title: Automatic Segmentation of Drosophila Neural Compartments Using GAL4 Expression Data Reveals Novel Visual Pathways.
abstract: Identifying distinct anatomical structures within the brain and developing genetic tools to target them are fundamental steps for understanding brain function. We hypothesize that enhancer expression patterns can be used to automatically identify functional units such as neuropils and fiber tracts. We used two recent, genome-scale Drosophila GAL4 libraries and associated confocal image datasets to segment large brain regions into smaller subvolumes. Our results (available at https://strawlab.org/braincode) support this hypothesis because regions with well-known anatomy, namely the antennal lobes and central complex, were automatically segmented into familiar compartments. The basis for the structural assignment is clustering of voxels based on patterns of enhancer expression. These initial clusters are agglomerated to make hierarchical predictions of structure. We applied the algorithm to central brain regions receiving input from the optic lobes. Based on the automated segmentation and manual validation, we can identify and provide promising driver lines for 11 previously identified and 14 novel types of visual projection neurons and their associated optic glomeruli. The same strategy can be used in other brain regions and likely other species, including vertebrates.
authors.affiliation: Research Institute of Molecular Pathology (IMP), Vienna Bio-Center, Doktor-Bohr-Gasse 7, 1030 Vienna, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Panser
authors.affiliation: Research Institute of Molecular Pathology (IMP), Vienna Bio-Center, Doktor-Bohr-Gasse 7, 1030 Vienna, Austria.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Tirian
authors.affiliation: VRVis Zentrum für Virtual Reality und Visualisierung Forschungs, Donau-City-Strasse 1, 1220 Vienna, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Schulze
authors.affiliation: Research Institute of Molecular Pathology (IMP), Vienna Bio-Center, Doktor-Bohr-Gasse 7, 1030 Vienna, Austria.
authors.forename: Santiago
authors.initials: S
authors.lastname: Villalba
authors.affiliation: Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK.
authors.forename: Gregory S X E
authors.initials: GSXE
authors.lastname: Jefferis
authors.affiliation: VRVis Zentrum für Virtual Reality und Visualisierung Forschungs, Donau-City-Strasse 1, 1220 Vienna, Austria.
authors.forename: Katja
authors.initials: K
authors.lastname: Bühler
authors.affiliation: Research Institute of Molecular Pathology (IMP), Vienna Bio-Center, Doktor-Bohr-Gasse 7, 1030 Vienna, Austria; Department of Neurobiology and Behavior, Institute of Biology I, University of Freiburg, Hauptstrasse 1, 79104 Freiburg, Germany. Electronic address: andrew.straw@biologie.uni-freiburg.de.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Straw
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics; D009474:Neurons / Q000502:physiology*; D009899:Optic Lobe, Nonmammalian / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D014795:Visual Pathways / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; C557617:GAL4 protein, Drosophila; D014157:Transcription Factors
keywords: clustering; enhancers; neuroanatomy; vision