Publications

2017
Chen Y, Granger AJ, Tran T, Saulnier JL, Kirkwood A, Sabatini BL. Endogenous Gαq-Coupled Neuromodulator Receptors Activate Protein Kinase A. Neuron. 2017;96 (5) :1070-1083.e5.Abstract
Protein kinase A (PKA) integrates inputs from G-protein-coupled neuromodulator receptors to modulate synaptic and cellular function. Gαs signaling stimulates PKA activity, whereas Gαi inhibits PKA activity. Gαq, on the other hand, signals through phospholipase C, and it remains unclear whether Gαq-coupled receptors signal to PKA in their native context. Here, using two independent optical reporters of PKA activity in acute mouse hippocampus slices, we show that endogenous Gαq-coupled muscarinic acetylcholine receptors activate PKA. Mechanistically, this effect is mediated by parallel signaling via either calcium or protein kinase C. Furthermore, multiple Gαq-coupled receptors modulate phosphorylation by PKA, a classical Gαs/Gαi effector. Thus, these results highlight PKA as a biochemical integrator of three major types of GPCRs and necessitate reconsideration of classic models used to predict neuronal signaling in response to the large family of Gαq-coupled receptors.
Wallace ML, Saunders A, Huang KW, Philson AC, Goldman M, Macosko EZ, McCarroll SA, Sabatini BL. Genetically Distinct Parallel Pathways in the Entopeduncular Nucleus for Limbic and Sensorimotor Output of the Basal Ganglia. Neuron. 2017;94 (1) :138-152.e5.Abstract
The basal ganglia (BG) integrate inputs from diverse sensorimotor, limbic, and associative regions to guide action-selection and goal-directed behaviors. The entopeduncular nucleus (EP) is a major BG output nucleus and has been suggested to channel signals from distinct BG nuclei to target regions involved in diverse functions. Here we use single-cell transcriptional and molecular analyses to demonstrate that the EP contains at least three classes of projection neurons-glutamate/GABA co-releasing somatostatin neurons, glutamatergic parvalbumin neurons, and GABAergic parvalbumin neurons. These classes comprise functionally and anatomically distinct output pathways that differentially affect EP target regions, such as the lateral habenula (LHb) and thalamus. Furthermore, LHb- and thalamic-projecting EP neurons are differentially innervated by subclasses of striatal and pallidal neurons. Therefore, we identify previously unknown subdivisions within the EP and reveal the existence of cascading, molecularly distinct projections through striatum and globus pallidus to EP targets within epithalamus and thalamus.
Granger AJ, Wallace ML, Sabatini BL. Multi-transmitter neurons in the mammalian central nervous system. Curr Opin Neurobiol. 2017;45 :85-91.Abstract
It is firmly established that many mammalian neurons release various combinations of amino acids, their derivatives, and other small molecules from presynaptic terminals in order to signal to their postsynaptic targets. Here we discuss recent findings about four types of multi-transmitter neurons-those that release GABA and acetylcholine (Ach); dopamine (DA) and GABA or glutamate; and glutamate and GABA. The mechanisms of co-release in each class differ and highlight the complex and dynamic nature of neurotransmitter release. Furthermore, identifying the neurotransmitter signature of each neuron and the post-synaptic targets of each neurotransmitter remain challenging. The existence of multi-transmitter neurons complicates the interpretation of connectomic wiring diagrams and poses interesting challenges for our understanding of circuit function in the brain.
