scholarly journals miR-409-3p represses Cited2 at the evolutionary emergence of the callosal and corticospinal projections

2021 ◽  
Author(s):  
Nikolaus R Wagner ◽  
Ashis Sinha ◽  
Verl B Siththanandan ◽  
Angelica N Kowalchuk ◽  
Jessica MacDonald ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Cognitive Abilities ◽  
Molecular Mechanisms ◽  
Deep Layer ◽  
Projection Neuron ◽  
Superficial Layer ◽  
Projection Neurons ◽  
Loss Of Function ◽  
Full Extension ◽  
Callosal Projection

Callosal projection neurons are a broad population of interhemispheric projection neurons that extend an axon across the corpus callosum to connect the two cerebral hemispheres. The corticospinal tract, comprised of the axons of corticospinal projection neurons, is unique to mammals, and its full extension to the lumbar segments that control walking is, like the corpus callosum, unique to placental mammals. The emergence of these two distinct axonal tracts is thought to underpin the evolutionary expansion of complex motor and cognitive abilities. The molecular mechanisms regulating the divergence of corticospinal and callosal projection neurons are incompletely understood. Our recent work identifies a genomic cluster of microRNAs (12qF1/Mirg) unique to placental mammals. These clustered miRNAs are specifically expressed by corticospinal vs. callosal projection neurons during the molecular refinement of corticospinal vs. callosal projection neuron fate (1). One of these, miR-409-3p, can convert layer V callosal into corticospinal projection neurons, acting in part through repression of the callosal-expressed transcriptional regulator Lmo4. This conversion is partial, however, suggesting that miR-409-3p represses multiple callosal projection neuron control genes in order to specify corticospinal projection neurons. One potential additional target of miR-409-3p repression is the callosal-expressed transcriptional co-activator Cited2. Cited2 interacts genetically with Lmo4, and Lmo4 can partially functionally compensate for Cited2 in thymus development(2). Further, Cited2 and Lmo4 function as opposing molecular controls over specific areal identity within superficial layer callosal projection neurons of the somatosensory and motor cortices, respectively (3). Cited2 is highly expressed by callosal, relative to corticospinal, projection neurons from the earliest stages of neurogenesis. Cited2 is necessary for the expansion of intermediate progenitor cells (IPCs) in the subventricular zone (SVZ), and the resulting generation of superficial layer callosal projection neurons. Here we show that miR-409-3p and Cited2 interact in IPCs and in corticospinal vs. deep layer callosal projection neuron development. miR-409-3p represses the Cited2 3UTR in luciferase assays. Mirg, which encodes miR-409-3p, and Cited2, are reciprocally expressed in IPCs at e15.5 by qPCR. Furthermore, miR-409-3p gain-of-function results in a phenocopy of established Cited2 loss-of-function in IPCs. Later on, miR-409-3p and Cited2 exert opposing effects on the adoption of corticospinal vs. callosal projection neuron subtype identity. Taken together, our work suggests that miR-409-3p, and possibly other 12qF1 miRNAs, represses Cited2 in IPCs to limit their proliferation, and in developing corticospinal and deep layer callosal projection neurons to favor corticospinal fate.

scholarly journals An evolutionarily acquired microRNA shapes development of mammalian cortical projections

2020 ◽  
Author(s):  
Jessica L Diaz ◽  
Verl B Siththanandan ◽  
Victoria Lu ◽  
Nicole Gonzalez-Nava ◽  
Lincoln Pasquina ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Cognitive Skills ◽  
Corticospinal Tract ◽  
Projection Neuron ◽  
Projection Neurons ◽  
Cortical Projection ◽  
Complex Motor ◽  
Callosal Projection ◽  
Cortical Projection Neuron

