Myosin-based contraction is not necessary for cardiac c-looping in the chick embryo
- 167 Downloads
During the initial phase of cardiac looping, known as c-looping, the heart bends and twists into a c-shaped tube with the convex outer curvature normally directed toward the right side of the embryo. Despite intensive study for more than 80 years, the biophysical mechanisms that drive and regulate looping remain poorly understood, although some investigators have speculated that differential cytoskeletal contraction supplies the driving force for c-looping. The purpose of this investigation was to test this hypothesis. To inhibit contraction, embryonic chick hearts at stages 10–12 (10–16 somites, 33–48 h) were exposed to the myosin inhibitors 2,3-butanedione monoxime (BDM), ML-7, Y-27632, and blebbistatin. Experiments were conducted in both whole embryo culture and, to focus on bending alone, isolated heart culture. Measurements of heart stiffness and phosphorylation of the myosin regulatory light chains showed that BDM, Y-27632, and blebbistatin significantly reduced myocardial contractility, while ML-7 had a lesser effect. None of these drugs significantly affected looping during the studied stages. These results suggest that active contraction is not required for normal c-looping of the embryonic chick heart between stages 10 and 12.
KeywordsHeart development BDM Y-27632 Blebbistatin Cytoskeletal contraction
The authors wish to thank William B. McConnaughey, Kenneth M. Pryse, and Tetsuro Wakatsuki for their help and advice with the indentation experiments. This work was supported by NIH grant R01 HL64347 (LAT).
- Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002) Molecular biology of the cell. Garland, New YorkGoogle Scholar
- Butler JK (1952) An experimental analysis of cardiac loop formation in the chick. MS Thesis, University of TexasGoogle Scholar
- de la Cruz MV, Sanchez-Gomez C (1998) Straight heart tube. Primitive cardiac cavities vs. primitive cardiac segments. In: de la Cruz MV, Markwald RR (eds) Living morphogenesis of the heart. Birkhauser, Boston, pp 85–98Google Scholar
- Manasek FJ (1976) Heart development: interactions involved in cardiac morphogenesis. In: Poste G, Nicholson GL (eds) Cell surface in animal embryogenesis and development. North-Holland, New York, pp 545–598Google Scholar