Embryonic stem cells (ESCs) are capable of indefinite self-renewal while retaining the ability to differentiate to any of the three germ layers that give rise to all somatic cell types. An emerging view is that a core set of transcription factors, including Oct4, Sox2, and Nanog, form a robust autoregulatory circuit that maintains ESCs in a self-renewing state. To accommodate the capacity of such cells to undergo germ layer-specific differentiation, we predicted a posttranslational mechanism that could negatively regulate these core self-renewal factors. Here we report caspase-induced cleavage of Nanog in differentiating ESCs. Stem cells lacking the Casp3 gene showed marked defects in differentiation, while forced expression of a caspase cleavage-resistant Nanog mutant in ESCs strongly promoted self-renewal. These results link a major component of the programmed cell-death pathway to the regulation of ESC development.
Bibliographical noteFunding Information:
We thank Dr. David Spencer (Baylor College of Medicine) for providing us with the EF1a-Luc-IRES-NEO vector and Kimberly Smuga-Otto and Kristopher Murphy for technical assistance. This work was supported by the Lance Armstrong Foundation (T.P.Z.), the Gillson Longenbaugh Foundation (T.P.Z.), the Tilker Medical Research Foundatiom (T.P.Z.), the Diana Helis Henry Medical Research Foundation (T.P.Z.), the Huffington Foundation (T.P.Z.), the Uehara Memorial Foundation (J.F.), and by the NIH (grants R01 EB005173-01, P20 EB007076, and P01 GM81627). R.A.F. is an investigator of the Howard Hughes Medical Institute.