Figure 4.

Dominant-negative forms of DLK enhance the long-term survival of SN DA neurons after intrastriatal 6OHDA. A, At 3 weeks after intranigral injection of AAV, mice received intrastriatal 6OHDA. At 28 d after 6OHDA, mice were killed and processed for immunoperoxidase staining of TH within SN neurons and axons. At this postlesion time point, there is no suppression of TH phenotype, and SN DA neuron counts determined by TH staining are approximately equal to those determined by Fluorogold retrograde labeling (Sauer and Oertel, 1994). AAV DN-DLK(K152A) increased the number of surviving DA neurons to 55% of the contralateral control (CON) noninjected side, which represents an 80% increase over the number of surviving neurons in the AAV GFP group [p = 0.005, ANOVA; n = 8 and 7, AAV GFP and AAV DN-DLK(K152A), respectively]. B, In a similar experiment, AAV DLK-LZ increased the number of surviving DA neurons to 75% of the contralateral control, which represents a 153% increase over the number of surviving neurons in the AAV GFP group (p < 0.001, ANOVA; n = 6 and 8 AAV GFP and AAV DN-DLK-LZ, respectively). C, A representative set of sections stained for TH (brown) and Nissl-counterstained after injection of AAVs and unilateral intrastriatal 6OHDA. At 28 d after 6OHDA, a mouse given AAV GFP shows very few surviving DA neurons in the SNpc. A mouse given AAV DN-DLK-LZ shows substantial preservation of DA neurons. D, AAV DN-DLZ-LZ preserves DA neuron size after 6OHDA. In the AAV GFP control condition, there is a 24% loss of cross-sectional area (p < 0.001, ANOVA; n = 100 neurons), whereas in the AAV DN-DLK-LZ condition there is only a 7% trend (p = 0.4, NS). Error bars indicate SEM. E, Neither AAV DN-DLK(K152A) nor AAV DN-DLK-LZ protected dopaminergic axons. Representative TH-immunostained striatal sections demonstrate that, for both GFP (top) and AAV DLK-LZ (bottom), there is near-complete loss of striatal TH staining after intrastriatal 6OHDA. Similar results were observed with AAV DN-DLK(K152A) (data not shown).