Figure 7

HDAC activity is required during LR development. (A) In this study, we found that early HDAC activity between stages 1-7 is important to proper set the pattern of expression of XNr-1 at stage 21. In addition, we also show that HDAC activity and Mad3 are important on the right side of the embryo to set XNr-1's expression and that Mad's biological activity is dependent on 5HT. Despite HDAC and Mad3 mRNAs present a symmetric pattern of expression, one theory is that because 5HT is asymmetrically distributed in the right blastomeres at stage 7 (red), 5HT binding on Mad3 (blue) may recruit HDAC activity (orange) to the intronic region of XNr-1 on the right of the embryo. HDAC activity, at early developmental stages, may be important to decrease the levels of acetylation of histone H3 and H4 on the intronic region of Nr1. (B) At stage 21, low levels of acetylation on histones (H3 and H4), set by early HDAC activity, would contribute to repress the expression of Nr1, that will be expressed only on the left side of the embryo (blue box). V-ventral; D-dorsal; R-right; L-left.