SMAD6 and craniosynostosis: Recent reports focusing on patients with non-syndromic craniosynostosis showed that single nucleotide polymorphisms (SNPs) were found in a Smad6 exon and a putative enhancer region of BMP2, and frameshift mutations in Smad6 were found (Justice et al., 2012; Komatsu and Mishina, 2016; Timberlake et al., 2016; Timberlake et al., 2018).