839A Poster - 13. Neural development and physiology
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Inês Lago-Baldaia ¹; Austin Seroka ²; Chintan Trivedi ¹; Maia Cooper ¹; Gareth Powell ¹; Stephen Wilson ¹; Sarah Ackerman ²; Vilaiwan Fernandes ¹

Affiliations:
1) Department of Cell and Developmental Biology, University College London, London, UK; 2) Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, USA

Keywords:
k. glia; p. single cell sequencing

Glia form a vital part of the nervous system and play pivotal roles in nervous system development and function. Nonetheless, they have been understudied and are poorly characterised. In Drosophila, glia are broadly classed as surface glia, cortex glia, ensheathing glia and astrocyte-like glia. Whether these categories can be further subdivided to define unique cell types is unclear. Recent advances in single cell transcriptomics have been invaluable for rapidly characterising and defining cell types in molecular terms. Here we used published single cell RNA sequencing (scRNA seq) datasets of the complex but spatially ordered Drosophila optic lobe to characterise glial diversity in molecular terms. The optic lobe contains ~14 morphologically distinct glia, making it an ideal system to study glial diversity. We first used the R Seurat package to integrate two independent glial scRNA seq datasets (Özel et al., 2020; Kurmangaliyev et al., 2020) for the adult optic lobe. This analysis generated 17 distinct clusters. We used in situ hybridisation chain reaction (HCR) and reporter lines to test in vivo expression of cluster markers and annotated 15 of the clusters. We determined that the majority of specialisation exists between the lamina neuropil and the rest of the optic lobe, with lamina-specific subtypes of cortex, astrocyte-like and ensheathing glia. While our bioinformatic analysis of non-lamina glia generated multiple clusters with either astrocyte-like, ensheathing or cortex glial molecular characteristics, these could not be explained by morphological or regional differences when we validated markers in vivo. We speculate that at least some of these clusters may correspond to distinct cell ‘states’ rather than ‘types’. On the other hand, our analysis also uncovered unexpected diversity within the chiasm glia. We have used annotated glial clusters from the adult dataset to identify glia from earlier developmental stages beginning with the third larval instar (Konstantinides et al., 2021). We have also compared glial transcriptomes of the embryonic central nervous system (unpublished) and adult optic lobe and found remarkable overlap in gene expression, suggesting a very strong maintenance of cell identity. Thus, by creating a Drosophila glial atlas, our work has begun to provide important insights into glial diversity and development.