LRP4 mutations, dental anomalies, and oral exostoses.

BACKGROUND: In order to generate a normal set of teeth, fine-tuning of Wnt/β-catenin signaling is required, in which WNT ligands bind to their inhibitors or WNT inhibitors bind to their co-receptors. Lrp4 regulates the number of teeth and their morphology by modulating Wnt/β-catenin signaling as a Wnt/β-catenin activator or inhibitor, depending on its interactions with the partner proteins, such as Sostdc1 and Dkk1.

AIM: To investigate genetic etiologies of dental anomalies involving LRP4 in a Thai cohort of 250 children and adults with dental anomalies.

DESIGN: Oral and radiographic examinations and whole exome sequencing were performed for every patient.

RESULTS: Two novel (p.Leu1356Arg and p.Ala1702Gly) and three recurrent (p.Arg263His, p.Gly1314Ser, and p.Asn1385Ser) rare variants in low-density lipoprotein receptor-related protein 4 (LRP4: MIM 604270) were identified in 11 patients. Oral exostoses were observed in five patients.

CONCLUSION: Antagonism of Bmp signaling by Sostdc1 requires the presence of Lrp4. Mice lacking Lrp4 have been demonstrated to have alteration of Wnt-Bmp-Shh signaling and an abnormal number of incisors. Therefore, the LRP4 mutations found in our patients may disrupt Wnt-Bmp-Shh signaling, thereby resulting in dental anomalies and oral exostoses. Root maldevelopment in the patients suggests an important role of LRP4 in root morphogenesis.