Chen Y, Granger AJ, Tran T, Saulnier JL, Kirkwood A, Sabatini BL. Endogenous Gαq-Coupled Neuromodulator Receptors Activate Protein Kinase A. Neuron. 2017;20 (8) :1180-1188. [PDF]
Granger AJ, Wallace ML, Sabatini BL. Multi-transmitter neurons in the mammalian central nervous system. Current Opinion in Neurobiology. 2017;45 :85-91. PDF
Pisanello F, Mandelbaum G, Pisanello M, Oldenburg IA, Markowitz JE, Peterson RE, Patria DA, Haynes TM, Emara MS, Spagnolo B, et al. Dynamic illumination of spatially restricted or large brain volumes via a single tapered optical fiber. Nature Neuroscience. 2017;20 (8) :1180-1190. PDF
Wallace ML, Saunders A, Huang KW, Philson AC, Goldman M, Macosko EZ, McCarroll SA, Sabatini BL. Genetically Distinct Parallel Pathways in the Entopeduncular Nucleus for Limbic and Sensorimotor Output of the Basal Ganglia. Neuron. 2017;94 (1) :138-152. PDF
2016
Hou XH, Hyun M, Taranda J, Huang KW, Todd E, Feng D, Atwater E, Croney D, Zeidel ML, Osten P, et al. Central Control Circuit for Context-Dependent Micturition. Cell. 2016;167 (1) :73-86.e12.Abstract
Urine release (micturition) serves an essential physiological function as well as a critical role in social communication in many animals. Here, we show a combined effect of olfaction and social hierarchy on micturition patterns in adult male mice, confirming the existence of a micturition control center that integrates pro- and anti-micturition cues. Furthermore, we demonstrate that a cluster of neurons expressing corticotropin-releasing hormone (Crh) in the pontine micturition center (PMC) is electrophysiologically distinct from their Crh-negative neighbors and sends glutamatergic projections to the spinal cord. The activity of PMC Crh-expressing neurons correlates with and is sufficient to drive bladder contraction, and when silenced impairs micturition behavior. These neurons receive convergent input from widespread higher brain areas that are capable of carrying diverse pro- and anti-micturition signals, and whose activity modulates hierarchy-dependent micturition. Taken together, our results indicate that PMC Crh-expressing neurons are likely the integration center for context-dependent micturition behavior.
Chen Y, Saulnier JL, Yellen G, Sabatini BL. Corrigendum: A PKA activity sensor for quantitative analysis of endogenous GPCR signaling via 2-photon FRET-FLIM imaging. Front Pharmacol. 2016;7 :46.Abstract
[This corrects the article on p. 56 in vol. 5, PMID: 24765076.].
Granger AJ, Mulder N, Saunders A, Sabatini BL. Cotransmission of acetylcholine and GABA. Neuropharmacology. 2016;100 :40-6.Abstract
Neurons that produce acetylcholine (ACh) are positioned to broadly influence the brain, with axonal arborizations that extend throughout the cerebral cortex, striatum, and hippocampus. While the action of these neurons has typically been attributed entirely to ACh, neurons often release more than one primary neurotransmitter. Here, we review evidence for the cotransmission of the inhibitory neurotransmitter GABA from cholinergic neurons throughout the mammalian central nervous system. Functional cotransmission of ACh and GABA has been reported in the retina and cortex, and anatomical studies suggest that GABA cotransmission is a common feature of nearly all forebrain ACh-producing neurons. Further experiments are necessary to confirm the extent of GABA cotransmission from cholinergic neurons, and the contribution of GABA needs to be considered when studying the functional impact of activity in ACh-producing neurons. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
Kantevari S, Passlick S, Kwon H-B, Richers MT, Sabatini BL, Ellis-Davies GCR. Development of Anionically Decorated Caged Neurotransmitters: In Vitro Comparison of 7-Nitroindolinyl- and 2-(p-Phenyl-o-nitrophenyl)propyl-Based Photochemical Probes. Chembiochem. 2016;17 (10) :953-61.Abstract
Neurotransmitter uncaging, especially that of glutamate, has been used to study synaptic function for over 30 years. One limitation of caged glutamate probes is the blockade of γ-aminobutyric acid (GABA)-A receptor function. This problem comes to the fore when the probes are applied at the high concentrations required for effective two-photon photolysis. To mitigate such problems one could improve the photochemical properties of caging chromophores and/or remove receptor blockade. We show that addition of a dicarboxylate unit to the widely used 4-methoxy-7-nitroindolinyl-Glu (MNI-Glu) system reduced the off-target effects by about 50-70 %. When the same strategy was applied to an electron-rich 2-(p-Phenyl-o-nitrophenyl)propyl (PNPP) caging group, the pharmacological improvements were not as significant as in the MNI case. Finally, we used very extensive biological testing of the PNPP-caged Glu (more than 250 uncaging currents at single dendritic spines) to show that nitro-biphenyl caging chromophores have two-photon uncaging efficacies similar to that of MNI-Glu.
