Research Center for Genetic Medicine

Washington, DC, United States

Research Center for Genetic Medicine

Washington, DC, United States
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Gordon E.M.,Georgetown University | Stollstorff M.,Georgetown University | Devaney J.M.,Research Center for Genetic Medicine | Bean S.,Georgetown University | And 2 more authors.
Cerebral Cortex | Year: 2012

Functional connectivity between brain regions can define large-scale neural networks and provide information about relationships between those networks. We examined how relationships within and across intrinsic connectivity networks were 1) sensitive to individual differences in dopaminergic function, 2) modulated by cognitive state, and 3) associated with executive behavioral traits. We found that regardless of cognitive state, connections between frontal, parietal, and striatal nodes of Task-Positive networks (TPNs) and Task-Negative networks (TNNs) showed higher functional connectivity in 10/10 homozygotes of the dopamine transporter gene, a polymorphism influencing synaptic dopamine, than in 9/10 heterozygotes. However, performance of a working memory task (a state requiring dopamine release) modulated genotype differences selectively, such that cross-network connectivity between TPNs and TNNs was higher in 10/10 than 9/10 subjects during working memory but not during rest. This increased cross-network connectivity was associated with increased self-reported measures of impulsivity and inattention traits. By linking a gene regulating synaptic dopamine to a phenotype characterized by inefficient executive function, these findings validate cross-network connectivity as an endophenotype of executive dysfunction. © The Author 2011. Published by Oxford University Press. All rights reserved.

Hyldahl R.D.,Brigham Young University | Hubal M.J.,Research Center for Genetic Medicine
Muscle and Nerve | Year: 2014

The response of skeletal muscle to unaccustomed eccentric exercise has been studied widely, yet it is incompletely understood. This review is intended to provide an up-to-date overview of our understanding of how skeletal muscle responds to eccentric actions, with particular emphasis on the underlying molecular and cellular mechanisms of damage and recovery. This review begins by addressing the question of whether eccentric actions result in physical damage to muscle fibers and/or connective tissue. We next review the symptomatic manifestations of eccentric exercise (i.e., indirect damage markers, such as delayed onset muscle soreness), with emphasis on their relatively poorly understood molecular underpinnings. We then highlight factors that potentially modify the muscle damage response following eccentric exercise. Finally, we explore the utility of using eccentric training to improve muscle function in populations of healthy and aging individuals, as well as those living with neuromuscular disorders.© 2013 Wiley Periodicals, Inc.

Lepper C.,Carnegie Institution for Science | Partridge T.A.,Research Center for Genetic Medicine | Fan C.-M.,Carnegie Institution for Science
Development | Year: 2011

Skeletal muscle tissue provides mechanical force for locomotion of all vertebrate animals. It is prone to damage from acute physical trauma and physiological stress. To cope with this, it possesses a tremendous capacity for rapid and effective repair that is widely held to be accomplished by the satellite cells lying between the muscle fiber plasmalemma and the basement membrane. Cell transplantation and lineage-tracing studies have demonstrated that Pax7-expressing (Pax7 +) satellite cells can repair damaged muscle tissue repeatedly after several bouts of acute injury. These findings provided evidence that Pax7 + cells are muscle stem cells. However, stem cells from a variety of other origins are also reported to contribute to myofibers upon engraftment into muscles, questioning whether satellite cells are the only stem cell source for muscle regeneration. Here, we have engineered genetic ablation of Pax7 + cells to test whether there is any significant contribution to muscle regeneration after acute injury from cells other than this source. We find that such elimination of Pax7 + cells completely blocks regenerative myogenesis either following injury to the tibialis anterior (TA) muscle or after transplantation of extensor digitorum longus (EDL) muscles into nude mice. As Pax7 is specifically expressed in satellite cells, we conclude that they are essential for acute injury-induced muscle regeneration. It remains to be established whether there is any significant role for stem cells of other origins. The implications of our results for muscle stem cell-based therapy are discussed. © 2011. Published by The Company of Biologists Ltd.

