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Cazemier JL, Clascá F, Tiesinga PHE. Connectomic Analysis of Brain Networks: Novel Techniques and Future Directions. Front Neuroanat 2016; 10:110. [PMID: 27881953 PMCID: PMC5101213 DOI: 10.3389/fnana.2016.00110] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 10/25/2016] [Indexed: 12/31/2022] Open
Abstract
Brain networks, localized or brain-wide, exist only at the cellular level, i.e., between specific pre- and post-synaptic neurons, which are connected through functionally diverse synapses located at specific points of their cell membranes. "Connectomics" is the emerging subfield of neuroanatomy explicitly aimed at elucidating the wiring of brain networks with cellular resolution and a quantified accuracy. Such data are indispensable for realistic modeling of brain circuitry and function. A connectomic analysis, therefore, needs to identify and measure the soma, dendrites, axonal path, and branching patterns together with the synapses and gap junctions of the neurons involved in any given brain circuit or network. However, because of the submicron caliber, 3D complexity, and high packing density of most such structures, as well as the fact that axons frequently extend over long distances to make synapses in remote brain regions, creating connectomic maps is technically challenging and requires multi-scale approaches, Such approaches involve the combination of the most sensitive cell labeling and analysis methods available, as well as the development of new ones able to resolve individual cells and synapses with increasing high-throughput. In this review, we provide an overview of recently introduced high-resolution methods, which researchers wanting to enter the field of connectomics may consider. It includes several molecular labeling tools, some of which specifically label synapses, and covers a number of novel imaging tools such as brain clearing protocols and microscopy approaches. Apart from describing the tools, we also provide an assessment of their qualities. The criteria we use assess the qualities that tools need in order to contribute to deciphering the key levels of circuit organization. We conclude with a brief future outlook for neuroanatomic research, computational methods, and network modeling, where we also point out several outstanding issues like structure-function relations and the complexity of neural models.
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Affiliation(s)
- J Leonie Cazemier
- Department of Neuroinformatics, Donders Institute, Radboud UniversityNijmegen, Netherlands; Department of Cortical Structure and Function, Netherlands Institute for NeuroscienceAmsterdam, Netherlands
| | - Francisco Clascá
- Department of Anatomy, Histology and Neuroscience, School of Medicine, Autónoma University Madrid, Spain
| | - Paul H E Tiesinga
- Department of Neuroinformatics, Donders Institute, Radboud University Nijmegen, Netherlands
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52
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Steculorum SM, Ruud J, Karakasilioti I, Backes H, Engström Ruud L, Timper K, Hess ME, Tsaousidou E, Mauer J, Vogt MC, Paeger L, Bremser S, Klein AC, Morgan DA, Frommolt P, Brinkkötter PT, Hammerschmidt P, Benzing T, Rahmouni K, Wunderlich FT, Kloppenburg P, Brüning JC. AgRP Neurons Control Systemic Insulin Sensitivity via Myostatin Expression in Brown Adipose Tissue. Cell 2016; 165:125-138. [PMID: 27015310 DOI: 10.1016/j.cell.2016.02.044] [Citation(s) in RCA: 199] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 01/21/2016] [Accepted: 02/20/2016] [Indexed: 12/14/2022]
Abstract
Activation of Agouti-related peptide (AgRP) neurons potently promotes feeding, and chronically altering their activity also affects peripheral glucose homeostasis. We demonstrate that acute activation of AgRP neurons causes insulin resistance through impairment of insulin-stimulated glucose uptake into brown adipose tissue (BAT). AgRP neuron activation acutely reprograms gene expression in BAT toward a myogenic signature, including increased expression of myostatin. Interference with myostatin activity improves insulin sensitivity that was impaired by AgRP neurons activation. Optogenetic circuitry mapping reveals that feeding and insulin sensitivity are controlled by both distinct and overlapping projections. Stimulation of AgRP → LHA projections impairs insulin sensitivity and promotes feeding while activation of AgRP → anterior bed nucleus of the stria terminalis (aBNST)vl projections, distinct from AgRP → aBNSTdm projections controlling feeding, mediate the effect of AgRP neuron activation on BAT-myostatin expression and insulin sensitivity. Collectively, our results suggest that AgRP neurons in mice induce not only eating, but also insulin resistance by stimulating expression of muscle-related genes in BAT, revealing a mechanism by which these neurons rapidly coordinate hunger states with glucose homeostasis.
