HBP1 and chondrosarcoma: The minor, OA-associated risk allele of rs4730222 appears to functionally underlie increased transcriptional levels of alternative isoform(s) of HBP1. This conclusion is supported by multiple lines of evidence, including the STARR-seq MPRA, observations of AEI in both a chondrosarcoma cell line and OA patient chondrocytes, and CRISPR/Cas9-mediated introduction of the exact allele into an osteosarcoma cell line.