Developmental cell death of cortical projection neurons is controlled by a Bcl11a/Bcl6-dependent pathway

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.

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Directional Asymmetry of Neurons in Cortical Areas MT and MST Projecting to the NOT-DTN in Macaques

Journal of Neurophysiology ◽

10.1152/jn.00488.2001 ◽

2002 ◽

Vol 87 (4) ◽

pp. 2113-2123 ◽

Cited By ~ 36

Author(s):

K.-P. Hoffmann ◽

F. Bremmer ◽

A. Thiele ◽

C. Distler

Keyword(s):

Cortical Neurons ◽

Optic Tract ◽

Directional Asymmetry ◽

Projection Neurons ◽

Cortical Projection ◽

Directional Bias ◽

Stimulus Movement ◽

Equal Distribution ◽

Temporal Area ◽

Optokinetic Reflex

The cortical projection to the subcortical pathway underlying the optokinetic reflex was studied using antidromic electrical stimulation in the midbrain structures nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system (NOT-DTN) while simultaneously recording from cortical neurons in the superior temporal sulcus (STS) of macaque monkeys. Projection neurons were found in all subregions of the middle temporal area (MT) as well as in the medial superior temporal area (MST). Antidromic latencies ranged from 0.9 to 6 ms with a median of 1.8 ms. There was a strong bias in the population of cortical neurons projecting to the NOT-DTN for ipsiversive stimulus movement (towards the recording side), whereas in the population of cortical neurons not projecting to the NOT-DTN a more or less equal distribution of stimulus directions was evident. Our data indicate that there is no special area in the posterior STS coding for ipsiversive horizontal stimulus movement. Instead, a specific selection of cortical neurons from areas MT and MST forms the projection to the NOT-DTN and as a subpopulation has the same directional bias as their subcortical target neurons. These findings are discussed in relation to the functional grouping of cortical output as an organizational principle for specific motor responses.

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MCF2 is linked to a complex perisylvian syndrome and affects cortical lamination

10.1101/733444 ◽

2019 ◽

Author(s):

Aude Molinard-Chenu ◽

Joël Fluss ◽

Sacha Laurent ◽

Michel Guipponi ◽

Alexandre G Dayer

Keyword(s):

Motor Neuron ◽

Missense Mutation ◽

Neuronal Migration ◽

Cortical Neurons ◽

In Utero ◽

Projection Neurons ◽

Cortical Projection ◽

Cortical Laminar ◽

Congenital Bilateral Perisylvian Syndrome ◽

Cortical Lamination

AbstractThe combination of congenital bilateral perisylvian syndrome (CBPS) with lower motor neuron dysfunction is unusual and suggests a potential common genetic insult affecting basic neurodevelopmental processes. Here we identify a putatively pathogenic missense mutation in the MCF2 gene in a boy with CBPS. Using in utero electroporation to genetically manipulate cortical neurons during corticogenesis, we demonstrate that the mouse Mcf2 gene controls the embryonic migration of cortical projection neurons. Strikingly, we find that the CBPS-associated MCF2 mutation impairs cortical laminar positioning, supporting the hypothesis that alterations in the process of embryonic neuronal migration can lead to rare cases of CBPS.

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Epigenomic diversity of cortical projection neurons in the mouse brain

Nature ◽

10.1038/s41586-021-03223-w ◽

2021 ◽

Vol 598 (7879) ◽

pp. 167-173 ◽

Cited By ~ 4

Author(s):

Zhuzhu Zhang ◽

Jingtian Zhou ◽

Pengcheng Tan ◽

Yan Pang ◽

Angeline C. Rivkin ◽

...

