Embryonic stem cell (ESC) lines derived from type <i>a</i> 4n blastocysts.

<p>(A) Inner cell mass (ICM) outgrowth on MEFs from a type <i>a Oct4</i>-EGFP 4n blastocyst at the 4^th day of culture in ESDM. (B) An embryonic remnant from a type <i>b</i> 4n blastocyst at the 4^th day of culture in ESDM. (C, D) ESCs derived from both 2n embryos and type <i>a</i> 4n embryos. Note the larger cell size for 4nESCs (D) than 2nESCs (C). (E) Karyotype of 4nESCs (4n = 80). (F) Efficiency of ESC line derivation for 4n blastocysts from <i>Oct4</i>-EGFP mouse strain. The efficiency of ESC derivation for type <i>a</i> 4n blastocysts is similar to that for 2n blastocysts, while the efficiency for type <i>b</i> 4n blastocysts is significantly decreased (<i>P</i><0.01). The type <i>a</i> and type <i>b</i> embryos were identified by visualization of the <i>Oct4</i>-EGFP under the fluorescence microscope.