AbstractThe corticospinal tract is unique to mammals and the corpus callosum is unique to placental mammals (eutherians). The emergence of these structures is thought to underpin the evolutionary acquisition of complex motor and cognitive skills. Corticospinal motor neurons (CSMN) and callosal projection neurons (CPN) are the archetypal projection neurons of the corticospinal tract and corpus callosum, respectively. Although a number of conserved transcriptional regulators of CSMN and CPN development have been identified in vertebrates, none are unique to mammals and most are co-expressed across multiple projection neuron subtypes. Here, we discover seventeen CSMN-enriched microRNAs (miRNAs), fifteen of which map to a single genomic cluster that is exclusive to eutherians. One of these, miR-409-3p, promotes CSMN subtype identity in part via repression of LMO4, a key transcriptional regulator of CPN development. In vivo, miR-409-3p is sufficient to convert deep-layer CPN into CSMN. This is the first demonstration of an evolutionarily acquired miRNA in eutherians that refines cortical projection neuron subtype development. Our findings implicate miRNAs in the eutherians’ increase in neuronal subtype and projection diversity, the anatomic underpinnings of their complex behavior.Significance StatementThe mammalian central nervous system contains unique projections from the cerebral cortex thought to underpin complex motor and cognitive skills, including the corticospinal tract and corpus callosum. The neurons giving rise to these projections - corticospinal and callosal projection neurons - develop from the same progenitors, but acquire strikingly different fates. The broad evolutionary conservation of known genes controlling cortical projection neuron fates raises the question of how the more narrowly conserved corticospinal and callosal projections evolved. We identify a microRNA cluster selectively expressed by corticospinal projection neurons and exclusive to placental mammals. One of these microRNAs promotes corticospinal fate via regulation of the callosal gene LMO4, suggesting a mechanism whereby microRNA regulation during development promotes evolution of neuronal diversity.

scholarly journals Area-specific development of distinct projection neuron subclasses is regulated by postnatal epigenetic modifications

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Kawssar Harb ◽  
Elia Magrinelli ◽  
Céline S Nicolas ◽  
Nikita Lukianets ◽  
Laura Frangeul ◽  
...  
Keyword(s):  
Somatosensory Cortex ◽  
Projection Neuron ◽  
Projection Neurons ◽  
Epigenetic Mechanisms ◽  
Loss Of Function ◽  
Long Distance ◽  
Molecular Determinants ◽  
Specific Manner ◽  
Contralateral Cortex ◽  
Callosal Projection

During cortical development, the identity of major classes of long-distance projection neurons is established by the expression of molecular determinants, which become gradually restricted and mutually exclusive. However, the mechanisms by which projection neurons acquire their final properties during postnatal stages are still poorly understood. In this study, we show that the number of neurons co-expressing Ctip2 and Satb2, respectively involved in the early specification of subcerebral and callosal projection neurons, progressively increases after birth in the somatosensory cortex. Ctip2/Satb2 postnatal co-localization defines two distinct neuronal subclasses projecting either to the contralateral cortex or to the brainstem suggesting that Ctip2/Satb2 co-expression may refine their properties rather than determine their identity. Gain- and loss-of-function approaches reveal that the transcriptional adaptor Lmo4 drives this maturation program through modulation of epigenetic mechanisms in a time- and area-specific manner, thereby indicating that a previously unknown genetic program postnatally promotes the acquisition of final subtype-specific features.

scholarly journals St18 specifies globus pallidus projection neuron identity in MGE lineage

2021 ◽  
Author(s):  
Luke Nunnelly ◽  
Melissa Campbell ◽  
Dylan Lee ◽  
Guoqiang Gu ◽  
Vilas Menon ◽  
...  
Keyword(s):  
Globus Pallidus ◽  
Long Range ◽  
Projection Neuron ◽  
Migratory Behavior ◽  
Projection Neurons ◽  
Loss Of Function ◽  
Downstream Target ◽  
Neuronal Populations ◽  
Downstream Effector ◽  
Large Expansion

The medial ganglionic eminence (MGE) is a progenitor domain in the subpallium that produces both locally-projecting interneurons which undergo tangential migration in structures such as the cortex as well as long-range projection neurons that occupy subcortical nuclei. Very little is known about the transcriptional mechanisms specifying the migratory behavior and axonal projection patterns of these two broad classes of MGE-derived neurons. In this study, we identify St18 as a novel transcriptional determinant specifying projection neuron fate in the MGE lineage. St18 is transiently expressed in the MGE subventricular zone (SVZ) and mantle, and we assessed its function using an ES cell-based model of MGE development. Induction of St18 is sufficient to direct ES-derived MGE neurons to adopt a projection neuron-like identity as defined by migration and morphology. Using genetic loss-of-function in mice, we find that St18 is required for the production of globus pallidus pars externa (GPe) prototypic projection neurons. Single cell RNA sequencing revealed that St18 regulates MGE output of specific neuronal populations: in the absence of St18, we observe a large expansion of cortical interneurons at the expense of putative GPe neurons. Through gene expression analysis we identified a downstream effector of St18, Cbx7, which is a component of Polycomb repressor complex 1. We find that Cbx7 is essential for projection neuron-like migration and is not involved in St18-mediated projection neuron-like morphology. Our results characterize a novel transcriptional determinant that directs GPe prototypic projection neuron identity. Further, we identified a downstream target of St18, Cbx7, which regulates only the migratory behavior of long-range projection neurons, suggesting that specific features of MGE projection neuron identity may be governed in a compartmentalized fashion by distinct transcriptional modules downstream of St18.

