MINIREVIEW The EBF/Olf/Collier Family of Transcription Factors: Regulators of Differentiation in Cells Originating from All Three Embryonal Germ Layers

One major mechanism for achieving cell-type-specific func-tions in somatic cells is the differential usage of stage- and tissue-specific genes. This is in large part regulated by tran-scription factors that interact directly with DNA elements con-trolling transcription of these genes. Several groups of tran-scription factors with key roles in cellular differentiation and function have been characterized, and the list of transactivat-ing proteins with crucial functions in vivo is continuously growing. One group of evolutionarily conserved proteins with defined roles in a large variety of species are the basic helix-loop-helix (bHLH) proteins (42, 44). These factors are in-volved in a large number of differentiation processes, including such diverse events as sex determination in Drosophila mela-nogaster and B-lymphopoiesis in mice (9, 15, 38, 42, 48). In 1993, two independent reports presented a novel type of HL