<P> Other transcription factors include Ikaros (B cell development), and Gfi1 (promotes Th2 development and inhibits Th1) or IRF8 (basophils and mast cells). Significantly, certain factors elicit different responses at different stages in the haematopoiesis . For example, CEBPα in neutrophil development or PU. 1 in monocytes and dendritic cell development . It is important to note that processes are not unidirectional: differentiated cells may regain attributes of progenitor cells . </P> <P> An example is PAX5 factor, which is important in B cell development and associated with lymphomas . Surprisingly, pax5 conditional knock out mice allowed peripheral mature B cells to de-differentiate to early bone marrow progenitors . These findings show that transcription factors act as caretakers of differentiation level and not only as initiators . </P> <P> Mutations in transcription factors are tightly connected to blood cancers, as acute myeloid leukaemia (AML) or acute lymphoblastic leukemia (ALL). For example, Ikaros is known to be regulator of numerous biological events . Mice with no Ikaros lack B cells, Natural killer and T cells . Ikaros has six zinc fingers domains, four are conserved DNA - binding domain and two are for dimerization . Very important finding is, that different zinc fingers are involved in binding to different place in DNA and this is the reason for pleiotropic effect of Ikaros and different involvement in cancer, but mainly are mutations associated with BCR - Abl patients and it is bad prognostic marker . </P> <P> For a decade now, the evidence is growing that HSC maturation follows a myeloid - based model instead of the' classical' schoolbook dichotomy model . In the latter model, the HSC first generates a common myeloid - erythroid progenitor (CMEP) and a common lymphoid progenitor (CLP). The CLP produces only T or B cells . The myeloid - based model postulates that HSCs first diverge into the CMEP and a common myelo - lymphoid progenitor (CMLP), which generates T and B cell progenitors through a bipotential myeloid - T progenitor and a myeloid - B progenitor stage . The main difference is that in this new model, all erythroid, T and B lineage branches retain the potential to generate myeloid cells (even after the segregation of T and B cell lineages). The model proposes the idea of erythroid, T and B cells as specialized types of a prototypic myeloid HSC . Read more in Kawamoto et al. 2010 . </P>

What type of red bone marrow cells can become any type of formed element