Adhesion molecule profile of E14.5 AA4.1⁺FL cells. Total RNA was isolated from either whole FLs or AA4.1⁺ enriched cells from E14.5 WT andPU.1^−/− embryos. RNA expression was examined using primers specific for integrins CD11b, ₄, ₅, β₁, β₂, and β₇. Expression of the house keeping gene HPRT was used to normalize variation between RNA samples. Results are displayed as either ethidium bromide-stained PCR products or, to enhance sensensitivity of the expression analysis, the RT-PCR products were further analyzed by Southern blot hybridization using cDNA fragments as hybridization probes.