A Comparative Analysis of Transmedullary (Tm & TmY) Neurons in the Drosophila melanogaster Optic Lobe

Abstract

The D. melanogaster visual system consists of ~60,000 neurons that organize in a retinotopic fashion. In addition to the retina, these neurons are distributed in a network across four neuropils: lamina, medulla, lobula, and lobula plate, collectively termed the optic lobe (OL). The organization of these neurons endows flies with functions crucial to fitness and survival, such as color vision, motion detection, and spatial navigation. Previous research has detailed the anatomy of medullary neurons, but molecular mechanisms underlying their terminal morphology are not well defined. Medullary neurons—neurons that process inputs from photoreceptors in the retina and lamina— can be subcategorized into projection neurons termed transmedullary neurons and local interneurons. Transmedullary neurons process and project visual information through the medulla towards deeper OL structures. This anatomical feature implicates them in color vision and visual motion. Transmedullary neurons are classified into two types: Tm and TmY neurons. Tm neuronal axons target the lobula, while TmY neuronal axons bifurcate to target, in most cases, the lobula and lobula plate. Identifying the molecules and genes involved in Tm and TmY neuronal development remains an outstanding aim in neurobiology. In this study, we took advantage of published OL single-cell RNA sequencing (scRNA-seq) data from pupal data across development to delineated genes implicated in the development of Tm/TmY neuronal cell types. To that end, we employed a range of bioinformatic and AI-based approaches. In conjunction, we validated these findings using immunofluorescent staining experiments of RNAi x GAL4-driver lines to assess and compare neuronal morphological changes vis-à-vis GAL4-driver controls. Findings of this study may potentially aid in better understanding of the mechanisms underlying neuronal development and axonal pathfinding and bifurcation.

Date of Award	16 Dec 2024
Original language	American English
Supervisor	Aamna Alshehhi (Supervisor)