Charting the development of Drosophila leg sensory organs at single-cell resolution

To respond to the world around them, animals rely on the input of a network of sensory organs distributed across the body. A single individual will generally express several distinct classes of sensory organ, each bearing features that appear to enhance the detection of specific stimuli, such as strain, pressure, or light. The features that underlie this specialization relate both to the neurons housed within a sensory organ and to the various accessory cells that they are composed of. This diversity of cell types, both within and between sensory organs, raises two fundamental questions: (1) How is this diversity generated during development? And (2) What makes these cell types distinct from one another? To address these questions, we performed single-cell RNA-sequencing on a region of the pupal male Drosophila melanogaster foreleg that displays a wide variety of functionally and structurally distinct sensory organs: the first tarsal segment. Our work characterizes the cellular landscape in which the sensory organs reside; identifies a novel glia  cell type that appears to contribute towards the construction of the neural lamella; resolves and validates a combinatorial transcription factor code unique to each of mechanosensory, sex comb, and campaniform sensilla neurons, as well as four distinct gustatory receptor neuron classes; matches receptors and membrane channels to specific neurons; and characterizes the transcriptomic differences between and within sensory organ support cell types. Collectively, our work identifies core genetic features of a variety of sensory organs and provides a rich, annotated resource for studying their development and function. First tarsal segment cells from pupal male Drosophila melanogaster (DGRP line RAL-517) were isolated separately at 24h and 30h after puparium formation