Meher Lad, Michael H. Parkinson, Myriam Rai, Massimo Pandolfo, Petya Bogdanova-Mihaylova, Richard A. Walsh, Sinéad Murphy, Anton Emmanuel, Jalesh Panicker† and Paola Giunti; Orphanet Journal of Rare Diseases 201712:158 doi:10.1186/s13023-017-0709-y
Pelvic symptoms are distressing symptoms experienced by patients with Friedreich’s Ataxia (FRDA). The aim of this study was to describe the prevalence of lower urinary tract symptoms (LUTS), bowel and sexual symptoms in FRDA.
A high proportion of FRDA have symptoms suggestive of LUTS, bowel and sexual dysfunction. This is more marked with greater disease duration and later disease onset. These symptoms need to be addressed by clinicians as they can have a detrimental effect on patients.
Wednesday, September 27, 2017
Tuesday, September 26, 2017
Management of Cardiac Involvement Associated With Neuromuscular Diseases: A Scientific Statement From the American Heart Association
Brian Feingold, William T. Mahle, Scott Auerbach, Paula Clemens, Andrea A. Domenighetti, John L. Jefferies, Daniel P. Judge, Ashwin K. Lal, Larry W. Markham, W. James Parks, Takeshi Tsuda, Paul J. Wang, Shi-Joon Yoo
and On behalf of the American Heart Association Pediatric Heart Failure Committee of the Council on Cardiovascular Disease in the Young; Council on Clinical Cardiology; Council on Cardiovascular Radiology and Intervention; Council on Functional Genomics and Translational Biology; and Stroke Council; Circulation. 2017;136:e200-e231 doi:10.1161/CIR.0000000000000526
For many neuromuscular diseases (NMDs), cardiac disease represents a major cause of morbidity and mortality. The management of cardiac disease in NMDs is made challenging by the broad clinical heterogeneity that exists among many NMDs and by limited knowledge about disease-specific cardiovascular pathogenesis and course-modifying interventions.
Cardiac manifestations consist of LV hypertrophy with fibrosis and scarring, arrhythmias, and progressive HF. Cardiac dysfunction is the most frequent cause of death in FA.
Because no relationship between severity of cardiac involvement and neurological status has been identified, regular cardiac evaluation regardless of neurological status is likely warranted.
and On behalf of the American Heart Association Pediatric Heart Failure Committee of the Council on Cardiovascular Disease in the Young; Council on Clinical Cardiology; Council on Cardiovascular Radiology and Intervention; Council on Functional Genomics and Translational Biology; and Stroke Council; Circulation. 2017;136:e200-e231 doi:10.1161/CIR.0000000000000526
For many neuromuscular diseases (NMDs), cardiac disease represents a major cause of morbidity and mortality. The management of cardiac disease in NMDs is made challenging by the broad clinical heterogeneity that exists among many NMDs and by limited knowledge about disease-specific cardiovascular pathogenesis and course-modifying interventions.
Cardiac manifestations consist of LV hypertrophy with fibrosis and scarring, arrhythmias, and progressive HF. Cardiac dysfunction is the most frequent cause of death in FA.
Because no relationship between severity of cardiac involvement and neurological status has been identified, regular cardiac evaluation regardless of neurological status is likely warranted.
Sunday, September 24, 2017
Diabetes mellitus as the presenting feature of Friedreich's ataxia
Garg M, Kulkarni SD, Shah KN, Hegde AU. J Neurosci Rural Pract 2017;8, Suppl S1:117-9 DOI: 10.4103/jnrp.jnrp_112_17
This is an unusual report of diabetes as the initial presentation in a patient with FA. This patient has also shown accelerated course of disease. However, the genetic mechanisms accounting for phenotypic variations in FA remain to be fully elucidated. In patients with diabetes who present with early sensory neuropathy or ataxia, FA should be a consideration even in the pediatric age group. A better understanding of molecular mechanisms will certainly pave the way for improved therapeutic strategies in the near future.
