ALS Research Journal News - October 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:

Feature News Story
FUS/SMN Interaction Links ALS and Spinal Muscular Atrophy

Cellular, Molecular, and Genetic Research

• RNA Debranching Enzyme Required for TDP-43 Toxicity
• TDP-43 Binds to and Represses Transposable Element Transcripts
• Overlap in TDP-43 and FUS RNA Targets May Be Significant
• TDP-43 Binds to UPS Targeting Protein
• Overexpression of human wild-type FUS Causes Progressive Motor Neuron Degeneration
• P62 Mutations Linked to FTD
• Female Sex and Hormonal Influence on ALS Explored

Clinical Research and Drug Development

• Potential Biomarker in Blood Associated with Faster Short-term Decline
• Neurodegenerative Disease Fibroblasts Publicly Available
• MuSK Signaling Improves Motor Performance
• Sigma-1R Activation Improves Multiple Disease Parameters
• Neuroprotection from Aminopropyl Carbazoles
• Serotonin Receptor Agonist Mitigates Motor Neuron Damage in SBMA

Feature News Story

FUS/SMN Interaction Links ALS and Spinal Muscular Atrophy

FUS directly interacts with? SMN, linking ALS and spinal muscular atrophy, two disorders of motor neurons, according to a new study. SMN is a key protein in nuclear Gems, dynamic nuclear structures involved in RNA processing, and mutations in SMN lead to loss of Gems and development of SMA. The new study shows that the two proteins physically interact, and that FUS is required for Gem formation. An ALS-causing FUS mutation leads to Gem loss, and Gem reduction was seen in fibroblasts in patients with ALS due to either FUS or TDP-43. “The physical and functional interactions among SMN, FUS, TDP-43, and Gems indicate that ALS and SMA share a biochemical pathway, providing strong support for the view that these motor neuron diseases are related,” the authors state.

“This finding will help accelerate the understanding of the causes of ALS,” according to ALS Association Chief Scientist Lucie Bruijn, Ph.D., “because we have now identified a critical link that unites the two diseases. That link is likely to play an important role in the ALS disease pathway.”

Meanwhile, SMA researchers have shown that SMN expression in proprioceptive neurons and interneurons is required for restoration of neuromuscular structure and function, indicating that “SMN depletion disrupts the motor system subsequent to circuit development,” according to the authors. “These results establish sensory-motor circuit dysfunction as the origin of motor system deficits in this SMA model and suggest that enhancement of motor neural network activity could ameliorate the disease.”

The same group also showed that “SMN deficiency perturbs splicing and decreases the expression of a subset of U12 intron-containing genes” in animal models, including a protein called Stasimon, which is required for motor circuit function.

http://www.ncbi.nlm.nih.gov/pubmed/23022481
http://www.cell.com/cell-reports/fulltext/S2211-1247%2812%2900265-3
Yamazaki T, Chen S, Yu Y, Yan B, Haertlein TC, Carrasco MA, Tapia JC, Zhai B, Das R, Lalancette-Hebert M, Sharma A, Chandran S, Sullivan G, Nishimura AL, Shaw CE, Gygi SP, Shneider NA, Maniatis T, Reed R. FUS-SMN Protein Interactions Link the Motor Neuron Diseases ALS and SMA. Cell Rep. 2012 Sep 25. pii: S2211-1247(12)00265-3. doi: 10.1016/j.celrep.2012.08.025. [Epub ahead of print]

http://www.ncbi.nlm.nih.gov/pubmed/23063130
Imlach WL, Beck ES, Choi BJ, Lotti F, Pellizzoni L, McCabe BD. SMN Is Required for Sensory-Motor Circuit Function in Drosophila. Cell. 2012 Oct 12;151(2):427-39. doi: 10.1016/j.cell.2012.09.011.

http://www.ncbi.nlm.nih.gov/pubmed/23063131
Lotti F, Imlach WL, Saieva L, Beck ES, Hao le T, Li DK, Jiao W, Mentis GZ, Beattie CE, McCabe BD, Pellizzoni L. An SMN-Dependent U12 Splicing Event Essential for Motor Circuit Function. Cell. 2012 Oct 12;151(2):440-54. doi: 10.1016/j.cell.2012.09.012.

Cellular, Molecular, and Genetic Research

RNA Debranching Enzyme Required for TDP-43 Toxicity
The deleterious effects of TDP-43 mutation can be mitigated by loss of Dbr1, which encodes RNA lariat debranching enzyme. In the absence of the enzyme, “intronic lariats accumulate in the cytoplasm and likely act as decoys to sequester TDP-43 away from interfering with other essential cellular RNAs and RNA-binding proteins,” the authors propose, suggesting that “decreasing the debranching enzymatic activity of Dbr1 could be a potential therapeutic approach for ALS.”

