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Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional spinal deformity. The incidence of AIS in females is 8.4 times higher than in males. Several hypotheses on the role of estrogen have been postulated for the progression of AIS. Recently, Centriolar protein gene POC5 ( POC5 ) was identified as a causative gene of AIS. POC5 is a centriolar protein that is important for cell cycle progression and centriole elongation. However, the hormonal regulation of POC5 remains to be determined. Here, we identify POC5 as an estrogen-responsive gene under the regulation of estrogen receptor ERα in normal osteoblasts (NOBs) and other ERα-positive cells. Using promoter activity, gene, and protein expression assays, we found that the POC5 gene was upregulated by the treatment of osteoblasts with estradiol (E2) through direct genomic signaling. We observed different effects of E2 in NOBs and mutant POC5 A429V AIS osteoblasts. Using promoter assays, we identified an estrogen response element (ERE) in the proximal promoter of POC5 , which conferred estrogen responsiveness through ERα. The recruitment of ERα to the ERE of the POC5 promoter was also potentiated by estrogen. Collectively, these findings suggest that estrogen is an etiological factor in scoliosis through the deregulation of POC5.

Adolescent idiopathic scoliosis (AIS) is a complex common disorder of multifactorial etiology defined by a deviation of the spine in three dimensions that affects approximately 2% to 4% of adolescents. Risk factors include other affected family members, suggesting a genetic component to the disease. The POC5 gene was identified as one of the first ciliary candidate genes for AIS, as three variants were identified in large families with multiple members affected with idiopathic scoliosis. To assess the prevalence of p.(A429V), p.(A446T), and p.(A455P) POC5 variants in patients with AIS, we used next-generation sequencing in our cohort of French-Canadian and British families and sporadic cases. Our study highlighted a prevalence of 13% for POC5 variants, 7.5% for p.(A429V), and 6.4% for p.(A446T). These results suggest a higher prevalence of the aforementioned POC5 coding variants in patients with AIS compared to the general population.