Fig. 4. Attraction of tangentially migrating cells to netrin 1. (A-D) Co-cultures of rhodamine-labeled strips with aggregates (blue outline) of HEK cells expressing netrin 1 (A,B) and the mock control cells (C,D). The boundary between the neocortex and the GE is stained with anti-reticulon 1 antibody (green in A,C). Many rhodamine-labeled cells migrate toward the netrin 1-secreting cells, but not the control cells. (E) The Dcc mutant strip labeled with rhodamine and cultured for 2 days. The cells migrate normally to the LOT area. (F) Co-culture of the Dcc mutant strip with a cell aggregate expressing netrin 1 (blue outline). The cells are not attracted to the aggregate. (G) The Dcc mutant strip cultured with 10 µM cyclopamine. The migration of rhodamine-labeled cells is not affected by the treatment. (H) The percentage of dye-labeled cells that reside in the halves of strips proximal to cell aggregates. The average values and the standard errors (thin horizontal bars) are calculated from the wild-type strips cultured with mock-transfected cells (upper) and netrin 1-expressing cells (middle) and Dcc homozygous mutant strips culture with netrin 1-expressing cells (bottom). The numbers of strips used for quantification are indicated by n in the parentheses. Scale bars: 500 µm.