Researchers at the MRC London Institute of Medical Sciences identified a novel DNA-based 'attenuator' element controlling the transient expression of the key developmental gene Cdx2, which shapes posterior body formation in embryos. Unlike classical enhancers or silencers, this dimmer-like regulatory element fine-tunes temporal gene activity critical for spinal cord progenitor formation. Using CRISPR-Cas9, study authors demonstrated that mutations disrupting this element impair gene expression dynamics and cause developmental malformations in mice, offering new insights for precise gene expression modulation in therapeutic contexts.