Developmental cell death of cortical projection neurons is controlled by a Bcl11a/Bcl6-dependent pathway I
Ontology highlight
ABSTRACT: Developmental neuron death plays a pivotal role in refining organization and wiring during neocortex formation. Aberrant regulation of this process results in neurodevelopmental disorders including impaired learning and memory. Underlying molecular pathways are incompletely determined. Loss of Bcl11a in cortical projection neurons induces pronounced cell death in upper-layer cortical projection neurons during postnatal corticogenesis. We used this genetic model to explore genetic mechanisms by which developmental neuron death is controlled. Unexpectedly, we found Bcl6, previously shown to be involved in transition of cortical neurons from progenitor to postmitotic differentiation state to provide a major check point regulating neuron survival during late cortical development. We show that Bcl11a is a direct transcriptional regulator of Bcl6. Deletion of Bcl6 exerts death of cortical projection neurons. In turn, reintroduction of Bcl6 into Bcl11a mutants prevents induction of cell death in these neurons. Together, our data identify a novel Bcl11a/Bcl6-dependent molecular pathway in regulation of developmental cell death during corticogenesis.
Project description:Developmental neuron death plays a pivotal role in refining organization and wiring during neocortex formation. Aberrant regulation of this process results in neurodevelopmental disorders including impaired learning and memory. Underlying molecular pathways are incompletely determined. Loss of Bcl11a in cortical projection neurons induces pronounced cell death in upper-layer cortical projection neurons during postnatal corticogenesis. We used this genetic model to explore genetic mechanisms by which developmental neuron death is controlled. Unexpectedly, we found Bcl6, previously shown to be involved in transition of cortical neurons from progenitor to postmitotic differentiation state to provide a major check point regulating neuron survival during late cortical development. We show that Bcl11a is a direct transcriptional regulator of Bcl6. Deletion of Bcl6 exerts death of cortical projection neurons. In turn, reintroduction of Bcl6 into Bcl11a mutants prevents induction of cell death in these neurons. Together, our data identify a novel Bcl11a/Bcl6-dependent molecular pathway in regulation of developmental cell death during corticogenesis.
Project description:During development of the human cerebral cortex, multipotent neural progenitors generate excitatory neurons and glial cells. Investigations of the transcriptome and epigenome have revealed important gene regulatory networks underlying this crucial developmental event. However, the post-transcriptional control of gene expression and protein abundance during human corticogenesis remains poorly understood. We addressed this issue by using a dual reporter cell line to isolate neural progenitors and neurons from the telencephalic brain organoid tissue and performed cell type and developmental stage-specific transcriptome and proteome analysis. Integrating the two datasets revealed temporal modules of gene expression during human corticogenesis, both at RNA and protein level. Our multiomics approach reveals novel posttranscriptional regulatory mechanisms crucial for fidelity of cortical development.
Project description:The cerebral cortex contains layers of neurons sequentially generated by distinct lineage-related progenitors. At the onset of corticogenesis, the first-born progenitors are apical progenitors (APs) whose asymmetric division give birth directly to neurons. Later, they switch to indirect neurogenesis by generating intermediate progenitors (IPs), which give rise to projection neurons of all cortical layers. While a direct lineage relationship between APs and IPs has been established, the molecular mechanism that controls their transition remains elusive. Our data suggest that interfering with codon translation speed triggers endoplasmic reticulum stress and the unfolded protein response (UPR), further impairing the generation of IPs and leading to microcephaly. Moreover, we demonstrate that a progressive downregulation of UPR in cortical progenitors acts as physiological signal to amplify IPs and promotes indirect neurogenesis. Thus, our findings reveal a hitherto unrecognized contribution of UPR to cell fate acquisition during mammalian brain development. Ribosome profiling and RNA-Seq of forebrains from E14.5 mouse embryos from wild type animals and mutants carrying a conditional knockout of ELP3 in cortical progenitors
Project description:Cortical projection neurons comprise classes of neurons connecting the cerebral cortex to distant targets in the nervous system. Each projection neuron class acquires a distinct molecular identity and develops characteristic patterns of axonal projection and dendritic arborization that determine their inputs, outputs, and distinct functions. How different aspects of neuron identity, including axonal and dendritic morphology, are coordinated appropriately in each specific neuron type is not known. A network of transcription factors, including the selector gene Fezf2, is central to specifying cortical projection neuron fates. However, regulation down-stream of these fate-determinant transcription factors to control different aspects of neuron identity is not understood, particularly as it relates to the development of distinct dendritic arbors that determine the inputs to each projection neuron class. Here we show that the miR-193b~365 microRNA cluster downstream of Fezf2 cooperatively represses the signaling molecule Mapk8 to regulate dendritic development in a neuron subtype-specific manner.