Rocha C.T.,Research Center for Genetic Medicine | Hoffman E.P.,Research Center for Genetic Medicine
Current Neurology and Neuroscience Reports | Year: 2010

The muscular dystrophies show muscle degeneration and regeneration (necrotizing myopathy) on muscle biopsy, typically associated with elevated serum creatine kinase, and muscle weakness. In 1986, the first causative gene was identified for the most prevalent and best-characterized form of muscular dystrophy, Duchenne muscular dystrophy. Over the past 25 years, the number of other genes determined to cause different subtypes has grown rapidly. This review gives a synopsis of the 45 genetically defined types of muscular dystrophies and describes the clinical, pathologic, and molecular aspects of each disease. DNA diagnosis remains the most sensitive and specific method for differential diagnosis, but molecular diagnostics can be expensive and complex (because of multiple genes at multiple testing facilities) and reimbursement may be challenging to obtain. However, emerging DNA sequencing technologies (eg, single-molecule thirdgeneration sequencing units) promise to dramatically reduce the complexity and costs of DNA diagnostics. Treatment for nearly all forms remains supportive and is aimed at preventing complications. However, several promising approaches have entered clinical trials, providing tangible hope that quality of life will improve for many patients in the near future. © Springer Science+Business Media, LLC 2010.

Partridge T.A.,Research Center for Genetic Medicine
Current Opinion in Neurology | Year: 2011

Purpose of Review: As the first genetic disease for which the culpable gene was identified by positional cloning, Duchenne muscular dystrophy has served as a paradigm for therapeutic approaches to neuromuscular disease, in which role it has proved especially testing. The large mass and broad distribution of the target tissue, skeletal muscle, have stretched the patience and ingenuity of those seeking therapeutic delivery of the largest known gene. The most promising recent advances are summarized in this article. Recent Findings: The main obstacle to genetic therapies has been the development of vectors able to efficiently deliver large, potentially therapeutic, genetic constructs to the large and widely dispersed mass of body musculature. Recombinant viral vectors that efficiently transduce muscle are unable to carry the full-length construct. Myogenic cells that are able both to carry full-length genes and to repair muscles are technically challenging to produce in sufficient quantity. A recent promising approach is the use of agents that obviate the mutation. Summary: Although genetic and cell-mediated approaches are currently showing genuine promise in preclinical and clinical trials, there remains considerable interest in the development of agents that ameliorate the downstream pathology. One general challenge is the three-way tension between the interests of patients, regulators, and the biotechnology industry. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Hamed S.A.,Assiut University | Hamed S.A.,Research Center for Genetic Medicine
Restorative Neurology and Neuroscience | Year: 2010

Cumulative evidences from experimental and clinical studies indicate that in some patients, not only prolonged but also repetitive brief seizures, may trigger series of damage promoting mechanisms which evolve over a period of time (up to years). They result in progressive degeneration and loss of function of several neuronal cell populations, thus rending the brain abnormal and resistant to antiepileptic medications (AEDs). This probably explains that in some patients, a) there is a delay from the onset of brain insult to the seizure onset, and b) suppression of seizures by AEDs is alone insufficient without clear prediction of disease progression. In this review, the analysis of information follows the assumption that epilepsy is a slowly progressive and a neurobiologically pleotropic disorder. Interaction between genes, neurotransmitters, ion channels, acid-base balance, mitochondria, calcium, glutamate and oxidative/antioxidants mechanisms, will determine the fate of the epilepsy process. The concept of neuroprotection aims not only to suppress seizures (anticonvulsant effect), but also to strengthen the auto-protective and repair mechanisms (antiepileptogenic and disease-modification effects) which prevent the development of spontaneous seizures, cognitive and behavioral problems later in life. This review is focusing on molecular evaluation of several models of epilepsy for the potential to follow disease modification and neuroprotection. Although AEDs of today possess multiple mechanisms of action, but mostly they are treating one part of the disease which is the seizures and do not offer high prospects of modification of the disease. This review is also discussing the prospects of novel drugs, molecular manipulations and cell therapy which address disease modification as approachs that will dominate the field of drug development and research on epilepsy in the future. © 2010-IOS Press and the authors. All rights reserved.

