Establishing A-P polarity in the embryonic heart tube: a conserved function of Hox genes in Drosophila and vertebrates?

The correct establishment of anterior-posterior (A-P) polarity in the vertebrate embryonic heart tube during embryogenesis is crucial for the proper morphogenesis of the mature heart, but the molecular details of this process are poorly understood. Elucidation of this process should be facilitated by findings of recent studies regarding the establishment of A-P polarity in the Drosophila equivalent of the heart, the dorsal vessel. These studies have demonstrated that members of the Drosophila homeotic selector (Hox) gene family play important roles in this process. It appears that the homeotic gene abdominal-A is a key determinant of A-P polarity in the dorsal vessel, due to its function in specifying the posterior chamber of the dorsal vessel, and that other homeotic genes may function in specifying more anterior portions of the dorsal vessel. Another role of certain homeotic genes is to determine the extent of the cardiogenic region within the early embryonic mesoderm. These results suggest that the Hox genes may also play some role in the positioning of the embryonic heart field and the determination of A-P polarity in the vertebrate embryonic heart tube.