Stepwise wiring of the Drosophila olfactory map requires specific Plexin B levels

Li, Jiefu; Guajardo, Ricardo; Xu, Chuanyun; Wu, Bing; Li, Hongjie; Li, Tongchao; Luginbuhl, David J.; Xie, Xiaojun; Luo, Liqun

doi:10.7554/elife.39088

Cited by 17 publications

(35 citation statements)

References 63 publications

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“…Over the next 6 hours, these two axon bundles circumnavigate the antennal lobe (Figure 2A, left panel). Previously, we found that ORN axon fasciculation is mediated by PlexB-dependent axon-axon interactions (Joo et al, 2013; Li et al, 2018b). In PlexB loss-of-function mutants ( plexB –/– ), ORN axon defasciculation was observed in almost every antennal lobe with differing severity (Figure 2A, middle and right panels; Figure 2B).…”

Section: Resultsmentioning

confidence: 98%

“…We previously found that only a small fraction of endogenous PlexB proteins in brains are in a full-length form (Li et al, 2018b), suggesting that cleavage may play a role in tuning PlexB signaling. In the current study, we found that uncleavable PlexB produces more full-length proteins in vivo and possesses higher activity in axon fasciculation and trajectory choice than wild-type PlexB.…”

Section: Discussionmentioning

confidence: 99%

“…Flies were raised on standard cornmeal medium with a 12 hr/12 hr light cycle at 25°C (excepting experiments described in Figure 4, where 29°C was used for enhanced transgenic expression). The following lines were used: C155-GAL4 (pan-neuronal) (Lin and Goodman, 1994), Pebbled-GAL4 ( Peb-GAL4 , pan-ORN) (Sweeney et al, 2007), Or92a-rCD2 (VA2 ORNs) (Li et al, 2018b), UAS-mtdTomato (Potter et al, 2010), plexB KG00878 (PlexB mutant) (Bellen et al, 2004), as well as our newly generated UAS transgenes encoding PlexB variants: WT, ΔSema, GAP mut , ΔRac1, Rac1 mut , ΔRho1, Uncleav, Cleav Sec , and Cleav TMCyto . Complete genotypes of figure panels are described in Supplementary File 1.…”

Section: Methodsmentioning

confidence: 99%

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Functional divergence of Plexin B structural motifs in distinct steps ofDrosophilaolfactory circuit assembly

Guajardo

Luginbuhl

Han

et al. 2019

Preprint

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10Plexins exhibit multitudinous, evolutionarily conserved functions in the development of nervous 11 systems. However, how Plexins employ their diverse structural motifs in vivo to perform distinct 12 roles in the stepwise assembly of neural circuits is unclear. Here, we systematically mutagenized 13 65 fasciculation of olfactory receptor neurons (ORNs) and level-dependent tasks in ORN axon 66 trajectory choice and subsequent glomerular targeting (Li et al., 2018b). These findings reveal 67 that, within one system, PlexB regulates several fundamental cellular processes of neural wiring, 68 namely axon-axon interaction (fasciculation), axon guidance (trajectory choice), and synaptic 69 partner selection (glomerular targeting) ( Figure 1C). Given that this level dependence is only 70 observed in trajectory choice and glomerular targeting but not in fasciculation, it is likely that PlexB 71 signals in different ways when executing these distinct tasks. The multi-step development of the 72 fly olfactory map thus provides an excellent system for characterizing the structure-to-function 73 relationship of Plexin in vivo. 74Through systematic mutagenesis of PlexB structural motifs ( Figure 1A, B) and functional 75 interrogation in the context of fly olfactory circuit assembly ( Figure 1C), we report here the 76 differential engagement of PlexB structural motifs in distinct neurodevelopmental processes. 77From the global necessity of Sema domain to the overall expendability of GAP catalytic integrity, 78 3 as well as the involvement of GTPase-binding motifs in trajectory choice and glomerular targeting 79 but not in fasciculation, our findings link the categorical diversity of PlexB-dependent wiring 80 processes to its varied utilization of distinct signaling modules. Moreover, we identified a 81 regulatory role of PlexB cleavage in vivo and surprisingly found that the cleaved fragments can 82 functionally reconstitute for signaling. Collectively, our analysis reveals how a single molecule, 83PlexB, plays multitudinous roles in instructing cellular behaviors through the varied use of its 84 distinct structural motifs. 86 Results 87Systematic mutagenesis of PlexB structural motifs and in vivo functional assays 88To dissect the structure-to-function relationship of PlexB in the assembly of the fly olfactory map, 89we generated nine UAS transgenic lines carrying PlexB variants (described below; Figure 1B) 90 produced by site-directed mutagenesis. A V5 tag was added to the C-terminus of each variant. 91To obtain comparable expression levels, all transgenes were mutagenized from a single wild-type 92 UAS-PlexB construct (Joo et al., 2013) and integrated into the same genomic locus, ZH-attP-93 86Fb (Bischof et al., 2007). Their expression in Drosophila neurons in vivo was verified by 94Western blotting with an anti-V5 antibody (Figure 1-figure supplement 1). 95Sema Domain The extracellular Sema domain is a molecular signature of Plexins and 96 Semaphorins -the canonical Plexin ligands. It mediates binding between Plexins and ...

