Method for selecting clone of induced pluripotent stem cells
To efficiently identify and select a clone from clones of induced pluripotent stem cells (iPS cell) having low tumor formation rate in vivo when allowed to differentiate and transplanted in a living body, iPS cells of the clones are induced to differentiate, undifferentiated cells among the cells after the induction of differentiation are detected, and a clone having the content of the undifferentiated cell below a control is selected.
1. A method for selecting induced pluripotent stem cells (iPS cells) comprising:
(1) providing iPS cell clones,
(2) differentiating the iPS cell clones into neurospheres,
(3) measuring the percentage of cells that express Nanog gene in the neurospheres, and
(4) selecting iPS cell clones corresponding to neurospheres measured in step (3) having decreased percentage of cells expressing Nanog as compared to neurospheres obtained from embryonic stem (ES) or iPS cell clones known not to cause tumor formation when differentiated and transplanted into a living body.
2. The method according to claim 1 , wherein less than 0.042% of the cells of the neurospheres corresponding to the iPS cell clones selected in step (4) express Nanog gene, based on an average value from multiple measurements.
3. The method according to claim 1 , wherein less than 0.066% of the cells of the neurospheres corresponding to the iPS cell clones selected in step (4) express Nanog gene, based on a maximum value from multiple measurements.
4. The method according to claim 1 , wherein the iPS cell clones have been established by introducing genes comprising Oct3/4 gene, Sox2 gene, and Klf4 gene, or Oct3/4 gene, Sox2 gene, Nanog gene, and Lin28 gene.