A C-ELEGANS HOX GENE SWITCHES ON, OFF, ON AND OFF AGAIN TO REGULATE PROLIFERATION, DIFFERENTIATION AND MORPHOGENESIS

Hox genes establish body pattern throughout the animal kingdom, but th e role these genes play at the cellular level to modify and shape part s of the body remains a mystery, We find that the C. elegans Antennape dia homolog, mab-5, sequentially programs many independent events with in individual cell lineages, In one body region, mab-5 first switches ON in a lineage to stimulate proliferation, then OFF to specify epider mal structures, then ON in just one branch of the lineage to promote n euroblast formation, finally OFF to permit proper sense organ morpholo gy, In a neighboring lineage, continuous mab-5 expression leads to a d ifferent pattern of development, Thus, this Hox gene achieves much of its power to diversify the anteroposterior axis through fine spatiotem poral differences in expression coupled with a changing pattern of cel lular response.