Publications by authors named "Matthew R Fleming"

14 Publications

  • Page 1 of 1

The importance of differentiating between qualitative, semi-quantitative, and quantitative imaging-close only counts in horseshoes.

Eur J Nucl Med Mol Imaging 2020 04;47(4):753-755

Eastern Virginia Medical School, Norfolk, VA, USA.

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http://dx.doi.org/10.1007/s00259-019-04668-yDOI Listing
April 2020

Quantitative stress-redistribution sequential imaging optimises MPI with the lowest dose of radiation per patient.

BMJ Open Qual 2019 24;8(3):e000774. Epub 2019 Aug 24.

Nuclear Imaging, Sebec Consulting & Media, Rock Hill, South Carolina, USA.

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http://dx.doi.org/10.1136/bmjoq-2019-000774DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6711426PMC
August 2019

Correction to: FMTVDM-TFM: True quantification requires standardization of the tool being used to measure, with a known, unchanging standard to produce accurate, consistent and reproducible quantified measurements.

J Nucl Cardiol 2019 Oct;26(5):1784

Eastern Virginia Medical School, Norfolk, USA.

The Editor wishes to clarify that the authors of the above named Letter provided ICMJE Conflict of Interest forms at the time of submission, and that the Journal omitted to include the resulting statement in the published Letter.
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http://dx.doi.org/10.1007/s12350-019-01807-8DOI Listing
October 2019

Letter to the Editor: A response to Hruska's case study on molecular breast imaging and the need for true tissue quantification.

Breast Cancer Res 2019 01 29;21(1):15. Epub 2019 Jan 29.

FHHI-Omnific Imaging-Camelot, Los Angeles, CA, 90245, USA.

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http://dx.doi.org/10.1186/s13058-019-1103-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352358PMC
January 2019

Semiquantification Limitations: FMTVDM Demonstrates Quantified Tumor Response to Treatment with Both Regional Blood Flow and Metabolic Changes.

J Nucl Med 2018 10 20;59(10):1643-1644. Epub 2018 Jul 20.

FHHI-OmnificImaging-Camelot 707 E. Grand Ave., #8 El Segundo, CA 90245 E-mail:

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http://dx.doi.org/10.2967/jnumed.118.217018DOI Listing
October 2018

FMTVDM-TFM: True quantification requires standardization of the tool being used to measure, with a known, unchanging standard to produce accurate, consistent and reproducible quantified measurements.

J Nucl Cardiol 2019 Oct 19;26(5):1780-1783. Epub 2018 Jun 19.

Eastern Virginia Medical School, Norfolk, USA.

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http://dx.doi.org/10.1007/s12350-018-1343-3DOI Listing
October 2019

Stimulation of Slack K(+) Channels Alters Mass at the Plasma Membrane by Triggering Dissociation of a Phosphatase-Regulatory Complex.

Cell Rep 2016 08 18;16(9):2281-8. Epub 2016 Aug 18.

Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA. Electronic address:

Human mutations in the cytoplasmic C-terminal domain of Slack sodium-activated potassium (KNa) channels result in childhood epilepsy with severe intellectual disability. Slack currents can be increased by pharmacological activators or by phosphorylation of a Slack C-terminal residue by protein kinase C. Using an optical biosensor assay, we find that Slack channel stimulation in neurons or transfected cells produces loss of mass near the plasma membrane. Slack mutants associated with intellectual disability fail to trigger any change in mass. The loss of mass results from the dissociation of the protein phosphatase 1 (PP1) targeting protein, Phactr-1, from the channel. Phactr1 dissociation is specific to wild-type Slack channels and is not observed when related potassium channels are stimulated. Our findings suggest that Slack channels are coupled to cytoplasmic signaling pathways and that dysregulation of this coupling may trigger the aberrant intellectual development associated with specific childhood epilepsies.
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http://dx.doi.org/10.1016/j.celrep.2016.07.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123741PMC
August 2016

Kv3.3 Channels Bind Hax-1 and Arp2/3 to Assemble a Stable Local Actin Network that Regulates Channel Gating.

