Fig. S3.

Histochemical stain for PPT1 activity in the spinal cord. PPT1 activity is depicted in blue, in transverse sections of the spinal cord that are not counterstained. There is diffuse staining in the gray matter of the wild-type spinal cord, which is not seen in the Ppt1^−/− tissue. Following intrathecal injection into Ppt1^−/− mice, diffuse blue staining is visible primarily in the gray matter. Intracranial injection into Ppt1^−/− mice results in no obvious blue staining in any part of the spinal cord. In contrast, combination intracranial and intrathecal (IC+IT) injection into Ppt1^−/− mice results in widespread intense staining across white matter and gray matter of the spinal cord. Dotted lines demarcate the borders between spinal gray and white matter.