Maria Armakola, Matthew J Higgins, Matthew D Figley, Sami J Barmada, Emily A Scarborough, Zamia Diaz, Xiaodong Fang, James Shorter, Nevan J Krogan, Steven Finkbeiner, Robert V Farese Jr & Aaron D Gitler. Inhibition of RNA lariat debranching enzyme suppresses TDP-43 toxicity in ALS disease models. Nature Genetics 2012 doi:10.1038/ng.2434

TDP-43 Binds to and Represses Transposable Element Transcripts
TDP-43 binds extensively to transcripts of transposable elements, according to a new report, and these interactions are decreased in FTD. Transposable elements are a type of repetitive DNA that make up a large fraction of the genome, and which are transcribed into RNA. While most of the transcripts are believed to be nonfunctional, some can become reverse transcribed and reinserted as DNA at new locations elsewhere in the genome. In this study, the authors found that mutation to TDP-43 reduced its binding to transposable element transcripts and elevated the level of these transcripts, potentially contributing to pathogenesis.
http://www.ncbi.nlm.nih.gov/pubmed/22957047
http://dx.plos.org/10.1371/journal.pone.0044099
Li W, Jin Y, Prazak L, Hammell M, Dubnau J. Transposable Elements in TDP-43-Mediated Neurodegenerative Disorders. PLoS One. 2012;7(9):e44099. Epub 2012 Sep 5.

Overlap in TDP-43 and FUS RNA Targets May Be Significant
RNA binding profiles for FUS and TDP-43 reveal that the two proteins largely bind independent targets, but they both bind 45 RNAs, among which were “mRNAs that were transcribed from genes with exceptionally long introns and that encode proteins that are essential for neuronal integrity,” according to the authors. Depletion of TDP-43 or FUS in stem cell-derived motor neurons and motor neurons from sporadic ALS lowered expression of a subset of these 45 RNAs, “supporting a common loss-of-function pathway as one component underlying motor neuron death from misregulation of TDP-43 or FUS/TLS.”
http://www.ncbi.nlm.nih.gov/pubmed/23023293
Divergent roles of ALS-linked proteins FUS/TLS and TDP-43 intersect in processing long pre-mRNAs.
Lagier-Tourenne C, Polymenidou M, Hutt KR, Vu AQ, Baughn M, Huelga SC, Clutario KM, Ling SC, Liang TY, Mazur C, Wancewicz E, Kim AS, Watt A, Freier S, Hicks GG, Donohue JP, Shiue L, Bennett CF, Ravits J, Cleveland DW, Yeo GW.
Nat Neurosci. 2012 Sep 30. doi: 10.1038/nn.3230. [Epub ahead of print]

TDP-43 Binds to UPS Targeting Protein
TDP-43 binds to Nucleus Accumbens 1 (NAC1), a protein that helps recruit the ubiquitin-proteasome system to dendritic spines. Elevation of glutamate led to selective loss of motor neurons in culture and increased the exit of TDP-43 from the nucleus and binding to cytoplasmic NAC1. “These findings suggest that NAC1 may function to link TDP-43 to the proteasome; thereby, facilitating the post-translational modifications of TDP-43 that lead to the development of ALS,” the authors state.

http://www.ncbi.nlm.nih.gov/pubmed/23022214
Scofield MD, Korutla L, Jackson TG, Kalivas PW, Mackler SA. Nucleus Accumbens 1, a Pox virus and Zinc finger/Bric-a-brac Tramtrack Broad protein binds to TAR DNA-binding protein 43 and has a potential role in Amyotrophic Lateral Sclerosis. Neuroscience. 2012 Sep 25;227C:44-54. doi: 10.1016/j.neuroscience.2012.09.043.

Also of interest:
http://www.ncbi.nlm.nih.gov/pubmed/22961620
Mitchell JC, McGoldrick P, Vance C, Hortobagyi T, Sreedharan J, Rogelj B, Tudor EL, Smith BN, Klasen C, Miller CC, Cooper JD, Greensmith L, Shaw CE. Overexpression of human wild-type FUS causes progressive motor neuron degeneration in an age- and dose-dependent fashion. Acta Neuropathol. 2012 Sep 9. [Epub ahead of print]

P62 Mutations Linked to FTD
Genetic analysis of patients with ALS or FTD revealed several mutations in the sequestosome 1 (SQSTM1) gene, which encodes p62 protein. No mutations were found in controls. “P62 is a multifunctional adapter protein mainly involved in selective autophagy, oxidative stress response, and cell signaling pathways,” the authors note.

http://www.ncbi.nlm.nih.gov/pubmed/22972638
Neurology. 2012 Sep 12. [Epub ahead of print]
SQSTM1 mutations in frontotemporal lobar degeneration and amyotrophic lateral sclerosis.
Rubino E, Rainero I, Chiò A, Rogaeva E, Galimberti D, Fenoglio P, Grinberg Y, Isaia G, Calvo A, Gentile S, Bruni AC, St George-Hyslop PH, Scarpini E, Gallone S, Pinessi L; For the TODEM Study Group.

