Figure 4

Co-expression analysis of sea urchin putative regulatory factors at the tip of the archenteron by double confocal fluorescent in situ hybridization (FISH). Relative disposition of FoxF (A-C, E, H and K) , FoxC (A, D and G) , FoxY (D-F and J) , FoxL1 (C) , Six1/2 (K and L) , SoxE (B, F, I and L) , Tbx6 (J) and SoxC (G-I) transcripts by double FISH in the late gastrula stage, 48 to 50 h. Every picture is a full projection of merged confocal stacks. FoxF is stained in red, FoxY and FoxL1 in green, FoxC in purple, Six1/2 and Tbx6 in magenta, SoxE in cyan and SoxC in yellow. Panel K is the only exception where Six1/2 is depicted in green. Full projection of split channels showing enlarged details of the tip of the archenteron are placed aside each picture. Yellow circles indicated by yellow arrowheads show cells co-expressing the analyzed genes. White arrows in G-I indicate the position of the presumptive anal and cardiac sphincters. The ectodermal staining in C corresponds to ciliary band expression of the FoxL1 gene. All the embryos are viewed in a lateral view along the animal top/vegetal down axis with the oral side on the left. Nuclei are labeled blue with 4',6-diamidino-2-phenylindole (DAPI).