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Affiliation(s)
- Sophie M Steculorum
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Johan Ruud
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Ismene Karakasilioti
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Heiko Backes
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Linda Engström Ruud
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Katharina Timper
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Martin E Hess
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Eva Tsaousidou
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Jan Mauer
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Merly C Vogt
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Lars Paeger
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Biocenter, Institute for Zoology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
| | - Stephan Bremser
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Biocenter, Institute for Zoology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
| | - Andreas C Klein
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Biocenter, Institute for Zoology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
| | - Donald A Morgan
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Peter Frommolt
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Paul T Brinkkötter
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Department II of Internal Medicine, University Hospital Cologne, Kerpener Strasse 62, 50937 Cologne, Germany
| | - Philipp Hammerschmidt
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany
| | - Thomas Benzing
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Department II of Internal Medicine, University Hospital Cologne, Kerpener Strasse 62, 50937 Cologne, Germany
| | - Kamal Rahmouni
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 55242, USA
| | - F Thomas Wunderlich
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Peter Kloppenburg
- Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Biocenter, Institute for Zoology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
| | - Jens C Brüning
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931 Cologne, Germany; Center for Endocrinology, Diabetes and Preventive Medicine (CEDP), University Hospital Cologne, Kerpener Strasse 26, 50924 Cologne, Germany; Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD) and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; National Center for Diabetes Research (DZD) Ingolstädter Land Strasse 1, 85764 Neuherberg, Germany.
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53
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Joesch M, Mankus D, Yamagata M, Shahbazi A, Schalek R, Suissa-Peleg A, Meister M, Lichtman JW, Scheirer WJ, Sanes JR. Reconstruction of genetically identified neurons imaged by serial-section electron microscopy. eLife 2016; 5. [PMID: 27383271 PMCID: PMC4959841 DOI: 10.7554/elife.15015] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 06/27/2016] [Indexed: 11/24/2022] Open
Abstract
Resolving patterns of synaptic connectivity in neural circuits currently requires serial section electron microscopy. However, complete circuit reconstruction is prohibitively slow and may not be necessary for many purposes such as comparing neuronal structure and connectivity among multiple animals. Here, we present an alternative strategy, targeted reconstruction of specific neuronal types. We used viral vectors to deliver peroxidase derivatives, which catalyze production of an electron-dense tracer, to genetically identify neurons, and developed a protocol that enhances the electron-density of the labeled cells while retaining the quality of the ultrastructure. The high contrast of the marked neurons enabled two innovations that speed data acquisition: targeted high-resolution reimaging of regions selected from rapidly-acquired lower resolution reconstruction, and an unsupervised segmentation algorithm. This pipeline reduces imaging and reconstruction times by two orders of magnitude, facilitating directed inquiry of circuit motifs. DOI:http://dx.doi.org/10.7554/eLife.15015.001 Neurons connect with each other to form complex circuits that underlie mental activities. Mapping these connections to obtain a so-called wiring diagram is an essential step in learning how the brain works. The only way to do this precisely enough is by using electron microscopy. However, this technique is so time-consuming that thousands of hours of work are typically required to image even the smallest of tissue samples. Electron microscopes fire beams of electrons at tissue samples, and detect the scattering of the electrons. Stains are used to make specific neurons less permeable to electrons, or more “electron dense”. Labeled cells scatter more electrons, which increases the contrast of the images. In an approach called serial-section electron microscopy, a tissue sample is first cut into extremely thin sections. These are imaged individually, and the images are then pieced together to reconstruct the sample. Joesch et al. have now developed a new procedure – named ARTEMIS – that uses a combination of multiple techniques to speed up the mapping of neurons and their connections. ARTEMIS makes use of genetic engineering, serial-scanning electron microscopy, an enhanced chemical staining procedure and a new image processing approach. First, gene technology is used to selectively stain specific types of neurons in mice and flies. Then, a tissue sample is collected and treated with a chemical that enhances the electron density of the stained neurons, without disrupting the tissue’s structure. Next, a labeled target neuron is imaged at relatively low resolution to reveal its overall structure. Small areas of that neuron are then re-imaged at higher resolution to map the connections between neurons. Lastly, an algorithm pieces together the individual images to produce a reconstruction of the cell. This pipeline of steps reduces the time required to map the shapes and connectivity of neurons with electron microscopy by some two orders of magnitude. This should enable neuroscientists to obtain more rapid insights into the roles of specific neural circuits in the brains of healthy animals, and to identify cases where this wiring goes awry and leads to disease. DOI:http://dx.doi.org/10.7554/eLife.15015.002