Stathmin a potential target for axon regeneration
The neurotrophic effect of ciliary neurotrophic factor (CNTF) is partially mediated through activation of STAT3, acting within the axon, according to new research. STAT3 inhibits a microtubule destabilizing protein called stathmin, the authors found, and CNTF promoted interaction of the two, thus leading to microtubule stabilization and growth. Treatment restored axon elongation and maintenance in motor neurons from progressive motor neuronopathy mutant mice, a mouse model of motoneuron disease.

http://www.ncbi.nlm.nih.gov/pubmed/23109669
http://jcb.rupress.org/content/199/3/403
Selvaraj BT, Frank N, Bender FL, Asan E, Sendtner M. Local axonal function of STAT3 rescues axon degeneration in the pmn model of motoneuron disease. J Cell Biol. 2012 Oct 29;199(3):437-51. doi: 10.1083/jcb.201203109.

Female Sex and Hormonal Influence on ALS Explored
Three studies examine the interaction of female sex, estrogens and ALS. In a population-based, case-control study, de Jong et al. found that increased reproductive time-span was associated with a decreased risk for ALS, and both reproductive time-span and lifetime endogenous estrogen exposure were associated with longer survival. In SOD1 mice, Li et al. show that overexpression of mutant SOD reduced proliferation of male, but not female, neural progenitor cells. Finally, Kim et al. show that ablation of the mitochondrial calcium homeostatic protein cyclophilin-D abolished the phenotypic advantage experienced by female SOD1 mice, with no effect on males, and showed that the protective effects of estradiol on motor neurons against glutamate toxicity was lost in the absence of cyclophilin D.

http://www.ncbi.nlm.nih.gov/pubmed/22972621
de Jong S, Huisman M, Sutedja N, van der Kooi A, de Visser M, Schelhaas J, van der Schouw Y, Veldink J, van den Berg L. Endogenous female reproductive hormones and the risk of amyotrophic lateral sclerosis. J Neurol. 2012 Sep 13. [Epub ahead of print]
Li R, Strykowski R, Meyer M, Mulcrone P, Krakora P, Suzuki M. Male-specific differences in proliferation, neurogenesis, and sensitivity to oxidative stress in neural progenitor cells derived from a rat model of ALS. PloS  ONE, 2012.

http://www.ncbi.nlm.nih.gov/pubmed/22961554
Kim HJ, Magranè J, Starkov AA, Manfredi G. The mitochondrial calcium regulator cyclophilin D is an essential component of oestrogen-mediated neuroprotection in amyotrophic lateral sclerosis. Brain. 2012 Sep;135(Pt 9):2865-74.

Clinical Research and Drug Development

Potential Biomarker in Blood Associated with Faster Short-term Decline
Higher concentrations of phosphorylated neurofilament heavy subunit (pNF-H) in cerebrospinal fluid, serum, and plasma each correlate with faster rate of decline in the ALSFRS-R over 4 months, according to a new study. Higher CSF concentration was also correlated with faster decline over 12 months. A doubling in the serum or plasma concentration, but not CSF concentration, was associated with a doubled risk of death over the 12 months following sample collection. Patients with bulbar onset tended to have higher levels than those with spinal onset. The results suggest that pNF-H levels may provide a clinically useful biomarker for predicting the clinical course of ALS over the durations explored in this study.

Boylan KB, Glass JD, Crook JE, Yang C, Thomas CS, Desaro P, Johnston A, Overstreet K, Kelly C, Polak M, Shaw G. Phosphorylated neurofilament heavy subunit (pNF-H) in peripheral blood and CSF as a potential prognostic biomarker in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry 2012;doi: 10.1136/jnnp-2012-303768

Neurodegenerative Disease Fibroblasts Publicly Available
Researchers studying multiple neurodegenerative diseases, including ALS, have created a repository of fibroblasts from patients carrying disease-causing mutations at the National Institute for Neurological Disorders and Stroke (NINDS) Repository at the Coriell Institute for Medical Research. The cells “can be requested by any research group for use in in vitro disease modeling. There are currently 71 mutation-defined cell lines available for request from a wide range of neurological disorders and this collection will be continually expanded,” the authors state.

