Waves of differentiation in the fly visual system

Abstract

Sequential progression of differentiation in a tissue or in multiple tissues in a synchronized manner plays important roles in development. Such waves of differentiation are especially important in the development of the Drosophila visual system, which is composed of the retina and the optic lobe of the brain. All of the components of the fly visual system are topographically connected, and each ommatidial unit in the retina corresponds to a columnar unit in the optic lobe, which is composed of lamina, medulla, lobula and lobula plate. In the developing retina, the wave of differentiation follows the morphogenetic furrow, which progresses in a posterior-to-anterior direction. At the same time, differentiation of the lamina progresses in the same direction, behind the lamina furrow. This is not just a coincidence: differentiated photoreceptor neurons in the retina sequentially send axons to the developing lamina and trigger differentiation of lamina neurons to ensure the progression of the lamina furrow just like the furrow in the retina. Similarly, development of the medulla accompanies a wave of differentiation called the proneural wave. Thus, the waves of differentiation play important roles in establishing topographic connections throughout the fly visual system. In this article, we review how neuronal differentiation and connectivity are orchestrated in the fly visual system by multiple waves of differentiation.

Notch-mediated lateral inhibition regulates proneural wave propagation when combined with EGF-mediated reaction diffusion

“…Therefore, we formulated a four-component model of the proneural wave using a reaction diffusion system for EGF and a lateral inhibition system for Notch based on previous observations and our own findings (Figs. 1G, black and red arrows, respectively, and 3A) (23,24,26,27,30,31). In this model, E is a composite variable for the EGF ligand concentration and EGF signaling.…”

“…In this study, we focused on a wave of differentiation called the "proneural wave" (23,24), which occurs in the largest component of the fly visual center, the "medulla." During proneural wave progression, the sheet-like NEs sequentially differentiate to neural stem cells called neuroblasts (NBs) (Fig.…”

Self-Similarity, Distortion Waves, and the Essence of Morphogenesis: A Generalized View of Color Pattern Formation in Butterfly Wings

“…Morphogenesis is three-dimensionally dynamic in any developmental system, but a good example of three-dimensional dynamism of the epithelial sheet is the morphogenetic furrow in the Drosophila retina (Greenwood and Struhl 1999;Schlichting and Dahmann 2008;Sato et al 2013). The furrow is a physical distortion of the imaginal eye disk.…”

Live-imaging of the <em>Drosophila</em> Pupal Eye

“…During larval development, the photoreceptor cores of each ommatidium are recruited as a wave that travels from the posterior to anterior side of the eye disc 11 . This developmental gradient was retained in the pupal eye.…”