Keyword(s):

Single Cell ◽

Cortical Neurons ◽

Neuronal Cell ◽

Cell Types ◽

Molecular Properties ◽

Projection Neurons ◽

Long Distance ◽

Cortical Projection ◽

Retrograde Labelling ◽

Projection Properties

AbstractNeuronal cell types are classically defined by their molecular properties, anatomy and functions. Although recent advances in single-cell genomics have led to high-resolution molecular characterization of cell type diversity in the brain1, neuronal cell types are often studied out of the context of their anatomical properties. To improve our understanding of the relationship between molecular and anatomical features that define cortical neurons, here we combined retrograde labelling with single-nucleus DNA methylation sequencing to link neural epigenomic properties to projections. We examined 11,827 single neocortical neurons from 63 cortico-cortical and cortico-subcortical long-distance projections. Our results showed unique epigenetic signatures of projection neurons that correspond to their laminar and regional location and projection patterns. On the basis of their epigenomes, intra-telencephalic cells that project to different cortical targets could be further distinguished, and some layer 5 neurons that project to extra-telencephalic targets (L5 ET) formed separate clusters that aligned with their axonal projections. Such separation varied between cortical areas, which suggests that there are area-specific differences in L5 ET subtypes, which were further validated by anatomical studies. Notably, a population of cortico-cortical projection neurons clustered with L5 ET rather than intra-telencephalic neurons, which suggests that a population of L5 ET cortical neurons projects to both targets. We verified the existence of these neurons by dual retrograde labelling and anterograde tracing of cortico-cortical projection neurons, which revealed axon terminals in extra-telencephalic targets including the thalamus, superior colliculus and pons. These findings highlight the power of single-cell epigenomic approaches to connect the molecular properties of neurons with their anatomical and projection properties.

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Multi-hit autism genomic architecture evidenced from consanguineous families with involvement of FEZF2 and mutations in high-risk genes

10.1101/759480 ◽

2019 ◽

Author(s):

Mounia Bensaid ◽

Yann Loe-Mie ◽

Aude-Marie Lepagnol-Bestel ◽

Wenqi Han ◽

Gabriel Santpere ◽

...

Keyword(s):

High Risk ◽

Cortical Neurons ◽

De Novo ◽

Deep Layer ◽

Autism Spectrum ◽

Projection Neurons ◽

Cortical Projection ◽

Linkage Region ◽

Genomic Architecture ◽

A Genome

ABSTRACTAutism Spectrum Disorders (ASDs) are a heterogeneous collection of neurodevelopmental disorders with a strong genetic basis. Recent studies identified that a single hit of either a de novo or transmitted gene-disrupting, or likely gene-disrupting, mutation in a subset of 65 strongly associated genes can be sufficient to generate an ASD phenotype. We took advantage of consanguineous families with an ASD proband to evaluate this model. By a genome-wide homozygosity mapping of ten families with eleven children displaying ASD, we identified a linkage region of 133 kb in five families at the 3p14.2 locus that includes FEZF2 with a LOD score of 5.8 suggesting a founder effect. Sequencing FEZF2 revealed a common deletion of four codons. However, the damaging FEZF2 mutation did not appear to be sufficient to induce the disease as non-affected parents also carry the mutation and, similarly, Fezf2 knockout mouse embryos electroporated with the mutant human FEZF2 construct did not display any obvious defects in the corticospinal tract, a pathway whose development depends on FEZF2. We extended the genetic analysis of these five FEZF2-linked families versus five FEZF2 non-linked families by studying de novo and transmitted copy number variation (CNV) and performing Whole Exome Sequencing (WES). We identified damaging mutations in the subset of 65 genes strongly associated with ASD whose co-expression analysis suggests an impact on the prefrontal cortex during the mid-fetal periods. From these results, we propose that both FEZF2 deletion and multiple hits in the repertoire of these 65 genes are necessary to generate an ASD phenotype.Significance StatementThe human neocortex is a highly organized laminar structure with neuron positioning and identity of deep-layer cortical neurons that depend on key transcription factors, such as FEZF2, SATB2, TSHZ3 and TBR1. These genes have a specific spatio-temporal pattern of expression in human midfetal deep cortical projection neurons and display mutations in patients with Autism Spectrum Disorder (ASD). Here, we identified a linkage region involving FEZF2 gene in five consanguineous families with an ASD proband. For these FEZF2-allele linked probands, we identified a four-codon deletion in FEZF2 and damaging mutations in other high-risk ASD genes, that exhibit regional and cell type–specific convergence in neocortical deep-layer excitatory neurons, suggesting a multi-hit genomic architecture of ASD in these consanguineous families.

