateral Sclerosis Genetics (ALSGEN).

The strongest association with age of onset was within 1p34.1, a region harboring multiple genes. Individuals with a specific SNP (single nucleotide polymorphism) marker had an age of onset approximately two-and-half years earlier than those without it (the average age at onset was approximately 56.5 years versus approximately 59 years). In addition, the study, published in the journal The Neurobiology of Aging, confirmed known genetic risks for ALS and suggested novel regions that merit more study.

Of potential significance is that the locus appears to influence age of onset independent of the underlying cause of ALS, and thus may reveal a mechanism common to multiple ALS etiologies. “Although much work remains to unravel the mechanism or pathway involved in the chromosome 1 locus,” the authors write, “this may represent the first identification of a component of the final common pathway of motor neuron degeneration.”

The ALSGEN Consortium. Age of onset of amyotrophic lateral sclerosis is modulated by a locus on 1p34.1. Neurobiol Aging. 2012 Sep 4. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22959728

C9ORF72 Round-up
A series of new studies continues to increase the understanding of the clinical, imaging, and epidemiology of the C9ORF72 expansion. The mutation, which expands a hexanucleotide sequence in this gene of unknown function, is the most common genetic cause of ALS. Rutherford et al. report in Neurology on the frequency of the mutation and its associated clinical phenotypes in a cohort of patients obtained from the Coriell Cell Repository. These samples were collected as part of a large collaboration with The ALS Association, NINDS, MDA and the ALSRG and provide an important resource for researchers globally. Of the 617 samples analyzed, 11.8% carry the pathogenic repeat expansion, including 37% among familial ALS cases and 4.9% of the sporadic cases. In an ALS patient group of Dutch descent, Van Rheenen et al. found the repeat expansion in 37% of familial ALS patients, 6% of sporadic ALS patients, and 2% of patients with progressive muscular atrophy. Rutherford et al. report in The Neurobiology of Aging that “no meaningful association between the repeat length of the normal alleles of the GGGGCC repeat in C9ORF72 and [ALS] disease phenotype or age at onset was observed in C9ORF72 mutation carriers or nonmutation carriers.” Sha et al. report that carriers of the C9ORF72 expansion with frontotemporal dementia are similar clinically to non-carrier FTD patients, but with a trend for longer survival and more thalamic atrophy.  Meanwhile, Satoh et al. report that an antibody to the expanded repeat RNA stains dystrophic neurites in Alzheimer’s disease.

Rutherford NJ, Heckman MG, Dejesus-Hernandez M, Baker MC, Soto-Ortolaza AI, Rayaprolu S, Stewart H, Finger E, Volkening K, Seeley WW, Hatanpaa KJ, Lomen-Hoerth C, Kertesz A, Bigio EH, Lippa C, Knopman DS, Kretzschmar HA, Neumann M, Caselli RJ, White CL 3rd, Mackenzie IR, Petersen RC, Strong MJ, Miller BL, Boeve BF, Uitti RJ, Boylan KB, Wszolek ZK, Graff-Radford NR, Dickson DW, Ross OA, Rademakers R. Length of normal alleles of C9ORF72 GGGGCC repeat do not influence disease phenotype. Neurobiol Aging. 2012 Jul 26. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22840558
Rutherford NJ, Dejesus-Hernandez M, Baker MC, Kryston TB, Brown PE, Lomen-Hoerth C, Boylan K, Wszolek ZK, Rademakers R. C9ORF72 hexanucleotide repeat expansions in patients with ALS from the Coriell Cell Repository. Neurology. 2012 Jul 31;79(5):482-3. Epub 2012 Jul 18.
http://www.ncbi.nlm.nih.gov/pubmed/22815561

Satoh JI, Tabunoki H, Ishida T, Saito Y, Arima K. Dystrophic neurites express C9orf72 in Alzheimer's disease brains. Alzheimers Res Ther. 2012 Aug 16;4(4):33. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22898310

Sha SJ, Takada LT, Rankin KP, Yokoyama JS, Rutherford NJ, Fong JC, Khan B, Karydas A, Baker MC, Dejesus-Hernandez M, Pribadi M, Coppola G, Geschwind DH, Rademakers R, Lee SE, Seeley W, Miller BL, Boxer AL. Frontotemporal dementia due to C9ORF72 mutations: Clinical and imaging features. Neurology. 2012 Aug 8. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22875087

van Rheenen W, van Blitterswijk M, Huisman MH, Vlam L, van Doormaal PT, Seelen M, Medic J, Dooijes D, de Visser M, van der Kooi AJ, Raaphorst J, Schelhaas HJ, van der Pol WL, Veldink JH, van den Berg LH.Hexanucleotide repeat expansions in C9ORF72 in the spectrum of motor neuron diseases. Neurology. 2012 Aug 28;79(9):878-82. Epub 2012 Jul 25.
http://www.ncbi.nlm.nih.gov/pubmed/22843265

VCP Round-up
Mutations in the gene for valosin-containing protein (VCP) are a rare cause of ALS. VCP mutation is also implicated in inclusion body myositis and some forms of frontotemporal dementia. Mehta et al. analyzed the largest dataset of patients to date with mutation in the VCP gene, and identified ALS in 9% and Parkinson’s disease in 3% of the cohort. There were no genotype/phenotype correlations found for either disease. Yin et al. found “age-dependent degeneration of ventral horn motor neurons, TDP-43-positive cytosolic inclusions, mitochondrial aggregation and progressive astrogliosis” in a VCP-mutant mouse.

