Adrianna Mostowska

Axis inhibition protein 2 (AXIN2) polymorphisms may be a risk factor for selective tooth agenesis

AbstractSelective tooth agenesis is the most common developmental abnormality of the human dentition. To date, this abnormality has been associated only with mutations in MSX1 and PAX9 mutations, however it has recently been suggested that mutations of axis inhibition protein 2 (AXIN2) may also contribute to this complex anomaly. The protein product of this gene is a negative regulator of the Wnt-signaling pathway. We searched for AXIN2 variants in a group of patients with tooth agenesis who did not have mutations of MSX1 and PAX9. Using multi-temperature single-stranded conformational polymorphism and sequencing analysis, we identified three novel AXIN2 gene variants: c.956+16A>G, c.1060-17C>T and c.2062C>T. We also observed that individuals carrying the c.956+16G and c.2062T alleles exhibited an increased risk of tooth agenesis. The calculated odds ratio was 2.94 (95% CI 1.104-7.816; p=0.026; pcorr=0.234) and 4.01 (95% CI 1.563-10.301; p=0.002; pcorr=0.018), respectively. Moreover, we found that the c.2062C>T transition may change exon splice enhancer-specific binding sites of the protein splicing regulators SC35 and SF2/ASF. This alternation may negatively affect the splicing process and cellular concentration of AXIN2 protein. Our findings suggest that AXIN2 polymorphic variants may be associated with both hypodontia and oligodontia.

Maternal MTR genotype contributes to the risk of non-syndromic cleft lip and palate in the Polish population.

The aetiology of non‐syndromic cleft lip with or without cleft palate (CL/P) is very complex. It has been shown that polymorphic variants of genes encoding key proteins of folate and methionine metabolism might be important maternal risk factors of having a child with this craniofacial anomaly. Therefore, in our study, mothers with CL/P children as well as control mothers were examined for prevalence of polymorphisms of genes that encode methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), 5,10‐methylenetetrahydrofolate dehydrogenase, 5,10‐methenyltetrahydrofolate cyclohydrolase and 10‐formyltetrahydrofolate synthetase (MTHFD1) and reduced folate carrier 1 (RFC1). We observed that there were no statistical differences in allele and genotype frequencies of MTHFR c.677C>T, MTHFD1 c.1958G>A and RFC1 c.80G>A between mothers who had children with CL/P and control mothers. However, mothers with MTR c.2756AG or GG genotype displayed a 2.195‐fold increased risk of having a child with CL/P (95% CI 1.189–4.050, p = 0.011). The mechanism by which polymorphic transition of MTR gene might increase the maternal risk of having CL/P progeny is unknown. Our observations are consistent with a significant role of the methyl cycle in the development of craniofacial structures in humans.

Association of 677C>T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene with bipolar disorder and schizophrenia

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism 677C>T has been shown to be a risk factor for psychiatric disorders. We investigated the genotype and allelic frequencies of MTHFR 677C>T polymorphism in the group of patients with bipolar disorder type I (BDI) (n=200) and schizophrenia (n=200), and in the control group (n=300). Odds ratio (OR) for patients with BD and schizophrenia with 677T allele was 1.988 ((95% CI=1.370-2.883); P=0.0003 (P=0.0006 after Bonferroni correction)) and 1.796 ((95% CI=1.237-2.609); P=0.0020 (P=0.0040 after Bonferroni correction)), respectively. The stratification of patients based on gender revealed significant association of 677T allele with male patients with BDI and schizophrenia (OR=2.393; 95% CI=1.429-4.006; P=0.0008 and OR=2.036; 95% CI=1.207-3.433; P=0.0073, respectively). This finding indicates possible association of BD and schizophrenia with the 1p36.3 MTHFR locus.

