FOXG1 drives transcriptomic networks to specify principal neuron subtypes during the development of the medial pallium
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ABSTRACT: The medial pallium (MP) is the major forebrain region underlying learning and memory, spatial navigation, and emotion; however, the mechanisms underlying the specification of its principal neuron subtypes remain largely unexplored. Here, by postmitotic deletion of FOXG1 (a transcription factor linked to autism and FOXG1 syndrome) and single-cell RNA sequencing, we found that FOXG1 controls the specification of upper-layer retrosplenial cortical pyramidal neurons (RSC-PyNs (UL)), subiculum PyNs (SubC-PyNs), CA1-PyNs, CA3-PyNs and dentate gyrus granule cells (DG-GCs) in the mouse MP. We uncovered subtype-specific and subtype-shared FOXG1-regulated transcriptomic networks orchestrating MP neuron specification.
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:We report that the two adult neurogenic niches of the mammalian brain – the dentate gyrus of the hippocampal formation and the subependymal zone of the lateral ventricles - displayed differential vulnerability to increased FoxG1 dosage: high FoxG1 levels severely compromised survival and glutamatergic dentate granule neuron fate acquisition in the hippocampal neurogenic niche, but left neurogenesis of GABAergic neurons in the subependymal zone / olfactory bulb system unaffected. Comparative transcriptomic analyses revealed a significantly higher expression of the apoptosis-linked nuclear receptor Nr4a1 in FoxG1-overexpressing hippocampal neural precursors. Our results reveal differential vulnerability of neuronal subtypes to increased FoxG1 dosage and suggest that activity of a FoxG1/Nr4a1 axis contributes to such subtype-specific response.
Project description:Subiculum pyramidal cells constitute a prominent output neuron class of the hippocampus. Here, we examined diversity in this cell type using single-cell RNA-seq.
Project description:Current comprehension of micropapillary (MP)-subtype lung adenocarcinoma (LUAD) remains circumscribed to biological behaviors and genomic landscapes. Unraveling the core regulatory programs underlying MP-pattern malignancy offers opportunities to identify more feasible therapeutic targets for patients with MP-LUAD. We show aberrant activation of the MYC pathway in MP-subtype LUAD compared with other subtypes. MP-pattern malignancy cannot be solely induced by aberrant MYC expression in vitro or xenograft mouse models but requires the assistance of M2-like macrophages to accomplish. Redundantly expressed MYC aggregates M2-like macrophages derived from the bone marrow to secrete TGFβ, inducing the expression of FOSL2 in tumor cells, thereby remodeling chromatin accessibility in MP-pattern gene promoters to assist MYC in occupying de novo transcriptional regulation. Moreover, effective alleviation of MP-pattern malignancy can be achieved by disrupting the TGFβ-FOSL2 axis. These findings elucidate functions of M2-like macrophage-TGFβ-FOSL2 axis in MYC-redundant MP-subtype LUAD, defining targetable vulnerabilities.
Project description:Neurons in posterior parietal cortex contribute to the execution of goal-directed navigation and other decision-making tasks. Although molecular studies have catalogued over fifty cortical cell types, it remains unknown what distinct functions they serve during goal-directed navigation. Here, we identified a molecularly defined subset of somatostatin (Sst) inhibitory neurons that, in mouse posterior parietal cortex, carry a novel cell type-specific error correction signal for navigation. We obtained repeatable experimental access to these cells using an adeno-associated virus (AAV) in which gene expression is driven by an enhancer that functions specifically in a subset of Sst cells. We found that during goal-directed navigation in a virtual environment, this subset of Sst neurons activates in a synchronous pattern that is distinct from the activity of surrounding neurons, including other Sst neurons. Using in vivo two-photon photostimulation and ex vivo paired patch clamp recordings, we show that nearby cells of this Sst subtype excite each other through gap junctions, revealing a self-excitation circuit motif that contributes to the synchronous activity of this cell type. Remarkably, these cells selectively activate as mice execute course corrections for deviations in their virtual heading during navigation toward a reward location, both for self- and experimentally-induced deviations. We propose that this subtype of Sst neurons provides a self-reinforcing and cell type-specific error-correction signal in posterior parietal cortex that may aid the execution and learning of accurate goal-directed navigation trajectories.
