Correlation of gene expression profiles and thymocyte differentiation. The top panel illustrates the relative expression of genes (rows) differentially expressed during thymocyte cell differentiation in T-ALL samples (columns). Normalized expression values are indicated by red (levels greater than the mean) and blue (levels less than the mean). The bar at the bottom left shows the correlation between shift in color and differences in gene expression, from - 3 to + 3 standard deviations. LYL1⁺ samples are arrested at the earliest stages of T-cell differentiation, as demonstrated by expression of genes such as CD34, BCL2, and L-selectin. MLL-ENL⁺ cases combine the expression of this early developmental signature with the expression of genes associated with the TCR signaling machinery, such as LCK, CD3, and the TCRG and TCRD, suggesting commitment to the γδ lineage. By contrast, HOX11⁺ samples (characterized by the expression of CD10 and CD1 genes) show arrest at the early cortical stage of thymocyte development, while TAL1⁺ samples express the TCR signaling genes (eg, CD3 and LCK) together with TCRA and TCRB, demonstrating progression into the late cortical stage of thymocyte differentiation within the αβ lineage.