Yokota T.,Research Center for Genetic Medicine
Methods in molecular biology (Clifton, N.J.) | Year: 2011

Exon skipping is currently one of the most promising molecular therapies for Duchenne muscular -dystrophy (DMD). We have recently developed multiple exon skipping targeting exons 6 and 8 in -dystrophin mRNA of canine X-linked muscular dystrophy (CXMD), an animal model of DMD, which exhibits severe dystrophic phenotype in skeletal muscles and cardiac muscle. We have induced efficient exon skipping both in vitro and in vivo by using cocktail antisense 2'O-methyl oligonucleotides (2'OMePS) and cocktail phosphorodiamidate morpholino oligomers (morpholinos, or PMOs) and ameliorated phenotype of dystrophic dogs by systemic injections. The multiple exon skipping (double exon skipping) shown here provides the prospect of choosing deletions that optimize the functionality of the truncated dystrophin protein for DMD patients by using a common cocktail that could be validated as a single drug and also potentially applicable for more than 90% of DMD patients.

Samantha Sevilla M.F.S.,Research Center for Genetic Medicine | Hubal M.J.,Research Center for Genetic Medicine
Seminars in Pediatric Surgery | Year: 2014

Obesity is a highly heritable trait. While acute and chronic changes in body weight or obesity-related comorbidities are heavily influenced by environmental factors, there are still strong genomic modifiers that help account for inter-subject variability in baseline traits and in response to interventions. This review is intended to provide an up-to-date overview of our current understanding of genetic influences on obesity, with emphasis on genetic modifiers of baseline traits and responses to intervention. We begin by reviewing how genetic variants can influence obesity. We then examine genetic modifiers of weight loss via different intervention strategies, focusing on known and potential modifiers of surgical weight loss outcomes. We will pay particular attention to the effects of patient age on outcomes, addressing the risks and benefits of adopting early intervention strategies. Finally, we will discuss how the field of bariatric surgery can leverage knowledge of genetic modifiers to adopt a personalized medicine approach for optimal outcomes across this widespread and diverse patient population. © 2014 Elsevier Inc.

Cohen T.V.,Research Center for Genetic Medicine | Cohen J.E.,Research Center for Genetic Medicine | Partridge T.A.,Research Center for Genetic Medicine
Neuromuscular Disorders | Year: 2012

Limb-girdle muscular dystrophy type 2B results from mutations in dysferlin, a membrane-associated protein involved in cellular membrane repair. Primary myoblast cultures derived from dysferlinopathy patients show reduced myogenic potential, suggesting that dysferlin may regulate myotube fusion and be required for muscle regeneration. These observations contrast with the findings that muscle develops normally in pre-symptomatic dysferlinopathy patients. To better understand the role of dysferlin in myogenesis, we investigated this process in vitro using cells derived from two mouse models of dysferlinopathy: SJL/J and A/J mice. We observed that myotubes derived from dysferlin-deficient muscle were of significantly smaller diameters, contained fewer myonuclei, and displayed reduced myogenic gene expression compared to dysferlin-sufficient cells. Together, these findings suggest that the absence of dysferlin from myoblasts is detrimental to myogenesis. Pro-inflammatory NFκB signaling was upregulated in dysferlin-deficient myotubes; the anti-inflammatory agent celastrol reduced the NFκB activation and improved myogenesis in dysferlin-deficient cultures. The results suggest that decreased myotube fusion in dysferlin deficiency is attributable to intrinsic inflammatory activation and can be improved using anti-inflammatory mediators. © 2012 Elsevier B.V.

Hathout Y.,Research Center for Genetic Medicine
Expert Review of Proteomics | Year: 2015

Noninvasive molecular biomarkers are becoming attractive tools to monitor disease progression, aid drug development programs and use as surrogate outcome measures in clinical trials. Cutting edge proteomic methods to assay biomarkers in body fluids have been developed in the past few years, but transitioning them to clinical practice has been slow and depends on the qualification of both the method and the biomarker. © Informa UK, Ltd.

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