Dr. Jaksic Lab: Samuel Bourgeat - Searching for the genetic basis of natural variation of brain morphology in Drosophila melanogaster

Hybrid - By invitation only

From genomics to connectomics, the fruit fly has helped us build better and more precise comprehension of the functioning of the nervous system.
However, our knowledge of the genetic basis of natural variation in brain size and morphology is still incomplete, while it can help us shed light onto the genetic architecture of this trait and the evolutionary potential of the behaviours it may affect.
Quantifying subtle natural genetic diversity of brain morphology is challenging because brain morphology is malleable to not only genetic, but also developmental and environmental factors that are difficult to control. To overcome this issue, we developed a high-throughput and sensitive imaging method to quantify brain morphology of diverse fly lines from the Drosophila Genetic Reference Panel (DGRP) reared in tightly controlled environmental conditions.
In our method, we use a micro-computed tomography scanner with a multiple-sample-holder system to image up to 24 whole fly heads per day at a 3 micron/pixel resolution. To unbiasedly capture the full range of morphological diversity of fly brains we first reconstruct a 3D model of heads and manually segment the brains for a range of diverse DGRP lines. This segmentation data is used to train a convolutional neural network which is then used to automatically and unbiasedly segment brains from all available DGRP lines. We then extract the volumes as well as morphology of the brains using topological data analysis. By using a topological variable called persistence entropy we can summarise, cluster and classify topological features of brains based on their morphological similarities. Our quantification method could capture genetic variation underlying brain's shape and size. The mapping of those phenotypic variations onto the variation in DNA sequence of all DGRP lines will enable us to identify and characterize the genetic variation influencing brain morphology and size.