Mutations in masquerade, a novel serine-protease-like molecule, affect axonal guidance and taste behavior in Drosophila.

The masquerade (mas) locus encodes an extracellular molecule with a striking similarity to serine proteases. The serine residue, which is essential for enzymatic activity, has been substituted by glycine, suggesting that MAS could serve to antagonize serine protease activity [Murugasu-Oei et al. (1995), Genes Dev. 9, 139-154]. We describe the expression pattern of mas mRNA and protein in the developing embryonic, larval and pupal nervous system and in the epidermis. Total loss of mas function is lethal and results in aberrations in the embryonic central and peripheral nervous systems, consistent with a role in axonal guidance. The possibility that the observed deficits in taste behavior, exhibited by animals with partial loss of mas function, are a result of defects in the adult brain are discussed.