This is an unusual report of diabetes as the initial presentation in a patient with FA. This patient has also shown accelerated course of disease. However, the genetic mechanisms accounting for phenotypic variations in FA remain to be fully elucidated. In patients with diabetes who present with early sensory neuropathy or ataxia, FA should be a consideration even in the pediatric age group. A better understanding of molecular mechanisms will certainly pave the way for improved therapeutic strategies in the near future.
Saturday, September 23, 2017
Lipophilic methylene violet analogues as modulators of mitochondrial function and dysfunction
Sandipan Roy Chowdhury, Omar M. Khdour, Indrajit Bandyopadhyay, Sidney M. Hecht. In Bioorganic & Medicinal Chemistry, 2017,ISSN 0968-0896, doi:10.1016/j.bmc.2017.08.021.
The methylene violet analogues were evaluated for their ability to preserve mitochondrial function in Friedreich’s ataxia (FRDA) lymphocytes. The analogues were shown to be efficient ROS scavengers, and able to protect cultured FRDA lymphocytes from oxidative stress resulting from inhibition of complex I. The analogues also preserved mitochondrial membrane potential and augmented ATP production. The analogues were found to be better antioxidants than the parent compounds methylene blue and methylene violet.
Keywords: Methylene blue; Methylene violet; Mitochondria; Reactive oxygen species; Friedreich’s ataxia; Cytoprotection
The methylene violet analogues were evaluated for their ability to preserve mitochondrial function in Friedreich’s ataxia (FRDA) lymphocytes. The analogues were shown to be efficient ROS scavengers, and able to protect cultured FRDA lymphocytes from oxidative stress resulting from inhibition of complex I. The analogues also preserved mitochondrial membrane potential and augmented ATP production. The analogues were found to be better antioxidants than the parent compounds methylene blue and methylene violet.
Keywords: Methylene blue; Methylene violet; Mitochondria; Reactive oxygen species; Friedreich’s ataxia; Cytoprotection
Friday, September 22, 2017
Manuela Corti, assistant professor in the department of pediatrics at the University of Florida in Gainesville, was awarded an MDA research grant totaling $298,954 over three years to study gene therapy in Friedreich’s ataxia (FA).
Source: MDA.org, 09/21/2017.
Our objective is to develop a treatment strategy for FA, one of the most common forms of ataxia. Specifically, our research plan focuses on the correction of both the cardiac and neurological degeneration found in the disease. These changes are due to harmful changes in the frataxin gene.
This work will specifically answer important mechanistic questions in a new FA mouse model, which has many of the symptoms of the human patients. First, we will identify the best route of delivery for the frataxin gene in the nervous system by comparing three different strategies for injecting the vector (delivery vehicle). Second, we will test the safety of repeated delivery of the frataxin gene vector in combination with medications that will prevent reactions against the frataxin protein and the vector components. Completion of this project will be an important milestone in the development of a treatment strategy that will dramatically improve quality of life for FA patients.
Our objective is to develop a treatment strategy for FA, one of the most common forms of ataxia. Specifically, our research plan focuses on the correction of both the cardiac and neurological degeneration found in the disease. These changes are due to harmful changes in the frataxin gene.
This work will specifically answer important mechanistic questions in a new FA mouse model, which has many of the symptoms of the human patients. First, we will identify the best route of delivery for the frataxin gene in the nervous system by comparing three different strategies for injecting the vector (delivery vehicle). Second, we will test the safety of repeated delivery of the frataxin gene vector in combination with medications that will prevent reactions against the frataxin protein and the vector components. Completion of this project will be an important milestone in the development of a treatment strategy that will dramatically improve quality of life for FA patients.
Bioavailability of resveratrol: Possibilities for enhancement
Konrad de Vries, Morné Strydom, Vanessa Steenkamp, Journal of Herbal Medicine, Available online 12 September 2017, ISSN 2210-8033, doi:10.1016/j.hermed.2017.09.002.