Cell 2016 Apr 17;165(2):434-448. Epub 2016 Mar 17.

Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520.

Mutations in the Kv3.3 potassium channel (KCNC3) cause cerebellar neurodegeneration and impair auditory processing. The cytoplasmic C terminus of Kv3.3 contains a proline-rich domain conserved in proteins that activate actin nucleation through Arp2/3. We found that Kv3.3 recruits Arp2/3 to the plasma membrane, resulting in formation of a relatively stable cortical actin filament network resistant to cytochalasin D that inhibits fast barbed end actin assembly. These Kv3.3-associated actin structures are required to prevent very rapid N-type channel inactivation during short depolarizations of the plasma membrane. The effects of Kv3.3 on the actin cytoskeleton are mediated by the binding of the cytoplasmic C terminus of Kv3.3 to Hax-1, an anti-apoptotic protein that regulates actin nucleation through Arp2/3. A human Kv3.3 mutation within a conserved proline-rich domain produces channels that bind Hax-1 but are impaired in recruiting Arp2/3 to the plasma membrane, resulting in growth cones with deficient actin veils in stem cell-derived neurons.
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http://dx.doi.org/10.1016/j.cell.2016.02.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826296PMC
April 2016

Use of label-free optical biosensors to detect modulation of potassium channels by G-protein coupled receptors.

J Vis Exp 2014 Feb 10(84):e51307. Epub 2014 Feb 10.

Department of Pharmacology, Yale School of Medicine; Department of Cellular and Molecular Physiology, Yale School of Medicine;

Ion channels control the electrical properties of neurons and other excitable cell types by selectively allowing ions to flow through the plasma membrane(1). To regulate neuronal excitability, the biophysical properties of ion channels are modified by signaling proteins and molecules, which often bind to the channels themselves to form a heteromeric channel complex(2,3). Traditional assays examining the interaction between channels and regulatory proteins require exogenous labels that can potentially alter the protein's behavior and decrease the physiological relevance of the target, while providing little information on the time course of interactions in living cells. Optical biosensors, such as the X-BODY Biosciences BIND Scanner system, use a novel label-free technology, resonance wavelength grating (RWG) optical biosensors, to detect changes in resonant reflected light near the biosensor. This assay allows the detection of the relative change in mass within the bottom portion of living cells adherent to the biosensor surface resulting from ligand induced changes in cell adhesion and spreading, toxicity, proliferation, and changes in protein-protein interactions near the plasma membrane. RWG optical biosensors have been used to detect changes in mass near the plasma membrane of cells following activation of G protein-coupled receptors (GPCRs), receptor tyrosine kinases, and other cell surface receptors. Ligand-induced changes in ion channel-protein interactions can also be studied using this assay. In this paper, we will describe the experimental procedure used to detect the modulation of Slack-B sodium-activated potassium (KNa) channels by GPCRs.
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http://dx.doi.org/10.3791/51307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122194PMC
February 2014

Clinical whole-genome sequencing in severe early-onset epilepsy reveals new genes and improves molecular diagnosis.

Hum Mol Genet 2014 Jun 25;23(12):3200-11. Epub 2014 Jan 25.

Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK, NIHR Biomedical Research Centre, Oxford, UK,

