Protocol for electron microscopy of Drosophila photoreceptor cells

In Drosophila, mutations in genes that prevent normal Ca²⁺ influx after light stimulation usually cause light-dependent retinal degeneration or neurodegeneration, detectable by defects in eye morphology. Here, we present a protocol based on electron microscopy (EM) to observe the morphological structure of photoreceptor cells in Drosophila. We detail how to fix, dehydrate, embed, and polymerize compound eye samples, followed by sectioning, post-staining, and image acquisition, to assess the eye morphology at the ultrastructural level. For complete details on the use and execution of this protocol, please refer to Gu et al. (2020).