SC	spinal cord
DRG	dorsal root ganglia
Cx	connexin
CNS	central nervous system
Shh	Sonic hedgehog
BMPs	bone morphogenetic proteins
INL	inner layer
DIL	dorsal part of the intermediate layer
VIL	ventral part of the intermediate layer
RP	roof plate
FP	floor plate
PGP9.5	protein gene product 9.5
PM	pia mater
AM	arachnoid
DM	dura mater
GFAP	glial fibrillary acidic protein
ATP	adenosine triphosphate
AP	alar plate
BP	basal plate
TEM	transmission electron microscopy
PBS	phosphate buffer saline
sg	sympathetic ganglion