Western blot analysis
Lumbar DRG from E16.5 embryos were isolated, mechanically disrupted, homogenized using glass beads (Sigma), and lysed in standard lysis buffer supplemented with protease and phosphatase inhibitors as described [47]. Protein extracts were resolved by SDS-PAGE, and immunoblotting was performed using antibodies against Akt, p-Akt (Ser473), CREB, p-CREB (Ser133), Bax, Bcl-xl (Cell Signaling Technology, Beverly, Massachusetts, United States), and Bcl2 (BD Pharmingen, San Diego, California, United States). For quantification, films (X-OMAT AR, Eastman Kodak, Rochester, New York, United States) were scanned and densitometry was performed using IMAGEQUANT 5.2 (Molecular Dynamics, Amersham, Uppsala, Sweden).