Abstract
UTF1 (undifferentiated embryonic cell transcription factor 1) is a marker for the pluripotency of embryonic stem (ES) cells but how it affects differentiation remains unclear. To study its role in the process, we used both ES cells and embryonic carcinoma (EC) cells, which are pluripotent teratocarcinoma cells. We found that UTF1-deficient clones, isolated from P19 EC cells, showed higher neuronal-differentiating potential than the parental cell line. Consistent with this observation, suppression of UTF1 expression by RNA interference enhanced retinoic acid (RA)-induced neuronal differentiation in P19 cells. Moreover, reconstitution of UTF1 expression in UTF1-deficient clones decreased their ability to undergo neuronal differentiation. Interestingly, the growth rates of UTF1-deficient P19 cells did not differ from that of parental cells in adherent cultures, but increased in embryoid bodies during RA-induced differentiation. In ES cells, reduction of UTF1 expression increased expression of neuronal-ectoderm marker Gap43 during both spontaneous and RA-induced differentiation; this was consistent with the results in P19 cells. Therefore, we proposed that endogenous UTF1 prevented EC and ES cells from neuronal differentiation, and that the loss of UTF1 directed EC and ES cells toward a neuronal fate. Recently, Pin1, a peptidyl-prolyl isomerase, has been found to maintain self-renewal via modulating phosphorylation of Oct4 and Nanog. We demonstrated that Pin1 bond to UTF1 directly, but surprisingly, this interaction did not require phosphorylation of UTF1. UTF1 mutant that had lost Pin1 binding ability failed to suppress RA-induced neuronal differentiation in P19 cells. These results indicated that the function of UTF1 in inhibition of neuronal differentiation could be regulated by Pin1 in mouse EC cells.