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 (alpha1beta1gamma1) 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 beta1 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.
2008 Wiley-Liss, Inc.