Fig. 4: Gap junction-mediated inter-neuronal communication regulates axon degeneration.

a Wildtype DRG neurons were cultured as two separate islands, allowing axonal contact to form. Axotomy was then performed at the indicated sites (denoted by dashed lines), and bright-field microscope images were captured at specified times. Scale bar: 10 μm. b The degeneration index of axons from the left island was quantified using ImageJ and plotted over time. c Wildtype or SARM1-KO DRG neurons were seeded. Following the axonal contacts, the cultures were pretreated with 5 μM mefloquine, and the axotomy were conducted. 24 h later, images were taken. d Degeneration indices of the axons from c, were calculated and plotted. e Experiments were performed as in c, but with infection with AAV-PHP.eB encoding Cx36-specific shRNA or scramble shRNA instead of mef treatment. Images were shown in Supplementary Fig. S3c. Degeneration indices were calculated and plotted. All experiments were repeated at least three times, and data are presented as means ± SDs (n = 3). Statistical significance was determined using Student’s t test following two-way ANOVA in b; using Student’s t test with Bonferroni correction (P < 0.0024, 0.05/21) in e and d (ns no significance; ***P < 0.001; ****P < 0.0001). f A proposed model illustrating the intercellular regulation of SARM1 activation was shown.