複選題38. Which of the following statements about stem cells is (are) CORRECT? (A) Stem cells are widespread during development and continue to exist in all human and mammalian tissues in adult (B) The proliferative potential of a cell is gradually restricted when it becomes more differentiated (C) A differentiated somatic cell nucleus could be reprogrammed into a more undifferentiated state when transplanted into an oocyte whose own nucleus is removed (D) A limited number of transcription factors are sufficient to confer stemness to the cell, and activation of this set of genes could reprogram somatic cells to become pluripotent stem cell (iPS cell) (E) Differentiation of a stem cell into more mature cell types is determined by both genetic factors and extrinsic signals