Resveratrol is a naturally occurring polyphenol that has been shown to elicit a variety of beneficial effects in vitro. Translating these gains to in vivo and clinical settings has proven to be a major challenge, because of its poor oral bioavailability. This caveat was confirmed after reviewing clinical trials conducted on this investigational product over the past two years. This review provides alternative methods of administration of resveratrol which may enhance its bioavailability. However, these methods: remain to be validated.
From current literature, it is clear that orally administered resveratrol has low bioavailability in vivo. A variety of methods that could overcome the inherent issues with resveratrol bioavailability have been proposed, however these need to be further validated in order to determine which are safe, effective and superior to traditional oral administration of resveratrol before clinical evaluation can take place.
Resveratrol is a naturally occurring polyphenol that has been shown to elicit a variety of beneficial effects in vitro. Translating these gains to in vivo and clinical settings has proven to be a major challenge, because of its poor oral bioavailability. This caveat was confirmed after reviewing clinical trials conducted on this investigational product over the past two years. This review provides alternative methods of administration of resveratrol which may enhance its bioavailability. However, these methods: remain to be validated.
From current literature, it is clear that orally administered resveratrol has low bioavailability in vivo. A variety of methods that could overcome the inherent issues with resveratrol bioavailability have been proposed, however these need to be further validated in order to determine which are safe, effective and superior to traditional oral administration of resveratrol before clinical evaluation can take place.
Thursday, September 21, 2017
Friedreich Ataxia: Treatment with Genetic Approach
Martin L. Nelwan, Journal of Advances in Biology & Biotechnology, 2394-1081,Vol.: 14, Issue.: 4
Adequate treatments are unavailable for this disorder at present. However, to treat FA, genetic approach can be used. The approach may comprise genetic counseling and use of advanced therapy, gene therapy for instance.
Adequate treatments are unavailable for this disorder at present. However, to treat FA, genetic approach can be used. The approach may comprise genetic counseling and use of advanced therapy, gene therapy for instance.
Wednesday, September 20, 2017
Molecular Alterations in a Mouse Cardiac Model of Friedreich’s Ataxia: An Impaired Nrf2 Response Mediated via Up-Regulation of Keap1 and Activation of the Gsk3β Axis
Amy Anzovino, Shannon Chiang, Bronwyn E. Brown, Clare L. Hawkins, Des R. Richardson, Michael L.-H. Huang, The American Journal of Pathology, Available online 19 September 2017, ISSN 0002-9440, doi:10.1016/j.ajpath.2017.08.021.
Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a master regulator of the anti-oxidant response. However, studies in models of Friedreich’s ataxia (FA), a neuro- and cardio-degenerative disease associated with oxidative stress, reported decreased Nrf2 expression due to unknown mechanisms.
Collectively, cardiac frataxin-deficiency reduces Nrf2 levels via two potential mechanisms: increased levels of cytosolic Keap1, and activation of Gsk3β-signaling that decreases nuclear Nrf2. These findings are in contrast to the frataxin-deficient skeletal muscle, where Nrf2 was not decreased.
Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a master regulator of the anti-oxidant response. However, studies in models of Friedreich’s ataxia (FA), a neuro- and cardio-degenerative disease associated with oxidative stress, reported decreased Nrf2 expression due to unknown mechanisms.
Collectively, cardiac frataxin-deficiency reduces Nrf2 levels via two potential mechanisms: increased levels of cytosolic Keap1, and activation of Gsk3β-signaling that decreases nuclear Nrf2. These findings are in contrast to the frataxin-deficient skeletal muscle, where Nrf2 was not decreased.
Tuesday, September 19, 2017
Movement disorders hidden in the neuromuscular clinic
J. Reimann, S. Paus, Neuromuscular Disorders, Volume 27, Supplement 2, October 2017, Page S243, ISSN 0960-8966, doi:10.1016/j.nmd.2017.06.531.
