Searched for: school:SOM
Department/Unit:Neuroscience Institute
A novel role for MuSK and non-canonical Wnt signaling during segmental neural crest cell migration
Banerjee, Santanu; Gordon, Laura; Donn, Thomas M; Berti, Caterina; Moens, Cecilia B; Burden, Steven J; Granato, Michael
Trunk neural crest cells delaminate from the dorsal neural tube as an uninterrupted sheet; however, they convert into segmentally organized streams before migrating through the somitic territory. These neural crest cell streams join the segmental trajectories of pathfinding spinal motor axons, suggesting that interactions between these two cell types might be important for neural crest cell migration. Here, we show that in the zebrafish embryo migration of both neural crest cells and motor axons is temporally synchronized and spatially restricted to the center of the somite, but that motor axons are dispensable for segmental neural crest cell migration. Instead, we find that muscle-specific receptor kinase (MuSK) and its putative ligand Wnt11r are crucial for restricting neural crest cell migration to the center of each somite. Moreover, we find that blocking planar cell polarity (PCP) signaling in somitic muscle cells also results in non-segmental neural crest cell migration. Using an F-actin biosensor we show that in the absence of MuSK neural crest cells fail to retract non-productive leading edges, resulting in non-segmental migration. Finally, we show that MuSK knockout mice display similar neural crest cell migration defects, suggesting a novel, evolutionarily conserved role for MuSK in neural crest migration. We propose that a Wnt11r-MuSK dependent, PCP-like pathway restricts neural crest cells to their segmental path
PMCID:3133918
PMID: 21750038
ISSN: 1477-9129
CID: 136499
Rapid monitoring of iron-chelating therapy in thalassemia major by a new cardiovascular MR measure: the reduced transverse relaxation rate
Kim, Daniel; Jensen, Jens H; Wu, Ed X; Feng, Li; Au, Wing-Yan; Cheung, Jerry S; Ha, Shau-Yin; Sheth, Sujit S; Brittenham, Gary M
In iron overload, almost all the excess iron is stored intracellularly as rapidly mobilizable ferritin iron and slowly exchangeable hemosiderin iron. Increases in cytosolic iron may produce oxidative damage that ultimately results in cardiomyocyte dysfunction. Because intracellular ferritin iron is evidently in equilibrium with the low-molecular-weight cytosolic iron pool, measurements of ferritin iron potentially provide a clinically useful indicator of changes in cytosolic iron. The cardiovascular magnetic resonance (CMR) index of cardiac iron used clinically, the effective transverse relaxation rate (R(2)*), is principally influenced by hemosiderin iron and changes only slowly over several months, even with intensive iron-chelating therapy. Another conventional CMR index of cardiac iron, the transverse relaxation rate (R(2)), is sensitive to both hemosiderin iron and ferritin iron. We have developed a new MRI measure, the 'reduced transverse relaxation rate' (RR(2)), and have proposed in previous studies that this measure is primarily sensitive to ferritin iron and largely independent of hemosiderin iron in phantoms mimicking ferritin iron and human liver explants. We hypothesized that RR(2) could detect changes produced by 1 week of iron-chelating therapy in patients with transfusion-dependent thalassemia. We imaged 10 patients with thalassemia major at 1.5 T in mid-ventricular short-axis planes of the heart, initially after suspending iron-chelating therapy for 1 week and subsequently after resuming oral deferasirox. After resuming iron-chelating therapy, significant decreases were observed in the mean myocardial RR(2) (7.8%, p < 0.01) and R(2) (5.5%, p < 0.05), but not in R(2)* (1.7%, p > 0.90). Although the difference between changes in RR(2) and R(2) was not significant (p > 0.3), RR(2) was consistently more sensitive than R(2) (and R(2)*) to the resumption of iron-chelating therapy, as judged by the effect sizes of relaxation rate differences detected. Although further studies are needed, myocardial RR(2) may be a promising investigational method for the rapid assessment of the effects of iron-chelating therapy in the heart
PMCID:3138893
PMID: 21190261
ISSN: 1099-1492
CID: 138284
Comprehensive behavioral phenotyping of Ts65Dn mouse model of Down Syndrome: activation of beta1-adrenergic receptor by xamoterol as a potential cognitive enhancer
Faizi, Mehrdad; Bader, Patrick L; Tun, Christine; Encarnacion, Angelo; Kleschevnikov, Alexander; Belichenko, Pavel; Saw, Nay; Priestley, Matthew; Tsien, Richard W; Mobley, William C; Shamloo, Mehrdad