Associations of folate and choline metabolism gene polymorphisms with orofacial clefts

Background Non-syndromic isolated cleft lip with or without cleft palate (NCL/P) is a common congenital anomaly in humans, the aetiology of which is complex and associated with both genetic and environmental factors. It has been reported that maternal nutritional factors are likely to play a major role in development of NCL/P in the embryo. Objective As the mechanism by which folic acid and choline supplementation prevents NCL/P is poorly understood, the relationship between 16 polymorphic variants of 12 genes encoding enzymes involved in the metabolism of these two nutrients and the risk of facial clefts was investigated. Results It was found that individuals with the AA genotype of the BHMT rs3733890 polymorphism have a significantly lower risk of orofacial clefts (OR 0.1450, 95% CI 0.0420 to 0.4995; p=0.0005; pcorr=0.008). It was also demonstrated that the rs7639752 polymorphism of the PCYT1A gene increases the risk of NCL/P nearly twofold in the Polish population (OR 1.891, 95% CI 1.151 to 3.107; p=0.011), but this association would not withstand correction for multiple testing (pcorr=0.176). The genetic variations in CBS, MTHFD1, MTHFR, MTR, MTRR, TCN2, BHMT2, CHDH, CHKA, and PEMT were not separately correlated with NCL/P risk. However, the Multifactor Dimensionality Reduction (MDR) analysis showed a significant epistatic interaction between MTHFR (rs1801133), MTR (rs1805087), and PEMT (rs4646406) in NCL/P susceptibility. Conclusion This study demonstrates that choline metabolism may play an important role in the aetiology of NCL/P. Polymorphic variants of BHMT and PCYT1A and interactions between genes of choline and folate metabolism might influence the risk of NCL/P in the Polish population.

Association between genetic variants of reported candidate genes or regions and risk of cleft lip with or without cleft palate in the polish population

BACKGROUND Cleft lip with or without cleft palate (CL/P) is one of the most common craniofacial malformations, with a complex and multifactorial etiology. Because of the genetic heterogeneity of facial clefts, the aim of this study was to investigate the contribution of previously reported candidate genes and chromosomal loci to the risk of CL/P in the Polish population. METHODS We performed an analysis of 18 polymorphisms of FOXE1, IRF6, MSX1, PAX9, TBX10, FGF10, FGFR1, TGFalpha, TGFbeta3, SUMO1, and the chromosomal region 8q24 in a group of 175 patients with CL/P and a properly matched control group. RESULTS Highly significant results were observed for the IRF6 rs642961 variant and the 8q24 regions rs987525 (odds ratio [OR](AG+AAvsGG), 1.635; 95% confidence interval [CI], 1.153-2.319; p = 0.005; and OR(AC+AAvsCC), 1.962; 95% CI, 1.382-2.785; p = 1.4 x 10(-4), respectively). For rs987525, the results were also significant after correction for multiple comparisons. Borderline association with an increased risk of CL/P was also identified for the SUMO1 locus (rs2350350; OR(CGvsGG), 1.580; 95% CI, 1.056-2.363; p = 0.025). CONCLUSIONS Our findings confirmed that genetic variants of IRF6 and the polymorphism located in the 8q24 gene desert are strongly involved in the etiology of facial clefts in the Polish population sample.

A novel mutation in PAX9 causes familial form of molar oligodontia.

PAX9 is a paired domain transcription factor that plays a critical role in odontogenesis. All mutations of PAX9 identified to date have been associated with nonsyndromic form of tooth agenesis. The present report describes an unusual novel mutation in PAX9 identified in a family with severe molar oligodontia. This heterozygous deletion combined with 24 bp insertion (including a 5′ splice site) is localized in the second exon beyond the highly conserved paired box sequence, and might result either in a premature termination of translation at aa 210 or in an aberrant splicing, leading to a frameshift and premature termination of translation at aa 314. Real-time PCR analysis revealed no mutated transcript in cultured lymphocytes of one of the affected individuals indicating that the novel mutation might result in rapid degradation of the mutated transcript leading to haploinsufficiency of PAX9. Our results support the view that mutations in PAX9 constitute a causative factor in nonsyndromic oligodontia.

