LIM Genes Parcellate the Embryonic Amygdala and Regulate Its Development

113

During embryogenesis, the lateral cortical stream (LCS) emerges from the corticostriatal border (CSB), the boundary between the developing cerebral cortex and striatum. The LCS is comprised of a mix of pallial-and subpallial-derived neural progenitor cells that migrate to the developing structures of the basal telencephalon, most notably the piriform cortex and amygdala. Using a combination of in vitro and in vivo approaches, we analyzed the timing, composition, migratory modes, origin, and requirement of the homeodomaincontaining transcription factor Gsh2 (genomic screened homeobox 2) in the development of this prominent migratory stream. We reveal that Pax6 (paired box gene 6)-positive pallial-derived and Dlx2 (distal-less homeobox 2)-positive subpallial-derived subpopulations of LCS cells are generated in distinct temporal windows during embryogenesis. Furthermore, our data indicate the CSB border not only is comprised of separate populations of pallial-and subpallial-derived progenitors that contribute to the LCS but also a subpopulation of cells coexpressing Pax6 and Dlx2. Moreover, despite migrating along a route outlined by a cascade of radial glia, the Dlx2-positive population appears to migrate primarily in an apparent chain-like manner, with LCS migratory cells being generated locally at the CSB with little contribution from other subpallial structures such as the medial, lateral, or caudal ganglionic eminences. We further demonstrate that the generation of the LCS is dependent on the homeodomain-containing gene Gsh2, revealing a novel requirement for Gsh2 in telencephalic development.

Section: Discussionmentioning

confidence: 98%

Cell Migration along the Lateral Cortical Stream to the Developing Basal Telencephalic Limbic System

Carney¹,

Alfonso²,

Cohen³

et al. 2006

113

“…Pax6 and Emx2 do not label this nucleus, whereas Lhx2 and Lhx9 are expressed only in layer 1 of the nLOT (Fig. 2a-e) (Remedios et al, 2004). Tbr1 also marks the La, BL, and BM at more caudal levels (Puelles et al, 2000) (Fig.…”

Section: Identification Of Distinct Amygdaloid Nuclei At Late Embryonmentioning

confidence: 98%

“…We used a comprehensive panel of markers (Remedios et al, 2004) to assess the roles of Pax6 and Emx2 in the development of this structure. We found a selective requirement for Pax6, but not Emx2, in the formation of specific amygdaloid nuclei, revealing distinct functions for these genes in the development of this complex structure.…”

Section: Introductionmentioning

confidence: 99%

Selective Requirement of Pax6, But Not Emx2, in the Specification and Development of Several Nuclei of the Amygdaloid Complex

Tole¹,

Remedios²,

Saha³

et al. 2005

178

The amygdaloid complex is a group of nuclei that are thought to originate from multiple sites of the dorsal and ventral telencephalic neuroepithelium. The mechanisms that regulate their development are essentially unknown. We studied the role of Pax6 and Emx2, two transcription factors that regulate regional specification and growth of the telencephalon, in the morphogenesis of the amygdaloid complex. We used a set of specific marker genes that identify distinct amygdaloid nuclei to analyze Pax6/Small eye and Emx2 knock-out mutant mouse brains. We found that there is a selective requirement for Pax6, but not Emx2, in the formation a subset of nuclei within the amygdaloid complex. Specifically, structures that were not previously considered to be developmentally linked, the nucleus of the lateral olfactory tract and the lateral, basolateral, and basomedial nuclei, all appear to have a common requirement for Pax6. Together, our findings provide new insights into the origins and mechanisms underlying the development of the amygdaloid complex.

“…Second, using this definition, the CGE cannot be identified in mouse mutants in which the sulcus separating the MGE from the LGE is compromised, as it is the case of Nkx2-1 mutants. Third, the CGE contains both pallial and subpallial territories (Kim et al, 2001;Medina et al, 2004;Remedios et al, 2004;Tole et al, 2005). Thus, in the same way that LGE and MGE has proven to be ambiguous terms when referring to distinct progenitor pools, the term CGE can only bring confusion to this issue.…”

Section: The Cge Contains the Caudal Extension Of Lge And Mge Progenimentioning

confidence: 99%

Delineation of Multiple Subpallial Progenitor Domains by the Combinatorial Expression of Transcriptional Codes

Flames¹,

Pla²,

Gelman³

et al. 2007

514

792

The mammalian telencephalon is considered the most complex of all biological structures. It comprises a large number of functionally and morphologically distinct types of neurons that coordinately control most aspects of cognition and behavior. The subpallium, for example, not only gives rise to multiple neuronal types that form the basal ganglia and parts of the amygdala and septum but also is the origin of an astonishing diversity of cortical interneurons. Despite our detailed knowledge on the molecular, morphological, and physiological properties of most of these neuronal populations, the mechanisms underlying their generation are still poorly understood. Here, we comprehensively analyzed the expression patterns of several transcription factors in the ventricular zone of the developing subpallium in the mouse to generate a detailed molecular map of the different progenitor domains present in this region. Our study demonstrates that the ventricular zone of the mouse subpallium contains at least 18 domains that are uniquely defined by the combinatorial expression of several transcription factors. Furthermore, the results of microtransplantation experiments in vivo corroborate that anatomically defined regions of the mouse subpallium, such as the medial ganglionic eminence, can be subdivided into functionally distinct domains.