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.