A genome wide linkage scan for cleft lip and palate and dental anomalies

Prevalence of Dental Anomalies in Taiwanese Children with Cleft Lip and Cleft Palate

The aim of this study was to investigate the prevalence of tooth agenesis, tooth malformation, and eruption patterns of upper canines/first premolars in Taiwanese children. A total of 132 cleft lip and cleft palate (CLCP) patients (82 boys and 50 girls) underwent alveolar bone grafting (ABG) between 2012 and 2022. The patients' dental records and X-ray images were inspected. We examined dental anomalies, including congenital missing teeth, microdontia, and transposition from the upper canines to the upper first premolars in these CLCP patients. Additionally, we investigated the mean ABG operation age (9.27 ± 0.76 years) of our patient; 40.9% of them received pre-ABG orthodontic treatment at 8.72 ± 0.70 years. Among the 132 cleft subjects, the prevalence of tooth agenesis is 73.5% (97/132). The most frequently missing teeth are the maxillary lateral incisors (right side: 46.2%; left side: 47.0%). In this study, microdontia are found in all the upper incisors, of which the highest percentage (18.9%) is observed in the upper left lateral incisors. The prevalence of upper canine and first premolar transposition is 10.6%. The pattern of tooth agenesis and microdontia of the upper lateral incisors shows a strong correlation with the cleft sites of these CLCP patients in our study. These results may support the idea that the patterns of dental anomalies in CLCP patients are region-specific.

Could maternal stress be a causal factor for nonsyndromic cleft lip and/or palate: A retrospective study

BACKGROUND

The etiology of the nonsyndromic cleft lip and palate is multifactorial and not clearly defined.

OBJECTIVE

To determine whether maternal stress could be a causal factor for the occurrence of nonsyndromic cleft lip and palate.

MATERIALS AND METHODS

We conducted a retrospective observational study in which data from 50 mothers of children born with nonsyndromic cleft lip and palate and 50 mothers of noncleft children were analyzed. The outcomes defined were to study the association between the increased stress scores and the occurrence of nonsyndromic cleft lip and/or palate. Statistical analysis was performed using the Chi-square test.

RESULTS

The association between the high maternal stress scores and the occurrence of nonsyndromic cleft lip and/or palate was not found to be significant (P = 0.3220). A significant association was noted between increased maternal age and increased stress levels in the cleft group (P = 0.0001).

CONCLUSION

No significant association was found between the increased stress scores and the occurrence of nonsyndromic cleft lip and/or palate. However, mothers of cleft children whose age was 35 years and above at the time of conception were noted to have higher stress levels.

Pulp enlargement in individuals born with cleft lip and palate pulp, a radiographic study from the cleft lip and palate service of paraiba, Brazil'

PURPOSE

Pulp chamber enlargement impacts endodontic treatment planning. The aim of this study was to evaluate alterations in pulp chamber size of posterior teeth in individuals born with cleft lip with or without cleft palate.

METHODS

Ninety individuals were treated at the Cleft Lip and Palate Service of the University Hospital Lauro Wanderley, Federal University of Paraíba, between the ages of 4 and 15 years born with cleft lip with or without cleft palate were selected. Ninety-nine patients from the archives of the residency program in Orthodontics of the Brazilian Dental Association (ABO) were paired by sex and age as a comparison group. Radiographs were evaluated by a single examiner, observing the presence/absence of an enlarged pulp chamber in the first and second permanent molars of all quadrants. Chi square or Fisher's exact tests were used (α = 0.05) in all comparisons.

RESULTS

Pulp enlargement was more frequently found among individuals born with cleft lip with or without cleft palate (p = 0.0005). However, pulp enlargement frequency was different among subjects born with clefts (p = 0.0006). Pulp enlargement was more common in the maxilla, in both groups. Individuals born with cleft lip with or without cleft palate more often had six or more teeth affected (p = 0.02). Furthermore, individuals with a bilateral cleft more often had six or more teeth affected in comparison to unilateral cases (p = 0.002).

CONCLUSION

Pulp enlargement is a frequent finding, particularly among individuals born with cleft lip with or without cleft palate, with a higher prevalence in the maxilla.

Prevalence of Dental Anomalies in Patients With Unilateral Cleft Lip and Alveolus Treated With Gingivoperiosteoplasty

OBJECTIVE

To compare the prevalence of dental malformations and agenesis in patients who received or did not receive gingivoperiosteoplasty (GPP).

DESIGN

Retrospective cohort study.

PATIENTS

Review of patients born January 1, 2000, to December 31, 2007, with unilateral cleft lip and alveolus, with or without clefting of the secondary palate, who received GPP and/or secondary alveolar bone grafting (ABG). Patients were included if they had clinical images and dental radiographs available at ages 5 to 9 and 10 to 12 years. Ninety-four patients met the inclusion criteria; 46 treated with GPP, and 48 who did not receive GPP.

OUTCOME MEASURES

Records were assessed for supernumerary, missing, and malformed teeth by a blinded examiner, and prevalence compared between groups using χ² tests.

