Samuel Pfaff - Academia.edu (original) (raw)

Papers by Samuel Pfaff

Research paper thumbnail of Dependence of Hippocampal Function on ERRγ-Regulated Mitochondrial Metabolism

Cell Metabolism, 2015

Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for... more Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for survival, function, and behavioral output. Unlike most cells that burn both fat and sugar, neurons only burn sugar. Despite its importance, how neurons meet the increased energy demands of complex behaviors such as learning and memory is poorly understood. Here we show that the estrogen-related receptor gamma (ERRγ) orchestrates the expression of a distinct neural gene network promoting mitochondrial oxidative metabolism that reflects the extraordinary neuronal dependence on glucose. ERRγ(-/-) neurons exhibit decreased metabolic capacity. Impairment of long-term potentiation (LTP) in ERRγ(-/-) hippocampal slices can be fully rescued by the mitochondrial OxPhos substrate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ in cerebral cortex and hippocampus exhibit defects in spatial learning and memory. These findings implicate neuronal ERRγ in the metabolic adaptations required for memory formation.

Research paper thumbnail of Slit and semaphorin signaling governed by Islet transcription factors positions motor neuron somata within the neural tube

Experimental neurology, Jan 2, 2015

Motor neurons send out axons to peripheral muscles while their cell bodies remain in the ventral ... more Motor neurons send out axons to peripheral muscles while their cell bodies remain in the ventral spinal cord. The unique configuration of motor neurons spanning the border between the CNS and PNS has been explained by structural barriers such as boundary cap (BC) cells, basal lamina and radial glia. However, mechanisms in motor neurons that retain their position have not been addressed yet. Here we demonstrate that the Islet1 (Isl1) and Islet2 (Isl2) transcription factors, which are essential for acquisition of motor neuron identity, also contribute to restrict motor neurons within the neural tube. In mice that lack both Isl1 and Isl2, large numbers of motor neurons exited the neural tube, even prior to the appearance of BC cells at the ventral exit points. Transcriptional profiling of motor neurons derived from Isl1 null embryonic stem cells revealed that transcripts of major genes involved in repulsive mechanisms were misregulated. Particularly, expression of Neuropilin1 (Npr1) an...

Research paper thumbnail of Magnitude of Binocular Vision Controlled by Islet2 Repression of a Genetic Program that Specifies Laterality of Retinal Axon Pathfinding

Cell, 2004

Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether R... more Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether RGCs project to ipsilateral or contralateral brain visual centers, critical for binocular vision. Using Isl2tau-lacZ knockin mice, we show that the LIM-homeodomain transcription factor Isl2 marks only contralaterally projecting RGCs. The transcription factor Zic2 and guidance receptor EphB1, required by RGCs to project ipsilaterally, colocalize in

Research paper thumbnail of LIM Factor Lhx3 Contributes to the Specification of Motor Neuron and Interneuron Identity through Cell-Type-Specific Protein-Protein Interactions

Cell, 2002

LIM homeodomain codes regulate the development of many cell types, though it is poorly understood... more LIM homeodomain codes regulate the development of many cell types, though it is poorly understood how these factors control gene expression in a cell-specific manner. Lhx3 is involved in the generation of two adjacent, but distinct, cell types for locomotion, motor neurons and V2 interneurons. Using in vivo function and protein interaction assays, we found that Lhx3 binds directly to

Research paper thumbnail of Spinal Cord Electrophysiology II: Extracellular Suction Electrode Fabrication

Journal of Visualized Experiments, 2011

Research paper thumbnail of Cholinergic Input Is Required during Embryonic Development to Mediate Proper Assembly of Spinal Locomotor Circuits

Research paper thumbnail of Spinal Cord Electrophysiology

Journal of Visualized Experiments, 2010

Research paper thumbnail of FGF as a Target-Derived Chemoattractant for Developing Motor Axons Genetically Programmed by the LIM Code

Neuron, 2006

Summary LIM transcription factors confer developing axons with specific navigational properties, ... more Summary LIM transcription factors confer developing axons with specific navigational properties, but the down- stream guidance receptors and ligands are not well defined. The dermomyotome, a transient structure from which axial muscles arise, is the source of a se- creted long-range chemoattractant specific for me- dial-class spinal motor neuron axons (MMCm axons). We show that fibroblast growth factors (FGFs) pro-

