Highlights • A scoliosis-associated region, PEC7, is an enhancer in the mouse tail and intervertebral disc • Deletion of Xe1 or both Xe1 and PEC7 enhancers leads to a kinky tail phenotype • Deletion of Xe1 and PEC7 together leads to a female-biased kinky tail • Tamoxifen suppresses the sex dimorphic phenotype, suggesting a role for estrogen signaling Summary Adolescent idiopathic scoliosis (AIS), a sideways curvature of the spine, is sexually dimorphic, with increased incidence in females.