RESULTS

Cleft side lateral incisors were absent in 54% of GPP patients, compared to 50% in the no-GPP group. Two patients in the GPP group and 1 in the no-GPP group had supernumerary lateral incisors. Most lateral incisors were undersized or peg shaped in both the no-GPP (83.3%) and GPP (71.4%) groups. In the GPP group, 5 (10.9%) patients exhibited central incisor agenesis, and 3 had significant hypoplasia. In the no-GPP group, 4 (8.3%) patients exhibited central incisor agenesis, and 5 (10.5%) significant hypoplasia. These differences were not statistically significant.

CONCLUSIONS

Gingivoperiosteoplasty was not associated with increased prevalence of dental malformation or agenesis. When performed appropriately, GPP is a safe treatment technique that does not increase the risk of dental anomalies.

Scandcleft randomized trials of primary surgery for unilateral cleft lip and palate: impact of maxillary dental agenesis on craniofacial growth and dental arch relationship in 8 year olds

BACKGROUND

It is suggested that dental agenesis affects maxillary protrusion and dental arch relationship in children with unilateral cleft lip and palate (UCLP). In addition, an association between the need for orthognathic surgery and dental agenesis is reported.

AIM

The aim was to study the impact of maxillary dental agenesis on craniofacial growth and dental arch relationship in 8-year-old children with UCLP.

SUBJECTS AND METHODS

The sample consisted of individuals with UCLP from Scandcleft randomized trials. The participants had available data from diagnosis of maxillary dental agenesis as well as cephalometric measurements (n = 399) and GOSLON assessment (n = 408) at 8 years of age.

RESULTS

A statistically significant difference was found for ANB between individuals with agenesis of two or more maxillary teeth (mean 1.52°) in comparison with those with no or only one missing maxillary tooth (mean 3.30° and 2.70°, respectively). Mean NSL/NL was lower among individuals with agenesis of two or more maxillary teeth (mean 9.90°), in comparison with individuals with no or one missing maxillary tooth (mean 11.46° and 11.45°, respectively). The number of individuals with GOSLON score 4-5 was 47.2% in the group with two or more missing maxillary teeth and 26.1% respectively 26.3% in the groups with no or one missing maxillary tooth. No statistically significant difference was found in the comparison between individuals with no agenesis or with agenesis solely of the cleft-side lateral.

CONCLUSION

Maxillary dental agenesis impacts on craniofacial growth as well as dental arch relationship and should be considered in orthodontic treatment planning.

Gene-environment interaction in molar-incisor hypomineralization

Molar incisor hypomineralization (MIH) is an enamel condition characterized by lesions ranging in color from white to brown which present rapid caries progression, and mainly affects permanent first molars and incisors. These enamel defects usually occur when there are disturbances during the mineralization or maturation stage of amelogenesis. Both genetic and environmental factors have been suggested to play roles in MIH’s development, but no conclusive risk factors have shown the source of the disease. During head and neck development, the interferon regulatory factor 6 (IRF6) gene is involved in the structure formation of the oral and maxillofacial regions, and the transforming growth factor alpha (TGFA) is an essential cell regulator, acting during proliferation, differentiation, migration and apoptosis. In this present study, it was hypothesized that these genes interact and contribute to predisposition of MIH. Environmental factors affecting children that were 3 years of age or older were also hypothesized to play a role in the disease etiology. Those factors included respiratory issues, malnutrition, food intolerance, infection of any sort and medication intake. A total of 1,065 salivary samples from four different cohorts were obtained, and DNA was extracted from each sample and genotyped for nine different single nucleotide polymorphisms. Association tests and logistic regression implemented in PLINK were used for analyses. A potential interaction between TGFA rs930655 with all markers tested in the cohort from Turkey was identified. These interactions were not identified in the remaining cohorts. Associations (p<0.05) between the use of medication after three years of age and MIH were also found, suggesting that conditions acquired at the age children start to socialize might contribute to the development of MIH.

Sella Turcica Bridging and Tooth Agenesis in Children With Unilateral Cleft Lip and Palate

AIM

To investigate differences in sella turcica size and bridging in children with unilateral cleft lip and palate (UCLP) with or without concomitant dental anomalies.

PATIENTS AND METHODS

A cross-sectional study was carried out looking at 56 children with nonsyndromic UCLP. Lateral cephalograms, taken before alveolar bone grafting, were used to assess sella turcica height, width, area, and bridging. Panoramic radiographs were used to evaluate the presence of dental anomalies in the cleft area including agenesis, supernumerary, and peg-shaped lateral incisors. Differences between sella turcica measurements in the presence or absence of dental anomalies were assessed using t tests. Differences between the prevalence of dental anomalies and sella turcica bridging were assessed using χ² and Fisher exact tests. Multinomial logistic regression was used to investigate potential associations between sella measurements and dental anomalies.

RESULTS

Twenty-six of the 56 children presented with agenesis of the cleft-side lateral incisor, while 7 had a supernumerary, and 19 had a peg-shaped lateral incisor. With regard to sella turcica bridging, 27 children had no calcification, 25 partial and 4 complete calcification. Children with agenesis of the cleft-side lateral incisor showed a shorter sella maximum height (P = .010) and a smaller area (P = .019). When looking at sella turcica bridging, 100% of children with complete calcification showed agenesis of the cleft-side lateral incisor, compared with 52% and 33% of children with partial calcification and no calcification, respectively (P = .034).

