Laminin peptide YIGSR and its receptor regulate sensory axonal response to the chemoattractive guidance cue in the chick embryo

During early development, centrally projecting dorsal root ganglion (DRG) neurons extend their axons toward the dorsal spinal cord. We previously reported the involvement of dorsal spinal cord-derived chemoattraction in this projection (Masuda et al. [2007] Neuroreport 18:1645-1649). However, the molecular nature of this attraction is not clear. Here we show that laminin-1 (α1β1γ1) is expressed strongly along the pathway of DRG axons and that its 67-kDa receptor (67LR) is present on DRG cells. This evidence suggests that laminin-1-67LR signaling may be involved in DRG axonal guidance. By employing culture assays, we show that laminin-1 or the YIGSR peptide, a soluble peptide of the laminin β1 chain, promotes the DRG axonal response to dorsal spinal cord-derived chemoattraction. By using a function-blocking antibody against 67LR, we show that the anti-67LR antibody blocks the modulation of DRG axonal response by the YIGSR peptide in vitro. Furthermore, the in ovo injection of the anti-67LR antibody inhibits the DRG axonal growth toward the dorsal spinal cord. These results provide evidence that the YIGSR peptide promotes dorsal spinal cord-derived chemoattraction via 67LR to contribute to the formation of the initial trajectories of developing DRG axons.