Research paper thumbnail of Segregation of Axial Motor and Sensory Pathways via Heterotypic Trans-Axonal Signaling

Research paper thumbnail of Small CTD Phosphatases Function in Silencing Neuronal Gene Expression

Science, 2005

Neuronal gene transcription is repressed in non-neuronal cells by the repressor element 1 (RE-1)-... more Neuronal gene transcription is repressed in non-neuronal cells by the repressor element 1 (RE-1)-silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) complex. To understand how this silencing is achieved, we examined a family of class-C RNA polymerase II (RNAPII) carboxyl-terminal domain (CTD) phosphatases [small CTD phosphatases (SCPs) 1 to 3], whose expression is restricted to non-neuronal tissues. We show that REST/NRSF recruits SCPs to neuronal genes that contain RE-1 elements, leading to neuronal gene silencing in non-neuronal cells. Phosphatase-inactive forms of SCP interfere with REST/NRSF function and promote neuronal differentiation of P19 stem cells. Likewise, small interfering RNA directed to the single Drosophila SCP unmasks neuronal gene expression in S2 cells. Thus, SCP activity is an evolutionarily conserved transcriptional regulator that acts globally to silence neuronal genes.

Research paper thumbnail of Synchronization of Neurogenesis and Motor Neuron Specification by Direct Coupling of bHLH and Homeodomain Transcription Factors

Neuron, 2003

Inductive signaling leads to the coactivation of regulatory pathways for specifying general neuro... more Inductive signaling leads to the coactivation of regulatory pathways for specifying general neuronal traits in parallel with instructions for neuronal subtype specification. Nevertheless, the mechanisms that ensure that these pathways are synchronized have not been defined. To address this, we examined how bHLH proteins Ngn2 and NeuroM controlling neurogenesis functionally converge with LIM-homeodomain (LIM-HD) factors Isl1 and Lhx3 involved in motor neuron subtype specification. We found that Ngn2 and NeuroM transcriptionally synergize with Isl1 and Lhx3 to specify motor neurons in the embryonic spinal cord and in P19 stem cells. The mechanism underlying this cooperativity is based on interactions that directly couple the activity of the bHLH and LIM-HD proteins, mediated by the adaptor protein NLI. This functional link acts to synchronize neuronal subtype specification with neurogenesis.

Research paper thumbnail of A Postmitotic Role for Isl-Class LIM Homeodomain Proteins in the Assignment of Visceral Spinal Motor Neuron Identity

Research paper thumbnail of Active Suppression of Interneuron Programs within Developing Motor Neurons Revealed by Analysis of Homeodomain Factor HB9

Research paper thumbnail of The Ubiquitin Ligase Phr1 Regulates Axon Outgrowth through Modulation of Microtubule Dynamics

Research paper thumbnail of Notch and MAML Signaling Drives Scl-Dependent Interneuron Diversity in the Spinal Cord

Research paper thumbnail of Regulation of Motor Neuron Specification by Phosphorylation of Neurogenin 2

Research paper thumbnail of Identification of a cellular node for motor control pathways

Nature Neuroscience, 2014

The rich behavioral repertoire of animals is encoded in the CNS as a set of motorneuron activatio... more The rich behavioral repertoire of animals is encoded in the CNS as a set of motorneuron activation patterns, also called 'motor synergies'. However, the neurons that orchestrate these motor programs as well as their cellular properties and connectivity are poorly understood. Here we identify a population of molecularly defined motor synergy encoder (MSE) neurons in the mouse spinal cord that may represent a central node in neural pathways for voluntary and reflexive movement. This population receives direct inputs from the motor cortex and sensory pathways and, in turn, has monosynaptic outputs to spinal motorneurons. Optical stimulation of MSE neurons drove reliable patterns of activity in multiple motor groups, and we found that the evoked motor patterns varied on the basis of the rostrocaudal location of the stimulated MSE. We speculate that these neurons comprise a cellular network for encoding coordinated motor output programs.