We present these exemplary cases to increase awareness of these disorders and the differential diagnosis for those working in neuromuscular clinics, as well as an incentive for more interaction with the movement disorder field, in particular when struggling to define a diagnosis. We also observe a number of referrals that turn out to be movement disorders. In some, this is caused by known neuromuscular manifestations while missing the CNS signs. Examples are our cases of Huntington’s disease presenting with weakness, pain and atrophy of the calves and of Friedreich ataxia send for work-up of sensory axonal neuropathy and scoliosis, where “restlessness” and “nasal speech”, respectively, were ignored as symptoms. In others, the attribution of the pathophysiology to muscle is simply wrong.
We present these exemplary cases to increase awareness of these disorders and the differential diagnosis for those working in neuromuscular clinics, as well as an incentive for more interaction with the movement disorder field, in particular when struggling to define a diagnosis. We also observe a number of referrals that turn out to be movement disorders. In some, this is caused by known neuromuscular manifestations while missing the CNS signs. Examples are our cases of Huntington’s disease presenting with weakness, pain and atrophy of the calves and of Friedreich ataxia send for work-up of sensory axonal neuropathy and scoliosis, where “restlessness” and “nasal speech”, respectively, were ignored as symptoms. In others, the attribution of the pathophysiology to muscle is simply wrong.
Monday, September 18, 2017
Relationship Between Neurological Disability and Visual Impairment in Patients With ALS or Friedreich's Ataxia
ClinicalTrials.gov Identifier: NCT03285204, First received: March 8, 2017
Principal Investigator: Jose L Urcelay, PhD HGU Gregorio Marañón.
Location: Madrid, Spain,
The aim of this study is to obtain an early biomarker of amyotrophic lateral sclerosis and Friedreich's Ataxia which allows to diagnose the disease in an initial stage and to follow up the patient with optic coherence tomography, a fast, non-invasive and comfortable method.
Principal Investigator: Jose L Urcelay, PhD HGU Gregorio Marañón.
Location: Madrid, Spain,
The aim of this study is to obtain an early biomarker of amyotrophic lateral sclerosis and Friedreich's Ataxia which allows to diagnose the disease in an initial stage and to follow up the patient with optic coherence tomography, a fast, non-invasive and comfortable method.
Saturday, September 16, 2017
Alternative mitochondrial electron transfer for the treatment of neurodegenerative diseases and cancers: Methylene blue connects the dots
Shao-Hua Yang, Wenjun Li, Nathalie Sumien, Michael Forster, James W. Simpkins, Ran Liu, In Progress in Neurobiology, Volume 157, 2017, Pages 273-291, ISSN 0301-0082, doi:10.1016/j.pneurobio.2015.10.005.
Highlights:
Reprogramming energetic metabolism is a common feature for neurodegenerative diseases and cancers.
Methylene blue functions as an alternative mitochondrial electron transfer carrier, enhancing bioenergetics and inhibiting biosynthetics.
Methylene blue provides protective effect in rodent models of Parkinson disease, Alzheimer's disease, Huntington's disease, and Friedreich's ataxia.
Methylene blue reverses Warburg's effect and inhibits cancers proliferation.
Alternative mitochondrial electron transfer may provide a common novel therapeutic mechanism for cancers and neurodegenerative diseases.
Highlights:
Reprogramming energetic metabolism is a common feature for neurodegenerative diseases and cancers.
Methylene blue functions as an alternative mitochondrial electron transfer carrier, enhancing bioenergetics and inhibiting biosynthetics.
Methylene blue provides protective effect in rodent models of Parkinson disease, Alzheimer's disease, Huntington's disease, and Friedreich's ataxia.
Methylene blue reverses Warburg's effect and inhibits cancers proliferation.
Alternative mitochondrial electron transfer may provide a common novel therapeutic mechanism for cancers and neurodegenerative diseases.
