Fig. 6. Expression of GtPax6A mRNA in regenerating G. tigrina, as detected by whole-mount in situ hybridization. (A-F) Dorsal view of fragments regenerating a head. Anterior is towards the top. (A) Activation of GtPax6A after 2 days of regeneration is detected as two hybridization spots located in the region close to the sectioned old nerve cords, where new cephalic ganglia are forming. (B) After 3 days of regeneration, GtPax6A-positive spots merge and follow the fibers emerging from the old nerve cords. (C-F) After 6, 8, 11 and 15 days of regeneration, GtPax6A expression becomes broader and follows the regenerating cephalic ganglia. (G) Dorsal view of a posterior regeneration. Six days after cutting, two labeling spots in the area corresponding to the regenerating nerve cords are observed. (H,I) Dorsal view of a lateral regeneration. An increased level of GtPax6A expression is observed where a cephalic ganglion is regenerating. A basal expression is detected in the corresponding non-regenerating ganglion. Scale bars: 0.5 mm.