Conserved cis-regulatory modules mediate complex neural expression patterns of the eyeless gene in the Drosophila brain

• Published in: Mechanisms of development 2003-10, Vol.120 (10), p.1113-1126
• Main Authors: Adachi, Yoshitsugu, Hauck, Bernd, Clements, Jason, Kawauchi, Hiroshi, Kurusu, Mitsuhiko, Totani, Yoko, Kang, Yuan Yuan, Eggert, Tanja, Walldorf, Uwe, Furukubo-Tokunaga, Katsuo, Callaerts, Patrick
• Format: Article
• Language: English
• Subjects: Animals; Brain - embryology; Brain - metabolism; DNA Transposable Elements; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Drosophila - embryology; Drosophila - metabolism; Drosophila hydei; Drosophila melanogaster; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Enhancer; Enhancer Elements, Genetic; Eye primordia; Eye Proteins; Eyeless; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Introns; Mice; Molecular Sequence Data; Mushroom body; Optic lobe; Organ Specificity; Paired Box Transcription Factors; PAX6 Transcription Factor; Repressor Proteins; RNAi; Trans-Activators - genetics; Trans-Activators - metabolism; Twin of eyeless
• ISSN: 0925-4773; 1872-6356
• DOI: 10.1016/j.mod.2003.08.007

The Drosophila Pax-6 homologs eyeless ( ey) and twin of eyeless ( toy) are expressed in the eyes and in the central nervous system (CNS). In addition to the pivotal functions in eye development, previous studies revealed that ey also plays important roles in axonal development of the mushroom bodies, centers for associative learning and memory. It has been reported that a second intron enhancer that contains several Pax-6 binding sites mainly controls the eye-specific expression, but the DNA sequences that control CNS expression are unknown. In this work, we have dissected transcriptional enhancer elements of the ey gene that are required for the CNS expression in various developmental stages. We first show that CNS expression is independent of the eye-specific enhancer of the second intron. By systematic reporter studies, we have identified several discrete DNA elements in the 5′ upstream region and in the second intron that cooperatively interact to generate most of the ey expression pattern in the CNS. DNA sequence comparison between the ey genes of distant Drosophila species has identified conserved modules that might be bound by the upstream regulatory factors of the ey gene in CNS development. Furthermore, by RNA interference and mutant studies, we show that ey expression in the brain is independent of the activity of toy and ey itself whereas in the eye primordia it requires both, supporting the notion that ey and toy are regulated by parallel and independent regulatory cascades in brain development.