CONCLUSIONS

Children with UCLP and sella turcica bridging are more likely to present with agenesis of the cleft-side maxillary lateral incisor.

Maxillary incisor enamel defects in individuals born with cleft lip/palate

Cleft lip with or without cleft palate (CLP) is considered the most frequent congenital malformations of the head and neck, with cleft individuals exhibiting more chances of presenting abnormalities such as developmental defects of enamel (DDE). Matrix metallopeptidase 2 (MMP2) is a membrane-bound protein with collagen-degrading ability and has important roles in tooth formation and mineralization. The aim of this study was to evaluate the frequency, location, severity and extent of DDE found in the maxillary incisors for groups of individuals born with CLP, as well as understanding their relationship with the cleft side. Besides, this study addresses the hypothesis that DDE can be influenced by variation in the MMP2 genes (rs9923304). Individual samples, clinical history, intraoral photographs and panoramic radiographs were obtained from 233 patients under treatment at the Cleft Lip and Palate Service of the University Hospital Lauro Wanderley at the Federal University of Paraíba. Digital images were examined by the same evaluator using the Classification of Defects According to the Modified DDE Index, and then loaded into the Image Tool software, where two measurements were made: total area of the buccal surface (SA) and the area of the DDE (DA), obtaining the percentage of the surface area affected (%SAD) (ICC = 0.99). Genomic DNA was extracted from saliva samples from 124 participants. Genotyping was carried out using TaqMan chemistry for one marker in MMP2 (rs9923304). Statistical analyses were performed by The Jamovi Project software. The Shapiro-Wilk test was applied, followed by the Student's t-test and the Mann-Whitney test. Chi-square and Fisher's exact tests, and odds ratio (OR) with 95% confidence interval (CI) calculations were used to determine Hardy-Weinberg equilibrium and statistically significant differences with an alpha of 0.05. No significant differences in the prevalence and extent of enamel defects were found between male and female individuals born with CLP (p = 0.058256). The frequency of individuals presenting teeth with DDE, in relation to the cleft and non-cleft side, was statistically different (p <0.001; OR = 7.15, CI: 4.674> 7.151> 10.942). However, the averages of %SAD were similar (p = 0.18). The highest means of the %SAD were found in individuals with bilateral cleft lip with or without cleft palate (BCLP) when compared to individuals with unilateral cleft lip with or without cleft palate (UCLP), for the teeth inside (IA) and outside the cleft area (OA) (p <0.001). Regardless of the cleft side, individuals with BCLP were 7.85 times more likely to have more than one third of the tooth surface affected, showing more frequently defects in the three thirds (OA: p <0.001) (IA: p = 0.03), as well as a higher frequency of more than one type of defect (OA: p = 0.000358) (IA: p = 0.008016), whereas in UCLP, defects were isolated and restricted to only one third, more frequently, the incisal third (OA: p = 0.009) (IA: p = 0.001), with greater frequency of milder defects, such as demarcated (p = 0.02) and diffuse (p = 0.008) opacities. A higher frequency of the T allele, less common, was observed in the group of CLP individuals who had all the affected teeth or at least two teeth with %SAD greater than 20% (p = 0.019843). Our results suggest that MMP2 may have a role in the cases that presented DDE and genotyping rs9923304 could serve as the basis for a genomic approach to define risks for individuals born with CLP. Frequency and severity of DDE is strongly related to the CLP phenotype, since the highest values were found for BCLP. However, the extent of the DDE is independent of its relationship with the side of the cleft.

Talon Cusp Associates With MMP2 in a Cohort of Individuals Born With Oral Clefts

OBJECTIVE

The aim of this study was to use dental development as a tool to subphenotype oral clefts and investigate the association of MMP2 with dentin-pulp complex anomalies, in order to identify dental anomalies that are a part of a "cleft syndrome."

DESIGN

Two hundred and ninety individuals born with cleft lip and palate were evaluated and several clinical features, such as cleft completeness or incompleteness, laterality, and presence of dental anomalies were used to assess each individual's cleft status. We tested for overrepresentation of MMP2 single nucleotide polymorphism rs9923304 alleles depending on individuals having certain dental anomalies. Chi-square and Fisher exact tests were used in all comparisons (α = .05).

RESULTS

All individuals studied had at least one dental anomaly outside the cleft area. Significant differences between individuals born with clefts with and without talon cusp (P = .04) were observed for the frequency of the MMP2 less common allele.

CONCLUSION

All individuals born with cleft lip and palate had alterations of the dentition, and a quarter to half of the individuals had alterations of the internal anatomy of their teeth, which further indicates that dental anomalies can be considered as an extended phenotype for clefts. MMP2 was associated with talon cusp in individuals born with oral clefts.

Scandcleft randomized trials of primary surgery for unilateral cleft lip and palate: dental anomalies in 8-year olds

BACKGROUND

Children born with unilateral cleft lip and palate (UCLP) are reported to display several dental anomalies including agenesis, supernumeraries, as well as variations in dental size, shape, and path of eruption. The extensive sample of individuals with UCLP included in the Scandcleft randomized control trials offers the opportunity to study more rare conditions, which is seldom possible with limited samples.

