Id1 maintains embryonic stem cell self-renewal by upregulation of Nanog and repression of Brachyury expression. Mus musculus

Understanding the mechanism by which embryonic stem (ES) cells self-renew is critical for the realization of their therapeutic potential. Previously it had been shown that in combination with LIF, Id proteins were sufficient to maintain mouse ES cells in a self-renewing state. Here we investigate the requirement for Id1 in maintaing ES cell self-renewal and blocking differentiation. We find that Id1-/- ES cells have a propensity to differentiate and a decreased capacity to self-renew. Chronic or acute loss of Id1 leads to a down-regulation of Nanog, a critical regulator of self-renewal. In addition, in the absence of Id1, ES cells express elevated levels of Brachyury, a marker of mesendoderm differentiation. We find that loss of both Nanog and Id1 is required for the up-regulation of Brachyury, and Id1 maintains Nanog expression by blocking the expression of Zeb1, a repressor of Nanog transcription. These results identify Id1 as an important factor in the maintenance of ES cell self-renewal and suggest a plausible mechanism for its control of lineage commitment. Overall design: Wild type and Id1-/- ES cells were grown on gelatin under normal self-renewing conditions (in the presence of serum and LIF).