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Epigenomic Diversity of Cortical Projection Neurons in the Mouse Brain

10.1101/2020.04.01.019612 ◽

2020 ◽

Cited By ~ 3

Author(s):

Zhuzhu Zhang ◽

Jingtian Zhou ◽

Pengcheng Tan ◽

Yan Pang ◽

Angeline Rivkin ◽

...

Keyword(s):

Single Cell ◽

Cortical Neurons ◽

Neuronal Cell ◽

Cell Types ◽

Molecular Properties ◽

Projection Neurons ◽

Long Distance ◽

Cortical Projection ◽

Axon Terminals ◽

Projection Properties

SummaryNeuronal cell types are classically defined by their molecular properties, anatomy, and functions. While recent advances in single-cell genomics have led to high-resolution molecular characterization of cell type diversity in the brain, neuronal cell types are often studied out of the context of their anatomical properties. To better understand the relationship between molecular and anatomical features defining cortical neurons, we combined retrograde labeling with single-nucleus DNA methylation sequencing to link epigenomic properties of cell types to neuronal projections. We examined 11,827 single neocortical neurons from 63 cortico-cortical (CC) and cortico-subcortical long-distance projections. Our results revealed unique epigenetic signatures of projection neurons that correspond to their laminar and regional location and projection patterns. Based on their epigenomes, intra-telencephalic (IT) cells projecting to different cortical targets could be further distinguished, and some layer 5 neurons projecting to extra-telencephalic targets (L5-ET) formed separate subclusters that aligned with their axonal projections. Such separation varied between cortical areas, suggesting area-specific differences in L5-ET subtypes, which were further validated by anatomical studies. Interestingly, a population of CC projection neurons clustered with L5-ET rather than IT neurons, suggesting a population of L5-ET cortical neurons projecting to both targets (L5-ET+CC). We verified the existence of these neurons by labeling the axon terminals of CC projection neurons and observed clear labeling in ET targets including thalamus, superior colliculus, and pons. These findings highlight the power of single-cell epigenomic approaches to connect the molecular properties of neurons with their anatomical and projection properties.

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The +TIP Navigator-1 is an actin–microtubule crosslinker that regulates axonal growth cone motility

The Journal of Cell Biology ◽

10.1083/jcb.201905199 ◽

2020 ◽

Vol 219 (9) ◽

Cited By ~ 1

Author(s):

Carlos Sánchez-Huertas ◽

Marion Bonhomme ◽

Amandine Falco ◽

Christine Fagotto-Kaufmann ◽

Jeffrey van Haren ◽

...

Keyword(s):

Cortical Neurons ◽

Actin Filaments ◽

Projection Neurons ◽

Dependent Manner ◽

Cortical Projection ◽

Axonal Growth Cone ◽

Neuronal Functions ◽

Developing Nervous System

Microtubule (MT) plus-end tracking proteins (+TIPs) are central players in the coordination between the MT and actin cytoskeletons in growth cones (GCs) during axon guidance. The +TIP Navigator-1 (NAV1) is expressed in the developing nervous system, yet its neuronal functions remain poorly elucidated. Here, we report that NAV1 controls the dynamics and motility of the axonal GCs of cortical neurons in an EB1-dependent manner and is required for axon turning toward a gradient of netrin-1. NAV1 accumulates in F-actin–rich domains of GCs and binds actin filaments in vitro. NAV1 can also bind MTs independently of EB1 in vitro and crosslinks nonpolymerizing MT plus ends to actin filaments in axonal GCs, preventing MT depolymerization in F-actin–rich areas. Together, our findings pinpoint NAV1 as a key player in the actin–MT crosstalk that promotes MT persistence at the GC periphery and regulates GC steering. Additionally, we present data assigning to NAV1 an important role in the radial migration of cortical projection neurons in vivo.

