We have recently generated Prep1 hypomorphic mice (Prep1i/i), in which the level of Prep1 is reduced to about 2–10% of wild type (wt), and found that Prep1i/i embryos die (in 80% of the cases) at E17.5-P0 with anemia and major defects in oculogenesis and angiogenesis [3], [4]. The gene discussed is PKNOX1; the disease is anemia (phenotype).