From the bottom of the heart: anteroposterior decisions in cardiac muscle differentiation.

Recently, studies on specification of axes in the developing embryo have focused on the heart, which is the first functional organ to form and probably responds to common cues controlling positional information in surrounding tissues. The early differentiation of heart cells affords an opportunity to link the acquisition of regional identity with the signals underlying terminal differentiation. In the past year, a wealth of information on these signals has emerged, elucidating the general pathways controlling body axes in the context of the developing heart.