The Company of Biologists Acta Medica Okayama 2046-6390 15 2 2026 Gap junction-mediated signaling coordinates Rhodopsin coupling for Drosophila color vision bio062463 EN Xuanshuo Zhang Division of Biological Sciences, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Ryoki Shinjo Division of Biological Sciences, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Manabu Kitamata Division of Health Science, Advanced Comprehensive Research Organization, Teikyo University Shinichi Otsune Division of Biological Sciences, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Hideki Nakagoshi Division of Biological Sciences, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University The Drosophila compound eye is composed of approximately 800 ommatidia, and every ommatidium contains eight photoreceptor cells, six outer cells (R1-R6) and two inner cells (R7 and R8), and accessory cells (cone and pigment cells). The expression of rhodopsin genes in R7 and R8 is highly coordinated through an instructive signal from R7 to R8. The activity of the homeodomain protein Defective proventriculus in R1 is also required to transmit this instructive signal, suggesting that cell–cell communication between R7, R1, and R8 is important to generate the pattern of Rh expression in R7/R8 (Rhodopsin coupling). As cell junctions play crucial roles in maintaining the structural and functional integrity of tissues, we tested whether cell junction proteins are involved in the interactions between photoreceptor cells. Here, we demonstrate that gap junction proteins innexin 2 and innexin 7 in accessory cells are necessary for transmitting signals from R7 to R8. In addition, Notch-mediated accessory cell development and Rhodopsin coupling in R7/R8 are highly correlated. Our results provide evidence that functional coupling of two different neurons, R7 and R8, is established through gap junction-mediated signaling from adjacent accessory cells. No potential conflict of interest relevant to this article was reported.

Academic Press Inc. Elsevier Science Acta Medica Okayama 0012-1606 356 2 2011 Defective proventriculus specifies the ocellar region in the Drosophila head 598 607 EN Takeshi Yorimitsu Naruto Kiritooshi Hideki Nakagoshi A pair of the Drosophila eye-antennal disc gives rise to four distinct organs (eyes, antennae, maxillary palps, and ocelli) and surrounding head cuticle. Developmental processes of this imaginal disc provide an excellent model system to study the mechanism of regional specification and subsequent organogenesis. The dorsal head capsule (vertex) of adult Drosophila is divided into three morphologically distinct subdomains: ocellar, frons, and orbital. The homeobox gene orthodenticle (otd) is required for head vertex development, and mutations that reduce or abolish ad expression in the vertex primordium lead to ocelliless flies. The homeodomain-containing transcriptional repressor Engrailed (En) is also involved in ocellar specification, and the En expression is completely lost in otd mutants. However, the molecular mechanism of ocellar specification remains elusive. Here, we provide evidence that the homeobox gene defective proventriculus (dye) is a downstream effector of Otd, and also that the repressor activity of Dye is required for en activation through a relief-of-repression mechanism. Furthermore, the Dye activity is involved in repression of the frons identity in an incoherent feedforward loop of Otd and Dye. No potential conflict of interest relevant to this article was reported.