OBJECTIVES

The aim was to study dental anomalies at 8 years of age in children born with UCLP included in the Scandcleft randomized control trials.

METHODS

Panoramic and intraoral radiographs from 425 individuals (279 males and 146 females) with a mean age of 8.1 years were assessed by four orthodontists regarding dental anomalies.

RESULTS

Agenesis was found in 52.5 per cent and supernumerary teeth in 16.9 per cent of the participants. The cleft lateral was missing in 43.8 per cent and was found peg shaped in 44.7 per cent. The distribution of ectopic eruption was 14.6 per cent, mainly affecting maxillary first molars, while transposition was found in 3.4 per cent of the individuals. In addition, infraocclusion of one or several primary molars was registered in 7.2 per cent of the participants.

CONCLUSION

We conclude that 8-year-old children born with UCLP display multiple dental anomalies. The Scandcleft sample allowed rarely studied conditions such as infraocclusion of primary molars and transposition to be studied in children born with UCLP.

TRIAL REGISTRATION

ISRCTN29932826.

Association between MSX1 rs12532 polymorphism with nonsyndromic unilateral complete cleft lip and palate and tooth agenesis

OBJECTIVES

To investigate the association of MSX1 rs12532 polymorphism with the risk of nonsyndromic unilateral complete cleft lip and palate (NSCLP) and tooth agenesis.

MATERIALS AND METHODS

The study is comprised of 384 individuals divided into 4 groups: group 1, patients with unilateral complete NSCLP and premolar agenesis (n = 57); group 2, patients with unilateral NSCLP without tooth agenesis (n = 117); group 3, patients with premolar agenesis without oral cleft (n = 53) and group 4 (n = 157), a control group with individuals without tooth agenesis and oral cleft. Genotyping of rs12532 was carried out with Taqman chemistry, and associations were investigated using logistic regression analyses.

RESULTS

Overall rs12532 allele and genotype distributions revealed no significant differences between the groups of NSCLP or tooth agenesis.

CONCLUSION

Although our results are consistent with a lack of association of MSX1 rs12532 and the risk of unilateral NSCLP and tooth agenesis, further studies with additional SNPs and a more diverse ethnic cohort are warranted.

Three GLI2 mutations combined potentially underlie non-syndromic cleft lip with or without cleft palate in a Chinese pedigree

Background

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is the most common craniofacial birth defect. Its etiology is complex and it has a lifelong influence on affected individuals. Despite many studies, the pathogenic gene alleles are not completely clear. Here, we recruited a Chinese NSCL/P family and explored the candidate causative variants in this pedigree.

Methods

We performed whole‐exome sequencing on two patients and two unaffected subjects of this family. Variants were screened based on bioinformatics analysis to identify the potential etiological alleles. Species conservation analysis, mutation function prediction, and homology protein modeling were also performed to preliminarily evaluate the influence of the mutations.

Results

We identified three rare mutations that are located on a single chromatid (c.2684C > T_p.Ala895Val, c.4350G > T_p.Gln1450His, and c.4622C > A_p.Ser1541Tyr) in GLI2 as candidate causative variants. All of these three mutations were predicted to be deleterious, and they affect amino acids that are conserved in many species. The mutation c.2684C > T was predicted to affect the structure of the GLI2 protein.

Conclusion

Our results further demonstrate that GLI2 variants play a role in the pathogenesis of NSCL/P, and the three rare missense mutations combined are probably the potential disease‐causing variants in this family.

Syndromes associated with dental agenesis

INTRODUCTION

Dental agenesis is the congenital absence of a variable number of teeth due to the lack of formation of the corresponding tooth germ. The aim of this work was to investigate the syndromic conditions characterized by dental agenesis.

EVIDENCE ACQUISITION

Based on the research conducted through the OMIM® (Online Mendelian Inheritance in Man) and PubMed online databases, more than ninety syndromes associated with severe or moderate agenesis have been found.

EVIDENCE SYNTHESIS

The main clinical features of these syndromes are described, especially those concerning the stomatognathic apparatus, referring to the most recent literature. Among these syndromes there are three clinical conditions associated with dental agenesis that are common for the clinician: Down Syndrome, ectodermal dysplasia and labio-palatal cleft.

CONCLUSIONS

It must be kept in mind that the success of the treatment of these patients is based on the compliance of the patient as well as on the collaboration among specialists.

Nucleotide variants of the NAT2 and EGF61 genes in patients in Northern China with nonsyndromic cleft lip with or without cleft palate

BACKGROUND

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common orofacial congenital anomaly. The objective of the present study was to analyze the association of single nucleotide polymorphisms (SNPs) in the NAT2 and EGF61genes with NSCL/P in a Chinese population.

METHODS

The frequencies of NAT2 (rs1799929)and EGF61 (rs4444903) gene variations were examined in a group of 285 NSCL/P patients and in 315 controls. Peripheral venous blood samples were collected for DNA extraction. Genotyping of the 2 SNPs was carried out using a mini sequencing (SNaPshot) method. Data were analyzed using the chi-square test.

