Fig. 8

NAD+ supplementation, but not paxillin overexpression, improves motility of dystrophic zebrafish.

(A-F) Individual panels from videos of escape responses after a touch stimulus at 2 dpf; time in milliseconds is denoted on panels. The outer circle is 10 mm in diameter. Red arrowheads point to the embryo′s location. (A) Control embryo. (B) dag1 morphant. (C) NAD+-supplemented dag1 morphant. (D) itga7 morphant. (E) NAD+-supplemented itga7 morphant. (F) dag1 MOs;Tg:paxillin:GFP embryo. (G) Average escape response times of 2 dpf dystrophic zebrafish after exogenous NAD+ treatment or overexpression of paxillin. Exogenous NAD+ or Emergen-C (not shown) significantly reduced the escape times of both dag1 and itga7 morphants. Overexpression of paxillin, however, did not reduce escape times of dag1 or itga7 morphants. *p<0.05; **p<0.01; ***p<0.001; N.S., not significant. (H) Model of cell adhesion at the MTJ. Our data show that laminin polymerization is necessary and sufficient for muscle fiber homeostasis and that NAD+ and paxillin increase laminin polymerization. We find that Dag1 and Nrk2b are required for paxillin localization to the MTJ. We hypothesize that NAD+, through mediating paxillin concentration at MTJs, invokes “inside-out” signaling through laminin receptors that results in increased laminin polymerization.