Intrinsic and extrinsic factors that shape neocortical specification

Pallas, Sarah L.

doi:10.1016/s0166-2236(00)01853-1

Cited by 136 publications

(90 citation statements)

References 89 publications

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“…An early characteristic of neocortical regionalization is the formation of region-specific projections from specific thalamic nuclei (Crandall and Caviness, 1984;O'Leary et al, 1994;Molnar and Blakemore, 1995;Ragsdale and Grove, 2001;O'Leary and Nakagawa, 2002). This process sets the framework for areaspecific connectivity with thalamic nuclei, which relay different types of sensory and motor information (O'Leary et al, 1994;Pallas, 2001;Sur and Leamey, 2001;O'Leary and Nakagawa, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…This issue has been and remains controversial (O'Leary et al, 1994;Levitt et al, 1997;Rubenstein and Rakic, 1999;Monuki and Walsh, 2001;Pallas, 2001;Ragsdale and Grove, 2001;Ruiz i Altaba et al, 2001;Sur and Leamey, 2001;O'Leary and Nakagawa, 2002). It has been proposed that regionalization is induced by extrinsic cues, in particular by incoming thalamic axons, which convey positional and functional specification (the 'protocortex' model) (O'Leary, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Molecular regionalization of the neocortex is disrupted inFgf8hypomorphic mutants

2003

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The neocortex is divided into multiple areas with specific architecture, molecular identity and pattern of connectivity with the dorsal thalamus. Gradients of transcription factor expression in the cortical primordium regulate molecular regionalization and potentially the patterning of thalamic projections. We show that reduction of Fgf8 levels in hypomorphic mouse mutants shifts early gradients of gene expression rostrally, thereby modifying the molecular identity of rostral cortical progenitors. This shift correlates with a reduction in the size of a molecularly defined rostral neocortical domain and a corresponding rostral expansion of more caudal regions. Despite these molecular changes, the topography of projections between the dorsal thalamus and rostral neocortex in mutant neonates appears the same as the topography of wild-type littermates. Overall, our study demonstrates the role of endogenous Fgf8 in regulating early gradients of transcription factors in cortical progenitor cells and in molecular regionalization of the cortical plate

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular regionalization of the neocortex is disrupted inFgf8hypomorphic mutants

2003

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“…In the mammalian brain, reciprocal connections between sensory nuclei of the dorsal thalamus and specific areas of the neocortex are essential for the relay and processing of visual, auditory, sensory and motor information Levitt et al, 1997;Monuki and Walsh, 2001;Pallas, 2001;Ragsdale and Grove, 2001;Ruiz i Altaba et al, 2001;Sur and Leamey, 2001;O'Leary and Nakagawa, 2002). During development, thalamocortical and corticothalamic axons grow into the subcortical telencephalon, where they meet and continue on their paths to the cortex and thalamus, respectively (Miller et al, 1993;Metin and Godement, 1996;Molnar et al, 1998a;Auladell et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

The early topography of thalamocortical projections is shifted inEbf1andDlx1/2mutant mice

Garel

Yun

Grosschedl³

et al. 2002

Development

109

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The prevailing model to explain the formation of topographic projections in the nervous system stipulates that this process is governed by information located within the projecting and targeted structures. In mammals, different thalamic nuclei establish highly ordered projections with specific neocortical domains and the mechanisms controlling the initial topography of these projections remain to be characterized. To address this issue, we examined Ebf1 -/-embryos in which a subset of thalamic axons does not reach the neocortex. We show that the projections that do form between thalamic nuclei and neocortical domains have a shifted topography, in the absence of regionalization defects in the thalamus or neocortex. This shift is first detected inside the basal ganglia, a structure on the path of thalamic axons, and which develops abnormally in Ebf1 -/-embryos. A similar shift in the topography of thalamocortical axons inside the basal ganglia and neocortex was observed in Dlx1/2 -/-embryos, which also have an abnormal basal ganglia development. Furthermore, Dlx1 and Dlx2 are not expressed in the dorsal thalamus or in cortical projections neurons. Thus, our study shows that: (1) different thalamic nuclei do not establish projections independently of each other; (2) a shift in thalamocortical topography can occur in the absence of major regionalization defects in the dorsal thalamus and neocortex; and (3) the basal ganglia may contain decision points for thalamic axons' pathfinding and topographic organization. These observations suggest that the topography of thalamocortical projections is not strictly determined by cues located within the neocortex and may be regulated by the relative positioning of thalamic axons inside the basal ganglia.

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“…The locations of the primary sensory cortices are similar in all mammals and set by gradients of differential gene expression during early development of the telencephalic vesicles (Lopez-Bendito and Molnar, 2003;Ragsdale and Grove, 2001). However, these intrinsically allocated cortical areas can shift or change their properties when thalamocortical inputs or sensory stimulation and distribution of receptors in the periphery are altered (Fox, 2002;Kaas, 2002;Kaas and Catania, 2002;Kossut, 1998;Pallas, 2001;Rauschecker, 2002). This plasticity allows the neocortex to adapt to changes in the environment, to loss of function in the sensory periphery or along the subcortical pathways that bring the sensory world to the neocortex.…”

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confidence: 99%

Somatosensory cortical plasticity: recruiting silenced barrels by active whiskers

Erzurumlu

2003

Experimental Neurology

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Intrinsic and extrinsic factors that shape neocortical specification

Cited by 136 publications

References 89 publications

Molecular regionalization of the neocortex is disrupted inFgf8hypomorphic mutants

Molecular regionalization of the neocortex is disrupted inFgf8hypomorphic mutants

The early topography of thalamocortical projections is shifted inEbf1andDlx1/2mutant mice

Somatosensory cortical plasticity: recruiting silenced barrels by active whiskers

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