Sunday, September 10, 2017
Market access of Spinraza (Nusinersen) for spinal muscular atrophy: intellectual property rights, pricing, value and coverage considerations
S Simoens and I Huys; Gene Therapy , (7 September 2017) | doi:10.1038/gt.2017.79
In December 2016, Spinraza (Nusinersen), Biogen (Durham, NC, USA) was the first treatment to be registered as an orphan drug by the US Food and Drug Administration for SMA. In Europe, a gene therapy in principle classifies as an Advanced Therapy Medicinal Product (ATMP), covered by a regulatory framework with particular incentives for drug developers. For Nusinersen, the European Medicines Agency recently granted the Accelerated Assessment status in 2016. With respect to its price, it has been reported that the annual wholesale costs of treating a patient with Nusinersen will amount to $750 000 for the first year and $375 000 for subsequent years. Biogen argues that this price is in line with that of other orphan drugs for rare diseases.
Despite marketing authorization of Nusinersen in the United States and in Europe, patient access to this new promising therapy remains uncertain. The price of this new drug clearly triggers several questions in terms of justification, transparency and responsibility.
The aim of this Comment is to identify and to discuss issues related to the market access of Nusinersen for SMA by focusing specifically on intellectual property rights, pricing, value and coverage considerations from the perspective of the company, patients and society.
The pricing of Nusinersen is a black box, although Biogen claims that the price of Nusinersen is in line with its clinical benefit and with prices of other orphan drugs. Any data about the value assessment of Nusinersen is not (publicly)available. This asymmetry (or even absence) of information between Biogen and insurers needs to be tackled in an era when insurers (and society at large) need to make and justify difficult choices. A quantifiable and evidence-driven approach to pricing and value assessment is required and such data need to be available to the stakeholders involved.
In December 2016, Spinraza (Nusinersen), Biogen (Durham, NC, USA) was the first treatment to be registered as an orphan drug by the US Food and Drug Administration for SMA. In Europe, a gene therapy in principle classifies as an Advanced Therapy Medicinal Product (ATMP), covered by a regulatory framework with particular incentives for drug developers. For Nusinersen, the European Medicines Agency recently granted the Accelerated Assessment status in 2016. With respect to its price, it has been reported that the annual wholesale costs of treating a patient with Nusinersen will amount to $750 000 for the first year and $375 000 for subsequent years. Biogen argues that this price is in line with that of other orphan drugs for rare diseases.
Despite marketing authorization of Nusinersen in the United States and in Europe, patient access to this new promising therapy remains uncertain. The price of this new drug clearly triggers several questions in terms of justification, transparency and responsibility.
The aim of this Comment is to identify and to discuss issues related to the market access of Nusinersen for SMA by focusing specifically on intellectual property rights, pricing, value and coverage considerations from the perspective of the company, patients and society.
The pricing of Nusinersen is a black box, although Biogen claims that the price of Nusinersen is in line with its clinical benefit and with prices of other orphan drugs. Any data about the value assessment of Nusinersen is not (publicly)available. This asymmetry (or even absence) of information between Biogen and insurers needs to be tackled in an era when insurers (and society at large) need to make and justify difficult choices. A quantifiable and evidence-driven approach to pricing and value assessment is required and such data need to be available to the stakeholders involved.
