Advanced Cardiac Morphogenesis Does Not Require Heart Tube Fusion
Shanru Li, Deying Zhou, Min Min Lu and Edward E. Morrisey
Science 10 September 2004: Vol. 305 no. 5690 pp. 1619-1622 doi: 10.1126/science.1098674
Fig. 3. Left-right asymmetry is retained in Foxp4 mutant embryos. (A) At E10.5, Foxp4 mutants clearly have two hearts bilateral to the ventral midline. R, right heart; L, left heart
The bilateral cardiac mesoderm migrates from the lateral region of the embryo to the ventral midline, where it fuses to form the primitive heart tube. It is generally accepted that migration and fusion are essential for subsequent stages of cardiac morphogenesis. We present evidence that, in Foxp4 mutant embryonic mice, each bilateral heart-forming region is capable of developing into a highly differentiated four-chambered mammalian heart in the absence of midline fusion. These data demonstrate that left-right chamber specification, cardiac looping, septation, cardiac myocyte differentiation, and endocardial cushion formation are preprogrammed in the precardiac mesoderm and do not require midline positional identity or heart tube fusion.