Precise Hox gene expression is crucial for embryonic patterning. Intra-Hox transcription
factor binding and distal enhancer elements have emerged as the major regulatory modules
controlling Hox gene expression. However, quantifying their relative contributions has
remained elusive. Here, we introduce “synthetic regulatory reconstitution,” a conceptual
framework for studying gene regulation, and apply it to the HoxA cluster. We synthesized
and delivered variant rat HoxA clusters (130 to 170 kilobases) to an ectopic location in the …