The expression of PLEXINA1 (PA1) and PLEXINA2 (PA2) differs between the thoracic and the lumbosacral levels of the spinal cord. Based on their expression pattern, none of the PlexinAs can be excluded as a binding partner for Sema6A . In addition to the dynamic changes over time, the expression of PLEXINA1 and PLEXINA2 differs strongly between thoracic and lumbosacral levels of the spinal cord. PLEXINA1 is strongly expressed in the ventral spinal cord at HH20, but remains to be expressed strongly only at the lumbosacral but not the thoracic level at HH24 and HH25. Even more pronounced are the changes of PLEXINA2 expression. At HH20, expression is detectable in lateral motoneurons only at the thoracic but not at the lumbosacral level of the spinal cord. This difference is even more pronounced at older stages. AS, antisense probe; TH, thoracic level; LS lumbosacral level. Arrowheads indicate expression of either PA1 or PA2; open arrowheads indicate no or very weak expression. Asterisks label the hind limb to indicate that sections were taken from the lumbosacral level of the spinal cord. Bar: 200 μm.