Figure 3.

Endothelial differentiation of CD34⁺ cells alters the expression pattern of clock genes. A: Lin⁻CD34^highCD45^mid cells were cultured in hematopoietic progenitor–supporting (stem cell maintenance media [black lines]) or endothelial differentiation conditions (differentiation [red lines]) and harvested every 4 h to analyze mRNA expression of clock genes (Clock, Bmal, Per1, Per2, Cry1, and Cry2). Each data point represents the experimentally observed mRNA expressions for clock genes, while the solid line shows simultaneous data set fitted for the cosine model (see research design and methods) over 96 h. The cosine model was used to predict the biological rhythm of individual clock genes. Clock constituting “positive arm” of circadian cycle showed suppressed expression with endothelial differentiation, while Bmal1, Per2, and Cry2 exhibited rapid oscillatory pattern in endothelial supporting conditions. There was no significant change in the expression pattern for Per1 and Cry1. B: Bar chart showing relative mRNA expression at day 4 for individual clock gene expression. n = 4.