Missense Pathogenic variants in KIF4A Affect Dental Morphogenesis Resulting in X-linked Taurodontism, Microdontia and Dens-Invaginatus

Abstract

The etiology of dental anomalies is multifactorial; and genetic and environmental factors that affect the dental lamina have been implicated. We investigated two families of European ancestry in which males were affected by taurodontism, microdontia and dens invaginatus. In both families, males were related to each other via unaffected females. A linkage analysis was conducted in a New Zealand family, followed by exome sequencing and focused analysis of the X-chromosome. In a US family, exome sequencing of the X-chromosome was followed by Sanger sequencing to conduct segregation analyses. We identified two independent missense variants in KIF4A that segregate in affected males and female carriers. The variant in a New Zealand family (p.Asp371His) predicts the substitution of a residue in the motor domain of the protein while the one in a US family (p.Arg771Lys) predicts the substitution of a residue in the domain that interacts with Protein Regulator of Cytokinesis 1 (PRC1). We demonstrated that the gene is expressed in the developing tooth bud during development, and that the p.Arg771Lys variant influences cell migration in an in vitro assay. These data implicate missense variations in KIF4A in a pathogenic mechanism that causes taurodontism, microdontia and dens invaginatus phenotypes.

Keywords: X-linked recessive; dens invaginatus; exome sequencing; microdontia; taurodontism.

Figure 1

(A and B) Pedigree for family 1 and 2 showing affected males shaded in black. Individuals included in segregation analyses in the family are shown with black Panel (C) Frontal view from one twin 1 from family 1 showing generalized microdontia and spacing. Panel (D) is a panoramic radiograph from the same twin as above. He is in the late mixed dentition, as his maxillary second premolars have not yet erupted. Taurodontism in the molars is evident (arrows).

Figure 2

Migration scratch assay. HEPM cells were seeded at high density 24 h after Kif4α Wild-type & Kif4α Mutant transfection. Pictures at 0, 4, 8, 20, and 30 h after scratch. The number of cells between the red lines were counted in the different groups. Box plots of the number of cells in the scratched area at the different time points.

Figure 3

The in situ hybridization of Kif4 in E12.5 and E14.5 embryos. Red asterisks show lower incisors, blue asterisks show mesenchyme adjacent the lower incisors. Tg, tongue; Md, mandible; Mx, maxilla; Ht, heart. Scale bar: 200 μm.