The development of a single eye is a complicated process. Multiply that by 750, the number of eyes in the fruit fly’s compound eye, and you’re bound to be impressed by the amazing cellular and developmental events that have to occur in order for a fruit fly to find its way to lunch.
During development of the Drosophila eye, photoreceptor neurons secrete an epidermal growth factor receptor called Spi. Spi can be secreted from either the cell body or axonal terminus of the neuron, and this polarized secretion leads to different responses from the same signal. A recent paper highlights the role of an ER-localized protein called Rho-3 in determining the site of Spi secretion in the axonal terminus. Images above show the developing eye disc and lamina of flies with (top) or without (bottom) Rho-3. Without Rho-3, the lamina (dotted lines) does not express Elav (red), which is normally expressed when Spi is secreted from photoreceptors. Black and white images show Elav staining alone.
Reference: Shaul Yogev, Eyal D. Schejter, Ben-Zion Shilo. Authors’ PLoS Biology paper can be found here.