Embryonic expression and activity of doughnut, a second RYK homolog in Drosophila

In the Drosophila embryo, a subset of muscles require expression and functi on of the RYK subfamily RTK gene derailed (drl) for correct attachment, We have isolated a second RYK homolog, doughnut (dnt), from Drosophila. The DN T protein exhibits 60% amino acid identity to DRL, and is structurally as s imilar to the mammalian RYK proteins as is DRL, indicating an ancient dupli cation event. dnt is expressed in dynamic patterns in the embryonic epiderm is, being found at high level in epithelia adjacent to cells that are invag inating into the interior of the embryo, including ventral furrow, cephalic furrow, fore- and hindgut, optic lobe and tracheal pits. dnt is capable of a partial rescue of the muscle attachment defect of drl(-/-) embryos, indi cating that it encodes a receptor with a related and significantly overlapp ing biochemical function. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.