RESULTS

We found a significant association between the EGF61 (rs4444903) and NSCL/P (P = .01) genes.Conversely, NAT2 (rs1799929) was not significantly different between the cases and the control group.The genotype frequencies of rs4444903GA showed a significant difference compared with GG genotype as a reference (odds ratio = 0.59; 95% confidence interval: 0.42-0.84, P = .01).

CONCLUSION

Our study showed that the EGF61 rs4444903GA genotype had a decreased risk of NSCL/P. Our data provides further evidence regarding the role of EGF61 variations in the development of NSCL/P in families of the studied populations.

The prevalence, penetrance, and expressivity of etiologic IRF6 variants in orofacial clefts patients from sub-Saharan Africa

Background

Orofacial clefts are congenital malformations of the orofacial region, with a global incidence of one per 700 live births. Interferon Regulatory Factor 6 (IRF6) (OMIM:607199) gene has been associated with the etiology of both syndromic and nonsyndromic orofacial clefts. The aim of this study was to show evidence of potentially pathogenic variants in IRF6 in orofacial clefts cohorts from Africa.

Methods

We carried out Sanger Sequencing on DNA from 184 patients with nonsyndromic orofacial clefts and 80 individuals with multiple congenital anomalies that presented with orofacial clefts. We sequenced all the nine exons of IRF6 as well as the 5′ and 3′ untranslated regions. In our analyses pipeline, we used various bioinformatics tools to detect and describe the potentially etiologic variants.

Results

We observed that potentially etiologic exonic and splice site variants were nonrandomly distributed among the nine exons of IRF6, with 92% of these variants occurring in exons 4 and 7. Novel variants were also observed in both nonsyndromic orofacial clefts (p.Glu69Lys, p.Asn185Thr, c.175‐2A>C and c.1060+26C>T) and multiple congenital anomalies (p.Gly65Val, p.Lys320Asn and c.379+1G>T) patients. Our data also show evidence of compound heterozygotes that may modify phenotypes that emanate from IRF6 variants.

Conclusions

This study demonstrates that exons 4 and 7 of IRF6 are mutational ‘hotspots’ in our cohort and that IRF6 mutants‐induced orofacial clefts may be prevalent in the Africa population, however, with variable penetrance and expressivity. These observations are relevant for detection of high‐risk families as well as genetic counseling. In conclusion, we have shown that there may be a need to combine both molecular and clinical evidence in the grouping of orofacial clefts into syndromic and nonsyndromic forms.

Discovery of candidate genes for nonsyndromic cleft lip palate through genome-wide linkage analysis of large extended families in the Malay population

BACKGROUND

Nonsyndromic orofacial clefts are one of the most common birth defects worldwide. It occurs as a result of genetic or environmental factors. This study investigates the genetic contribution to nonsyndromic cleft lip and/or palate through the analysis of family pedigrees. Candidate genes associated with the condition were identified from large extended families from the Malay population.

RESULTS

A significant nonparametric linkage (NPL) score was detected in family 100. Other suggestive NPL and logarithm of the odds (LOD) scores were attained from families 50, 58, 99 and 100 under autosomal recessive mode. Heterogeneity LOD (HLOD) score ≥ 1 was determined for all families, confirming genetic heterogeneity of the population and indicating that a proportion of families might be linked to each other. Several candidate genes in linkage intervals were determined; LPHN2 at 1p31, SATB2 at 2q33.1-q35, PVRL3 at 3q13.3, COL21A1 at 6p12.1, FOXP2 at 7q22.3-q33, FOXG1 and HECTD1 at 14q12 and TOX3 at 16q12.1.

CONCLUSIONS

We have identified several novel and known candidate genes for nonsyndromic cleft lip and/or palate through genome-wide linkage analysis. Further analysis of the involvement of these genes in the condition will shed light on the disease mechanism. Comprehensive genetic testing of the candidate genes is warranted.

Cleft lip and palate and related factors: A 10 years study in university hospitalised patients at Mashhad--Iran

BACKGROUND

Oral-facial clefts including cleft lip and palate are the most common congenital malformations of the head and neck. Environmental factors such as maternal hormonal disorders, use of psychiatric medications, vitamin and folic acid deficiency, hypoxia, cigarette smoking and maternal obesity and overweight can affect the incidence of these disorders. In Iran, one of the associated problems is a lack of accurate statistics regarding the present status of the patients, which can cause a disturbance in the health programmes of Ministry of Health and Medical Education. The aim of this study was to report the status of 398 cases of cleft lip and palate in Sheikh and Imam Reza Hospitals of Mashhad over a 10-year period.

MATERIALS AND METHODS

This retrospective descriptive study was performed using data collection method and included the evaluation of the recorded files and completing the data forms. In this study, the file records of 398 patients referring to Mashhad Sheikh and Imam Reza (P.U.H) Hospitals were studied, from the beginning of 2002 to the end of 2011; the obtained data from the files were collected and classified.

RESULTS

The highest frequency was related to cleft palate alone (40.7%); frequencies were lower regarding the cleft lip and palate and cleft lip alone (34.41% and 24.87%, respectively). Approximately, half of the patients were from rural areas of the city and had articulation disorders. Most of the patients were the first-born children of the family and their parents were consanguineously married; about one-third of the patients had a family history of the disease.

