Non-HSCs show striking similarity in ABC transporter expression profiles clearly distinct from HSCs. (A) TLDA expression data plot. The expression levels relative to GAPDH are shown in log-scale, plotted against the ABC transporter genes ranked in descending order by expression levels in 11 CD34+38- HSC samples. The expression profile of CD34+38- HSCs here serves as reference . The transporters are further divided into two groups (left and right) according to the detection frequency (whether above 10/11) in the HSCs. Count of detectable samples out of the 11 reference HSC samples is indicated on the top of the figure for each transporter. Transporters genes in the right part are ranked first by detection frequency and then by the expression level. The error bars show the standard deviations. In this plot the background threshold applied for unsupervised hierarchical clustering and PCA was not used. (B) Unsupervised hierarchical clustering allowing a separation between HSCs and non-HSCs based on ABC transporter expression profiles. Red and blue indicate high and low expression, respectively. (C) PCA of HSCs and non-HSCs based on ABC transporter expression profiles verified the resemblance among non-HSCs. This PCA mapping represents 68.1% of gene expression information. (D) Detection frequency of each transporter gene in HSCs, MSCs and USSCs. Note that some transporters are detected in all studied USSCs and MSCs but not in HSCs (e.g. ABCA4 and ABCC9).