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: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:People with Down syndrome (DS) have intellectual disability (ID) and develop hallmark Alzheimer’s disease (AD) pathology during midlife. There are several circuits underlying memory and executive function in the DS and AD brain that are particularly vulnerable and degenerate early in disease, most notably the septohippocampal circuit and the trisynaptic loop in the hippocampus. A fundamental lack of knowledge exists as to the etiology and mechanisms of disease progression within these critical circuits vulnerable to degeneration in DS, AD, and relevant models. This is compounded by new evidence that suggests spatial localization of neurons has profound effects on activity and innervation within the hippocampal CA1 region. We postulated gene expression changes in a DS mouse model, at a time that these circuits of input to the CA1 are degraded, would have a significant effect on gene expression in CA1 pyramidal neurons. Further, this dysfunction may be specific to spatial localization and innervation. Laser capture microscopy on pyramidal neurons from CA1 was performed, isolating the entire CA1 pyramidal neuron layer, which was compared to select populations of deep and superficial pyramidal neurons from CA1a (distal CA1, adjacent to the subiculum). RNA-seq and bioinformatic analysis was performed where profound differences in dysregulation in the DS mouse model based on their spatial location and postulated circuitry were examined.
Project description:TRAP (translating ribosome affinity purification) from CA1 pyramidal neurons and cerebellar granule cells in wildtype and Fmr1 KO littermate pairs. These data show a global downregulation of FMRP targets in Fmr1 KO mice in these cell types.
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:Loss of the neuronal RNA binding protein FMRP causes Fragile X Syndrome (FXS), the most common cause of inherited intellectual disability, yet it is unknown which brain regions and cell types within them contribute to disease pathophysiology. We used conditional tagging of FMRP and CLIP (cTag FMRP CLIP) to examine FMRP targets specifically in CA1 hippocampal neurons, a critical cell type for learning and memory known to have altered synaptic function in FXS. Integrating this data with analysis of ribosome-bound transcripts from the same neuronal population revealed CA1-enriched binding of autism-relevant mRNAs, and unexpected CA1-specific regulation of transcripts encoding circadian proteins.
Project description:Structural, functional, and molecular reorganization of denervated neural networks is often observed in neurological conditions. The loss of input is accompanied by homeostatic synaptic adaptations, which can affect the reorganization of denervated networks. However, a major challenge of denervation-induced homeostatic plasticity operating in complex neural networks is the specialization of neuronal inputs. Therefore, it remains unclear whether neurons respond similarly to the loss of distinct inputs. Here, we used in vitro entorhinal cortex lesion (ECL) and Schaffer collateral lesion (SCL) in mouse organotypic entorhino-hippocampal tissue cultures of either sex, and studied denervation-induced plasticity of CA1 pyramidal neurons. We observed accumulation of microglia, degeneration of presynaptic buttons and a reduction in dendritic spine numbers in the denervated layers three days after SCL and ECL, respectively. Transcriptome analysis of the CA1 region showed complex changes in differential gene expression following SCL and ECL compared to non-lesioned controls. An enrichment of differentially expressed synapse-related genes was observed specifically after ECL. Consistent with this finding, denervation-induced homeostatic plasticity of excitatory synapses was observed three days after ECL but not after SCL. Chemogenetic silencing of the EC but not CA3 confirmed the pathway-specific induction of homeostatic synaptic plasticity in CA1. Moreover, increased RNA oxidation was observed after SCL and ECL. These results reveal important commonalities and differences of distinct pathway lesions, and demonstrate a pathway-specific induction of denervation-induced homeostatic synaptic plasticity.