Correct patterning and development of many mammalian tissues depends on the activity on cis-regulatory interactions at ultra-long range. We are interested to understand how such long range regulatory interactions are established, and how they derive specificity. Several examples we are studying in the lab include distal enhancers for Pitx1 expression in posterior limbs (300 kb), distal enhancers of Myc (700 kb) the limb enhancer of Shh (1 Mb), distal enhancers of the Hoxa and Hoxd clusters (1 Mb), and some of the cranial neural crest enhancers of Sox9 (1.4 Mb).