Research paper thumbnail of Differential Expression of LIM Homeobox Genes among Motor Neuron Subpopulations in the Developing Chick Brain Stem

Molecular and Cellular Neuroscience, 1996

Research paper thumbnail of Axon fasciculation defects and retinal dysplasias in mice lacking the immunoglobulin superfamily adhesion molecule BEN/ALCAM/SC1

Molecular and Cellular Neuroscience, 2004

The immunoglobulin superfamily adhesion molecule BEN (other names include ALCAM, SC1, DM-GRASP, n... more The immunoglobulin superfamily adhesion molecule BEN (other names include ALCAM, SC1, DM-GRASP, neurolin, and CD166) has been implicated in the control of numerous developmental and pathological processes, including the guidance of retinal and motor axons to their targets. To test hypotheses about BEN function, we disrupted its gene via homologous recombination and analyzed the resulting mutant mice. Mice lacking BEN are viable and fertile, and display no external morphological defects. Despite grossly normal trajectories, both motor and retinal ganglion cell axons fasciculated poorly and were occasionally misdirected. In addition, BEN mutant retinae exhibited evaginated or invaginated regions with photoreceptor ectopias that resembled the "retinal folds" observed in some human retinopathies. Together, these results demonstrate that BEN promotes fasciculation of multiple axonal populations and uncover an unexpected function for BEN in retinal histogenesis.

Research paper thumbnail of Homeodomain transcription factors in the development of subsets of hindbrain reticulospinal neurons

Molecular and Cellular Neuroscience, 2005

Hindbrain reticulospinal neurons are involved in complex neural functions that are mediated by sp... more Hindbrain reticulospinal neurons are involved in complex neural functions that are mediated by spinal elements, including posture control and modulation of respiration and cardiovascular function. Recent descriptive studies with chick, mouse, and rat embryos have provided anatomical insight into the development of the different reticulospinal nuclei and the establishment of their axonal projection pathways into the spinal cord. In this study, we have addressed the molecular control of this process. Retrograde labeling of reticulospinal neurons in chick and mouse embryos combined with immunostaining for the homeodomain factors Lhx1/Lhx5, Lhx3/Lhx4, and Chx10 have defined transcriptional codes that label subsets of neurons with different axon projection patterns. Gain of function and loss of function experiments using in ovo electroporation implicate these transcription factors in the determination of reticulospinal neuron identity. Furthermore, our studies reveal novel gene interactions between the transcription factors analyzed that may determine the final patterns of reticulospinal axon projection.

Research paper thumbnail of Dependence of Hippocampal Function on ERRγ-Regulated Mitochondrial Metabolism

Cell Metabolism, 2015

Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for... more Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for survival, function, and behavioral output. Unlike most cells that burn both fat and sugar, neurons only burn sugar. Despite its importance, how neurons meet the increased energy demands of complex behaviors such as learning and memory is poorly understood. Here we show that the estrogen-related receptor gamma (ERRγ) orchestrates the expression of a distinct neural gene network promoting mitochondrial oxidative metabolism that reflects the extraordinary neuronal dependence on glucose. ERRγ(-/-) neurons exhibit decreased metabolic capacity. Impairment of long-term potentiation (LTP) in ERRγ(-/-) hippocampal slices can be fully rescued by the mitochondrial OxPhos substrate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ in cerebral cortex and hippocampus exhibit defects in spatial learning and memory. These findings implicate neuronal ERRγ in the metabolic adaptations required for memory formation.

Research paper thumbnail of Slit and semaphorin signaling governed by Islet transcription factors positions motor neuron somata within the neural tube

Experimental neurology, Jan 2, 2015

Motor neurons send out axons to peripheral muscles while their cell bodies remain in the ventral ... more Motor neurons send out axons to peripheral muscles while their cell bodies remain in the ventral spinal cord. The unique configuration of motor neurons spanning the border between the CNS and PNS has been explained by structural barriers such as boundary cap (BC) cells, basal lamina and radial glia. However, mechanisms in motor neurons that retain their position have not been addressed yet. Here we demonstrate that the Islet1 (Isl1) and Islet2 (Isl2) transcription factors, which are essential for acquisition of motor neuron identity, also contribute to restrict motor neurons within the neural tube. In mice that lack both Isl1 and Isl2, large numbers of motor neurons exited the neural tube, even prior to the appearance of BC cells at the ventral exit points. Transcriptional profiling of motor neurons derived from Isl1 null embryonic stem cells revealed that transcripts of major genes involved in repulsive mechanisms were misregulated. Particularly, expression of Neuropilin1 (Npr1) an...

