Odd Oz: a novel Drosophila pair rule gene.

We have identified a novel pair rule gene in Drosophila, odd Oz (odz). Every odd-numbered body segment is deleted in odz mutant embryos. The odz gene product is strongly expressed in the embryonic central nervous system and heart, and both of these tissues are malformed in mutant embryos. Odz represents the only known pair rule gene that does not encode a transcription factor. Instead, it encodes a protein with EGF-like repeats homologous to those of the extracellular matrix protein tenascin. The protein is also a putative transmembrane tyrosine kinase substrate. On the basis of its structure, odz must act in a cellularized embryo. This is consistent with odz expression, whose temporal appearance is indicative of a very late-acting pair rule gene.