scholarly journals Human-specific enrichment of schizophrenia risk-genes in callosal neurons of the developing neocortex

2021 ◽  
Author(s):  
Emanuela Zuccaro ◽  
Vanessa Murek ◽  
Kwanho Kim ◽  
Hsu-Hsin Chen ◽  
Sara Mancinelli ◽  
...  
Keyword(s):  
Disease Risk ◽  
Cell Types ◽  
Projection Neuron ◽  
Inhibitory Interneuron ◽  
Projection Neurons ◽  
Risk Genes ◽  
Neuropsychiatric Diseases ◽  
Excitatory Projection ◽  
Callosal Projection ◽  
Human Specific

SummaryHuman genetic studies have provided a wealth of information on genetic risk factors associated with neuropsychiatric diseases. However, whether different brain cell types are differentially affected in disease states and when in their development and maturation alterations occur is still poorly understood. Here we generated a longitudinal transcriptional map of excitatory projection neuron (PN) and inhibitory interneuron (IN) subtypes of the cerebral cortex, across a timeline of mouse embryonic and postnatal development, as well as fetal human cortex and human cortical organoids. We found that three types of gene signatures uniquely defined each cortical neuronal subtype: dynamic (developmental), adult (terminal), and constitutive (stable), with individual neuronal subtypes varying in the degree of similarity of their signatures between species. In particular, human callosal projection neurons (CPN) displayed the greatest species divergence, with molecular signatures highly enriched for non-coding, human-specific RNAs. Evaluating the association of neuronal class-specific signatures with neuropsychiatric disease risk genes using linkage disequilibrium score regression showed that schizophrenia risk genes were enriched in CPN identity signatures from human but not mouse cortex. Human cortical organoids confirmed the association with excitatory projection neurons. The data indicate that risk gene enrichment is both species- and cell type-specific. Our study reveals molecular determinants of cortical neuron diversification and identifies human callosal projection neurons as the most species-divergent population and a potentially vulnerable neuronal class in schizophrenia.

scholarly journals New Molecular Players in the Development of Callosal Projections

Cells ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 29
Author(s):  
Ray Ku ◽  
Masaaki Torii
Keyword(s):  
Corpus Callosum ◽  
Recent Progress ◽  
Neural Circuitry ◽  
Projection Neurons ◽  
The Novel ◽  
Cellular Processes ◽  
Axonal Projections ◽  
Main Component ◽  
Callosal Projection ◽  
The Brain

Cortical development in humans is a long and ongoing process that continuously modifies the neural circuitry into adolescence. This is well represented by the dynamic maturation of the corpus callosum, the largest white matter tract in the brain. Callosal projection neurons whose long-range axons form the main component of the corpus callosum are evolved relatively recently with a substantial, disproportionate increase in numbers in humans. Though the anatomy of the corpus callosum and cellular processes in its development have been intensively studied by experts in a variety of fields over several decades, the whole picture of its development, in particular, the molecular controls over the development of callosal projections, still has many missing pieces. This review highlights the most recent progress on the understanding of corpus callosum formation with a special emphasis on the novel molecular players in the development of axonal projections in the corpus callosum.

scholarly journals Endocannabinoid signalling in stem cells and cerebral organoids drives differentiation to deep layer projection neurons via CB1 receptors

Development ◽  
2020 ◽  
Vol 147 (24) ◽  
pp. dev192161
Author(s):  
Juan Paraíso-Luna ◽  
José Aguareles ◽  
Ricardo Martín ◽  
Ane C. Ayo-Martín ◽  
Samuel Simón-Sánchez ◽  
...  
Keyword(s):  
Neuronal Differentiation ◽  
Deep Layer ◽  
Embryonic Stem ◽  
Projection Neuron ◽  
Projection Neurons ◽  
Neuron Development ◽  
Receptor Agonists ◽  
Pluripotent Embryonic Stem Cell

ABSTRACTThe endocannabinoid (eCB) system, via the cannabinoid CB1 receptor, regulates neurodevelopment by controlling neural progenitor proliferation and neurogenesis. CB1 receptor signalling in vivo drives corticofugal deep layer projection neuron development through the regulation of BCL11B and SATB2 transcription factors. Here, we investigated the role of eCB signalling in mouse pluripotent embryonic stem cell-derived neuronal differentiation. Characterization of the eCB system revealed increased expression of eCB-metabolizing enzymes, eCB ligands and CB1 receptors during neuronal differentiation. CB1 receptor knockdown inhibited neuronal differentiation of deep layer neurons and increased upper layer neuron generation, and this phenotype was rescued by CB1 re-expression. Pharmacological regulation with CB1 receptor agonists or elevation of eCB tone with a monoacylglycerol lipase inhibitor promoted neuronal differentiation of deep layer neurons at the expense of upper layer neurons. Patch-clamp analyses revealed that enhancing cannabinoid signalling facilitated neuronal differentiation and functionality. Noteworthy, incubation with CB1 receptor agonists during human iPSC-derived cerebral organoid formation also promoted the expansion of BCL11B+ neurons. These findings unveil a cell-autonomous role of eCB signalling that, via the CB1 receptor, promotes mouse and human deep layer cortical neuron development.