Detection of long repeat expansions from PCR-free whole-genome sequence data
Egor Dolzhenko, Joke J.F.A. van Vugt, Richard J. Shaw, Mitchell A. Bekritsky, Marka van Blitterswijk, Giuseppe Narzisi, Subramanian S. Ajay, Vani Rajan, Bryan Lajoie, Nathan H. Johnson, Zoya Kingsbury, Sean J. Humphray, Raymond D. Schellevis, William J. Brands, Matt Baker, Rosa Rademakers, Maarten Kooyman, Gijs H.P. Tazelaar, Michael A. van Es, Russell McLaughlin, William Sproviero, Aleksey Shatunov, Ashley Jones, Ahmad Al Khleifat, Alan Pittman, Sarah Morgan, Orla Hardiman, Ammar Al-Chalabi, Chris Shaw, Bradley Smith, Edmund J. Neo, Karren Morrison, Pam Shaw, Catherine Reeves, Lara Winterkorn, Nancy S. Wexler, The US-Venezuela Collaborative Research Group, David E. Housman, Christopher W. Ng, Alina L. Li, Ryan J. Taft, Leonard H. van den Berg, David R. Bentley, Jan H. Veldink, and Michael A. Eberle. Genome Res. gr. 225672.117 Published in Advance September 8, 2017, doi:10.1101/gr.225672.117
We further applied our algorithm to a set of 152 samples where every sample had one of eight different pathogenic repeat expansions including those associated with fragile X syndrome, Friedreich's ataxia and Huntington's disease and correctly flagged all but one of the known repeat expansions. Thus, ExpansionHunter can be used to accurately detect known pathogenic repeat expansions and provides researchers with a tool that can be used to identify new pathogenic repeat expansions. The software is licensed under GPL v3.0 and the source code is freely available on GitHub.
We further applied our algorithm to a set of 152 samples where every sample had one of eight different pathogenic repeat expansions including those associated with fragile X syndrome, Friedreich's ataxia and Huntington's disease and correctly flagged all but one of the known repeat expansions. Thus, ExpansionHunter can be used to accurately detect known pathogenic repeat expansions and provides researchers with a tool that can be used to identify new pathogenic repeat expansions. The software is licensed under GPL v3.0 and the source code is freely available on GitHub.
Saturday, September 9, 2017
Nitric oxide prevents Aft1 activation and metabolic remodeling in Frataxin-deficient yeast
David Alsina, Joaquim Ros, Jordi Tamarit, Redox Biology, Available online 6 September 2017, ISSN 2213-2317, doi:10.1016/j.redox.2017.09.001.
A major conclusion of this work is that Yfh1 deficiency activates the iron regulon by a different pathway than iron-sulfur loss. Therefore, alternative pathways for Aft1 activation may exist in yeast which, as discussed above, could be related to the presence of anomalous iron species. We have also observed that metabolic status can be efficiently monitored using a targeted proteomics strategy focusing on key metabolic enzymes. Finally, the observation that NO can mitigate the defects caused by Yfh1 deficiency supports the hypothesis that Yfh1 loss leads to the increased presence of anomalous iron forms, and that this anomalous iron plays a central role in the events caused by Yfh1 deficiency. It also suggests that NO donors could have a therapeutic effect in FRDA patients. NO donors such as SNP or nitroglycerin have been used for more than a century for controlling congestive heart failure associated with heart attack or lowering blood pressure during surgery. Beyond its vasodilating action, neuroprotective properties have been demonstrated for NO in an iron-induced model of Parkinson's disease. This observation, together with the results presented in this work, opens the possibility to explore the potential therapeutic effect of NO donors in mammalian models of FRDA.
A major conclusion of this work is that Yfh1 deficiency activates the iron regulon by a different pathway than iron-sulfur loss. Therefore, alternative pathways for Aft1 activation may exist in yeast which, as discussed above, could be related to the presence of anomalous iron species. We have also observed that metabolic status can be efficiently monitored using a targeted proteomics strategy focusing on key metabolic enzymes. Finally, the observation that NO can mitigate the defects caused by Yfh1 deficiency supports the hypothesis that Yfh1 loss leads to the increased presence of anomalous iron forms, and that this anomalous iron plays a central role in the events caused by Yfh1 deficiency. It also suggests that NO donors could have a therapeutic effect in FRDA patients. NO donors such as SNP or nitroglycerin have been used for more than a century for controlling congestive heart failure associated with heart attack or lowering blood pressure during surgery. Beyond its vasodilating action, neuroprotective properties have been demonstrated for NO in an iron-induced model of Parkinson's disease. This observation, together with the results presented in this work, opens the possibility to explore the potential therapeutic effect of NO donors in mammalian models of FRDA.