Mehta SG, Khare M, Ramani R, Watts GD, Simon M, Osann KE, Donkervoort S, Dec E, Nalbandian A, Platt J, Pasquali M, Wang A, Mozaffar T, Smith CD, Kimonis VE. Genotype-Phenotype studies of VCP-associated Inclusion Body Myopathy with Paget Disease of Bone and/or Frontotemporal Dementia. Clin Genet. 2012 Aug 21. doi: 10.1111/cge.12000. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22909335

Yin HZ, Nalbandian A, Hsu CI, Li S, Llewellyn KJ, Mozaffar T, Kimonis VE, Weiss JH. Slow development of ALS-like spinal cord pathology in mutant valosin-containing protein gene knock-in mice. Cell Death Dis. 2012 Aug 16;3:e374. doi: 10.1038/cddis.2012.115.
http://www.ncbi.nlm.nih.gov/pubmed/22898872
full text: http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22898872/

Ubiquilin and FTD
UBQLN2 encodes ubiquilin-2, a protein that plays a role in protein degradation. Mutations in UBQLN2 are a rare cause of ALS. Synofzik et al. report new mutations in UBQLN2 associated with pure frontotemporal dementia (FTD) of apparently sporadic origin, as well as ALS. The new mutations were not in the PXX region, and they, therefore, recommend that “UBQLN2 screening in neurodegenerative patients should not be limited to this region.”

Synofzik M, Maetzler W, Grehl T, Prudlo J, Vom Hagen JM, Haack T, Rebassoo P, Munz M, Schöls L, Biskup S. Screening in ALS and FTD patients reveals 3 novel UBQLN2 mutations outside the PXX domain and a pure FTD phenotype. Neurobiol Aging. 2012 Aug 11. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22892309

Calcium Channel Linked to Normal Shuttling of TDP-43
TDP-43 is an RNA-binding protein. Mutations in the gene are a rare cause of ALS, but the protein is found in cytoplasmic inclusions in most forms of ALS. A key feature of normal TDP-43 is that it shuttles between nucleus and cytoplasm. A new study in Human Molecular Genetics identifies an endoplasmic reticulum calcium channel, called type 1 inositol-1,4,5-trisphosphate receptor (ITPR1), as central to the movement of TDP-43. Inhibition of ITPR1 increased clearance of TDP-43 through the autophagosome pathway, suggesting that ITPR1 inhibition may represent a promising drug target for preventing accumulation of TDP-43.

Kim SH, Zhan L, Hanson KA, Tibbetts RS. High-content RNAi screening identifies the Type 1 inositol triphosphate receptor as a modifier of TDP-43 localization and neurotoxicity. Hum Mol Genet. 2012 Aug 27. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22872699

Autophagy Activators Mitigate TDP-43 Proteinopathy
Autophagy is a cellular pathway for disposal of damaged proteins and organelles. In a mouse model of FTD with ubiquitin inclusions (FTLD-U) due to TDP-43 overexpression, treatment with rapamycin, an autophagy activator, rescued early cognitive deficits and slowed age-dependent motor impairment. Improvements were accompanied by a reduction in protein aggregation. Other autophagy activators had similar effects.

Wang IF, Guo BS, Liu YC, Wu CC, Yang CH, Tsai KJ, Shen CK. Autophagy activators rescue and alleviate pathogenesis of a mouse model with proteinopathies of the TAR DNA-binding protein 43. Proc Natl Acad Sci U S A. 2012 Aug 29. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22932872

TDP-43 Mislocalization Linked to Decline in RNA Editing Enzyme
Hideyama et al. show that in fast fatigable motor neurons in aged mice, the expression of an RNA editing enzyme called adenosine deaminase acting on RNA 2 (ADAR2) progressively declined. The decline was associated with mislocalization of TDP-43, as well as elevated expression of the Q/R site-unedited AMPA receptor subunit 2 (GluA2) mRNA, a substrate for ADAR2, which has been shown to be lethal to motor neurons. “These results suggest that age-related decreases in ADAR2 activity play a mechanistic role in aging and serve as one of risk factors for ALS,” the authors conclude.

