Identification by whole-exome sequencing of new single-nucleotide polymorphisms associated with molar-incisor hypomineralisation among the Lebanese population.

Objective: Molar-incisor hypomineralization (MIH) is a developmental qualitative enamel defect, causing a worldwide challenging dental problem. The etiology of this defect remains unclear. Here we identify by whole-exome sequencing (WES) new single-nucleotide polymorphisms (SNPs) in genes expressed during enamel mineralization and in those modulating prenatal, natal and postnatal risk factors among the Lebanese MIH children: immune system and xenobiotic detoxification.

Design: Dental examination for MIH was performed based on the MIH index for diagnostic criteria. Saliva samples were collected from 37 non-related, MIH-diagnosed subjects for DNA extraction. WES was performed on the Illumina HiSeq2000 platform. The χ test and Fisher's exact test were used to determine relationship between SNPs frequencies and MIH. OR and its 95% CI were used to report the strength of association. The significance threshold was set at 0.05.

Results: Among the Lebanese population, 37 SNPs presented a significant association with MIH in the following genes: AMTN, MMP-20, STIM1, STIM2, ORAI1, SLC34A2, SLC34A3, VDR, PVALB, HSP90B1, TRPM7, SLC24A4, CA6, SLC4A2, TNFRSF11A, IL10RB, ARNT, ESR1 and CYP1B1.

Conclusion: This is the first WES study conducted in patients with MIH. Yet, interactions between polymorphisms in different gene categories are to be investigated for a better assessment of MIH susceptibility.