GREM2 nucleotide variants and the risk of tooth agenesis.

OBJECTIVE: The etiology of tooth agenesis (TA) is multifactorial and still not fully understood. The aim of the study was to test whether variants of GREM2, encoding a bone morphogenetic protein (BMP) antagonist, are associated with the risk of this common dental anomaly in a Polish population. SUBJECTS AND METHODS: Direct sequencing of the GREM2 coding sequence including exon/intron boundaries was performed in 95 patients with both hypodontia and oligodontia. All identified GREM2 variants were then further tested in an independent group of patients (n = 163) and controls (n = 184). RESULTS: The previously described, functional GREM2 mutation (c.226C > G, p.Gln76Glu) was identified in two patients with hypodontia and associated dental anomalies, including taurodontism and microdontia. This mutation generating an allele with increased inhibitory activity was not detected in the control group. The second identified GREM2 variant, c.-1-21C > T (rs11806449), was not associated with the risk TA. The polymorphism allele frequency in both patients and controls was 0.21 (OR = 1.0, 95%CI: 0.76-1.46). The rs11806449 did not correlate either with the overall TA phenotype or hypodontia/oligodontia phenotypes. CONCLUSION: Our study confirmed that GREM2 is a candidate gene for tooth agenesis, which mutations can explain, however, only a small fraction of the genetic contribution to the pathogenesis of this anomaly.

Common variants in DLG1 locus are associated with non-syndromic cleft lip with or without cleft palate.

Non-syndromic cleft lip with or without cleft palate (nsCL/P) is a common craniofacial anomaly with a complex and heterogeneous aetiology. Knowledge regarding specific genetic factors underlying this birth defect is still not well understood. Therefore, we conducted an independent replication analysis for the top-associated variants located within the DLG1 locus at chromosome 3q29, which was identified as a novel cleft-susceptibility locus in our genome-wide association study (GWAS). Mega-analysis of the pooled individual data from the GWAS and replication study confirmed that common DLG1 variants are associated with the risk of nsCL/P. Two single nucleotide polymorphisms (SNPs), rs338217 and rs7649443, were statistically significant even at the genome-wide level (Ptrend = 9.70E-10 and Ptrend = 8.96E-09, respectively). Three other SNPs, rs9826379, rs6805920 and rs6583202, reached a suggestive genome-wide significance threshold (Ptrend < 1.00E-05). The location of the strongest individual SNP in the intronic sequence of the gene encoding DLG1 antisense RNA suggests that the true causal variant implicated in the risk of nsCL/P may affect the DLG1 gene expression level rather than structure of the encoded protein. In conclusion, we identified a novel cleft-susceptibility locus at chromosome 3q29 with a DLG1 as a novel candidate gene for this common craniofacial anomaly.

Nucleotide variants of genes encoding components of the Wnt signalling pathway and the risk of non-syndromic tooth agenesis.

Tooth agenesis is one of the most common dental anomalies, with a complex and not yet fully elucidated aetiology. Given the crucial role of the Wnt signalling pathway during tooth development, the purpose of this study was to determine whether nucleotide variants of genes encoding components of this signalling pathway might be associated with hypodontia and oligodontia in the Polish population. A set of 34 single nucleotide polymorphism (SNPs) in 13 WNT and WNT-related genes were analyzed in a group of 157 patients with tooth agenesis and a properly matched control group (n = 430). In addition, direct sequencing was performed to detect mutations in the MSX1, PAX9 and WNT10A genes. Both single-marker and haplotype analyses showed highly significant association between SNPs in the WNT10A gene and the risk for tooth agenesis. Moreover, nine pathogenic mutations within the coding region of the WNT10A gene were identified in 26 out of 42 (62%) tested patients. One novel heterozygous mutation was identified in the PAX9 gene. Borderline association with the risk of non-syndromic tooth agenesis was also observed for the APC, CTNNB1, DVL2 and WNT11 polymorphisms. In conclusion, nucleotide variants of genes encoding important components of the Wnt signalling pathway might influence the risk of tooth agenesis.

The novel polymorphic variants within the paired box of the PAX9 gene are associated with selective tooth agenesis.

It has been reported that two genes MSX1 and PAX9, which encode transcription factors, are associated with selective tooth agenesis. Expression of these genes specifically marks the regions of the mesenchyme where the tooth buds are formed. A mutation in the MSX1 gene, detected in a single family, resulting in an Arg-->Pro substitution in the homeodomain of the protein product of this gene has previously been associated with the deficiency of second premolars and third molars. However, mutations of the MSX1 gene were excluded in the patients with agenesis of the other type of teeth. In a single family with the lack of first and second molars, a mutation in the PAX9 gene was found. In our group of patients with the deficiency of various teeth, in 20% of the patients and their relatives sequence analysis revealed a C-->T transition in the coding sequence of the PAX9 gene. However, this polymorphism does not alter amino acid sequence of the protein product of this gene.