Thursday, September 7, 2017
RNA biology of disease-associated microsatellite repeat expansions
Kushal J. Rohilla and Keith T. Gagnon, Acta Neuropathologica 20175:63, doi:10.1186/s40478-017-0468-y
This review focuses on the potential impact that simple tandem repeat expansions can have on the biology and metabolism of RNA that contain them and underscores important gaps in understanding. Merging the molecular biology of repeat expansion disorders with the current understanding of RNA biology, including splicing, transcription, transport, turnover and translation, will help clarify mechanisms of disease and improve therapeutic development.
Repeat expansion sequences are known to inhibit or impede RNA Polymerase II (Pol II) initiation or elongation either directly or via induction of a repressed chromatin state. Expansions like the GAA repeat in FRDA have been implicated in reduced or silenced transcription.
Examples of microsatellite repeat expansions modulating splicing include the GAA repeat expansion associated with FRDA. When placed near reporter gene exons or in the first intron of a frataxin minigene system, the GAA repeat caused complex splicing defects and accumulation of aberrant splice products. The mechanism proposed involved binding of various splicing factors to the GAA repeat-containing transcripts.
Therapeutic approaches to control xtrRNA transcription and splicing:
Characterizing the effect of microsatellite expansions on transcription and splicing will directly benefit therapeutic approaches for repeat expansion disorders. Proof-of-principle methods to locally disrupt the interactions of xtrRNA at repeat expansion loci, such as R-loops, have been demonstrated for FXS and FRDA using small molecules and nucleic acids.
For splicing-based therapeutics, blocking inclusion of repeat expansion-containing introns, such as with splice-modulating antisense oligonucleotides or small RNAs, could prove to be useful for disorders like FRDA and C9FTD/ALS.
With the emergence of gene editing technologies, the direct removal of repeat expansions from the genome may also be possible. Removal of genomic repeat expansions could eliminate the possibility of xtrRNA expression or reverse repressive epigenetic states.While potential CRISPR-based therapeutics are exciting, precautions must be taken to address potential pitfalls and challenges like off-target effects, delivery, and cell-type specific mechanisms of DNA damage repair
This review focuses on the potential impact that simple tandem repeat expansions can have on the biology and metabolism of RNA that contain them and underscores important gaps in understanding. Merging the molecular biology of repeat expansion disorders with the current understanding of RNA biology, including splicing, transcription, transport, turnover and translation, will help clarify mechanisms of disease and improve therapeutic development.
Repeat expansion sequences are known to inhibit or impede RNA Polymerase II (Pol II) initiation or elongation either directly or via induction of a repressed chromatin state. Expansions like the GAA repeat in FRDA have been implicated in reduced or silenced transcription.
Examples of microsatellite repeat expansions modulating splicing include the GAA repeat expansion associated with FRDA. When placed near reporter gene exons or in the first intron of a frataxin minigene system, the GAA repeat caused complex splicing defects and accumulation of aberrant splice products. The mechanism proposed involved binding of various splicing factors to the GAA repeat-containing transcripts.
Therapeutic approaches to control xtrRNA transcription and splicing:
Characterizing the effect of microsatellite expansions on transcription and splicing will directly benefit therapeutic approaches for repeat expansion disorders. Proof-of-principle methods to locally disrupt the interactions of xtrRNA at repeat expansion loci, such as R-loops, have been demonstrated for FXS and FRDA using small molecules and nucleic acids.
For splicing-based therapeutics, blocking inclusion of repeat expansion-containing introns, such as with splice-modulating antisense oligonucleotides or small RNAs, could prove to be useful for disorders like FRDA and C9FTD/ALS.
