Fig. 4: Post-injury changes in pMN connexin proteins abundance affect the electrical and dye coupling.

a Whole-mount image shows the expression of Cx35/36 (green) in the pMNs (asterisks). The expression of Cx35/36 (green) in proximal neurites of the retrogradely traced pMN (magenta; n = 11 zebrafish). b Representative immunofluorescent images show the Cx35/36 expression in traced pMN somata in different experimental conditions. c The Cx35/36 normalized intensity and the number of aggregations (puncta) in the pMN somata. d Ex vivo setup that allows dual recordings between pMNs (asterisks). The white dashed line indicates the recorded pMNs. e Sample average traces (∼40 sweeps) show the bidirectional electrical coupling between pMNs. f Mean coupling coefficient (CC) between two pMNs. g Representative confocal images showing the dye coupling (NB⁺-cells, magenta) after intracellular loading of a single pMN (white dashed line) with NB in control (n = 13 zebrafish), 3 dpi (n = 16 zebrafish) and 7 dpi (n = 6 zebrafish). Arrowheads indicate the NB⁺ neurons. h Representative spatial distribution of dye-coupled neurons (colored filled circles) from a pMN (centered asterisk) in the adult zebrafish spinal cord (segment 14). Data are presented as a group of 3 animals per experimental condition. i Proximity analysis of the dye-coupled cells (NB⁺). j Quantification of the number and soma size of the dye-coupled neurons (NB⁺). k Ex vivo setup for performing pair recordings between a pMN and other spinal neurons (unknown) to define the electrical coupling probability (connected/not-connected). Image showing a pair of connected neurons (pMN and spinal neuron) and the definition of their Euclidean distance. The white dashed line indicates the recorded neurons. l Analysis of the distance and probability of electrical connectivity (%) from a pMN. m Coupling coefficient (in %) analysis. Asterisks indicate the pMN cell bodies. μ population mean, CC coupling coefficient, Cx connexin, dpi days post-injury, pMN primary motoneuron, SCI spinal cord injury. Data are presented as violin plots and box plots showing the median with 25/75 percentile (box and line) and minimum–maximum (whiskers). *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, not significant. For detailed statistics, see Supplementary Table 1. Source data are provided as a Source Data file.