LRP6 and tooth agenesis: WES and Sanger sequencing revealed an unreported heterozygous missense mutation in exon 13 of the LRP6 (c.2840 T > C;p.Met947Thr) in three family members with tooth agenesis (IV:1, III:4, and IV:2) and two family members with tooth agenesis accompanied by hand polydactyly (III:3 and II:3) (Fig. 1o and Supplementary Fig. 1a).