Abstract

Arising from: S. K. Singh, M. N. Kagalwala, J. Parker-Thornburg, H. Adams & S. Majumder Nature 453, 223–227 (2008); Singh et al. reply

Establishment and maintenance of the pluripotent state of ESCs is a key issue in stem cell biology and regenerative medicine, and consequently identification of transcription factors that regulate ESC pluripotency is an important goal. Singh et al.¹ claim that the transcriptional repressor REST is such a regulator and that a 50% reduction of REST in ESCs leads to activation of a specific microRNA, miR-21, and that this subsequently results in loss of pluripotency markers and a reciprocal gain in some lineage-specific differentiation markers. In contrast, we show that, in haplodeficient Rest^+/- ESCs, we detected no change in pluripotency markers, no precocious expression of differentiated neuronal markers and no interaction of REST with miR-21. It is vital that identification of factors that regulate pluripotency is based on robust, consistent data, and the contrast in data reported here undermines the claim by Singh et al.¹ that REST is such a regulator.