SMAD6 and craniosynostosis: In contrast, common variants at the BBS9 locus that also showed strong association with midline craniosynostosis in case-control analysis (OR > 4) (Justice et al., 2012) showed no significant interaction with SMAD6 (TDT p=0.89; Supplementary file 1B), demonstrating specificity of the observed interaction of rare variants in SMAD6 and a common variant near BMP2.