FIG. 6. CONCLUSIONS. IN VERTEBRATE LIMBS TWO RELATED APTEROUS GENES, LMX1 AND LHX2, HAVE BEEN SHOWN TO ACT SEPARATELY TO DEFINE DORSAL IDENTITY AND LIMB OUTGROWTH. IN THE DROSOPHILA WING, APTEROUS INDUCES LIMB OUTGROWTH BY CONTROLLING DV SIGNALING AND SPECIFIES DORSAL IDENTITY. DORSAL IDENTITY IS DEFINED BY THE APTEROUS TARGET GENE MSH/DLW.