Compartments and their boundaries in vertebrate brain development

Abstract

Fifteen years ago, cell lineage restriction boundaries were discovered in the embryonic vertebrate hindbrain, subdividing it into a series of cell-tight compartments (known as rhombomeres). Compartition, together with segmentally reiterative neuronal architecture and the nested expression of Hox genes, indicates that the hindbrain has a truly metameric organization. This finding initiated a search for compartments in other regions of the developing brain. The results of recent studies have clarified where compartment boundaries exist, have shed light on molecular mechanisms that underlie their formation and have revealed an important function of these boundaries: the positioning and stabilization of local signalling centres.

Neuromolecular responses to social challenge: Common mechanisms across mouse, stickleback fish, and honey bee

“…Most of the behavioral toolkit TFs identified in our study (Nr4a3, Lhx1, Nr5a1, Irx3, Emx1, and Foxg1) are involved in brain or neural development, including postnatal neurogenesis (62)(63)(64), and the involvement of developmental processes also was revealed by both the GSEA and cis-motif analyses. Previous studies have associated developmental gene expression in the adult brain with plasticity in neural connectivity and the maintenance of regional boundaries (65,66); other examples of genetic toolkits also involve genes associated with developmental patterning (3).…”

Localization and requirement for Myosin II at the dorsal‐ventral compartment boundary of the Drosophila wing

“…The formation of compartment boundaries is a common process during development (Irvine and Rauskolb, 2001;Blair, 2003;Kiecker and Lumsden, 2005). Compartment boundaries prevent cells on one side from mixing with cells on the other side, and are identifiable as sites of lineage restriction.…”

“…They also characteristically establish a smooth interface between adjacent cell populations. Originally discovered in the imaginal discs of Drosophila, they are now known to be present in a variety of tissues and animals (Irvine and Rauskolb, 2001;Kiecker and Lumsden, 2005). Compartment boundaries play two key roles in tissue growth and patterning.…”

Brain diversity evolves via differences in patterning

“…Modifications of brain structure are responsible for novel behaviors that galvanized evolutionary radiation of the major vertebrate groups (1). Following decades of research in model organisms, we now know a great deal about how the process of development makes a brain (2). We know much less about evolutionary mechanisms of brain diversification.…”

“…We know much less about evolutionary mechanisms of brain diversification. The brain develops under the iterative influence of antagonistic anterior and posterior signaling molecules, inductive and repressive transcription factors that receive those signals, and lineage restriction boundaries that define compartments (2,3). Just after gastrulation, the initial anterior-posterior (AP) polarity of the brain is established by a tug-of-war between posteriorizing signals (e.g., wnt1) secreted from the midbrain-hindbrain boundary (MHB) and WNT antagonists (e.g., six3, tlc) expressed from the anterior neural ridge (ANR).…”