BT10 added at 24 hpf causes a defect in heart tube looping, similar to excess RA.

<p>Shown are representative embryos (n = 30) containing a <i>cmlc2:gfp</i> transgene were cultured in vehicle alone (control) or in the presence of ATRA or BT10 at the concentrations indicated, and as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010004#pone-0010004-g003" target="_blank">Fig. 3B</a>, beginning at 24 hpf. They were then photographed at 48 hpf in both brightfield and fluorescence, and the images overlayed to document the morphology of the heart tube (green). In control embryos the ventricle (V) is fully looped relative to the atrium (A), indicated by the dotted white line. In contrast, embryos cultured in the presence of ATRA or BT10 develop a relatively linear heart tube (at “low” or “high” concentrations), which is the major obvious morphological abnormality.