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Affiliation(s)
- Maximilian Joesch
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - David Mankus
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Masahito Yamagata
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Ali Shahbazi
- University of Notre Dame, Notre Dame, United States
| | - Richard Schalek
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Adi Suissa-Peleg
- School of Engineering and Applied Sciences, Harvard University, Cambridge, United States
| | - Markus Meister
- Division of Biology, California Institute of Technology, Pasadena, United States
| | - Jeff W Lichtman
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | | | - Joshua R Sanes
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
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54
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Melanocortin-4 receptor-regulated energy homeostasis. Nat Neurosci 2016; 19:206-19. [PMID: 26814590 DOI: 10.1038/nn.4202] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 11/13/2015] [Indexed: 12/11/2022]
Abstract
The melanocortin system provides a conceptual blueprint for the central control of energetic state. Defined by four principal molecular components--two antagonistically acting ligands and two cognate receptors--this phylogenetically conserved system serves as a prototype for hierarchical energy balance regulation. Over the last decade the application of conditional genetic techniques has facilitated the neuroanatomical dissection of the melanocortinergic network and identified the specific neural substrates and circuits that underscore the regulation of feeding behavior, energy expenditure, glucose homeostasis and autonomic outflow. In this regard, the melanocortin-4 receptor is a critical coordinator of mammalian energy homeostasis and body weight. Drawing on recent advances in neuroscience and genetic technologies, we consider the structure and function of the melanocortin-4 receptor circuitry and its role in energy homeostasis.
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55
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Vilmont V, Cadot B, Ouanounou G, Gomes ER. A system for studying mechanisms of neuromuscular junction development and maintenance. Development 2016; 143:2464-77. [PMID: 27226316 PMCID: PMC4958317 DOI: 10.1242/dev.130278] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 05/12/2016] [Indexed: 12/12/2022]
Abstract
The neuromuscular junction (NMJ), a cellular synapse between a motor neuron and a skeletal muscle fiber, enables the translation of chemical cues into physical activity. The development of this special structure has been subject to numerous investigations, but its complexity renders in vivo studies particularly difficult to perform. In vitro modeling of the neuromuscular junction represents a powerful tool to delineate fully the fine tuning of events that lead to subcellular specialization at the pre-synaptic and post-synaptic sites. Here, we describe a novel heterologous co-culture in vitro method using rat spinal cord explants with dorsal root ganglia and murine primary myoblasts to study neuromuscular junctions. This system allows the formation and long-term survival of highly differentiated myofibers, motor neurons, supporting glial cells and functional neuromuscular junctions with post-synaptic specialization. Therefore, fundamental aspects of NMJ formation and maintenance can be studied using the described system, which can be adapted to model multiple NMJ-associated disorders.
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Affiliation(s)
- Valérie Vilmont
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France
| | - Bruno Cadot
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France
| | - Gilles Ouanounou
- FRE CNRS 3693 (U.N.I.C), Unité de Neuroscience, Information et Complexité CNRS, Bât. 33, 1 Ave de la Terasse, Gif sur Yvette 91198, France
| | - Edgar R Gomes
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
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56
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Lerner TN, Ye L, Deisseroth K. Communication in Neural Circuits: Tools, Opportunities, and Challenges. Cell 2016; 164:1136-1150. [PMID: 26967281 PMCID: PMC5725393 DOI: 10.1016/j.cell.2016.02.027] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 01/27/2016] [Accepted: 02/03/2016] [Indexed: 11/27/2022]
Abstract
Communication, the effective delivery of information, is fundamental to life across all scales and species. Nervous systems (by necessity) may be most specifically adapted among biological tissues for high rate and complexity of information transmitted, and thus, the properties of neural tissue and principles of its organization into circuits may illuminate capabilities and limitations of biological communication. Here, we consider recent developments in tools for studying neural circuits with particular attention to defining neuronal cell types by input and output information streams--i.e., by how they communicate. Complementing approaches that define cell types by virtue of genetic promoter/enhancer properties, this communication-based approach to defining cell types operationally by input/output (I/O) relationships links structure and function, resolves difficulties associated with single-genetic-feature definitions, leverages technology for observing and testing significance of precisely these I/O relationships in intact brains, and maps onto processes through which behavior may be adapted during development, experience, and evolution.
