1) The Drosophila central brain is comprised of approximately 100 paired neuronal lineages, with each lineage derived from an embryonic progenitor cell (neuroblast) that produces neurons and glia. 2) Each lineage forms a cohesive bundle of axons that interconnect specific brain compartments. The primary neurons are produced during embryogenesis and form the larval brain circuitry, while secondary neurons produced during larval stages do not differentiate until pupal stages. 3) The researchers used genetic tools to label individual lineages and map their axonal projections throughout development. They identified over 80 distinct lineages and reconstructed their tracts through metamorphosis to develop a digital atlas of Drosophila brain organization by lineage.

1. Darren C.C. Wong, Jennifer K. Lovick, Kathy Ngo, Jaison J.
Omoto, Wichanee Borisuthirattana, Joseph D Nguyen, Volker
Hartenstein
MCDB, UCLA, Los Angeles, CA
April 6th 2013
“54th Annual Drosophila Research Conference”
“3D mapping of the adult
Drosophila brain: Towards a
comprehensive digital atlas of
secondary lineages”

2. Drosophila Brain Lineages
• Drosophila central brain is comprised of
approximately 100 paired lineages (focus on
SPG, but not on MB lineages)
40,000/hem 10-15,000/hem
Optic lobe
SPG
SOG
Optic lobe

3. What is a lineage?
• Group of neurons
and glia derived from
one embryonic
progenitor called
neuroblast

4. • 2 proliferative phases
• Embryonic:
– Neuroblast delaminate and divide
– One neuroblast produces 10-20 primary
neurons
– Neurons of one lineage emits axons that
fasciculate form primary axon tracts (PATs)
– Primary neurons differentiate in the late
embryo and generate larval brain circuitry
• Larval period:
– Neuroblast reinitiate mitosis
– One neuroblast produces ~100 secondary
neurons
– Axons of secondary neurons form cohesive
bundles (SATs)
– Most SATs follow PAT across the neuropile
– Secondary neurons generally do not further
differentiate until pupal stages

5. Lineages are visualized as MARCM clones

7. Gene Projection
envelope
Transcription Factor Axon Tract/
Terminal Arborization

9. Scaffolding of compartments
Proper development of the calyx requires a “scaffolding lineage.”
Control HU
-treated
BP104
NCAD
(Serway et al., 2009; Lovick et al.)

10. Neuropile Compartment Development
Loss of DALv2 leads to a loss of the ellipsoid body
compartment.
MOCK HU 5mg/ml HUPer>GFP HU 20-24hrs DALv2 in Adult
(Lovick et al.)

11. • Genetic and developmental unit
• Modules of brain organization
• Form structural units-axons from one
lineage form a cohesive fascicle that
interconnects specific domains
(compartments)
To sum up with regards to lineages

12. A Lineage-Based Approach of Brain Analysis

13. L3 brain mapping

14. Every single lineage has a defined SAT
Markers
BP104 (neuroglian)
BP106 (neurotactin)
Digitally extracted and models made

15. Clone generation

17. 56 unique 56 56
30 pairs 8 pairs same
envelope
16
7 pairs different
envelope
14
4 quartet 3 4
Clones Lineages
Raw Data analyzed 840 clones in 630 brains
Could identify 81 different classes

18. Assigning clones to lineages

19. Reconstruction of Lineage-Associated
Tracts Through Metamorphosis

20. Assigning Clones to Tracts
BP104 staining of adult stage

21. Representation of clones
• Show 1 paper of figure 2….fig 3 or 6
• Tools to describe projection envelopes

22. Future directions
• Register clones to one model brain to study
overlap (delineate sub-compartments)
• Link between gene and phenotype-decipher
the transcription factor code for neuroblast

23. Effect of expression of transcription factors on axonal arborization:
BAla1
BAla2
2 lineages

24. Acknowledgements
• NIH R01 NS29357-15
• MCDB, UCLA
• Volker Hartenstein
• Jennifer K Lovick
• Kathy Ngo
• Wichanee Borisuthirattana
• Joseph Duy Nguyen
• Kevin Wang
• Jaison J Omoto
• Patrick Aghajanian
• Amelia Hartenstein