SOX9 and polygenic risk score: To identify candidate hCNCC enhancer elements that map within regions of the SOX9 gene desert lost in PRS patients, we used chromatin immunoprecipitation sequencing (ChIP-seq) and assay for transposase-accessible chromatin using sequencing (ATAC-seq) datasets from in-vitro-derived hCNCCs (Prescott et al., 2015; this study; Figure 1A).