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Affiliation(s)
- Talia N Lerner
- Bioengineering Department, 318 Campus Drive, Stanford University, Stanford, CA 94305, USA
| | - Li Ye
- Bioengineering Department, 318 Campus Drive, Stanford University, Stanford, CA 94305, USA
| | - Karl Deisseroth
- Bioengineering Department, 318 Campus Drive, Stanford University, Stanford, CA 94305, USA; Psychiatry Department, 318 Campus Drive, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, 318 Campus Drive, Stanford University, Stanford, CA 94305, USA.
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57
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Abstract
Advances in neuro-technology for mapping, manipulating, and monitoring molecularly defined cell types are rapidly advancing insight into neural circuits that regulate appetite. Here, we review these important tools and their applications in circuits that control food seeking and consumption. Technical capabilities provided by these tools establish a rigorous experimental framework for research into the neurobiology of hunger.
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Affiliation(s)
- Scott M Sternson
- Janelia Research Campus, HHMI, 19700 Helix Drive, Ashburn, VA 20147, USA.
| | - Deniz Atasoy
- Department of Physiology, School of Medicine, Istanbul Medipol University, 34810 Istanbul, Turkey
| | - J Nicholas Betley
- Janelia Research Campus, HHMI, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Fredrick E Henry
- Janelia Research Campus, HHMI, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Shengjin Xu
- Janelia Research Campus, HHMI, 19700 Helix Drive, Ashburn, VA 20147, USA
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58
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Editorial overview: Endocrine and metabolic diseases: Waistline weapons: new therapeutic avenues for the treatment of obesity and metabolic disease. Curr Opin Pharmacol 2015; 25:iv-vi. [PMID: 26559147 DOI: 10.1016/j.coph.2015.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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59
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de Boer P, Hoogenboom JP, Giepmans BNG. Correlated light and electron microscopy: ultrastructure lights up! Nat Methods 2015; 12:503-13. [PMID: 26020503 DOI: 10.1038/nmeth.3400] [Citation(s) in RCA: 308] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 04/15/2015] [Indexed: 12/15/2022]
Abstract
Microscopy has gone hand in hand with the study of living systems since van Leeuwenhoek observed living microorganisms and cells in 1674 using his light microscope. A spectrum of dyes and probes now enable the localization of molecules of interest within living cells by fluorescence microscopy. With electron microscopy (EM), cellular ultrastructure has been revealed. Bridging these two modalities, correlated light microscopy and EM (CLEM) opens new avenues. Studies of protein dynamics with fluorescent proteins (FPs), which leave the investigator 'in the dark' concerning cellular context, can be followed by EM examination. Rare events can be preselected at the light microscopy level before EM analysis. Ongoing development-including of dedicated probes, integrated microscopes, large-scale and three-dimensional EM and super-resolution fluorescence microscopy-now paves the way for broad CLEM implementation in biology.
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Affiliation(s)
- Pascal de Boer
- Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Jacob P Hoogenboom
- Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
| | - Ben N G Giepmans
- Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
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60
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Wanner AA, Kirschmann MA, Genoud C. Challenges of microtome-based serial block-face scanning electron microscopy in neuroscience. J Microsc 2015; 259:137-142. [PMID: 25907464 PMCID: PMC4745002 DOI: 10.1111/jmi.12244] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 02/11/2015] [Indexed: 01/14/2023]
Abstract
Serial block-face scanning electron microscopy (SBEM) is becoming increasingly popular for a wide range of applications in many disciplines from biology to material sciences. This review focuses on applications for circuit reconstruction in neuroscience, which is one of the major driving forces advancing SBEM. Neuronal circuit reconstruction poses exceptional challenges to volume EM in terms of resolution, field of view, acquisition time and sample preparation. Mapping the connections between neurons in the brain is crucial for understanding information flow and information processing in the brain. However, information on the connectivity between hundreds or even thousands of neurons densely packed in neuronal microcircuits is still largely missing. Volume EM techniques such as serial section TEM, automated tape-collecting ultramicrotome, focused ion-beam scanning electron microscopy and SBEM (microtome serial block-face scanning electron microscopy) are the techniques that provide sufficient resolution to resolve ultrastructural details such as synapses and provides sufficient field of view for dense reconstruction of neuronal circuits. While volume EM techniques are advancing, they are generating large data sets on the terabyte scale that require new image processing workflows and analysis tools. In this review, we present the recent advances in SBEM for circuit reconstruction in neuroscience and an overview of existing image processing and analysis pipelines.