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Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Functional divergence of Plexin B structural motifs in distinct steps ofDrosophilaolfactory circuit assembly

Guajardo

Luginbuhl

Han

et al. 2019

Preprint

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show abstract

“…To identify molecules underlying Drosophila olfactory-circuit wiring specificity, we previously carried out genetic screens for ORN axon and PN dendrite targeting to the anteriorlateral side of the antennal lobe (11,16). While certain molecules broadly contribute to the precise wiring of many types of olfactory neurons (17,18), others have been found to be region-and even glomerulus-specific (9,11,16,(19)(20)(21). We reasoned that neurons in different locations in the antennal lobe might use a different set of wiring molecules for their circuit assembly.…”

Section: Resultsmentioning

confidence: 99%

Transsynaptic Fish-lips signaling prevents misconnections between nonsynaptic partner olfactory neurons

Xie

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Our understanding of the mechanisms of neural circuit assembly is far from complete. Identification of wiring molecules with novel mechanisms of action will provide insights into how complex and heterogeneous neural circuits assemble during development. In the Drosophila olfactory system, 50 classes of olfactory receptor neurons (ORNs) make precise synaptic connections with 50 classes of partner projection neurons (PNs). Here, we performed an RNA interference screen for cell surface molecules and identified the leucine-rich repeat–containing transmembrane protein known as Fish-lips (Fili) as a novel wiring molecule in the assembly of the Drosophila olfactory circuit. Fili contributes to the precise axon and dendrite targeting of a small subset of ORN and PN classes, respectively. Cell-type–specific expression and genetic analyses suggest that Fili sends a transsynaptic repulsive signal to neurites of nonpartner classes that prevents their targeting to inappropriate glomeruli in the antennal lobe.

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“…To identify new molecules underlying the Drosophila olfactory circuit wiring specificity, we have previously carried out genetic screens for ORN axon and PN dendrite targeting to the anterior-lateral side of the antennal lobe (18,19). While certain molecules broadly contribute to the precise wiring of many types of olfactory neurons (20,21), others have been found to be region-and even glomerulus-specific (6,7,11,13,18,22). We reasoned that neurons in different locations in the antennal lobe might use a different set of wiring molecules for their circuit assembly.…”

Section: A Novel Leucine-rich Repeat Protein Fish-lips Is Required mentioning

confidence: 99%

Trans-synaptic Fish-lips Signaling Prevents Misconnections between Non-synaptic Partner Olfactory Neurons

Xie

et al. 2019

Preprint

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Significance StatementIn the fruit fly olfactory system, 50 classes of olfactory receptor neurons (ORNs) make precise synaptic connections with 50 classes of corresponding projection neurons (PNs).Identification of wiring molecules in this circuit can provide insight into understanding neural circuit assembly. This paper reports the role of a transmembrane protein, Fish-lips (Fili), in forming specific connections in this circuit. We found that some ORN axons are repelled by Fili, which is present on dendrites of non-matching PN class, preventing them from targeting inappropriate glomeruli. Similarly, some PN dendrites are repelled by Fili expressed by non-matching ORN class for their correct targeting. Together, these results suggest that Fili mediates repulsion between axons and dendrites of non-synaptic partners to ensure precise wiring patterns.

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Stepwise wiring of the Drosophila olfactory map requires specific Plexin B levels

Cited by 17 publications

References 63 publications

Functional divergence of Plexin B structural motifs in distinct steps ofDrosophilaolfactory circuit assembly

Functional divergence of Plexin B structural motifs in distinct steps ofDrosophilaolfactory circuit assembly

Transsynaptic Fish-lips signaling prevents misconnections between nonsynaptic partner olfactory neurons

Trans-synaptic Fish-lips Signaling Prevents Misconnections between Non-synaptic Partner Olfactory Neurons

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