A Hox complex activates and potentiates the Epidermal Growth Factor signaling pathway to specify Drosophila oenocytes

Hox transcription factors specify distinct cell types along the anterior-posterior axis of metazoans by regulating target genes that modulate signaling pathways. a well-established example is the induction of epidermal growth factor (egf) signaling by an abdominal-a (abd-a) hox complex during the specification of drosophila hepatocyte-like cells (oenocytes). previous studies revealed that abd-a is non-cell autonomously required to promote oenocyte fate by directly activating a gene (rhomboid) that triggers egf secretion from sensory organ precursor (sop) cells. neighboring cells that receive the egf signal initiate a largely unknown pathway to promote oenocyte fate. here,we show that abd-a also plays a cell autonomous role in inducing oenocyte fate by activating the expression of the pointed-p1 (pntp1) ets transcription factor downstream of egf signaling. genetic studies demonstrate that both pntp1 and pntp2 are required for oenocyte specification. moreover,we found that pntp1 contains a conserved enhancer (pntp1oe) that is activated in oenocyte precursor cells by egf signaling via direct regulation by the pnt transcription factors as well as a transcription factor complex consisting of abd-a,extradenticle,and homothorax. our findings demonstrate that the same abd-a hox complex required for sending the egf signal from sop cells,enhances the competency of receiving cells to select oenocyte cell fate by up-regulating pntp1. since pntp1 is a downstream effector of egf signaling,these findings provide insight into how a hox factor can both trigger and potentiate the egf signal to promote an essential cell fate along the body plan. © 2017 wang et al.