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Affiliation(s)
- A A Wanner
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058, Basel, Switzerland
| | - M A Kirschmann
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058, Basel, Switzerland
| | - C Genoud
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058, Basel, Switzerland
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61
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Mandelblat-Cerf Y, Ramesh RN, Burgess CR, Patella P, Yang Z, Lowell BB, Andermann ML. Arcuate hypothalamic AgRP and putative POMC neurons show opposite changes in spiking across multiple timescales. eLife 2015; 4. [PMID: 26159614 PMCID: PMC4498165 DOI: 10.7554/elife.07122] [Citation(s) in RCA: 169] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 06/19/2015] [Indexed: 12/18/2022] Open
Abstract
Agouti-related-peptide (AgRP) neurons—interoceptive neurons in the arcuate nucleus of the hypothalamus (ARC)—are both necessary and sufficient for driving feeding behavior. To better understand the functional roles of AgRP neurons, we performed optetrode electrophysiological recordings from AgRP neurons in awake, behaving AgRP-IRES-Cre mice. In free-feeding mice, we observed a fivefold increase in AgRP neuron firing with mounting caloric deficit in afternoon vs morning recordings. In food-restricted mice, as food became available, AgRP neuron firing dropped, yet remained elevated as compared to firing in sated mice. The rapid drop in spiking activity of AgRP neurons at meal onset may reflect a termination of the drive to find food, while residual, persistent spiking may reflect a sustained drive to consume food. Moreover, nearby neurons inhibited by AgRP neuron photostimulation, likely including satiety-promoting pro-opiomelanocortin (POMC) neurons, demonstrated opposite changes in spiking. Finally, firing of ARC neurons was also rapidly modulated within seconds of individual licks for liquid food. These findings suggest novel roles for antagonistic AgRP and POMC neurons in the regulation of feeding behaviors across multiple timescales. DOI:http://dx.doi.org/10.7554/eLife.07122.001 Appetite is controlled in part by the opposing actions of the ‘hunger hormone’ (called ghrelin) and the ‘satiety hormone’ (called leptin). Ghrelin is released by the stomach when empty and stimulates appetite, whereas leptin is released by fat stores and induces feelings of fullness. Both hormones travel via the bloodstream and are detected by a region of the brain called the hypothalamus. Ghrelin and leptin act specifically on a group of cells in the hypothalamus that contains at least two major cell types: AgRP neurons and POMC neurons. Electrode recordings from slices of mouse brain show that AgRP neurons fire more rapidly at night—when mice normally feed—than during the day, whereas POMC neurons do the opposite. This suggests that the activity of AgRP neurons drives food-seeking behavior, whereas POMC firing inhibits it. However, the absence of circulating hormones such as leptin and ghrelin in brain slices makes it difficult to draw firm conclusions about the role of these cells in controlling appetite. Mandelblat-Cerf, Ramesh, Burgess et al. have addressed this issue by performing the first recordings of spiking activity in individual AgRP neurons and other cells that are likely to be POMC neurons in awake mice. Consistent with the results of slice experiments, the firing rate of AgRP neurons increased steadily over the course of the day, suggesting that their activity signals an increasing need for food. Furthermore, as soon as food became available, the firing rate of the AgRP neurons suddenly dropped—even though the animals' energy reserves would still have been low. These results are consistent with the findings of two recent studies reported earlier this year that used different methods to indirectly measure neuronal activity in awake mice. Notably, even after the drop in activity, the firing rates of AgRP neurons remained above those recorded in fully sated mice—which possibly reflects the fact that the animals' energy reserves were still low. The putative POMC neurons generally showed opposite effects to the AgRP neurons. The results of these electrode recordings in awake mice thus suggest that AgRP and POMC neurons together maintain a drive to seek out food sources as energy reserves fall, and to refrain from doing so when energy reserves are plentiful. Moreover, the seemingly paradoxical drop in AgRP firing and increase in POMC firing upon receiving food may act as a signal to temporarily stop searching for food, so that feeding itself can begin. Alternatively, since the release of satiety hormones after eating a meal is slow, these rapid changes in firing may provide more immediate feedback to the neuronal circuits that regulate the drives to seek and consume food. DOI:http://dx.doi.org/10.7554/eLife.07122.002
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Affiliation(s)
- Yael Mandelblat-Cerf
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Rohan N Ramesh
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Christian R Burgess
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Paola Patella
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Zongfang Yang
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Bradford B Lowell
