Zeidler MP, Perrimon N, Strutt DI. Polarity determination in the Drosophila eye: a novel role for unpaired and JAK/STAT signaling. Genes Dev. 1999;13 (10) :1342-53. Abstract

The JAK/STAT signaling pathway is required for many processes including cytokine signaling, hematopoiesis, gliagenesis, and Drosophila segmentation. In this report we present evidence demonstrating that the JAK/STAT pathway is also central to the establishment of planar polarity during Drosophila eye development. We show that a localized source of the pathway ligand, Unpaired, is present at the midline of the developing eye, which is capable of activating the JAK/STAT pathway over long distances. A gradient of JAK/STAT activity across the DV axis of the eye regulates ommatidial polarity via an unidentified second signal. Additionally, localized Unpaired influences the position of the equator via repression of mirror.

1999_Genes & Dev_Zeidler.pdf
Harrison DA, McCoon PE, Binari R, Gilman M, Perrimon N. Drosophila unpaired encodes a secreted protein that activates the JAK signaling pathway. Genes Dev. 1998;12 (20) :3252-63. Abstract

In vertebrates, many cytokines and growth factors have been identified as activators of the JAK/STAT signaling pathway. In Drosophila, JAK and STAT molecules have been isolated, but no ligands or receptors capable of activating the pathway have been described. We have characterized the unpaired (upd) gene, which displays the same distinctive embryonic mutant defects as mutations in the Drosophila JAK (hopscotch) and STAT (stat92E) genes. Upd is a secreted protein, associated with the extracellular matrix, that activates the JAK pathway. We propose that Upd is a ligand that relies on JAK signaling to stimulate transcription of pair-rule genes in a segmentally restricted manner in the early Drosophila embryo.

1998_Genes Dev_Harrison.pdf