brakeless is required for photoreceptor growth-cone targeting in Drosophila

brakeless is required for photoreceptor growth-cone targeting in Drosophila

^†Department of Neurology and Neurosurgery, Centre for Research in Neuroscience, McGill University and the Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada; and ^‡Howard Hughes Medical Institute and Department of Biological Chemistry, Molecular Biology Institute, University of California School of Medicine, Los Angeles, CA 90095

Communicated by Elizabeth F. Neufeld, University of California, Los Angeles, CA (received for review February 25, 2000)

Abstract

The R1-R6 subclass of photoreceptor neurons (R cells) in the Drosophila compound eye form specific connections with targets in the optic ganglia. In this paper, we report the identification of a gene, brakeless (bks), that is essential for R1-R6 growth cone targeting. In brakeless mutants, R1-R6 growth cones frequently fail to terminate migration in their normal target, the lamina, and instead project through it and terminate in the second optic ganglion, the medulla. Genetic mosaic analysis and transgene rescue experiments indicate that bks functions in R cells and not within the lamina target region. bks encodes a nuclear protein. We propose that it participates in a gene expression pathway regulating one or more growth cone components controlling R1-R6 targeting.

Footnotes

↵ * To whom reprint requests should be addressed. E-mail: ezdz{at}musica.mcgill.ca or zipursky{at}hhmi.ucla.edu.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database [accession no. AF238858 (brakeless)].
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.110135297.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.110135297
Abbreviations:

bks,

brakeless;

EST,

expressed sequence tag