Table 1.
Components of axon guidance pathways involved in midline crossing, midline repulsion, commissure choice, and guidance of longitudinal axons in the Drosophila embryonic CNS.
| Protein | Role(s) | Pathway or cognate ligand/receptor | References |
|---|---|---|---|
| Ligands | Cognate receptor(s) | ||
| Amalgam (Ama) | midline crossing | Nrt | Liebl et al. [164] |
| Hedgehog (Hh) | midline crossing | Ptc | Ricolo et al. [66] |
| Netrin A (NetA) | midline crossing, longitudinal axon guidance | Fra, other (unknown) | Mitchell et al. [26], Harris et al. [25], Hiramoto et al. [160] |
| Netrin B (NetB) | midline crossing, longitudinal axon guidance | Fra, Dscam | Mitchell et al. [26], Harris et al. [25], Hiramoto et al. [160], Andrews et al. [45] |
| Sema-1a | lateral pathway formation, D/V patterning | PlexA | Yu et al. [76], Zlatic et al. [81] |
| Sema-2a | intermediate pathway formation, midline crossing, D/V patterning | PlexB, Sema-1a | Wu et al. [80], Hernandez-Fleming et al. [84], Zlatic et al. [81] |
| Sema-2b | intermediate pathway formation, midline crossing | PlexB, Sema-1a | Wu et al. [80], Hernandez-Fleming et al. [84], Zlatic et al. [81] |
| Slit | midline repulsion, longitudinal axon growth, longitudinal pathway formation | Robo1, Robo2, Robo3, Dscam | Kidd et al. [98], Brose et al. [87], Hiramoto et al. [161], Alavi et al. [56] |
| Turtle (Tutl) | midline crossing | unknown | Bodily et al [48], Al-Anzi et al [47] |
| Wnt5 | commissure choice | Drl | Yoshikawa et al [144] |
| Receptors | Cognate ligand(s) | ||
| Derailed (Drl) | commissure choice | Wnt5 | Callahan et al [145] |
| Down syndrome cell adhesion molecule (Dscam) | midline crossing, longitudinal axon growth | SlitN, NetB | Andrews et al. [45], Alavi et al. [56] |
| Flamingo (Fmi) | midline crossing | unknown | Organisti et al. [42] |
| Frazzled (Fra) | midline crossing, comm transcription, longitudinal axon guidance (Net redistribution) | NetA, NetB, other (unknown) | Kolodziej et al. [23], Yang et al. [36], Hiramoto et al. [160] |
| Neurotactin (Nrt) | midline crossing | Ama | Liebl et al. [164] |
| Patched (Ptc) | midline crossing | Hh | Ricolo et al. [66] |
| Plexin A (PlexA) | lateral pathway formation, D/V patterning | Sema-1a | Winberg et al. [77], Zlatic et al. [81] |
| Plexin B (PlexB) | intermediate pathway formation, D/V patterning | Sema-2a, Sema-2b | Ayoob et al. [79], Zlatic et al. [81] |
| Robo1 | midline repulsion, longitudinal axon growth | Slit | Kidd et al. [86], Hiramoto et al. [161], Alavi et al. [56] |
| Robo2 | midline repulsion, lateral pathway formation | Slit | Simpson et al. [99], Simpson et al. [102], Rajagopalan et al. [100], Rajagopalan et al. [103] |
| Robo3 | intermediate pathway formation | Slit | Simpson et al. [102], Rajagopalan et al. [103] |
| Sema-1a | midline crossing | Sema-2a, Sema-2b | Hernandez-Fleming et al. [84] |
| Downstream effectors and pathway regulators | Associated pathway(s) | ||
| Abelson tyrosine kinase (Abl) | midline crossing | Net-Fra, Slit-Robo, Ama-Nrt | Bashaw et al. [101], Forsthoefel et al. [33], O’Donnell et al. [35] |
| Beta-spectrin | midline repulsion | Slit-Robo | Garbe et al. [153] |
| Calmodulin (CaM) | midline crossing | unknown | Hsouna et al. [165] |
| Canoe (Cno) | midline repulsion | Slit-Robo | Slovakova et al. [132] |
| Commissureless (Comm) | midline crossing | Slit-Robo, Fra (Net-independent) | Kidd et al. [119], Keleman et al. [120,121], Gilestro et al. [122], Yang et al. [36] |
| Dally-like protein (Dlp) | midline repulsion | Slit-Robo | Johnson et al. [118] |
| Dreadlocks (Dock) | midline repulsion | Slit-Robo | Fan et al. [137] |
| Enabled (Ena) | midline crossing, midline repulsion | Net-Fra, Slit-Robo | Bashaw et al. [101], Forsthoefel et al. [33] |
| GEF64C | midline crossing | unknown | Bashaw et al. [166] |
| Kuzbanian (Kuz) | midline repulsion | Slit-Robo | Coleman et al. [135] |
| Mummy (Mmy) | midline repulsion | Slit-Robo | Manavalan et al. [114] |
| Mushroom body defect (Mud) | midline crossing | Frizzled | Cate et al. [43] |
| Myosin II | midline crossing | Net-Fra | Dorsten et al. [167] |
| Neurexin IV (Nrx IV) | midline repulsion | Slit-Robo | Banerjee et al. [168] |
| Pak | midline repulsion | Slit-Robo | Fan et al. [137] |
| Presenilin (Psn) | midline attraction | Fra (Net-independent) | Neuhaus-Follini et al. [37] |
| RhoGAPp190 | Sema2-Sema1a | Hernandez-Fleming et al. [84] | |
| Robo2 | midline crossing | Slit-Robo | Spitzweck et al. [44], Evans et al. [104,125] |
| RPTP10D | midline repulsion | Slit-Robo | Sun et al. [134] |
| RPTP69D | midline repulsion | Slit-Robo | Sun et al. [134] |
| Son of sevenless (Sos) | midline repulsion | Slit-Robo | Yang et al. [138] |
| Src42A | midline crossing, inhibition of midline crossing, commissure choice | Hh, Wnt5-Drl, other (unknown) | Ricolo et al. [66], Wouda et al [149], O’Donnell et al. [169] |
| Src64B | inhibition of midline crossing, commissure choice | Wnt5-Drl, unknown | Wouda et al [149], O’Donnell et al. [169] |
| Syndecan (Sdc) | midline crossing | Slit-Robo | Johnson et al. [118], Steigemann et al. [117] |
| Trio | midline crossing | Net-Fra, other (unknown) | Forsthoefel et al. [33] |
| Vilse/CrGAP | midline repulsion | Slit-Robo | Hu et al. [170], Lundstrom et al. [171] |