Hideyama T, Teramoto S, Hachiga K, Yamashita T, Kwak S. Co-Occurrence of TDP-43 Mislocalization with Reduced Activity of an RNA Editing Enzyme, ADAR2, in Aged Mouse Motor Neurons. PLoS One. 2012;7(8):e43469. Epub 2012 Aug 20.
http://www.ncbi.nlm.nih.gov/pubmed/22916266
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0043469

Also of Interest:

Vaccaro A, Patten SA, Ciura S, Maios C, Therrien M, Drapeau P, Kabashi E, Parker JA. Methylene Blue Protects against TDP-43 and FUS Neuronal Toxicity in C. elegans and D. rerio. PLoS One. 2012;7(7):e42117. Epub 2012 Jul 27.
http://www.ncbi.nlm.nih.gov/pubmed/22848727

Full text: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0042117

Droppelmann CA, Keller BA, Campos-Melo D, Volkening K, Strong MJ. Rho guanine nucleotide exchange factor is an NFL mRNA destabilizing factor that forms cytoplasmic inclusions in amyotrophic lateral sclerosis. Neurobiol Aging. 2012 Jul 24. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22835604

Clinical Research and Drug Development

Pooled Analysis Indicates No Effect on ALS Risk from NSAID Use
Pooled data from five large prospective studies identified 708 cases of ALS among 780,000 participants. There was no association between risk of ALS and use of either aspirin or non-aspirin NSAIDs, “but because NSAIDs have heterogeneous effects, a role of individual compounds cannot be excluded,” the authors concluded.

Fondell E, O'Reilly EJ, Fitzgerald KC, Falcone GJ, McCullough ML, Thun MJ, Park Y, Kolonel LN, Ascherio A. Non-steroidal anti-inflammatory drugs and amyotrophic lateral sclerosis: Results from five prospective cohort studies. Amyotroph Lateral Scler. 2012 Aug 7. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22871075

Patient-Derived iPS Cells for ALS Drug Screening
Researchers report developing iPS cell-derived motor neurons from patients carrying TDP-43 mutations that manifest several key features of human disease, including protein aggregates and shorter neurites. They also report initial drug screening results suggesting that a histone acetyltransferase inhibitor called anacardic acid may be a promising compound for therapeutic development.

Egawa N, Kitaoka S, Tsukita K, Naitoh M, Takahashi K, Yamamoto T, Adachi F, Kondo T, Okita K, Asaka I, Aoi T, Watanabe A, Yamada Y, Morizane A, Takahashi J, Ayaki T, Ito H, Yoshikawa K, Yamawaki S, Suzuki S, Watanabe D, Hioki H, Kaneko T, Makioka K, Okamoto K, Takuma H, Tamaoka A, Hasegawa K, Nonaka T, Hasegawa M, Kawata A, Yoshida M, Nakahata T, Takahashi R, Marchetto MC, Gage FH, Yamanaka S, Inoue H. Drug Screening for ALS Using Patient-Specific Induced Pluripotent Stem Cells. Sci Transl Med. 2012 Aug 1;4(145):145ra104.
http://www.ncbi.nlm.nih.gov/pubmed/22855461

Challenges of Neural Stem Cell Replacement Therapy
A study in SOD1 rats highlights the difficulties of developing stem cell transplantation as a therapy for ALS. Transplantation of human fetal spinal neural stem cells led to only local protection and transient improvement, with no effect on motor neurons distant from the transplant site. In particular, descending motor axons continued to degenerate despite treatment, indicating that multi-level treatment may be required to gain a therapeutic effect.

Hefferan MP, Galik J, Kakinohana O, Sekerkova G, Santucci C, Marsala S, Navarro R, Hruska-Plochan M, Johe K, Feldman E, Cleveland DW, Marsala M. Human neural stem cell replacement therapy for amyotrophic lateral sclerosis by spinal transplantation. PLoS One. 2012;7(8):e42614. Epub 2012 Aug 20.
http://www.ncbi.nlm.nih.gov/pubmed/22916141
full text: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0042614

TDP-43 as a Plasma Biomarker
TDP-43 is elevated in plasma of ALS patients, although they did not change with disease progression in most patients.

Verstraete E, Kuiperij HB, van Blitterswijk MM, Veldink JH, Schelhaas HJ, van den Berg LH, Verbeek MM. TDP-43 plasma levels are higher in amyotrophic lateral sclerosis. Amyotroph Lateral Scler. 2012 Sep;13(5):446-51. Epub 2012 Aug 8.
http://www.ncbi.nlm.nih.gov/pubmed/22873561

Reviews

Al-Chalabi A, Jones A, Troakes C, King A, Al-Sarraj S, van den Berg LH. The genetics and neuropathology of amyotrophic lateral sclerosis. Acta Neuropathol. 2012 Sep;124(3):339-52. Epub 2012 Aug 2.
http://www.ncbi.nlm.nih.gov/pubmed/22903397

Cooper-Knock J, Kirby J, Ferraiuolo L, Heath PR, Rattray M, Shaw PJ. Gene expression profiling in human neurodegenerative disease. Nat Rev Neurol. 2012 Aug 14. doi: 10.1038/nrneurol.2012.156. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22890216

Phani S, Re DB, Przedborski S. The Role of the Innate Immune System in ALS. Front Pharmacol. 2012;3:150. Epub 2012 Aug 14.
http://www.ncbi.nlm.nih.gov/pubmed/22912616
full text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3418523/

Paul P, de Belleroche J. The role of D: -amino acids in amyotrophic lateral sclerosis pathogenesis: a review. Amino Acids. 2012 Aug 14. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/22890612