Abstract
Compartments are units of cell lineage that subdivide territories with different developmental potential. In Drosophila, the wing and haltere discs are subdivided into anterior and posterior (A/P) compartments, which require the activity of Hedgehog, and into dorsal and ventral (D/V) compartments, needing Notch signaling. There is enrichment in actomyosin proteins at the compartment boundaries, suggesting a role for these proteins in their maintenance. Compartments also develop in the mouse hindbrain rhombomeres, which are characterized by the expression of different Hox genes, a group of genes specifying different structures along their main axis of bilaterians. We show here that the Drosophila Hox gene Ultrabithorax can maintain the A/P and D/V compartment boundaries when Hedgehog or Notch signaling is compromised, and that the interaction of cells with and without Ultrabithorax expression induces high levels of non-muscle myosin II. In the absence of Ultrabithorax there is occasional mixing of cells from different segments. We also show a similar role in cell segregation for the Abdominal-B Hox gene. Our results suggest that the juxtaposition of cells with different Hox gene expression leads to their sorting out, probably through the accumulation of non-muscle myosin II at the boundary of the different cell territories. The increase in myosin expression seems to be a general mechanism used by Hox genes or signaling pathways to maintain the segregation of different groups of cells.
Highlights
During animal development there is a progressive subdivision of the organism into distinct groups of cells that will form different organs and structures
We show here that cells with different expression of the Hox gene Ultrabithorax segregate from each other and that this difference is sufficient to maintain A/P and dorsal and ventral (D/V) boundaries in the wing, haltere or leg disc
We propose that Hox genes may separate cells with different identity through the control of myosin accumulation
Summary
During animal development there is a progressive subdivision of the organism into distinct groups of cells that will form different organs and structures. We show here that cells with different expression of the Hox gene Ultrabithorax segregate from each other and that this difference is sufficient to maintain A/P and D/V boundaries in the wing, haltere or leg disc.
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