http://www.ncbi.nlm.nih.gov/pubmed/22952635
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0043099
Wray S, Self M; NINDS Parkinson's Disease iPSC Consortium; NINDS Huntington's Disease iPSC Consortium; NINDS ALS iPSC Consortium, Lewis PA, Taanman JW, Ryan NS, Mahoney CJ, Liang Y, Devine MJ, Sheerin UM, Houlden H, Morris HR, Healy D, Marti-Masso JF, Preza E, Barker S, Sutherland M, Corriveau RA, D'Andrea M, Schapira AH, Uitti RJ, Guttman M, Opala G, Jasinska-Myga B, Puschmann A, Nilsson C, Espay AJ, Slawek J, Gutmann L, Boeve BF, Boylan K, Stoessl AJ, Ross OA, Maragakis NJ, Van Gerpen J, Gerstenhaber M, Gwinn K, Dawson TM, Isacson O, Marder KS, Clark LN, Przedborski SE, Finkbeiner S, Rothstein JD, Wszolek ZK, Rossor MN, Hardy J. Creation of an open-access, mutation-defined fibroblast resource for neurological disease research. PLoS One. 2012;7(8):e43099. Epub 2012 Aug 27.

MuSK Signaling Improves Motor Performance
Increasing activity of the receptor tyrosine kinase MuSK in SOD1 mice delayed disease onset and improved motor performance with no effect on survival. MuSK is required for retrograde signaling from muscle to axon terminal. “These findings suggest that increasing MuSK activity by pharmacological means has the potential to improve motor function in ALS,” the authors state.

http://www.ncbi.nlm.nih.gov/pubmed/22939980
Pérez-García MJ, Burden SJ. Increasing MuSK Activity Delays Denervation and Improves Motor Function in ALS Mice. Cell Rep. 2012 Aug 28. [Epub ahead of print]

Sigma-1R Activation Improves Multiple Disease Parameters
Daily administration of the sigma-1R receptor agonist PRE-084 from 8 to 18 weeks in SOD1 mice extended survival by 15% and improved multiple measures of electrophysiologic and histological function. Activation of the receptor  has been shown to promote neuroprotection after ischemic and traumatic injuries to the central nervous system.

http://www.ncbi.nlm.nih.gov/pubmed/22935988
Mancuso R, Oliván S, Rando A, Casas C, Osta R, Navarro X. Sigma-1R Agonist Improves Motor Function and Motoneuron Survival in ALS Mice. Neurotherapeutics. 2012 Aug 31. [Epub ahead of print]

Neuroprotection from Aminopropyl Carbazoles
Aminopropyl carbazoles may provide a chemical scaffold for development of neuroprotective drugs in ALS, according to new research. A member of the class called P7C3A20 protected spinal cord neurons in SOD1 mice when administered at symptom onset, reducing cell death and mitigating loss of motor function.

http://www.ncbi.nlm.nih.gov/pubmed/23027932
Tesla R, Wolf HP, Xu P, Drawbridge J, Estill SJ, Huntington P, McDaniel L, Knobbe W, Burket A, Tran S, Starwalt R, Morlock L, Naidoo J, Williams NS, Ready JM, McKnight SL, Pieper AA. Neuroprotective efficacy of aminopropyl carbazoles in a mouse model of amyotrophic lateral sclerosis. Proc Natl Acad Sci U S A. 2012 Oct 16;109(42):17016-21. doi: 10.1073/pnas.1213960109. Epub 2012 Oct 1.

Serotonin Receptor Agonist Mitigates Motor Neuron Damage in SBMA
Motor neuronal damage in a mouse model of spinal and bulbar muscular atrophy (SBMA) can be mitigated by suppressing the c-Jun N-terminal kinase (JNK) pathway, according to a new study. The authors show that the CAG triplet repeat within the androgen receptor (AR) gene upregulates calcitonin gene-related peptide α (CGRP1), which in turn activates the JNK pathway. CGRP1 expression could be reduced by naratriptan, a serotonin 1B/1D receptor agonist, and administration of naratriptan reduced damage to motor neurons in vitro and in vivo. “These observations suggest that pharmacological activation of the 5-HT1B/1D receptor may be used therapeutically to treat SBMA and other polyglutamine-related neurodegenerative diseases,” the authors state.

http://www.ncbi.nlm.nih.gov/pubmed/23023499
Minamiyama M, Katsuno M, Adachi H, Doi H, Kondo N, Iida M, Ishigaki S, Fujioka Y, Matsumoto S, Miyazaki Y, Tanaka F, Kurihara H, Sobue G. Naratriptan mitigates CGRP1-associated motor neuron degeneration caused by an expanded polyglutamine repeat tract. Nat Med. 2012 Sep 30;18(10):1531-8. doi: 10.1038/nm.2932. Epub 2012 Sep 30.