On rotation, torsion, lateralization, and handedness of the embryonic heart loop: new insights from a simulation model for the heart loop of chick embryos.

摘要: The internal organs of vertebrates show specific anatomical left-right asymmetries. embryonic heart is the first organ to develop such asymmetries during a process called dextro-looping. Thereby initially straight tube curves toward its original ventral side and resulting bend becomes displaced right embryo. Abnormal displacement loop left rare levo-looping. Descriptive studies have shown that lateralization driven by rotation around dorsal mesocardium. However, nothing was known on modes this process. To gain insight into subject, different were tested in simulation model for looping chick embryo heart. morphological phenotypes obtained compared with normal mirror-imaged hearts. following observations made. One, mesocardium has two consequences: first, lateral bending portion either (D-loop) or (L-loop) embryo, second, torsion cardiac helical structure wound clockwise (right-handed helix) counterclockwise (left-handed helix). presents as D-loop left-handed winding mirror image an L-loop right-handed winding. This conflicts use define D-loops right- L-loops structures. Two, dextro-looping might be almost exclusively rightward arterial pole loop. It complemented leftward venous subsequent phase looping. An inverse mode drive Three, configurations loops both can occur right-sided, median, left-sided positional variants. When viewed from front, all right-sided variants appear at end dextro- Their true asymmetric become fully apparent only after terms D- obviously do not chirality loops. their configuration should defined, too. implications these data respect molecular experimental are discussed. Anat Rec Part A 278A:481–492, 2004. © 2004 Wiley-Liss, Inc.