An embryonic stem cell-based system for rapid analysis of transcriptional enhancers.

With the growing use of genome-wide screens for cis-regulatory elements, there is a pressing need for platforms that enable fast and cost-effective experimental validation of identified hits in relevant developmental and tissue contexts. Here, we describe a murine embryonic stem cell (ESC)-based system that facilitates rapid analysis of putative transcriptional enhancers. Candidate enhancers are targeted with high efficiency to a defined genomic locus via recombinase-mediated cassette exchange. Targeted ESCs are subsequently differentiated in vitro into desired cell types, where enhancer activity is monitored by reporter gene expression. As a proof of principle, we analyzed a previously characterized, Sonic hedgehog (Shh)-dependent, V3 interneuron progenitor (pV3)-specific enhancer for the Nkx2.2 gene, and observed highly specific enhancer activity. Given the broad potential of ESCs to generate a spectrum of cell types, this system can serve as an effective platform for the characterization of gene regulatory networks controlling cell fate specification and cell function.