Gross GG, Straub C, Perez-Sanchez J, Dempsey WP, Junge JA, Roberts RW, Trinh LA, Fraser SE, De Koninck Y, De Koninck P, et al. An E3-ligase-based method for ablating inhibitory synapses. Nat Methods. 2016;13 (8) :673-8.Abstract
Although neuronal activity can be modulated using a variety of techniques, there are currently few methods for controlling neuronal connectivity. We introduce a tool (GFE3) that mediates the fast, specific and reversible elimination of inhibitory synaptic inputs onto genetically determined neurons. GFE3 is a fusion between an E3 ligase, which mediates the ubiquitination and rapid degradation of proteins, and a recombinant, antibody-like protein (FingR) that binds to gephyrin. Expression of GFE3 leads to a strong and specific reduction of gephyrin in culture or in vivo and to a substantial decrease in phasic inhibition onto cells that express GFE3. By temporarily expressing GFE3 we showed that inhibitory synapses regrow following ablation. Thus, we have created a simple, reversible method for modulating inhibitory synaptic input onto genetically determined cells.
Peixoto RT, Wang W, Croney DM, Kozorovitskiy Y, Sabatini BL. Early hyperactivity and precocious maturation of corticostriatal circuits in Shank3B(-/-) mice. Nat Neurosci. 2016;19 (5) :716-724.Abstract
Some autistic individuals exhibit abnormal development of the caudate nucleus and associative cortical areas, suggesting potential dysfunction of cortico-basal ganglia (BG) circuits. Using optogenetic and electrophysiological approaches in mice, we identified a narrow postnatal period that is characterized by extensive glutamatergic synaptogenesis in striatal spiny projection neurons (SPNs) and a concomitant increase in corticostriatal circuit activity. SPNs during early development have high intrinsic excitability and respond strongly to cortical afferents despite sparse excitatory inputs. As a result, striatum and corticostriatal connectivity are highly sensitive to acute and chronic changes in cortical activity, suggesting that early imbalances in cortical function alter BG development. Indeed, a mouse model of autism with deletions in Shank3 (Shank3B(-/-)) shows early cortical hyperactivity, which triggers increased SPN excitatory synapse and corticostriatal hyperconnectivity. These results indicate that there is a tight functional coupling between cortex and striatum during early postnatal development and suggest a potential common circuit dysfunction that is caused by cortical hyperactivity.
Saunders A, Huang KW, Sabatini BL. Globus Pallidus Externus Neurons Expressing parvalbumin Interconnect the Subthalamic Nucleus and Striatal Interneurons. PLoS One. 2016;11 (2) :e0149798.Abstract
The globus pallidus externus (GP) is a nucleus of the basal ganglia (BG), containing GABAergic projection neurons that arborize widely throughout the BG, thalamus and cortex. Ongoing work seeks to map axonal projection patterns from GP cell types, as defined by their electrophysiological and molecular properties. Here we use transgenic mice and recombinant viruses to characterize parvalbumin expressing (PV+) GP neurons within the BG circuit. We confirm that PV+ neurons 1) make up ~40% of the GP neurons 2) exhibit fast-firing spontaneous activity and 3) provide the major axonal arborization to the STN and substantia nigra reticulata/compacta (SNr/c). PV+ neurons also innervate the striatum. Retrograde labeling identifies ~17% of pallidostriatal neurons as PV+, at least a subset of which also innervate the STN and SNr. Optogenetic experiments in acute brain slices demonstrate that the PV+ pallidostriatal axons make potent inhibitory synapses on low threshold spiking (LTS) and fast-spiking interneurons (FS) in the striatum, but rarely on spiny projection neurons (SPNs). Thus PV+ GP neurons are synaptically positioned to directly coordinate activity between BG input nuclei, the striatum and STN, and thalamic-output from the SNr.
