Expression of a conditional AML1-ETO oncogene bypasses embryonic lethality and establishes a murine model of human t(8;21) acute myeloid leukemia..     ///    "To bypass the embryonic lethality, we generated a mouse strain with a conditional AML1-ETO knockin allele that contains a loxP bracketed transcriptional stop cassette 5' to the AML1-ETO fusion site. "    ///    "Paradoxically, expression of the acute myeloid leukemia-associated AML1-ETO fusion protein in mice results not in leukemia, but in embryonic lethality due to an absence of normal hematopoiesis. "