Project description:The medial pallium (MP) is the major forebrain region underlying learning and memory, spatial navigation, and emotion; however, the mechanisms underlying the specification of its principal neuron subtypes remain largely unexplored. Here, by postmitotic deletion of FOXG1 (a transcription factor linked to autism spectrum disorders and FOXG1 syndrome) and single-cell RNA sequencing of E17.5 MP in mice, we found that FOXG1 controls the specification of upper-layer retrosplenial cortical pyramidal neurons [RSC-PyNs (UL)], subiculum PyNs (SubC-PyNs), CA1-PyNs, CA3-PyNs, and dentate gyrus granule cells (DG-GCs) in the MP. We uncovered subtype-specific and subtype-shared FOXG1-regulated transcriptomic networks orchestrating MP neuron specification. We further demonstrated that FOXG1 transcriptionally represses Zbtb20, Prox1, and Epha4 to prevent CA3-PyN and DG-GC identities during the specification of RSC-PyNs (UL) and SubC-PyNs; FOXG1 directly activates Nr4a2 to promote SubC-PyN identity. We showed that TBR1, controlled by FOXG1 during CA1-PyN specification, was down-regulated. Thus, our study illuminates MP principal neuron subtype specification and related neuropathogenesis.
Project description:The forkhead box transcription factor FoxG1 is known to influence forebrain development by determining regional brain specification as well as by regulating expansion of neuronal progenitors and timing of their differentiation. In the adult brain, FoxG1 is expressed in cortex and hippocampus. In the latter it is involved in postnatal neurogenesis in the dentate gyrus by influencing maintenance of the progenitor pool as well as survival and maturation of postmitotic neurons. In humans, haploinsufficiency of FoxG1 causes the congenital version of the Rett syndrome, a progressive neurologic developmental disorder. We use FoxG1 mutant mice to screen for global changes in mRNA expression after partial loss of FoxG1 protein in hippocampi of six week-old mice. Data analysis points to a specific function for FoxG1 in adult hippocampus besides its known involvement in dentate gyrus neurogenesis. We analyse transcriptional changes in the different CA-fields and show that especially the CA-1 field is influenced by lack of FOXG1 protein. Furthermore, data analysis shows altered expression of genes that have also been implicated in the classical form of the Rett syndrome and other autism spectrum disorders.
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:[original Title] Rapid and synchronous clearance of PcG histone modifications from Hox genes anticipates motor neuron differentiation. Hox genes are expressed in patterns that are spatially and temporally collinear with their chromosomal organization. This feature is an evolutionarily conserved hallmark of embryonic development, and in vertebrates it is critical, among others, for the specification of motor neuron subtypes and the wiring of sensory-motor circuits. We show here that the differentiation of motor neurons from stem cells is accompanied by a synchronous, domain-wide clearance of M-bM-^@M-^\repressiveM-bM-^@M-^] Polycomb (PcG)-dependent histone methylation from Hox gene chromatin domains. These findings argue against the idea, advanced recently, that the collinear dynamics of Hox gene expression invariably reflects the progressive clearance of repressive chromatin modifications. The rapid establishment of stable chromatin domains in response to a transient patterning signal likely serves as a molecular correlate of enduring rostro-caudal neural identity, which underlies the specification of postmitotic motor neuron subtype diversity and neuronal circuit assembly. The differentiation of ventral motor neurons is induced by treating embryonic stem cell cultures with retinoic acid and hedgehog agonist. Here, ChIP-chip using a custom Agilent array is used to profile the occupancy of H3K27me3, H3K4me3, and H3K79me2 at various defined stages during the differentiation process.