Down syndrome (DS) is the most prevalent form of mental retardation caused by genetic abnormalities in humans. This has been successfully modeled in mice to generate the Ts65Dn mouse, a genetic model of DS. This transgenic mouse model shares a number of physical and functional abnormalities with people with DS, including changes in the structure and function of neuronal circuits. Significant abnormalities in noradrenergic (NE-ergic) afferents from the locus coeruleus to the hippocampus, as well as deficits in NE-ergic neurotransmission are detected in these animals. In the current study we characterized in detail the behavioral phenotype of Ts65Dn mice, in addition to using pharmacological tools for identification of target receptors mediating the learning and memory deficits observed in this model of DS. We undertook a comprehensive approach to mouse phenotyping using a battery of standard and novel tests encompassing: (i) locomotion (Activity Chamber, PhenoTyper, and CatWalk), (ii) learning and memory (spontaneous alternation, delayed matching-to-place water maze, fear conditioning, and Intellicage), and (iii) social behavior. Ts65Dn mice showed increased locomotor activity in novel and home cage environments. There were significant and reproducible deficits in learning and memory tests including spontaneous alternation, delayed matching-to-place water maze, Intellicage place avoidance and contextual fear conditioning. Although Ts65Dn mice showed no deficit in sociability in the 3-chamber test, a marked impairment in social memory was detected. Xamoterol, a beta1-adrenergic receptor (beta1-ADR) agonist, effectively restored the memory deficit in contextual fear conditioning, spontaneous alternation and novel object recognition. These behavioral improvements were reversed by betaxolol, a selective beta1-ADR antagonist. In conclusion, our results demonstrate that this mouse model of Down syndrome displays cognitive deficits which are mediated by an imbalance in the noradrenergic system. In this experimental model of Down syndrome a selective activation of beta1-ADR does restore some of these behavioral deficits. Further mechanistic studies will be needed to investigate the failure of noradrenergic system and the role of beta1-ADR in cognitive deficit and pathogenesis of DS in people. Restoring NE neurotransmission or a selective activation of beta1)-ADR needs to be further investigated for the development of any potential therapeutic strategy for symptomatic relief of memory deficit in DS. Furthermore, due to the significant involvement of noradrenergic system in the cardiovascular function further safety and translational studies will be needed to ensure the safety and efficacy of this approach
PMCID:3539757
PMID: 21527343
ISSN: 1095-953x
CID: 136716
The sarcoplasmic reticulum luminal thiol oxidase ERO1 regulates cardiomyocyte excitation-coupled calcium release and response to hemodynamic load
Chin, King-Tung; Kang, Guoxin; Qu, Jiaxiang; Gardner, Lawrence B; Coetzee, William A; Zito, Ester; Fishman, Glenn I; Ron, David
Two related ER oxidation 1 (ERO1) proteins, ERO1alpha and ERO1beta, dynamically regulate the redox environment in the mammalian endoplasmic reticulum (ER). Redox changes in cysteine residues on intralumenal loops of calcium release and reuptake channels have been implicated in altered calcium release and reuptake. These findings led us to hypothesize that altered ERO1 activity may affect cardiac functions that are dependent on intracellular calcium flux. We established mouse lines with loss of function insertion mutations in Ero1l and Ero1lb encoding ERO1alpha and ERO1beta. The peak amplitude of calcium transients in homozygous Ero1alpha mutant adult cardiomyocytes was reduced to 42.0 +/- 2.2% (n=10, P</=0.01) of values recorded in wild-type cardiomyocytes. Decreased ERO1 activity blunted cardiomyocyte inotropic response to adrenergic stimulation and sensitized mice to adrenergic blockade. Whereas all 12 wild-type mice survived challenge with 4 mg/kg esmolol, 6 of 8 compound Ero1l and Ero1lb mutant mice succumbed to this level of beta adrenergic blockade (P</=0.01). In addition, mice lacking ERO1alpha were partially protected against progressive heart failure in a transaortic constriction model [at 10 wk postprocedure, fractional shortening was 0.31+/-0.02 in the mutant (n=20) vs. 0.23+/-0.03 in the wild type (n=18); P</=0.01]. These findings establish a role for ERO1 in calcium homeostasis and suggest that modifying the lumenal redox environment may affect the progression of heart failure.-Chin, K. T., Kang, G., Qu, J., Gardner, L. B., Coetzee, W. A., Zito, E., Fishman, G. I., Ron, R. The sarcoplasmic reticulum luminal thiol oxidase ERO1 regulates cardiomyocyte excitation-coupled calcium release and response to hemodynamic load
