Drosophila olfactory local interneurons (LNs) in the antennal lobe are highly diverse and variable. How and when distinct types of LNs emerge, differentiate, and integrate into the olfactory circuit is unknown. Through systematic developmental analyses, we found that LNs are recruited to the adult olfactory circuit in three groups. Group 1 LNs are residual larval LNs. Group 2 are adult-specific LNs that emerge before cognate sensory and projection neurons establish synaptic specificity, and Group 3 LNs emerge after synaptic specificity is established. Group 1 larval LNs are selectively reintegrated into the adult circuit through pruning and re-extension of processes to distinct regions of the antennal lobe, while others die during metamorphosis. Precise temporal control of this pruning and cell death shapes the global organization of the adult antennal lobe. Our findings provide a road map to understand how LNs develop and contribute to constructing the olfactory circuit.
Bibliographical noteFunding Information:
We thank Dr. Thomas Clandinin for sharing the InSITE GAL4 lines that were established in his lab. The GAL4 screen was initiated in Dr. Liqun Luo’s lab by Y.H.C. Y.H.C. thanks Dr. Luo for his generosity to allow us continue this project. We thank Drs. Kristin Scott and Christoph Scheper for sharing the expression information for a subset of InSITE GAL4 lines, Shih-Yaw Yang for helping with the preliminarily characterizing developmental GAL4 expressions, Christopher Potter for sharing the nSybQF2 fly before publication, Liqun Luo, Richard Benton, Julie Simpson, Henry Y. Sun, Chi-Kuang Yao, and Guang-Chao Chen for sharing fly strains and antibodies. We thank Drs. Liqun Luo, Marcus Calkins and Mr. Kai Hsiang Chang for feedback. We thank Kyoto, Bloomington, and NIG-FLY stock centers for fly stains, and Developmental Studies Hybridoma Bank for antibodies. This work was supported by a NSC undergraduate research fellowship (101-2815-C-001-024-B) to N.F.L, MOST grants (101-2311-B-001-016-MY3 and 104-2311-B-001-033-MY3) to Y.H.C, and a Career Development Award (AS-102-CDA-L02) to Y.H.C.