Fig. 3

Sodium pump activity is required for extracellular matrix deposition around the cardiac cone. (A,B) Transverse microtome sections of 20S stage wild type and atp1a1^m883 embryos stained with methylene blue. In wild type embryos, sulfated proteoglycans are stained pink by methylene blue, allowing visualization of the abundant extracellular matrix present around the cardiomyocytes of the cardiac cone (*) at the 20S stage (A). In atp1a1^m883 mutants, the cardiac cone forms normally (*), but thickened extracellular matrix is completely absent (B). (C,D) Transverse vibratome sections of 20S stage wild type and atp1a1^m883 Tg(myl7:EGFP) embryos. Wild type embryos (C) have Fibronectin protein (green) surrounding the cardiomyocytes of the cardiac cone (blue), while atp1a1^m883 mutants (D) have extremely reduced Fibronectin protein deposition. (E,F) Dorsal views of fn1 expression in 20S stage wild type and atp1a1^m883 embryos. Fn1 is expressed in the cardiac region of wild type embryos (E), but is dramatically reduced in atp1a1^m883 mutants (F). (G,H) Lateral views of fn1 expression in 20S stage wild type and atp1a1^m883 embryos. Both wild type (G) and atp1a1^m883 mutant (H) embryos exhibit fn1 expression in posterior structures including the yolk extension and tail.