Figure 3. Identification of gene expression clusters during human embryo development.

Significant quadratic regressions were classified into four different clusters according to the expression trend versus time. The majority of genes included in Cluster 1 (n=29) were expressed in the zygote stage but decreased in expression by at least twofold between the start and the final time. Cluster 2 (n=4) was composed of genes that showed relatively constant expression as defined by an increase or decrease in expression of less than 1 point. Cluster 3 (n=10) consisted of genes with an expression value lower than 2 at time zero and at least a twofold difference at the final time point. Lastly, Cluster 4 (n=12) comprised those genes with expression higher than 2 at time zero, and twofold or more at the last time point. The most significant regressions from each gene cluster were selected by ANOVA test with P<1 × 10⁻⁶ and fold change>10 for Clusters 1, 3, 4 and P<0.05 for Cluster 2. Each expression data point corresponds to the mean value obtained from three technical replicates. A baseline of C_t=28 was used to obtained the showed expression values.