CONCLUSION

According to the results of the present study, cleft lip is more frequent in males and cleft palate is more prevalent in females; the obtained results are consistent with the global statistics.

Spectrum of Dental Phenotypes in Nonsyndromic Orofacial Clefting

Children with oral clefts show a wide range of dental anomalies, adding complexity to understanding the phenotypic spectrum of orofacial clefting. The evidence is mixed, however, on whether the prevalence of dental anomalies is elevated in unaffected relatives and is mostly based on small samples. In the largest international cohort to date of children with nonsyndromic clefts, their relatives, and controls, this study characterizes the spectrum of cleft-related dental anomalies and evaluates whether families with clefting have a significantly higher risk for such anomalies compared with the general population. A total of 3,811 individuals were included: 660 cases with clefts, 1,922 unaffected relatives, and 1,229 controls. Dental anomalies were identified from in-person dental exams or intraoral photographs, and case-control differences were tested using χ(2) statistics. Cases had higher rates of dental anomalies in the maxillary arch than did controls for primary (21% vs. 4%, P = 3 × 10(-8)) and permanent dentitions (51% vs. 8%, P = 4 × 10(-62)) but not in the mandible. Dental anomalies were more prevalent in cleft lip with cleft palate than other cleft types. More anomalies were seen in the ipsilateral side of the cleft. Agenesis and tooth displacements were the most common dental anomalies found in case probands for primary and permanent dentitions. Compared with controls, unaffected siblings (10% vs. 2%, P = 0.003) and parents (13% vs. 7%, P = 0.001) showed a trend for increased anomalies of the maxillary permanent dentition. Yet, these differences were nonsignificant after multiple-testing correction, suggesting genetic heterogeneity in some families carrying susceptibility to both overt clefts and dental anomalies. Collectively, the findings suggest that most affected families do not have higher genetic risk for dental anomalies than the general population and that the higher prevalence of anomalies in cases is primarily a physical consequence of the cleft and surgical interventions.

Heritability of the Human Craniofacial Complex

Quantifying normal variation and the genetic underpinnings of anatomical structures is one of the main goals of modern morphological studies. However, the extent of genetic contributions to normal variation in craniofacial morphology in humans is still unclear. The current study addresses this gap by investigating the genetic underpinnings of normal craniofacial morphology. The sample under investigation consists of 75 linear and angular measurements spanning the entire craniofacial complex, recorded from lateral cephalographs of 1,379 participants in the Fels Longitudinal Study. Heritabilities for each trait were estimated using SOLAR, a maximum-likelihood variance components approach utilizing all pedigree information for parameter estimation. Trait means and mean effects of the covariates age, sex, age(2) , sex × age, and sex × age(2) were simultaneously estimated in the analytic models. All traits of the craniofacial complex were significantly heritable. Heritability estimates ranged from 0.10 to 0.60, with the majority being moderate. It is important to note that we found similar ranges of heritability occurring across the different functional/developmental components of the craniofacial complex, the splanchnocranium, the basicranium, and the neurocranium. This suggests that traits from different regions of the craniofacial complex are of comparable utility for the purposes of population history and phylogeny reconstruction. At the same time, this genetic influence on craniofacial morphology signals a caution to researchers of nongenetic studies to consider the implications of this finding when selecting samples for study given their project design and goals.

Fine Mapping of 6q23.1 Identifies TULP4 as Contributing to Clefts

Objective

The aim of this work was to fine-map the region 6q23.1, which obtained suggestive linkage signal (logarithm of the odds [LOD] score = 2.22 under a recessive model) to cleft lip with or without cleft palate (CL±P) in our previous genome-wide linkage scan to identify possible genetic variants that may contribute to CL±P.

Design

We used densely spaced markers spanning the entire 6q23.1 region to test for association with CL±P in a family cohort sample.

Setting

Clinical information and DNA samples were obtained from families in the Philippines at their homes or primary health care clinics.

Participants

The study sample consisted of 477 subjects (224 females and 253 males), segregating isolated CL±P, from 72 living in the same area in the Philippines.

Main Outcome Measure

Overtransmission of alleles to persons born with CL±P.

Results

We found statistical evidence of association between a marker of TULP4 (rs651333) with CL±P ( P = .00007).

Conclusions

Our results further support the linkage results for the chromosome 6q region and reveal a novel candidate gene for CL±P.

Genetics of cleft lip and cleft palate

Orofacial clefts are common birth defects and can occur as isolated, nonsyndromic events or as part of Mendelian syndromes. There is substantial phenotypic diversity in individuals with these birth defects and their family members: from subclinical phenotypes to associated syndromic features that is mirrored by the many genes that contribute to the etiology of these disorders. Identification of these genes and loci has been the result of decades of research using multiple genetic approaches. Significant progress has been made recently due to advances in sequencing and genotyping technologies, primarily through the use of whole exome sequencing and genome-wide association studies. Future progress will hinge on identifying functional variants, investigation of pathway and other interactions, and inclusion of phenotypic and ethnic diversity in studies.