PMCID:3136342
PMID: 21507899
ISSN: 1530-6860
CID: 135555
H2O2: A Dynamic Neuromodulator
Rice, Margaret E
Increasing evidence implicates hydrogen peroxide (H(2)O(2)) as an intracellular and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H(2)O(2) can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H(2)O(2) activates ATP-sensitive K(+) (K-ATP) channels that inhibit DA neuron firing. In the striatum, H(2)O(2) generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via K-ATP channels. The source of dynamically generated H(2)O(2) is mitochondrial respiration; thus, H(2)O(2) provides a novel link between activity and metabolism via K-ATP channels. Additional targets of H(2)O(2) include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H(2)O(2) acting via K-ATP channels, TRP channel activation is excitatory. This review describes emerging roles of H(2)O(2) as a signaling agent in the nigrostriatal pathway and basal ganglia neurons
PMCID:3357131
PMID: 21666063
ISSN: 1089-4098
CID: 135259
TROMBONE: T(1) -relaxation-oblivious mapping of transmit radio-frequency field (B(1) ) for MRI at high magnetic fields
Fleysher, Roman; Fleysher, Lazar; Inglese, Matilde; Sodickson, Daniel
Fast, 3D radio-frequency transmit field (B(1) ) mapping is important for parallel transmission, spatially selective pulse design and quantitative MRI applications. It has been shown that actual flip angle imaging-two interleaved spoiled gradient recalled echo images acquired in steady state with two very short time delays (TR(1) , TR(2) )-is an attractive method of B(1) mapping. Herein, we describe the TROMBONE method that efficiently integrates actual flip angle imaging with EPI imaging, alleviates very short TR requirement of actual flip angle imaging and through their synergy yields up to 16 times higher precision in B(1) estimation in the same experimental time. High precision of TROMBONE can be traded for faster scans. The map of B(1) reconstructed from the ratio of intensities of two images is insensitive to longitudinal relaxation time (T(1) ) in the physiologically relevant range. A table of the optimal acquisition protocol parameters for various target experimental conditions is provided. Magn Reson Med, 2011. (c) 2011 Wiley-Liss, Inc
PMCID:3130840
PMID: 21394765
ISSN: 1522-2594
CID: 135536
Abnormal presynaptic short-term plasticity and information processing in a mouse model of fragile X syndrome
Deng, Pan-Yue; Sojka, David; Klyachko, Vitaly A
Fragile X syndrome (FXS) is the most common inherited form of intellectual disability and the leading genetic cause of autism. It is associated with the lack of fragile X mental retardation protein (FMRP), a regulator of protein synthesis in axons and dendrites. Studies on FXS have extensively focused on the postsynaptic changes underlying dysfunctions in long-term plasticity. In contrast, the presynaptic mechanisms of FXS have garnered relatively little attention and are poorly understood. Activity-dependent presynaptic processes give rise to several forms of short-term plasticity (STP), which is believed to control some of essential neural functions, including information processing, working memory, and decision making. The extent of STP defects and their contributions to the pathophysiology of FXS remain essentially unknown, however. Here we report marked presynaptic abnormalities at excitatory hippocampal synapses in Fmr1 knock-out (KO) mice leading to defects in STP and information processing. Loss of FMRP led to enhanced responses to high-frequency stimulation. Fmr1 KO mice also exhibited abnormal synaptic processing of natural stimulus trains, specifically excessive enhancement during the high-frequency spike discharges associated with hippocampal place fields. Analysis of individual STP components revealed strongly increased augmentation and reduced short-term depression attributable to loss of FMRP. These changes were associated with exaggerated calcium influx in presynaptic neurons during high-frequency stimulation, enhanced synaptic vesicle recycling, and enlarged readily-releasable and reserved vesicle pools. These data suggest that loss of FMRP causes abnormal STP and information processing, which may represent a novel mechanism contributing to cognitive impairments in FXS.