In severe early-onset epilepsy, precise clinical and molecular genetic diagnosis is complex, as many metabolic and electro-physiological processes have been implicated in disease causation. The clinical phenotypes share many features such as complex seizure types and developmental delay. Molecular diagnosis has historically been confined to sequential testing of candidate genes known to be associated with specific sub-phenotypes, but the diagnostic yield of this approach can be low. We conducted whole-genome sequencing (WGS) on six patients with severe early-onset epilepsy who had previously been refractory to molecular diagnosis, and their parents. Four of these patients had a clinical diagnosis of Ohtahara Syndrome (OS) and two patients had severe non-syndromic early-onset epilepsy (NSEOE). In two OS cases, we found de novo non-synonymous mutations in the genes KCNQ2 and SCN2A. In a third OS case, WGS revealed paternal isodisomy for chromosome 9, leading to identification of the causal homozygous missense variant in KCNT1, which produced a substantial increase in potassium channel current. The fourth OS patient had a recessive mutation in PIGQ that led to exon skipping and defective glycophosphatidyl inositol biosynthesis. The two patients with NSEOE had likely pathogenic de novo mutations in CBL and CSNK1G1, respectively. Mutations in these genes were not found among 500 additional individuals with epilepsy. This work reveals two novel genes for OS, KCNT1 and PIGQ. It also uncovers unexpected genetic mechanisms and emphasizes the power of WGS as a clinical tool for making molecular diagnoses, particularly for highly heterogeneous disorders.
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http://dx.doi.org/10.1093/hmg/ddu030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4030775PMC
June 2014

Regulation of neuronal excitability by interaction of fragile X mental retardation protein with slack potassium channels.

J Neurosci 2012 Oct;32(44):15318-27

Department of Pharmacology, Yale University, New Haven, Connecticut 06520, USA.

Loss of the RNA-binding protein fragile X mental retardation protein (FMRP) represents the most common form of inherited intellectual disability. Studies with heterologous expression systems indicate that FMRP interacts directly with Slack Na(+)-activated K(+) channels (K(Na)), producing an enhancement of channel activity. We have now used Aplysia bag cell (BC) neurons, which regulate reproductive behaviors, to examine the effects of Slack and FMRP on excitability. FMRP and Slack immunoreactivity were colocalized at the periphery of isolated BC neurons, and the two proteins could be reciprocally coimmunoprecipitated. Intracellular injection of FMRP lacking its mRNA binding domain rapidly induced a biphasic outward current, with an early transient tetrodotoxin-sensitive component followed by a slowly activating sustained component. The properties of this current matched that of the native Slack potassium current, which was identified using an siRNA approach. Addition of FMRP to inside-out patches containing native Aplysia Slack channels increased channel opening and, in current-clamp recordings, produced narrowing of action potentials. Suppression of Slack expression did not alter the ability of BC neurons to undergo a characteristic prolonged discharge in response to synaptic stimulation, but prevented recovery from a prolonged inhibitory period that normally follows the discharge. Recovery from the inhibited period was also inhibited by the protein synthesis inhibitor anisomycin. Our studies indicate that, in BC neurons, Slack channels are required for prolonged changes in neuronal excitability that require new protein synthesis, and raise the possibility that channel-FMRP interactions may link changes in neuronal firing to changes in protein translation.
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http://dx.doi.org/10.1523/JNEUROSCI.2162-12.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518385PMC
October 2012

De novo gain-of-function KCNT1 channel mutations cause malignant migrating partial seizures of infancy.

Nat Genet 2012 Nov 21;44(11):1255-9. Epub 2012 Oct 21.

Department of Pediatric Neurology, Centre de Reference Epilepsies Rares, Hôpital Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, France.

Malignant migrating partial seizures of infancy (MMPSI) is a rare epileptic encephalopathy of infancy that combines pharmacoresistant seizures with developmental delay. We performed exome sequencing in three probands with MMPSI and identified de novo gain-of-function mutations affecting the C-terminal domain of the KCNT1 potassium channel. We sequenced KCNT1 in 9 additional individuals with MMPSI and identified mutations in 4 of them, in total identifying mutations in 6 out of 12 unrelated affected individuals. Functional studies showed that the mutations led to constitutive activation of the channel, mimicking the effects of phosphorylation of the C-terminal domain by protein kinase C. In addition to regulating ion flux, KCNT1 has a non-conducting function, as its C terminus interacts with cytoplasmic proteins involved in developmental signaling pathways. These results provide a focus for future diagnostic approaches and research for this devastating condition.
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http://dx.doi.org/10.1038/ng.2441DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3687547PMC
November 2012

Use of optical biosensors to detect modulation of Slack potassium channels by G protein-coupled receptors.