Research paper thumbnail of Magnitude of Binocular Vision Controlled by Islet2 Repression of a Genetic Program that Specifies Laterality of Retinal Axon Pathfinding

Cell, 2004

Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether R... more Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether RGCs project to ipsilateral or contralateral brain visual centers, critical for binocular vision. Using Isl2tau-lacZ knockin mice, we show that the LIM-homeodomain transcription factor Isl2 marks only contralaterally projecting RGCs. The transcription factor Zic2 and guidance receptor EphB1, required by RGCs to project ipsilaterally, colocalize in

Research paper thumbnail of LIM Factor Lhx3 Contributes to the Specification of Motor Neuron and Interneuron Identity through Cell-Type-Specific Protein-Protein Interactions

Cell, 2002

LIM homeodomain codes regulate the development of many cell types, though it is poorly understood... more LIM homeodomain codes regulate the development of many cell types, though it is poorly understood how these factors control gene expression in a cell-specific manner. Lhx3 is involved in the generation of two adjacent, but distinct, cell types for locomotion, motor neurons and V2 interneurons. Using in vivo function and protein interaction assays, we found that Lhx3 binds directly to

Research paper thumbnail of Spinal Cord Electrophysiology II: Extracellular Suction Electrode Fabrication

Journal of Visualized Experiments, 2011

Research paper thumbnail of Cholinergic Input Is Required during Embryonic Development to Mediate Proper Assembly of Spinal Locomotor Circuits

Research paper thumbnail of Spinal Cord Electrophysiology

Journal of Visualized Experiments, 2010

Research paper thumbnail of FGF as a Target-Derived Chemoattractant for Developing Motor Axons Genetically Programmed by the LIM Code

Neuron, 2006

Summary LIM transcription factors confer developing axons with specific navigational properties, ... more Summary LIM transcription factors confer developing axons with specific navigational properties, but the down- stream guidance receptors and ligands are not well defined. The dermomyotome, a transient structure from which axial muscles arise, is the source of a se- creted long-range chemoattractant specific for me- dial-class spinal motor neuron axons (MMCm axons). We show that fibroblast growth factors (FGFs) pro-

Research paper thumbnail of Segregation of Axial Motor and Sensory Pathways via Heterotypic Trans-Axonal Signaling

Research paper thumbnail of Small CTD Phosphatases Function in Silencing Neuronal Gene Expression

Science, 2005

Neuronal gene transcription is repressed in non-neuronal cells by the repressor element 1 (RE-1)-... more Neuronal gene transcription is repressed in non-neuronal cells by the repressor element 1 (RE-1)-silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) complex. To understand how this silencing is achieved, we examined a family of class-C RNA polymerase II (RNAPII) carboxyl-terminal domain (CTD) phosphatases [small CTD phosphatases (SCPs) 1 to 3], whose expression is restricted to non-neuronal tissues. We show that REST/NRSF recruits SCPs to neuronal genes that contain RE-1 elements, leading to neuronal gene silencing in non-neuronal cells. Phosphatase-inactive forms of SCP interfere with REST/NRSF function and promote neuronal differentiation of P19 stem cells. Likewise, small interfering RNA directed to the single Drosophila SCP unmasks neuronal gene expression in S2 cells. Thus, SCP activity is an evolutionarily conserved transcriptional regulator that acts globally to silence neuronal genes.

Research paper thumbnail of Synchronization of Neurogenesis and Motor Neuron Specification by Direct Coupling of bHLH and Homeodomain Transcription Factors

Neuron, 2003

Inductive signaling leads to the coactivation of regulatory pathways for specifying general neuro... more Inductive signaling leads to the coactivation of regulatory pathways for specifying general neuronal traits in parallel with instructions for neuronal subtype specification. Nevertheless, the mechanisms that ensure that these pathways are synchronized have not been defined. To address this, we examined how bHLH proteins Ngn2 and NeuroM controlling neurogenesis functionally converge with LIM-homeodomain (LIM-HD) factors Isl1 and Lhx3 involved in motor neuron subtype specification. We found that Ngn2 and NeuroM transcriptionally synergize with Isl1 and Lhx3 to specify motor neurons in the embryonic spinal cord and in P19 stem cells. The mechanism underlying this cooperativity is based on interactions that directly couple the activity of the bHLH and LIM-HD proteins, mediated by the adaptor protein NLI. This functional link acts to synchronize neuronal subtype specification with neurogenesis.

