Area Patterning of the Mammalian Cortex

O’Leary, Dennis D.M.; Stocker, Adam M.; Zembrzycki, Andreas

doi:10.1016/b978-0-12-397265-1.00021-6

Cited by 111 publications

(169 citation statements)

References 142 publications

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“…The homeobox gene Emx2 encodes a transcription factor known to play key roles in cortical development by mediating neuroblast proliferation, migration and differentiation (37,38), astrogenesis (39), and cortical areal patterning and specification (40)(41)(42). This gene is regulated by two independent enhancer sequences, which present striking differences in activity levels across the forebrain (28,29).…”

Section: Discussionmentioning

confidence: 99%

Subset of early radial glial progenitors that contribute to the development of callosal neurons is absent from avian brain

García‐Moreno

Molnár

2015

Proc. Natl. Acad. Sci. U.S.A.

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The classical view of mammalian cortical development suggests that pyramidal neurons are generated in a temporal sequence, with all radial glial cells (RGCs) contributing to both lower and upper neocortical layers. A recent opposing proposal suggests there is a subgroup of fate-restricted RGCs in the early neocortex, which generates only upper-layer neurons. Little is known about the existence of fate restriction of homologous progenitors in other vertebrate species. We investigated the lineage of selected Emx2 + [vertebrate homeobox gene related to Drosophila empty spiracles (ems)] RGCs in mouse neocortex and chick forebrain and found evidence for both sequential and fate-restricted programs only in mouse, indicating that these complementary populations coexist in the developing mammalian but not avian brain. Among a large population of sequentially programmed RGCs in the mouse brain, a subset of self-renewing progenitors lack neurogenic potential during the earliest phase of corticogenesis. After a considerable delay, these progenitors generate callosal upper-layer neurons and glia. On the other hand, we found no homologous delayed population in any sectors of the chick forebrain. This finding suggests that neurogenic delay of selected RGCs may be unique to mammals and possibly associated with the evolution of the corpus callosum.S everal neural progenitor subtypes have been identified in the developing mammalian neocortex (1-4). At the onset of neurogenesis, multipotent proliferative radial glial cells (RGCs) reside at the ventricular surface. RGC divisions can be "self-renewing," a symmetrical division in which two identical RGCs are generated; "direct neurogenic," generating a neuroblast and a multipotent progenitor; or "indirect neurogenic," which gives rise to an intermediate progenitor that migrates to divide in the subventricular zone. The timing of these events is crucial for cell number and fate determination (5-7) and vary among different mammalian species. Importantly, very little is known about the homologous populations of RGCs in other vertebrate species and about their role in cortical evolution.Observations made from Golgi-stained material (4, 8), birthdating (5, 9), and lineage-tracing analysis (10-14) contributed to the formation of the "sequential" hypothesis. Accordingly, each RGC in the early brain generates most cortical cell types by sequential mitoses (15). Long-range subcortical projection neurons of the deep layers are generated first, followed by the callosal projection neurons of the upper layers, and finally the glial cells (16).However, recent genetic fate mapping of selected lineages has revealed a subpopulation of early RGCs expressing Cux2, which only gives rise to Satb2-positive upper-layer cortical neurons (17). This finding suggests that the early neurogenic brain may contain several types of cortical progenitors, each of which constrained to generating certain subpopulations of neurons, known as the "restricted progenitor hypothesis" (18). The existence of these restricted ...

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Section: Discussionmentioning

confidence: 99%

Subset of early radial glial progenitors that contribute to the development of callosal neurons is absent from avian brain

García‐Moreno

Molnár

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Coup-TF1 is expressed in greatest concentration in caudal-lateral regions, while SP8 is expressed in rostral-medial regions. As was the case with Pax6 and Emx2, blocking the expression of these genes results in dramatic alteration in the sensorimotor organization of the neocortex (O'Leary et al 2007;Zembrzycki et al 2007; O' Leary and Sahara 2008;Sansom and Livesey 2009).…”

Section: Neural Patterning In the Embryonic Periodmentioning

confidence: 93%

The Basics of Brain Development

Stiles¹,

Reilly²,

Levine³

et al. 2012

Neural Plasticity and Cognitive Development

235

291

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Over the past several decades, significant advances have been made in our understanding of the basic stages and mechanisms of mammalian brain development. Studies elucidating the neurobiology of brain development span the levels of neural organization from the macroanatomic, to the cellular, to the molecular. Together this large body of work provides a picture of brain development as the product of a complex series of dynamic and adaptive processes operating within a highly constrained, genetically organized but constantly changing context. The view of brain development that has emerged from the developmental neurobiology literature presents both challenges and opportunities to psychologists seeking to understand the fundamental processes that underlie social and cognitive development, and the neural systems that mediate them. This chapter is intended to provide an overview of some very basic principles of brain development, drawn from contemporary developmental neurobiology, that may be of use to investigators from a wide range of disciplines.

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“…Cortical development is known to be under both intrinsic and extrinsic factors. Environmental factors that are known to influence the development of the cortex (Kennedy and Dehay, 1993;O'Leary et al, 2007) could potentially have a differential impact on arealization and variability in cortical connectivity in mouse and macaque (Buckner and Krienen, 2013). Further, the laboratory mouse is a highly inbred strain that could exhibit less phenotypic variability than the macaque.…”

Section: Comparison Of Variability Of Deterministic Connectivity Mapsmentioning

confidence: 99%

The Mouse Cortical Interareal Network Reveals Well Defined Connectivity Profiles and an Ultra Dense Cortical Graph

Gămănuţ

Kennedy

Toroczkai

et al. 2017

Preprint

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The inter-areal wiring pattern of mouse cerebral cortex was analyzed in relation to an accurate parcellation of cortical areas. Twenty-seven retrograde tracer injections were made in 19 areas of a 41 area (plus 7 sub-area) parcellation of the mouse neo-, parahippocampal and perirhinal cortex. Flat mounts of the cortex and multiple histological markers enabled detailed counts of labeled neurons in individual areas. A weight index was determined for each area-to-area pathway based on the Fraction of Extrinsically Labeled Neurons (FLNe). Data analysis allowed cross species comparison with the macaque. Estimation of FLNe statistical variability based on repeat injections revealed high consistency across individuals and justifies using a single injection per area to characterize connectivity. The observed lognormal distribution of connections to each cortical area spanned 5 orders of magnitude and revealed a distinct connectivity profile for each area, analogous to that observed in macaque. The resulting graph has a density of 97% (i.e. 97% of connections that can exist do exist), considerably higher than the 66% density reported for the macaque. Our results provide more sharply defined connectivity profiles and a markedly higher graph density than shown in a recent probabilistic mouse connectome.All rights reserved. No reuse allowed without permission.

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Area Patterning of the Mammalian Cortex

Cited by 111 publications

References 142 publications

Subset of early radial glial progenitors that contribute to the development of callosal neurons is absent from avian brain

Subset of early radial glial progenitors that contribute to the development of callosal neurons is absent from avian brain

The Basics of Brain Development

The Mouse Cortical Interareal Network Reveals Well Defined Connectivity Profiles and an Ultra Dense Cortical Graph

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