Compartment (development)

Compartments can be simply defined as separate, different, adjacent cell populations, which upon juxtaposition, create a lineage boundary. This boundary prevents cell movement from cells from different lineages across this barrier, restricting them to their compartment. Subdivisions are established by morphogen gradients and maintained by local cell-cell interactions, providing functional units with domains of different regulatory genes, which give rise to distinct fates. Compartment boundaries are found across species. In the hindbrain of vertebrate embryos, rhobomeres are compartments of common lineage outlined by expression of Hox genes. In invertebrates, the wing imaginal disc of Drosophila provides an excellent model for the study of compartments. Although other tissues, such as the abdomen, and even other imaginal discs are compartmentalized, much of our understanding of key concepts and molecular mechanisms involved in compartment boundaries has been derived from experimentation in the wing disc of the fruit fly.

By separating different cell populations, the fate of these compartments are highly organized and regulated. In addition, this separation creates a region of specialized cells close to the boundary, which serves as a signaling center for the patterning, polarizing and proliferation of the entire disc. Compartment boundaries establish these organizing centers by providing the source of morphogens that are responsible for the positional information required for development and regeneration. The inability of cell competition to occur across the boundary, indicates that each compartment serves as an autonomous unit of growth. Differences in growth rates and patterns in each compartment, maintain the two lineages separated and each control the precise size of the imaginal discs.

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