Project description:Neuroserpin is a serine protease inhibitor that regulates the activity of tissue-type plasminogen activator (tPA) in the nervous system. Neuroserpin is strongly expressed during nervous system development as well as during adulthood, when it is predominantly found in regions eliciting synaptic plasticity. In the hippocampus, neuroserpin regulates developmental neurogenesis, synaptic maturation and in adult mice it modulates synaptic plasticity and controls cognitive and social behavior. High expression levels of neuroserpin in the cerebral cortex starting from prenatal stage and persisting during adulthood suggest an important role for the serpin in the formation of this brain region and in the maintenance of cortical functions. In order to uncover neuroserpin function in the cerebral cortex, in this work we performed a comprehensive investigation of its expression pattern during development and in the adulthood. Moreover, we assessed the role of neuroserpin in cortex formation by comparing cortical lamination and neuronal maturation between neuroserpin-deficient and control mice. Finally, we evaluated a possible regulatory role of neuroserpin at cortical synapses in neuroserpin-deficient mice. We observed that neuroserpin is expressed starting from the beginning of corticogenesis until adulthood throughout the cortex in both glutamatergic projection neurons and GABA-ergic interneurons. However, in the absence of neuroserpin we did not detect any alteration in cortical layer formation, in soma size, in dendritic length, and the ultrastructure. Furthermore no significant quantitative changes could be observed in the proteome of cortical synapses could be observed upon Neuroserpin deficiency. We conclude that, although strongly expressed in the cerebral cortex, absence of neuroserpin does not lead to developmental abnormalities, and does not perturb composition of the cortical synaptic proteome.
Project description:The mammalian neocortex is composed of diverse neuronal and glial cell classes that broadly arrange in six distinct laminae. Cortical layers emerge during development and defects in the developmental programs that orchestrate cortical lamination are associated with neurodevelopmental diseases. The developmental principle of cortical layer formation is based on concerted radial projection neuron migration, from their birthplace to their final target position. Radial migration occurs in defined sequential steps that are regulated by a large array of signaling pathways. However, based on genetic loss-offunction experiments, most studies have thus far focused on the role of cell-autonomous gene function. Yet, cortical neuron migration in situ is a complex process and migrating neurons traverse along diverse cellular compartments and environments. The role of tissue-wide properties and genetic state in radial neuron migration is however not well understood. Here, we utilized Mosaic Analysis with Double Markers (MADM) technology to either sparsely or globally delete gene function followed by quantitative single cell phenotyping. The MADM-based gene ablation paradigms in combination with computational modeling demonstrated that global tissue-wide effects predominates cell-autonomous gene function albeit in a gene-specific manner. Our results thus suggest that the genetic landscape in a tissue critically impacts the overall migration phenotype of individual cortical projection neurons. In a broader context our findings imply that global tissue-wide effects represent an essential component of the underlying etiology associated with focal malformations of cortical development (FMCD) in particular, and neurological diseases in general.
Project description:3 subtypes of cortical projection neurons were purified by fluorescence-activated cell sorting (FACS) at 4 different stages of development from mouse cortex. A detailed description of the data set is described in Arlotta, P et al (2005) and Molyneaux, BJ et al (2009). The hybridization cocktails used here were originally applied to the Affymetrix mouse 430A arrays and submitted as GEO accession number GSE2039. The same hybridization cocktails were then applied to the Affymetrix mouse 430 2.0 arrays, and those data are contained in this series. Experiment Overall Design: Three subtypes of cortical neurons were purified by FACS at multiple stages of mouse brain development. The neuron subtypes are: corticospinal motor neurons (CSMN), callosal projection neurons (CPN), and corticotectal projection neurons (CTPN). The stages of development included embryonic day 18 (E18), postnatal day 3 (P3), postnatal day 6 (P6), and postnatal day 14 (P14). CSMN and CPN were analyzed at all four stages, while CTPN were only analyzed at P14. The replicates included in the data set are all true biological replicates with independent sample collection for each.