MSX1 gene and nonsyndromic oral clefts in a Southern Brazilian population

Nonsyndromic oral clefts (NSOC) are the most common craniofacial birth defects in humans. The etiology of NSOC is complex, involving both genetic and environmental factors. Several genes that play a role in cellular proliferation, differentiation, and apoptosis have been associated with clefting. For example, variations in the homeobox gene family member MSX1, including a CA repeat located within its single intron, may play a role in clefting. The aim of this study was to investigate the association between MSX1 CA repeat polymorphism and NSOC in a Southern Brazilian population using a case-parent triad design. We studied 182 nuclear families with NSOC recruited from the Hospital de Clínicas de Porto Alegre in Southern Brazil. The polymorphic region was amplified by the polymerase chain reaction and analyzed by using an automated sequencer. Among the 182 families studied, four different alleles were observed, at frequencies of 0.057 (175 bp), 0.169 (173 bp), 0.096 (171 bp) and 0.67 (169 bp). A transmission disequilibrium test with a family-based association test (FBAT) software program was used for analysis. FBAT analysis showed overtransmission of the 169 bp allele in NSOC (P=0.0005). These results suggest that the CA repeat polymorphism of the MSX1 gene may play a role in risk of NSOC in populations from Southern Brazil.

Buccal cells DNA extraction to obtain high quality human genomic DNA suitable for polymorphism genotyping by PCR-RFLP and Real-Time PCR

Objective

The aim of this study was to evaluate, by PCR-RFLP and Real-time PCR, the yield and quality of genomic DNA collected from buccal cells by mouthwash after different storage times at room temperature.

Material and Methods

A group of volunteers was recruited to collect buccal cells using a mouthwash solution. The collected solution was divided into 3 tubes, one tube were used for immediate extraction and the remaining received ethanol and were kept at room temperature for 4 and 8 days followed by DNA extraction. The concentration, purity and integrity of the DNA were determined using spectrophotometry and electrophoresis. DNA quality differences among the three incubation times were also evaluated for genotyping EGF +61 A/G (rs 4444903) polymorphism by PCR-RFLP and for IRF6 polymorphism (rs 17015215) using Real-Time PCR.

Results

There was no significant difference of DNA yield (p=0.75) and purity (p=0.86) among the three different incubation times. DNA obtained from different incubation times presented high-molecular weight. The PCR-RFLP and Real time PCR reactions were successfully performed for all DNA samples, even those extracted after 8 days of incubation. All samples genotyped by Real-Time PCR presented C allele for IRF6 gene polymorphism (homozygous: CC; heterozygous: CT) and the C allele was used as a reference for Ct values. The samples presented the same genotype for the different times in both techniques.

Conclusion

We demonstrated that the method described herein is simple and low cost, and that DNA can be extracted and PCR amplified after storage in mouthwash solution at room temperature.

MSX1 gene polymorphisms in non-syndromic cleft lip and/or palate

OBJECTIVE

The aim of this study was to investigate the contribution of 6 polymorphic variants of the MSX1 gene in non-syndromic cleft lip and/or palate (NSCL/P).

METHODS

Three hundred and fifty-eight individuals (158 NSCL/P cases and 200 controls) were genotyped by TaqMan allelic discrimination using predesigned SNP assays. Statistical analyses were conducted using the software spss 15.0 and the r statistical suite. Haplotype block structure and haplotype frequencies were determined using the Haploview. A P-value of 0.05 and confidence interval of 95% were used for all of statistical tests.

RESULTS

The patients with non-syndromic cleft lip and/or palate were characterized by similar distribution of MSX1 genotypes and allele in comparison to subjects without oral clefts (P > 0.05). Two haplotype blocks were constructed with polymorphisms of MSX1 gene and haplotypes formed showed a similar frequency in patients with and without oral clefts.

CONCLUSIONS

The present study provides no evidence that MSX1 polymorphisms (rs3775261, rs1042484, rs12532, rs6446693, rs4464513 and rs1907998) play a major role in NSCL/P.

BCL3 gene role in facial morphology

BACKGROUND

Cleft lip (CL) with or without palate (CLP) and isolated cleft palate (CP) are etiologically complex diseases with interactions among various environmental and genetic factors. The aim of the current study was to identify association with genetic markers and phenotypic craniofacial data in patients with CL/CLP/CP parents.

METHODS

Posteroanterior and lateral digital radiographs of the cranium were obtained from 74 parents of patients with CL/CLP/CP. One hundred seventy-three patients with CL/CLP/CP and 190 controls were enrolled in the study for the association test. Five genetic markers of the IRF6 gene and 14 markers of the 19q13 locus were genotyped. Linear regression analysis was performed for the relationship of cephalometric measurements with genotype data adjusted for age, gender, and cleft type. Chi-square and transmission disequilibrium tests were performed to evaluate differences in alleles of the BCL3 gene. Positive findings were replicated in an independent sample (n = 95) of patients with CL/CLP/CP parents.

RESULTS

Genetic markers of the BCL3 gene at 19q13, rs7257231, and rs1979377 in the familial association test and rs10401176 in the case-control association test, were associated with craniofacial phenotype. Carriers of BCL3 allele rs7257231T had longer posterior cranial bases than noncarriers (p(adjusted) = 0.0028), and in the familial-based association test showed the statistically strongest relationship (p(adjusted) = 0.05) to phenotype. Relation of rs7257231 to facial formation was confirmed in the replication group (p = 0.0024).

