The effect of S309W mutation on SP7 genomic binding in chondrocytes

SP7/Osterix is a transcription factor critical for osteoblast maturation and bone formation. We identidied a missense variant (c.926C>G:p.S309W) in SP7 in a patient with a unique high turnover bone disease. Mice with the corresponding variant similarly showed a complex skeletal phenotype distinct from that of Sp7-null mice. We therefore performed ChIP-Seq in primary chondrocytes to study how the mutation alters the genomic binding of SP7. Primary mouse chondrocytes isolated from proximal tibia and distal femur of 7 day old male mice cardiomyocytes were cultured in DMEM/F12 media supplemented with 10% FBS, P/S, and 50 μg/mL ascorbic acid. Retrovirus expressing either wild-type SP7 or S309W variant of SP7 were produced with HEK-derived ECO cells and used for infecting primary chondrocytes. About 5 days post-infection, chondrocytes were harvested and cross-linked with 1% formaldehyde for genomic DNA isolation.