scholarly journals An evolutionarily acquired microRNA shapes development of mammalian cortical projections

2020 ◽  
Vol 117 (46) ◽  
pp. 29113-29122
Author(s):  
Jessica L. Diaz ◽  
Verl B. Siththanandan ◽  
Victoria Lu ◽  
Nicole Gonzalez-Nava ◽  
Lincoln Pasquina ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Motor Neurons ◽  
Cognitive Skills ◽  
Corticospinal Tract ◽  
Projection Neuron ◽  
Projection Neurons ◽  
Cortical Projection ◽  
Complex Motor ◽  
Genomic Cluster

The corticospinal tract is unique to mammals and the corpus callosum is unique to placental mammals (eutherians). The emergence of these structures is thought to underpin the evolutionary acquisition of complex motor and cognitive skills. Corticospinal motor neurons (CSMN) and callosal projection neurons (CPN) are the archetypal projection neurons of the corticospinal tract and corpus callosum, respectively. Although a number of conserved transcriptional regulators of CSMN and CPN development have been identified in vertebrates, none are unique to mammals and most are coexpressed across multiple projection neuron subtypes. Here, we discover 17 CSMN-enriched microRNAs (miRNAs), 15 of which map to a single genomic cluster that is exclusive to eutherians. One of these, miR-409-3p, promotes CSMN subtype identity in part via repression of LMO4, a key transcriptional regulator of CPN development. In vivo, miR-409-3p is sufficient to convert deep-layer CPN into CSMN. This is a demonstration of an evolutionarily acquired miRNA in eutherians that refines cortical projection neuron subtype development. Our findings implicate miRNAs in the eutherians’ increase in neuronal subtype and projection diversity, the anatomic underpinnings of their complex behavior.

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

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.

scholarly journals Circular RNA mmu_circ_0005019 inhibits fibrosis of cardiac fibroblasts and reverses electrical remodeling of cardiomyocytes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Na Wu ◽  
Chengying Li ◽  
Bin Xu ◽  
Ying Xiang ◽  
Xiaoyue Jia ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Cardiac Fibroblasts ◽  
Circular Rna ◽  
Protective Role ◽  
Luciferase Reporter ◽  
Loss Of Function ◽  
Candidate Target ◽  
Paired Control ◽  
Reporter Assays ◽  
And Migration

Abstract Background Circular RNA (circRNA) have been reported to play important roles in cardiovascular diseases including myocardial infarction and heart failure. However, the role of circRNA in atrial fibrillation (AF) has rarely been investigated. We recently found a circRNA hsa_circ_0099734 was significantly differentially expressed in the AF patients atrial tissues compared to paired control. We aim to investigate the functional role and molecular mechanisms of mmu_circ_0005019 which is the homologous circRNA in mice of hsa_circ_0099734 in AF. Methods In order to investigate the effect of mmu_circ_0005019 on the proliferation, migration, differentiation into myofibroblasts and expression of collagen of cardiac fibroblasts, and the effect of mmu_circ_0005019 on the apoptosis and expression of Ito, INA and SK3 of cardiomyocytes, gain- and loss-of-function of cell models were established in mice cardiac fibroblasts and HL-1 atrial myocytes. Dual-luciferase reporter assays and RIP were performed to verify the binding effects between mmu_circ_0005019 and its target microRNA (miRNA). Results In cardiac fibroblasts, mmu_circ_0005019 showed inhibitory effects on cell proliferation and migration. In cardiomyocytes, overexpression of mmu_circ_0005019 promoted Kcnd1, Scn5a and Kcnn3 expression. Knockdown of mmu_circ_0005019 inhibited the expression of Kcnd1, Kcnd3, Scn5a and Kcnn3. Mechanistically, mmu_circ_0005019 exerted biological functions by acting as a miR-499-5p sponge to regulate the expression of its target gene Kcnn3. Conclusions Our findings highlight mmu_circ_0005019 played a protective role in AF development and might serve as an attractive candidate target for AF treatment.

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