We used gene expression microarrays to identify genes whose expression was influenced differently by TNFa in Fancc-deficient mice compared to wild type (WT) mice. To identify genes whose expression was directly or indirectly influenced by Fancc, we looked in particular for genes either suppressed or induced by TNF in WT cells that were not affected by TNF in Fancc-deficient cells. Enriched populations of KSL cells (marrow mononuclear cells sorted for the c-Kit+/Sca-1+/Lineage (Lin)- fraction from WT and Fancc-deficient mice were exposed for 24 hours in vitro to either hematopoietic growth factors alone (IL-6, IL-11, Flt3L, and SCF) or to those factors plus TNFa (10 ng/ml) after which RNA was prepared and hybridized to Affymetrix microarrays (MOE430 2.0).