Detection and functional analysis of BMP2 gene mutation in patients with tooth agenesis

Abstract

To screen for BMP2 mutation with functional impact in patients with congenital tooth agenesis and to make oral and skeletal phenotype record and functional analysis with in vitro experiments. We enrolled eighteen patients with congenital tooth agenesis. The medical and dental history was collected,and clinical and dental examinations including the X-ray examination of oral-facial and skeletal bone were performed for the phenotypic analysis. Blood samples were collected to extract DNA and whole exome sequencing was conducted. The genes involved in oral-facial development and congenital skeletal diseases were investigated for mutation screening. The mutations with functional impact were then investigated. In one patient, the BMP2 mutation with putative functional impact was selected for functional analysis. Wild type and mutant BMP2 plasmids with green fluorescent protein (GFP) tag were constructed and transfected into HEK293T cells. Subcellular protein distribution was observed under laser scanning confocal microscope. The activation of downstream SMAD1/5/9 phosphorylation by BMP2 was detected by Western blotting to investigate the functional impact and genetic pathogenicity. BMP2 mutation NM_001200.3:c.393A>T (p.Arg131Ser), rs140417301 was detected in one patient with congenital tooth agenesis, while for other genes involved in oral-facial development and congenital skeletal diseases, no functionally significant mutation was found. The proband's parents didn't carry this mutation. The father had normal dentition, while the mother lacked one premolar, and both the parents showed normal palate and maxilla. The patient also had maxillary hypoplasia in both sagittal and coronal planes, palatal dysmorphology, and malocclusion, and was diagonsed with osteopenia after the X-ray examnination of his skeletal bone. Functional analysis showed this mutation had normal subcelluar localization but reduced phosphorylation of SMAD1/5/9 (reduction by 32%, 22%, and 27% in three independent replicates). Taken together with family co-segregation, this mutaion was considered as "likely pathogenic". BMP2 mutation c.393A>T (p. Arg131Ser) affects bone morphogenetic protein signaling activity, and may affect the number of teeth, growth of maxilla and palate, and bone mineral density.