PMID: 21795546
ISSN: 0270-6474
CID: 979462
Ascl1 genetics reveals insights into cerebellum local circuit assembly
Sudarov, Anamaria; Turnbull, Rowena K; Kim, Euiseok J; Lebel-Potter, Melanie; Guillemot, Francois; Joyner, Alexandra L
Two recently generated targeted mouse alleles of the neurogenic gene Ascl1 were used to characterize cerebellum circuit formation. First, genetic inducible fate mapping (GIFM) with an Ascl1(CreER) allele was found to specifically mark all glial and neuron cell types that arise from the ventricular zone (vz). Moreover, each cell type has a unique temporal profile of marking with Ascl1(CreER) GIFM. Of great utility, Purkinje cells (Pcs), an early cohort of Bergmann glia, and four classes of GABAergic interneurons can be genetically birth dated during embryogenesis using Ascl1(CreER) GIFM. Astrocytes and oligodendrocytes, in contrast, express Ascl1(CreER) throughout their proliferative phase in the white matter. Interestingly, the final position each neuron type acquires differs depending on when it expresses Ascl1. Interneurons (including candelabrum) attain a more outside position the later they express Ascl1, whereas Pcs have distinct settling patterns each day they express Ascl1. Second, using a conditional Ascl1 allele, we discovered that Ascl1 is differentially required for generation of most vz-derived cells. Mice lacking Ascl1 in the cerebellum have a major decrease in three types of interneurons with a tendency toward a loss of later-born interneurons, as well as an imbalance of oligodendrocytes and astrocytes. Double-mutant analysis indicates that a related helix-loop-helix protein, Ptf1a, functions with Ascl1 in generating interneurons and Pcs. By fate mapping vz-derived cells in Ascl1 mutants, we further discovered that Ascl1 plays a specific role during the time period when Pcs are generated in restricting vz progenitors from becoming rhombic lip progenitors
PMCID:3153985
PMID: 21795554
ISSN: 1529-2401
CID: 141263
Selective optical drive of thalamic reticular nucleus generates thalamic bursts and cortical spindles
Halassa, Michael M; Siegle, Joshua H; Ritt, Jason T; Ting, Jonathan T; Feng, Guoping; Moore, Christopher I
The thalamic reticular nucleus (TRN) is hypothesized to regulate neocortical rhythms and behavioral states. Using optogenetics and multi-electrode recording in behaving mice, we found that brief selective drive of TRN switched the thalamocortical firing mode from tonic to bursting and generated state-dependent neocortical spindles. These findings provide causal support for the involvement of the TRN in state regulation in vivo and introduce a new model for addressing the role of this structure in behavior.
PMCID:4169194
PMID: 21785436
ISSN: 1097-6256
CID: 586962
Short communication: flecainide exerts an antiarrhythmic effect in a mouse model of catecholaminergic polymorphic ventricular tachycardia by increasing the threshold for triggered activity
Liu, Nian; Denegri, Marco; Ruan, Yanfei; Avelino-Cruz, Jose Everardo; Perissi, Andrea; Negri, Sara; Napolitano, Carlo; Coetzee, William A; Boyden, Penelope A; Priori, Silvia G
Rationale: Flecainide prevents arrhythmias in catecholaminergic polymorphic ventricular tachycardia, but the antiarrhythmic mechanism remains unresolved. It is possible for flecainide to directly affect the cardiac ryanodine receptor (RyR2); however, an extracellular site of action is suggested because of the hydrophilic nature of flecainide. Objective: To investigate the mechanism for the antiarrhythmic action of flecainide in a RyR2(R4496C+/-) knock-in mouse model of catecholaminergic polymorphic ventricular tachycardia. Methods and Results: Flecainide prevented catecholamine-induced sustained ventricular tachycardia in RyR2(R4496C+/-) mice. Cellular studies were performed with isolated RyR2(R4496C+/-) myocytes. Isoproterenol caused the appearance of spontaneous Ca(2+) transients, which were unaffected by flecainide (6 mumol/L). Flecainide did not affect Ca(2+) transient amplitude, decay, or sarcoplasmic reticulum Ca(2+) content. Moreover, it did not affect the frequency of spontaneous Ca(2+) sparks in permeabilized myocytes. In contrast, flecainide effectively prevented triggered activity induced by isoproterenol. The threshold for action potential induction was increased significantly (P<0.01), which suggests a primary extracellular antiarrhythmic effect mediated by Na(+) channel blockade. Conclusions: Flecainide prevents catecholaminergic polymorphic ventricular tachycardia in RyR2(R4496C+/-) mice; however, at variance with previous reports, we observed minimal effects on intracellular Ca(2+) homeostasis. Our data suggest that the antiarrhythmic activity of the drug is caused by reduction of Na(+) channel availability and by an increase in the threshold for triggered activity
PMID: 21680895
ISSN: 1524-4571
CID: 135573