Mono-allelic deletions, point mutations and translocations of one or more of these transcription factors often occur in pediatric B-ALL.9, 22 Reduced levels of factors encoded by Ikzf1, Runx1, Tcf3, Pax5 and Ebf1 may each be important individually for predisposing EB mice to tumor development, while concerted loss of these factors, particularly in combination, would potently induce loss of differentiation. This evidence concerns the gene PAX5 and epidermolysis bullosa.