Odd-Paired: The Drosophila Zic Gene.

Zinc finger in the cerebellum (Zic) proteins are a family of transcription factors with multiple roles during development, particularly in neural tissues. The founding member of the Zic family is the Drosophila odd-paired (opa) gene. The Opa protein has a DNA binding domain containing five Cys2His2-type zinc fingers and has been shown to act as a sequence-specific DNA binding protein. Opa has significant homology to mammalian Zic1, Zic2, and Zic3 within the zinc finger domain and in two other conserved regions outside that domain. opa was initially identified as a pair-rule gene, part of the hierarchy of genes that establish the segmental body plan of the early Drosophila embryo. However, its wide expression pattern during embryogenesis indicates it plays additional roles. Embryos deficient in opa die before hatching with aberrant segmentation but also with defects in larval midgut formation. Post-embryonically, opa plays important roles in adult head development and circadian rhythm. Based on extensive neural expression, opa is predicted to be involved in many aspects of neural development and behavior, like other proteins of the Zic family. Consensus DNA binding sites have been identified for Opa and have been shown to activate transcription in vivo. However, there is evidence Opa may serve as a transcriptional regulator in the absence of direct DNA binding, as has been seen for other Zic proteins.