Temporal expression pattern of hLAMP‐1 and BMP‐2 during early heart development in the chick (542.4)

Abstract

The heart is the first organ to develop during embryogenesis in mammals and birds. Heart development requires coordinated activity of various factors, the disturbance of which can lead to congenital heart disease. The matrix protein hLAMP‐1 is expressed at Hamburger‐Hamilton stage 4 within the Hensen’s node and subsequently in the lateral mesoderm by stages 5‐6. At stage 7, its expression is enhanced within the left precardiac field. Later, by stages 15‐16, hLAMP‐1 expression has been shown in the atrioventricular (AV) canal and the outflow tract (OT). Also, BMP‐2 expression has been reported in comparable stages of chick embryo. To further elucidate the role of these two molecules in heart development, we examined their expression patterns during stages 8‐14 in chick embryos. In this study, we used antibodies specific to hLAMP‐1 or BMP‐2 to examine the expression pattern of both proteins. We detected hLAMP‐1 at the interface of the splanchnic mesoderm and endoderm at stages 8‐9 where the preendocardial cells delaminate from the precardiac mesoderm and migrate toward the endoderm. In contrast, BMP‐2 was not detected at stages 8‐9. After fusion of the bilateral heart field to form the heart tube at stage 10, both hLAMP‐1 and BMP‐2 expression is restricted to the arterial and venous poles of the heart tube. This expression pattern is maintained until stage 14. This pattern correlates with the time at which the cardiac progenitors being added to both ends of the heart tube. These findings point to a specific role for hLAMP‐1in heart development, possibly in formation of the endocardial tube and the role of BMP‐2 in elongation of the heart tube.