Research paper thumbnail of A Postmitotic Role for Isl-Class LIM Homeodomain Proteins in the Assignment of Visceral Spinal Motor Neuron Identity

Research paper thumbnail of Active Suppression of Interneuron Programs within Developing Motor Neurons Revealed by Analysis of Homeodomain Factor HB9

Research paper thumbnail of The Ubiquitin Ligase Phr1 Regulates Axon Outgrowth through Modulation of Microtubule Dynamics

Research paper thumbnail of Notch and MAML Signaling Drives Scl-Dependent Interneuron Diversity in the Spinal Cord

Research paper thumbnail of Regulation of Motor Neuron Specification by Phosphorylation of Neurogenin 2

Research paper thumbnail of Identification of a cellular node for motor control pathways

Nature Neuroscience, 2014

The rich behavioral repertoire of animals is encoded in the CNS as a set of motorneuron activatio... more The rich behavioral repertoire of animals is encoded in the CNS as a set of motorneuron activation patterns, also called 'motor synergies'. However, the neurons that orchestrate these motor programs as well as their cellular properties and connectivity are poorly understood. Here we identify a population of molecularly defined motor synergy encoder (MSE) neurons in the mouse spinal cord that may represent a central node in neural pathways for voluntary and reflexive movement. This population receives direct inputs from the motor cortex and sensory pathways and, in turn, has monosynaptic outputs to spinal motorneurons. Optical stimulation of MSE neurons drove reliable patterns of activity in multiple motor groups, and we found that the evoked motor patterns varied on the basis of the rostrocaudal location of the stimulated MSE. We speculate that these neurons comprise a cellular network for encoding coordinated motor output programs.

Research paper thumbnail of Differential Expression of LIM Homeobox Genes among Motor Neuron Subpopulations in the Developing Chick Brain Stem

Molecular and Cellular Neuroscience, 1996

Research paper thumbnail of Axon fasciculation defects and retinal dysplasias in mice lacking the immunoglobulin superfamily adhesion molecule BEN/ALCAM/SC1

Molecular and Cellular Neuroscience, 2004

The immunoglobulin superfamily adhesion molecule BEN (other names include ALCAM, SC1, DM-GRASP, n... more The immunoglobulin superfamily adhesion molecule BEN (other names include ALCAM, SC1, DM-GRASP, neurolin, and CD166) has been implicated in the control of numerous developmental and pathological processes, including the guidance of retinal and motor axons to their targets. To test hypotheses about BEN function, we disrupted its gene via homologous recombination and analyzed the resulting mutant mice. Mice lacking BEN are viable and fertile, and display no external morphological defects. Despite grossly normal trajectories, both motor and retinal ganglion cell axons fasciculated poorly and were occasionally misdirected. In addition, BEN mutant retinae exhibited evaginated or invaginated regions with photoreceptor ectopias that resembled the "retinal folds" observed in some human retinopathies. Together, these results demonstrate that BEN promotes fasciculation of multiple axonal populations and uncover an unexpected function for BEN in retinal histogenesis.

Research paper thumbnail of Homeodomain transcription factors in the development of subsets of hindbrain reticulospinal neurons

Molecular and Cellular Neuroscience, 2005

Hindbrain reticulospinal neurons are involved in complex neural functions that are mediated by sp... more Hindbrain reticulospinal neurons are involved in complex neural functions that are mediated by spinal elements, including posture control and modulation of respiration and cardiovascular function. Recent descriptive studies with chick, mouse, and rat embryos have provided anatomical insight into the development of the different reticulospinal nuclei and the establishment of their axonal projection pathways into the spinal cord. In this study, we have addressed the molecular control of this process. Retrograde labeling of reticulospinal neurons in chick and mouse embryos combined with immunostaining for the homeodomain factors Lhx1/Lhx5, Lhx3/Lhx4, and Chx10 have defined transcriptional codes that label subsets of neurons with different axon projection patterns. Gain of function and loss of function experiments using in ovo electroporation implicate these transcription factors in the determination of reticulospinal neuron identity. Furthermore, our studies reveal novel gene interactions between the transcription factors analyzed that may determine the final patterns of reticulospinal axon projection.