Genome-wide scanning of HoxB1-associated loci in mouse ES cells using an open-ended Chromosome Conformation Capture methodology.

Spatial proximity between genomic loci can play important roles in their function and regulation. We have developed an open-ended method based on Chromosome Conformation Capture technology allowing us to perform genome-wide scanning of the loci that form the spatial environment of a given locus at a given time. As a proof of principle we present the use of this methodology to investigate the dynamics of the spatial environment of the HoxB1 gene before and after the induction of its expression in mouse embryonic stem cells. Our results indicate that the HoxB1 locus' immediate spatial environment can be divided roughly into three parts: a first part is represented by a domain of immediate proximity on each side of the HoxB1 locus covering approximately 110 kb, a second part extends to a domain of 800 kb and a third part consists of distal intra-chromosomal and inter-chromosomal interactions. Consistent with FISH studies showing the decondensation and repositioning of HoxB1 outside of its chromosomal territory during its expression, the proportion of inter-chromosomal interactions between HoxB1 and the rest of the genome increases after its induction, while interactions with distal intra-chromosomal loci become less frequent. These results indicate that this technique can be used to determine the dynamics of loci interactions on a genome-wide scale.