Gravity adhesion assay to screen for adhesion mediators in human HSPCs. (A) Quantitative set analysis for gene expression showing significantly enriched gene sets, according to KEGG annotations, in adherent vs nonadherent CD34⁺ cells. The dotted horizontal line indicates the average log fold change for each gene set. (B) Overview of the screening procedure where the gravity adhesion assay was used to isolate adherent and nonadherent human HSPC populations. (C) Ratios of normalized shRNA counts in nonadherent vs adherent cell fractions for all shRNAs detected in the primary screen. (D) Steps to identify candidate genes. The bottom diagram shows all genes for which 2 or more shRNAs scored positively in the validation assays (ie, reduced adhesion). ITGβ1, integrin β1.