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A microRNA cluster downstream of the selector gene Fezf2 coordinates fate specification with dendritic branching in cortical neurons

10.1101/2021.11.03.467176 ◽

2021 ◽

Author(s):

Asha Iyer ◽

Verl B Siththanandan ◽

Victoria Lu ◽

Ramesh V Nair ◽

Lee O Vaasjo ◽

...

Keyword(s):

Transcription Factors ◽

Cortical Neurons ◽

Projection Neuron ◽

Projection Neurons ◽

Cortical Projection ◽

Dendritic Branching ◽

Microrna Cluster ◽

The Central Nervous System ◽

Callosal Projection ◽

Cortical Projection Neuron

In the cerebral cortex, cortical projection neurons comprise classes of neurons project to distant regions of the central nervous system. These neurons develop from the same progenitor pool, but they acquire strikingly different inputs and outputs to underpin strikingly different functions. The question of how corticospinal projection neurons - involved in motor function and implicated in paralysis - and callosal projection neurons - involved in cognitive function and implicated in autism - develop represents a fundamental and clinically important question in neurodevelopment. A network of transcription factors, including the selector gene Fezf2, is central to specifying cortical projection neuron fates. Gene regulation up- and down-stream of these transcription factors, however, is not well understood, particularly as it relates to the development of the major inputs to cortical projection neurons. Here we show that the miR-193b~365 microRNA cluster downstream of Fezf2 cooperatively represses the signaling molecule Mapk8, and impacts dendritic branching of cortical projection neurons.

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Abstract WP114: Retrograde Labeling, FACS Isolation, and Transcriptional Profiling of Layer 5 Cortical Neurons After White Matter Stroke Reveals Unique Pathways of Degeneration and Regeneration

Stroke ◽

10.1161/str.47.suppl_1.wp114 ◽

2016 ◽

Vol 47 (suppl_1) ◽

Author(s):

Stefanie Nunez ◽

Mary Teena Joy ◽

Jason D Hinman

Keyword(s):

White Matter ◽

Motor Cortex ◽

Cortical Neurons ◽

Neuronal Loss ◽

Minor Stroke ◽

Projection Neurons ◽

Molecular Response ◽

Cortical Projection ◽

Neuronal Tracing ◽

Neuronal Marker

Introduction: Small vessel ischemic strokes account for 25% of strokes in the US. They often occur silently, increasing the prevalence 5-10 fold and are progressive with new strokes occurring adjacent to prior strokes. In this common form of stroke, there is a local injury damaging axons and white matter, and a distant injury damaging the neurons with axons affected by the stroke, leading to cortical thinning in the connected cortex. This selective neuronal loss contributes to minor stroke related cognitive dysfunction and disability yet the molecular response of neurons with stroke-injured axons remains challenging to study. Hypothesis: White matter stroke injures cortical projection neurons and triggers a unique molecular program that contributes to selective neuronal loss. Methods: To determine the neuronal effects of a white matter stroke, we produced a subcortical white matter stroke below the forelimb motor cortex in adult male C57/Bl6 mice resulting in a focal white matter lesion. Retrograde neuronal tracing identifies individual neurons damaged by the white matter stroke. Layer 5 cortical neurons were isolated by magnetic microbead separation of non-neuronal cells, followed by fluorescent-activated cell sorting (FACS) isolation of retrogradely-labeled cells. Results: Stereologic measurement of the neurons with stroke-injured axons co-labeled with the Layer 5 neuronal marker CTIP-2 reveals that focal white matter stroke selectively identifies between 15-25% of the Layer 5 cortical neurons in both sensory and motor cortex with spanning the cortical regions of interest, compared to only ∼3% in sham injured animals. Using FACS isolation, we compared the transcriptional profile of white matter stroke injured cortical projection neurons to uninjured Layer 5 neurons at one week after stroke. An average of 6,297 cells were collected per isolation, RNA isolated and analyzed by qPCR and RNA-seq. Conclusions: Bioinformatic analysis of differentially expressed genes indicates that white matter stroke activates both degenerative and regenerative pathways in stroke-induced axonally-injured neurons. These data can be harnessed to prevent selective neuronal loss after white matter stroke and induce neural repair after stroke.

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