The rostro-caudal position of cardiac myocytes affect their fate

During chick embryogenesis, cells destined to form cardiac myocytes are loc ated within the primitive streak at stage 3 in the same relative anterior-p osterior distribution as in the prelooped heart. The most rostral cells con tribute to the extreme anterior pole of the heart, the bulbus cordis, and t he most caudal to the extreme posterior end, the sinoatrial region. After g astrulation, these cells commit to the myocyte lineage and, retaining their relative positions, migrate to the anterior lateral plate. From stages 5 t o 10 they diversify into atrial and ventricular myocytes, with the former l ocated posteriorly and the latter, anteriorly. To determine the effect of a change in the rostro-caudal position of these cells on their diversificati on, anterior lateral plate mesoderm and the underlying endoderm were cut an d rotated 180 degrees along the longitudinal axis, at stages 4-8, The subse quent diversification of these precursor cells into atrial and ventricular myocytes was examined using lineage-specific markers. Our results showed th at altering location along the longitudinal axis through stage 6 changed th e normal fate of a precursor cell. The orientation of the overlying ectoder m did not alter normal morphogenesis or determination of fate. (C) 2000 Wil ey-Liss, Inc.