With the emergence of gene editing technologies, the direct removal of repeat expansions from the genome may also be possible. Removal of genomic repeat expansions could eliminate the possibility of xtrRNA expression or reverse repressive epigenetic states.While potential CRISPR-based therapeutics are exciting, precautions must be taken to address potential pitfalls and challenges like off-target effects, delivery, and cell-type specific mechanisms of DNA damage repair
Wednesday, September 6, 2017
A Defective mRNA Cleavage and Polyadenylation Complex Facilitates Expansions of Transcribed (GAA)n Repeats Associated with Friedreich’s Ataxia
Ryan J. McGinty, Franco Puleo, Anna Y. Aksenova, Julia A. Hisey, Alexander A. Shishkin, Erika L. Pearson, Eric T. Wang, David E. Housman, Claire Moore, Sergei M. Mirkin, Cell Reports, Volume 20, Issue 10, 5 September 2017, Pages 2490-2500, ISSN 2211-1247, doi:10.1016/j.celrep.2017.08.051
Tuesday, September 5, 2017
Engineered Axonal Tracts as “Living Electrodes” for Synaptic-Based Modulation of Neural Circuitry
M. D. Serruya, J. P. Harris, D. O. Adewole, L. A. Struzyna, J. C. Burrell, A. D. Nemes, D. Petrov, R. H. Kraft, H. I. Chen, J. A. Wolf, D. K. Cullen, Adv. Funct. Mater. 2017, doi:10.1002/adfm.201701183
Brain–computer interface and neuromodulation strategies relying on penetrating non-organic electrodes/optrodes are limited by an inflammatory foreign body response that ultimately diminishes performance. A novel “biohybrid” strategy is advanced, whereby living neurons, biomaterials, and microelectrode/optical technology are used together to provide a biologically-based vehicle to probe and modulate nervous-system activity. Microtissue engineering techniques are employed to create axon-based “living electrodes”, which are columnar microstructures comprised of neuronal population(s) projecting long axonal tracts within the lumen of a hydrogel designed to chaperone delivery into the brain.
Friedrich’s ataxia: Patients develop severe motor impairments in the absence of proprioceptive and epicritic signals from the periphery. Living electrodes could provide an articial sensory arc: by tapping into signals from periphery (such as strain gauges, accelerometers and gyroscopes worn at joints in all four limbs, or from implanted cuff recordings of peripheral nerves), living electrodes implanted into primary sensory cortices could provide sensory feedback and allow improved voluntary move ment and functional independence. Grown with glutamatergic neurons, these living electrodes could be implanted to terminate in layer IV of the postcentral gyrus; because living electrodes are themselves quite small, multiple constructs could be implanted corresponding to different joints (e.g., gyros from the left knee driving a living electrode implanted in the right medial sensory cortex, left elbow and shoulder to right lateral sensory cortex, and viceversa for the right extremities and left hemisphere).
Brain–computer interface and neuromodulation strategies relying on penetrating non-organic electrodes/optrodes are limited by an inflammatory foreign body response that ultimately diminishes performance. A novel “biohybrid” strategy is advanced, whereby living neurons, biomaterials, and microelectrode/optical technology are used together to provide a biologically-based vehicle to probe and modulate nervous-system activity. Microtissue engineering techniques are employed to create axon-based “living electrodes”, which are columnar microstructures comprised of neuronal population(s) projecting long axonal tracts within the lumen of a hydrogel designed to chaperone delivery into the brain.
Friedrich’s ataxia: Patients develop severe motor impairments in the absence of proprioceptive and epicritic signals from the periphery. Living electrodes could provide an articial sensory arc: by tapping into signals from periphery (such as strain gauges, accelerometers and gyroscopes worn at joints in all four limbs, or from implanted cuff recordings of peripheral nerves), living electrodes implanted into primary sensory cortices could provide sensory feedback and allow improved voluntary move ment and functional independence. Grown with glutamatergic neurons, these living electrodes could be implanted to terminate in layer IV of the postcentral gyrus; because living electrodes are themselves quite small, multiple constructs could be implanted corresponding to different joints (e.g., gyros from the left knee driving a living electrode implanted in the right medial sensory cortex, left elbow and shoulder to right lateral sensory cortex, and viceversa for the right extremities and left hemisphere).
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