Project description:Tissue and organ function has been conventionally understood in terms of the interactions among discrete and homogeneous cell types. This approach has proven difficult in neuroscience due to the marked diversity across different neuron classes, but may also be further hampered by prominent within-class variability. Here, we considered a well-defined, canonical neuronal population â hippocampal CA1 pyramidal cells â and systematically examined the extent and spatial rules of transcriptional heterogeneity. Using next-generation RNA sequencing, we identified striking variability in CA1 PCs, such that the differences along the dorsal-ventral axis rivaled differences across distinct pyramidal neuron classes. This variability emerged from a spectrum of continuous expression gradients, producing a profile consistent with a multifarious continuum of cells. This work reveals an unexpected amount of variability within a canonical and narrowly defined neuronal population and suggests that continuous, within-class heterogeneity may be an important feature of neural circuits. Hippocampal RNA profiles were generated by deep sequencing on Illumina HiSeq 2500, with three biological replicates per population
Project description:Tissue and organ function has been conventionally understood in terms of the interactions among discrete and homogeneous cell types. This approach has proven difficult in neuroscience due to the marked diversity across different neuron classes, but may also be further hampered by prominent within-class variability. Here, we considered a well-defined, canonical neuronal population – hippocampal CA1 pyramidal cells – and systematically examined the extent and spatial rules of transcriptional heterogeneity. Using next-generation RNA sequencing, we identified striking variability in CA1 PCs, such that the differences along the dorsal-ventral axis rivaled differences across distinct pyramidal neuron classes. This variability emerged from a spectrum of continuous expression gradients, producing a profile consistent with a multifarious continuum of cells. This work reveals an unexpected amount of variability within a canonical and narrowly defined neuronal population and suggests that continuous, within-class heterogeneity may be an important feature of neural circuits.
Project description:The transcriptional repressor Zbtb20 is essential for specification of hippocampal CA1 pyramidal neurons. Moreover, ectopic expression of Zbtb20 is sufficient to transform subicular and retrosplenial areas of D6/Zbtb20S mice to CA1. We used microarrays to identify genes that are repressed by Zbtb20 in developing CA1 pyramidal neurons in the CA1-transformed cortex of D6/Zbtb20S mice.
Project description:The transcriptional repressor Zbtb20 is essential for specification of hippocampal CA1 pyramidal neurons. Moreover, ectopic expression of Zbtb20 is sufficient to transform subicular and retrosplenial areas of D6/Zbtb20S mice to CA1. We used microarrays to identify genes that are repressed by Zbtb20 in developing CA1 pyramidal neurons in the CA1-transformed cortex of D6/Zbtb20S mice. For RNA extraction and hybridization on Affymetrix microarrays, we isolated the CA1-transformed subiculum and retrosplenial cortex from postnatal day 1 D6/Zbtb20S mice, as well as corresponding areas from their wildtype littermates. Total RNA was extracted using the RNeasy Lipid Tissue Mini Kit (Qiagen). Each RNA sample represents a pool of RNA obtained from dissected tissues of seven animals.
Project description:Behavioral experiences activate the Fos transcription factor (TF) in sparse populations of neurons that are critical for encoding and recalling specific events. However, there is limited understanding of the mechanisms by which experience drives circuit reorganization to establish a network of Fos-activated cells. Additionally, it is unknown if Fos is required in this process beyond serving as a marker of recent neural activity and, if so, which of its many gene targets underlie circuit reorganization. Here we demonstrate that when mice engage in spatial exploration of novel environments, perisomatic inhibition of Fos-expressing hippocampal CA1 pyramidal neurons by parvalbumin (PV)-interneurons (INs) is enhanced, while perisomatic inhibition by cholecystokinin (CCK)-INs is weakened. This bidirectional modulation of inhibition is specific to Fos-expressing neurons and is abolished when the function of the Fos TF complex is disrupted. Single-cell RNA-sequencing, ribosome-associated mRNA profiling, and chromatin analyses, combined with electrophysiology reveal that Fos activates the transcription of Scg2 (secretogranin II), a gene that encodes multiple distinct neuropeptides, to coordinate these changes in inhibition. As PV- and CCK-INs mediate distinct features of pyramidal cell activity, the Scg2-dependent reorganization of inhibitory synaptic input might be predicted to affect network function in vivo. Consistent with this prediction, hippocampal gamma rhythms and pyramidal cell coupling to CA1 theta are significantly altered with loss of Scg2. Together these findings reveal an instructive role for Fos and Scg2 in establishing a network of Fos-activated neurons via the rewiring of local inhibition from an initially broad to a selectively modulated state. The opposing plasticity mechanisms on distinct inhibitory pathways may support the consolidation of memories over time.
