Similarly, in leukemias, NF1 loss in patient (Side et al., 1997) or murine (Bollag et al., 1996; Hiatt et al., 2001; Zhang et al., 1998) hematopoietic precursors, results in increased RAS-MEK/ERK pathway activation (Kim et al., 2007; Zhang et al., 1998). Here, NF1 is linked to leukemia.