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
| | - Mark L Andermann
- Department of Endocrinology, Beth Israel Deaconess Medical Center, Boston, United States
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Garfield AS, Li C, Madara JC, Shah BP, Webber E, Steger JS, Campbell JN, Gavrilova O, Lee CE, Olson DP, Elmquist JK, Tannous BA, Krashes MJ, Lowell BB. A neural basis for melanocortin-4 receptor-regulated appetite. Nat Neurosci 2015; 18:863-71. [PMID: 25915476 PMCID: PMC4446192 DOI: 10.1038/nn.4011] [Citation(s) in RCA: 293] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 03/30/2015] [Indexed: 12/14/2022]
Abstract
Pro-opiomelanocortin (POMC)- and agouti-related peptide (AgRP)-expressing neurons of the arcuate nucleus of the hypothalamus (ARC) are oppositely regulated by caloric depletion and coordinately stimulate and inhibit homeostatic satiety, respectively. This bimodality is principally underscored by the antagonistic actions of these ligands at downstream melanocortin-4 receptors (MC4R) in the paraventricular nucleus of the hypothalamus (PVH). Although this population is critical to energy balance, the underlying neural circuitry remains unknown. Using mice expressing Cre recombinase in MC4R neurons, we demonstrate bidirectional control of feeding following real-time activation and inhibition of PVH(MC4R) neurons and further identify these cells as a functional exponent of ARC(AgRP) neuron-driven hunger. Moreover, we reveal this function to be mediated by a PVH(MC4R)→lateral parabrachial nucleus (LPBN) pathway. Activation of this circuit encodes positive valence, but only in calorically depleted mice. Thus, the satiating and appetitive nature of PVH(MC4R)→LPBN neurons supports the principles of drive reduction and highlights this circuit as a promising target for antiobesity drug development.
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Affiliation(s)
- Alastair S Garfield
- 1] Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA. [2] Centre for Integrative Physiology, Hugh Robson Building, University of Edinburgh, Edinburgh, UK
| | - Chia Li
- 1] Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA. [2] National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA
| | - Joseph C Madara
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Bhavik P Shah
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Emily Webber
- 1] Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA. [2] National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA
| | - Jennifer S Steger
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - John N Campbell
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Charlotte E Lee
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
| | - David P Olson
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Joel K Elmquist
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
| | - Bakhos A Tannous
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Michael J Krashes
- 1] Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA. [2] National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA
| | - Bradford B Lowell
- 1] Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA. [2] Program in Neuroscience, Harvard Medical School, Boston, Massachusetts, USA
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Ma S, Gundlach AL. Ascending control of arousal and motivation: role of nucleus incertus and its peptide neuromodulators in behavioural responses to stress. J Neuroendocrinol 2015; 27:457-67. [PMID: 25612218 DOI: 10.1111/jne.12259] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 01/12/2015] [Accepted: 01/15/2015] [Indexed: 02/06/2023]
Abstract
Arousal is a process that involves the activation of ascending neural pathways originating in the rostral pons that project to the forebrain through the midbrain reticular formation to promote the activation of key cortical, thalamic, hypothalamic and limbic centres. Established modulators of arousal include the cholinergic, serotonergic, noradrenergic and dopaminergic networks originating in the pons and midbrain. Recent data indicate that a population of largely GABAergic projection neurones located in the nucleus incertus (NI) are also involved in arousal and motivational processes. The NI has prominent efferent connections with distinct hypothalamic, amygdalar and thalamic nuclei, in addition to dense projections to key brain regions associated with the generation and pacing of hippocampal activity. The NI receives strong inputs from the prefrontal cortex, lateral habenula and the interpeduncular and median raphe nuclei, suggesting it is highly integrated in circuits regulating higher cognitive behaviours (hippocampal theta rhythm) and emotion. Anatomical and functional studies have revealed that the NI is a rich source of multiple peptide neuromodulators, including relaxin-3, and may mediate extra-hypothalamic effects of the stress hormone corticotrophin-releasing factor, as well as other key modulators such as orexins and oxytocin. This review provides an overview of earlier studies and highlights more recent research that implicates this neural network in the integration of arousal and motivated behaviours and has begun to identify the associated mechanisms. Future research that should help to better clarify the connectivity and function of the NI in major experimental species and humans is also discussed.