Project description:Behavioral experiences activate the Fos transcription factor (TF) in sparse populations of neurons that are critical for encoding and recalling specific events. However, there is limited understanding of the mechanisms by which experience drives circuit reorganization to establish a network of Fos-activated cells. Additionally, it is unknown if Fos is required in this process beyond serving as a marker of recent neural activity and, if so, which of its many gene targets underlie circuit reorganization. Here we demonstrate that when mice engage in spatial exploration of novel environments, perisomatic inhibition of Fos-expressing hippocampal CA1 pyramidal neurons by parvalbumin (PV)-interneurons (INs) is enhanced, while perisomatic inhibition by cholecystokinin (CCK)-INs is weakened. This bidirectional modulation of inhibition is specific to Fos-expressing neurons and is abolished when the function of the Fos TF complex is disrupted. Single-cell RNA-sequencing, ribosome-associated mRNA profiling, and chromatin analyses, combined with electrophysiology reveal that Fos activates the transcription of Scg2 (secretogranin II), a gene that encodes multiple distinct neuropeptides, to coordinate these changes in inhibition. As PV- and CCK-INs mediate distinct features of pyramidal cell activity, the Scg2-dependent reorganization of inhibitory synaptic input might be predicted to affect network function in vivo. Consistent with this prediction, hippocampal gamma rhythms and pyramidal cell coupling to CA1 theta are significantly altered with loss of Scg2. Together these findings reveal an instructive role for Fos and Scg2 in establishing a network of Fos-activated neurons via the rewiring of local inhibition from an initially broad to a selectively modulated state. The opposing plasticity mechanisms on distinct inhibitory pathways may support the consolidation of memories over time.
Project description:Behavioral experiences activate the Fos transcription factor (TF) in sparse populations of neurons that are critical for encoding and recalling specific events. However, there is limited understanding of the mechanisms by which experience drives circuit reorganization to establish a network of Fos-activated cells. Additionally, it is unknown if Fos is required in this process beyond serving as a marker of recent neural activity and, if so, which of its many gene targets underlie circuit reorganization. Here we demonstrate that when mice engage in spatial exploration of novel environments, perisomatic inhibition of Fos-expressing hippocampal CA1 pyramidal neurons by parvalbumin (PV)-interneurons (INs) is enhanced, while perisomatic inhibition by cholecystokinin (CCK)-INs is weakened. This bidirectional modulation of inhibition is specific to Fos-expressing neurons and is abolished when the function of the Fos TF complex is disrupted. Single-cell RNA-sequencing, ribosome-associated mRNA profiling, and chromatin analyses, combined with electrophysiology reveal that Fos activates the transcription of Scg2 (secretogranin II), a gene that encodes multiple distinct neuropeptides, to coordinate these changes in inhibition. As PV- and CCK-INs mediate distinct features of pyramidal cell activity, the Scg2-dependent reorganization of inhibitory synaptic input might be predicted to affect network function in vivo. Consistent with this prediction, hippocampal gamma rhythms and pyramidal cell coupling to CA1 theta are significantly altered with loss of Scg2. Together these findings reveal an instructive role for Fos and Scg2 in establishing a network of Fos-activated neurons via the rewiring of local inhibition from an initially broad to a selectively modulated state. The opposing plasticity mechanisms on distinct inhibitory pathways may support the consolidation of memories over time.