Tritsch NX, Granger AJ, Sabatini BL. Mechanisms and functions of GABA co-release. Nat Rev Neurosci. 2016;17 (3) :139-45.Abstract
The 'one neuron, one neurotransmitter' doctrine states that synaptic communication between two neurons occurs through the release of a single chemical transmitter. However, recent findings suggest that neurons that communicate using more than one classical neurotransmitter are prevalent throughout the adult mammalian CNS. In particular, several populations of neurons previously thought to release only glutamate, acetylcholine, dopamine or histamine also release the major inhibitory neurotransmitter GABA. Here, we review these findings and discuss the implications of GABA co-release for synaptic transmission and plasticity.
Kong D, Dagon Y, Campbell JN, Guo Y, Yang Z, Yi X, Aryal P, Wellenstein K, Kahn BB, Sabatini BL, et al. A Postsynaptic AMPK→p21-Activated Kinase Pathway Drives Fasting-Induced Synaptic Plasticity in AgRP Neurons. Neuron. 2016;91 (1) :25-33.Abstract
AMP-activated protein kinase (AMPK) plays an important role in regulating food intake. The downstream AMPK substrates and neurobiological mechanisms responsible for this, however, are ill defined. Agouti-related peptide (AgRP)-expressing neurons in the arcuate nucleus regulate hunger. Their firing increases with fasting, and once engaged they cause feeding. AgRP neuron activity is regulated by state-dependent synaptic plasticity: fasting increases dendritic spines and excitatory synaptic activity; feeding does the opposite. The signaling mechanisms underlying this, however, are also unknown. Using neuron-specific approaches to measure and manipulate kinase activity specifically within AgRP neurons, we establish that fasting increases AMPK activity in AgRP neurons, that increased AMPK activity in AgRP neurons is both necessary and sufficient for fasting-induced spinogenesis and excitatory synaptic activity, and that the AMPK phosphorylation target mediating this plasticity is p21-activated kinase. This provides a signaling and neurobiological basis for both AMPK regulation of energy balance and AgRP neuron state-dependent plasticity.
Straub C, Saulnier JL, Bègue A, Feng DD, Huang KW, Sabatini BL. Principles of Synaptic Organization of GABAergic Interneurons in the Striatum. Neuron. 2016;92 (1) :84-92.Abstract
The striatum, the entry nucleus of the basal ganglia, lacks laminar or columnar organization of its principal cells; nevertheless, functional data suggest that it is spatially organized. Here we examine whether the connectivity and synaptic organization of striatal GABAergic interneurons contributes to such spatial organization. Focusing on the two main classes of striatal GABAergic interneurons (fast-spiking interneurons [FSIs] and low-threshold-spiking interneurons [LTSIs]), we apply a combination of optogenetics and viral tracing approaches to dissect striatal microcircuits in mice. Our results reveal fundamental differences between the synaptic organizations of both interneuron types. FSIs target exclusively striatal projection neurons (SPNs) within close proximity and form strong synapses on the proximal somatodendritic region. In contrast, LTSIs target both SPNs and cholinergic interneurons, and synaptic connections onto SPNs are made exclusively over long distances and onto distal dendrites. These results suggest fundamentally different functions of FSIs and LTSIs in shaping striatal output.
Hou XH, Hyun M, Taranda J, Huang KW, Todd E, Feng D, Atwater E, Croney D, Zeidel ML, Osten P, et al. Central Control Circuit for Context-Dependent Micturition. Cell. 2016;167 (1) :73-86. PDF
Gross GG, Straub C, Perez-Sanchez J, Dempsey WP, Junge JA, Roberts RW, Trinh LA, Fraser SE, Koninck DY, Koninck DP, et al. An E3-ligase-based method for ablating inhibitory synapses. Nature Methods. 2016;13 (8) :673-8. PDF
Kong D, Dagon Y, Campbell JN, Guo Y, Yang Z, Yi X, Aryal P, Wellenstein K, Kahn BB, Sabatini BL, et al. A Postsynaptic AMPK→p21-Activated Kinase Pathway Drives Fasting-Induced Synaptic Plasticity in AgRP Neurons. Neuron. 2016;91 (1) :25-33. PDF

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