J Recept Signal Transduct Res 2009 ;29(3-4):173-81

Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.

Ion channels control the electrical properties of neurons and other excitable cell types by selectively allowing ion to flow through the plasma membrane. To regulate neuronal excitability, the biophysical properties of ion channels are modified by signaling proteins and molecules, which often bind to the channels themselves to form a heteromeric channel complex. Traditional assays examining the interaction between channels and regulatory proteins generally provide little information on the time-course of interactions in living cells. We have now used a novel label-free technology to detect changes in the distribution of mass close to the plasma membrane following modulation of potassium channels by G protein-coupled receptors (GPCRs). This technology uses optical sensors embedded in microplates to detect changes in the refractive index at the surface of cells. Although the activation of GPCRs has been studied with this system, protein-protein interactions due to modulation of ion channels have not yet been characterized. Here we present data that the characteristic pattern of mass distribution following GPCR activation is significantly modified by the presence of a sodium-activated potassium channel, Slack-B, a channel that is known to be potently modulated by activation of these receptors.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3727623PMC
http://dx.doi.org/10.1080/10799890903056883DOI Listing
October 2009

Presynaptic protein kinase C controls maturation and branch dynamics of developing retinotectal arbors: possible role in activity-driven sharpening.

J Neurobiol 2004 Feb;58(3):328-40

Department of Biological Sciences and Center for Neuroscience Research, University at Albany-SUNY, 1400 Washington Avenue, Albany, New York 12222, USA.

Visual activity refines developing retinotectal maps and shapes individual retinal arbors via an NMDA receptor-dependent mechanism. As retinal axons grow into tectum, they slow markedly and emit many transient side branches behind the tip, assuming a "bottlebrush" morphology. Some branches are stabilized and branch further, giving rise to a compact arbor. The dynamic rate of branch addition and deletion is increased twofold when MK801 is used to block NMDA receptors, as if this prevents release of a stabilizing signal such as arachidonic acid (AA) from the postsynaptic neuron. In optic tract, AA mediates NCAM and L1 stimulation of axon growth by activating presynaptic protein kinase C (PKC) to phosphorylate GAP-43 and stabilize F-actin, and, if present in tectum, this growth control pathway could be modulated by postsynaptic activation. To test for the effects on arbor morphology of blocking PKC or AA release, we examined DiO-labeled retinal axons of larval zebrafish with time-lapse videomicroscopy. Bath application of the selective PKC inhibitor bisindolylmaleimide from 2 or 3 days onward doubled the rate at which side branches were added and deleted, as seen with MK801, and also prevented maturation of the arbor so that it retained a "bottlebrush" morphology. In order to selectively block the PKC being transported to retinal terminals, we injected the irreversible inhibitor calphostin C into the eye from which the ganglion cells were labeled, and this produced both effects seen with bath application. In contrast, there were no effects of control injections, which included Ringers into the same eye and the same dose into the opposite eye (actually much closer to the tectum of interest), to rule out the possibility that the inhibitor leaked from the eye to act on tectal cells. For comparison, we examined arbors treated with the NMDA blocker MK801 at half-hour time-lapse intervals, and detected the twofold rise in rates of branch addition and deletion previously reported in Xenopus larvae, but not the structural effect seen with the PKC inhibitors. In addition, we could produce both effects seen with PKC inhibitors by using RHC80267 to block AA release from DAG lipase, indicating that AA is the main drive for PKC activation. Thus, the results show a distinct role of AA and presynaptic PKC in both maturation of arbor structure and in the dynamic control of branching. The effects on branch dynamics were present regardless of the level of maturity of arbor structure. The fact that they mimicked those of MK801 suggests that presynaptic PKC may be involved in the NMDA receptor-driven stabilization of developing retinal arbors.
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http://dx.doi.org/10.1002/neu.10286DOI Listing
February 2004