Fig. 3.

Netrins are expressed at the fusion plate in chicks. (A-C) In situ hybridizations for chicken cNtn2 on E5 (A), E6 (B) and E6.25 (C) sections through the emerging posterior canal. cNtn2 is expressed in the presumptive fusion plate from an early age (A, E5 shown, n=3 animals), and this expression pattern is maintained during (B, n=5 animals) and after (C, n=3 animals) fusion in the canal rim. (D,D′) Double fluorescent in situ hybridization for cNtn1 (D′) and cNtn2 (D) confirmed co-expression in the center of the pouch (arrows) before fusion has begun (E6-6.25, n=3 animals). A merged image is shown in D″. cNtn1 is present at lower levels than cNtn2. Scale bars: 50 µm.