Originally published as Genetics Published Articles Ahead of Print on August 30, 2008.

Genetics, Vol. 180, 283-299, September 2008, Copyright © 2008
doi:10.1534/genetics.108.092155

Drosophila Nemo Promotes Eye Specification Directed by the Retinal Determination Gene Network

Lorena R. Braid and Esther M. Verheyen1

Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

1 Corresponding author: Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada.
E-mail: everheye{at}sfu.ca

Drosophila nemo (nmo) is the founding member of the Nemo-like kinase (Nlk) family of serine–threonine kinases. Previous work has characterized nmo's role in planar cell polarity during ommatidial patterning. Here we examine an earlier role for nmo in eye formation through interactions with the retinal determination gene network (RDGN). nmo is dynamically expressed in second and third instar eye imaginal discs, suggesting additional roles in patterning of the eyes, ocelli, and antennae. We utilized genetic approaches to investigate Nmo's role in determining eye fate. nmo genetically interacts with the retinal determination factors Eyeless (Ey), Eyes Absent (Eya), and Dachshund (Dac). Loss of nmo rescues ey and eya mutant phenotypes, and heterozygosity for eya modifies the nmo eye phenotype. Reducing nmo also rescues small-eye defects induced by misexpression of ey and eya in early eye development. nmo can potentiate RDGN-mediated eye formation in ectopic eye induction assays. Moreover, elevated Nmo alone can respecify presumptive head cells to an eye fate by inducing ectopic expression of dac and eya. Together, our genetic analyses reveal that nmo promotes normal and ectopic eye development directed by the RDGN.