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Affiliation(s)
- S Ma
- Neuropeptides Division, The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
| | - A L Gundlach
- Neuropeptides Division, The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
- Department of Anatomy and Neuroscience, The University of Melbourne, Melbourne, VIC, Australia
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Jackson VM, Breen DM, Fortin JP, Liou A, Kuzmiski JB, Loomis AK, Rives ML, Shah B, Carpino PA. Latest approaches for the treatment of obesity. Expert Opin Drug Discov 2015; 10:825-39. [DOI: 10.1517/17460441.2015.1044966] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- V Margaret Jackson
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - Danna M Breen
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - Jean-Philippe Fortin
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - Alice Liou
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - J Brent Kuzmiski
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - A Katrina Loomis
- 2Clinical Research, Pfizer PharmaTherapeutics, Eastern Point Road, Groton, CT 06340, USA
| | - Marie-Laure Rives
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - Bhavik Shah
- 1Cardiovascular and Metabolic Diseases Research Unit, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
| | - Philip A Carpino
- 3Cardiovascular and Metabolic Diseases Medicinal Chemistry, Pfizer PharmaTherapeutics, 610 Main Street, Cambridge, MA 02139, USA
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Ghamari-Langroudi M, Digby GJ, Sebag JA, Millhauser GL, Palomino R, Matthews R, Gillyard T, Panaro BL, Tough IR, Cox HM, Denton JS, Cone RD. G-protein-independent coupling of MC4R to Kir7.1 in hypothalamic neurons. Nature 2015; 520:94-8. [PMID: 25600267 PMCID: PMC4383680 DOI: 10.1038/nature14051] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/10/2014] [Indexed: 02/04/2023]
Abstract
The regulated release of anorexigenic α-melanocyte stimulating hormone (α-MSH) and orexigenic Agouti-related protein (AgRP) from discrete hypothalamic arcuate neurons onto common target sites in the central nervous system has a fundamental role in the regulation of energy homeostasis. Both peptides bind with high affinity to the melanocortin-4 receptor (MC4R); existing data show that α-MSH is an agonist that couples the receptor to the Gαs signalling pathway, while AgRP binds competitively to block α-MSH binding and blocks the constitutive activity mediated by the ligand-mimetic amino-terminal domain of the receptor. Here we show that, in mice, regulation of firing activity of neurons from the paraventricular nucleus of the hypothalamus (PVN) by α-MSH and AgRP can be mediated independently of Gαs signalling by ligand-induced coupling of MC4R to closure of inwardly rectifying potassium channel, Kir7.1. Furthermore, AgRP is a biased agonist that hyperpolarizes neurons by binding to MC4R and opening Kir7.1, independently of its inhibition of α-MSH binding. Consequently, Kir7.1 signalling appears to be central to melanocortin-mediated regulation of energy homeostasis within the PVN. Coupling of MC4R to Kir7.1 may explain unusual aspects of the control of energy homeostasis by melanocortin signalling, including the gene dosage effect of MC4R and the sustained effects of AgRP on food intake.
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Affiliation(s)
- Masoud Ghamari-Langroudi
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Gregory J Digby
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Julien A Sebag
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Glenn L Millhauser
- Department of Chemistry &Biochemistry, University of California, Santa Cruz, California 95064, USA
| | - Rafael Palomino
- Department of Chemistry &Biochemistry, University of California, Santa Cruz, California 95064, USA
| | - Robert Matthews
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Taneisha Gillyard
- 1] Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Meharry Medical College, Nashville, Tennessee 37208, USA
| | - Brandon L Panaro
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Iain R Tough
- King's College London, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Helen M Cox
- King's College London, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK
| | - Jerod S Denton
- 1] Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Roger D Cone
- Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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