Identification of microdeletions in candidate genes for cleft lip and/or palate

BACKGROUND Genome-wide association studies are now used routinely to identify genes implicated in complex traits. The panels used for such analyses can detect single nucleotide polymorphisms and copy number variants, both of which may help to identify small deleted regions of the genome that may contribute to a particular disease. METHODS We performed a candidate gene analysis involving 1,221 SNPs in 333 candidate genes for orofacial clefting, using 2,823 samples from 725 two- and three-generation families with a proband having cleft lip with or without cleft palate. We used SNP genotyping, DNA sequencing, high-resolution DNA microarray analysis, and long-range PCR to confirm and characterize the deletion events. RESULTS This dataset had a high duplicate reproducibility rate (99.98%), high Mendelian consistency rate (99.93%), and low missing data rate (0.55%), which provided a powerful opportunity for deletion detection. Apparent Mendelian inconsistencies between parents and children suggested deletion events in 15 individuals in 11 genomic regions. We confirmed deletions involving CYP1B1, FGF10, SP8, SUMO1, TBX1, TFAP2A, and UGT7A1, including both de novo and familial cases. Deletions of SUMO1, TBX1, and TFAP2A are likely to be etiologic. CONCLUSIONS These deletions suggest the potential roles of genes or regulatory elements contained within deleted regions in the etiology of clefting. Our analysis took advantage of genotypes from a candidate-gene-based SNP survey and proved to be an efficient analytical approach to interrogate genes potentially involved in clefting. This can serve as a model to find genes playing a role in complex traits in general.

A novel c.581C>T transition localized in a highly conserved homeobox sequence ofMSX1: is it responsible for oligodontia?

Even though selective tooth agenesis is the most common developmental anomaly of human dentition, its genetic background still remains poorly understood. To date, familial as well as sporadic forms of both hypodontia and oligodontia have been associated with mutations or polymorphisms ofMSX1, PAX9, AXIN2 andTGFα, whose protein products play a crucial role in odontogenesis. In the present report we described a novel mutation ofMSX1, which might be responsible for the lack of 14 permanent teeth in our proband. However, this c.581C>T transition, localized in a highly conserved homeobox sequence ofMSX1, was identified also in 2 healthy individuals from the proband’s family. Our finding suggests that this transition might be the first described mutation ofMSX1 that might be responsible for oligodontia and showing incomplete penetrance. It may also support the view that this common anomaly of human dentition might be an oligogenic trait caused by simultaneous mutations of different genes.

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.

Folate and choline metabolism gene variants and development of uterine cervical carcinoma

OBJECTIVE It has been reported that aberrant DNA methylation can be associated with HPV infection and cervical tumorigenesis. The aim of this study was to evaluate the possibility that polymorphic variants of genes that may affect DNA methylation status are associated with the risk of cervical cancer in the Polish population. DESIGN AND METHOD Employing PCR-RFLPs and HRM analyses, we examined the prevalence of BHMT Arg239Gln (rs3733890), MTR Asp919Gly (rs1805087), MTHFR Ala222Val (rs1801133), MTHFD1 Arg653Gln (rs2236225) and MTRR Ile22Met (rs1801394) genotypes and alleles in patients with advanced cervical cancer (n=124) and controls (n=168). RESULTS The odds ratio (OR) for BHMT Gln/Gln genotype was 0.433 (95% CI=0.1780-1.054; p=0.0602). The OR for patients having the BHMT Arg/Gln or Gln/Gln genotypes was 0.579 (95% CI=0.3622-0.924; p=0.0216). We also observed a significantly higher frequency of the BHMT 239Gln allele in controls than in patients, p=0.0165. The genotype and allele frequencies of the MTR Asp919Gly, MTHFR Ala222Val, MTHFD1 Arg653Gln and MTRR Ile22Met gene variants did not display statistical differences between patients with cervical cancer and controls. We also did not find a significant association between the distribution of any genotypes or alleles and cancer characteristics. CONCLUSION Our results might suggest the protective role of the BHMT 239Gln variant in cervical cancer incidence.