EMBRYONIC EXPRESSION AND CHARACTERIZATION OF A PTX1 HOMOLOG IN DROSOPHILA

We describe the molecular characterization of the paired-type homeobox gene D-Ptx1 of Drosophila, a close homolog of the mouse pituitary hom eobox gene Ptx1 and the unc-30 gene of C. elegans, characterized by a lysine residue at position 9 of the third alpha-helix of the homeodoma in. D-Ptx1 is expressed at various restricted locations throughout emb ryogenesis. Initial expression of D-Ptx1 in the posterior-most region of the blastoderm embryo is controlled by fork head activity in respon se to the activated Ras/Raf signaling pathway. During later stages of embryonic development, D-Ptx1 transcripts and protein accumulate in th e posterior portion of the midgut, in the developing Malpighian tubule s, in a subset of ventral somatic muscles, and in neural cells. Phenot ypic analysis of gain-of-function and lack-of-function mutant embryos show that the D-Ptxl gene is not involved in morphologically apparent differentiation processes. We conclude that D-Ptx1 is more likely to c ontrol physiological cell functions than pattern formation during Dros ophila embryogenesis. (C) 1997 Elsevier Science Ireland Ltd.