CONCLUSIONS

The results indicate that BCL3, which has functions related to cell adhesion and whose downregulation can cause disruption of ectodermal development, is likely to be important in facial formation. Birth Defects Research (Part A), 2012.

GWAS reveals new recessive loci associated with non-syndromic facial clefting

We have applied a GWAS to 40 consanguineous families segregating cases of non-syndromic cleft lip with or without cleft palate (NS CL/P) (a total of 160 affected and unaffected individuals) in order to trace potential recessive loci that confer susceptibility to this common facial malformation. Pedigree-based association test (PBAT) analyses reported nominal evidence of association and linkage over SNP markers located at 11q25 (rs4937877, P = 2.7 × 10(-6)), 19p12 (rs4324267, P = 1.6 × 10(-5)), 5q14.1 (rs4588572, P-value = 3.36 × 10(-5)), and 15q21.1 (rs4774497, P = 1.08 × 10(-4)). Using the Versatile Gene-Based Association Study to complement the PBAT results, we found clusters of markers located at chromosomes 19p12, 11q25, and 8p23.2 overcome the threshold for GWAS significance (P < 1 × 10(-7)). From this study, new recessive loci implicated in NS CL/P include: B3GAT1, GLB1L2, ZNF431, ZNF714, and CSMD1, even though the functional association with the genesis of NS CL/P remains to be elucidated. These results emphasize the importance of using homogeneous populations, phenotypes, and family structures for GWAS combined with gene-based association analyses, and should encourage. other researchers to evaluate these genes on independent patient samples affected by NS CL/P.

The evolution of human genetic studies of cleft lip and cleft palate

Orofacial clefts (OFCs)--primarily cleft lip and cleft palate--are among the most common birth defects in all populations worldwide, and have notable population, ethnicity, and gender differences in birth prevalence. Interest in these birth defects goes back centuries, as does formal scientific interest; scientists often used OFCs as examples or evidence during paradigm shifts in human genetics, and have also used virtually every new method of human genetic analysis to deepen our understanding of OFC. This review traces the evolution of human genetic investigations of OFC, highlights the specific insights gained about OFC through the years, and culminates in a review of recent key OFC genetic findings resulting from the powerful tools of the genomics era. Notably, OFC represents a major success for genome-wide approaches, and the field is poised for further breakthroughs in the near future.

Mesio-Distal and Buccal-Lingual Tooth Dimensions are Part of the Cleft Spectrum: A Pilot for Future Genetic Studies

Objective : Considering that oral clefts and tooth dimensions may be part of the same phenotypic spectrum, the aim of this study was to investigate tooth dimensions in permanent dentition and dental malformations, including tooth size discrepancies, of subjects born with clefts compared with individuals without clefts. Design : Cross-sectional study. Participants : The cleft group was composed of 66 subjects, and the noncleft group consisted of 66 healthy unrelated subjects. Main Outcome Measures : The mesio-distal and buccal-lingual crown diameter of fully erupted permanent teeth outside the cleft area was measured using a digital caliber. Clinical records and radiographs were used to evaluate the type of clefts and dental anomalies. Results : The lower second premolar was significantly reduced in the CLP and CP groups. The upper lateral incisor was found to be significantly smaller in the CP group, only for mesio-distal dimensions (P < .05). Dental agenesis was found in eight (12%) cleft subjects and supernumerary teeth in two (3%). Conclusions : Subjects born with oral clefts presented size reduction in specific dental groups.

Dental anomalies in children born with clefts: a case-control study

OBJECTIVE

To determine the presence of specific patterns of dental defects in a group of individuals born with clefts.

DESIGN

Case-control.

SETTING

Nossa Senhora do Loreto Municipal Hospital and Federal University of Rio de Janeiro Pediatric Dentistry Clinics, Rio de Janeiro, Brazil.

PATIENTS

642 radiographic and clinical records were evaluated for 321 cases and 321 controls.

RESULTS

Individuals born with clefts presented considerably more dental anomalies in comparison with controls (p  =  .0001). The most frequent was tooth agenesis (n  =  53; p  =  .001), followed by supernumerary teeth (n  =  14; p  =  .11) and tooth malposition (n  =  11; p  =  .33). Regarding tooth agenesis, the upper lateral incisors were more frequently absent in the cleft group (31/86), and control individuals presented more agenesis of the mandibular second premolars (19/45).

CONCLUSIONS

The higher prevalence of dental anomalies, especially number anomalies, opposite the cleft area, in individuals born with cleft lip and/or palate is the most common associated dental anomaly outside the cleft area.

Prevalence of dental anomalies in nonsyndromic individuals with cleft lip and palate: a systematic review and meta-analysis

OBJECTIVE

To assess whether individuals born with nonsyndromic oral clefts display a higher frequency of dental anomalies.

DESIGN

A search of MEDLINE, BIREME, OVID ALL EMB Reviews, and The Cochrane Library was conducted. The methodologic quality of the papers selected was assessed and scored. Papers reporting observational controlled studies of nonsyndromic forms of oral cleft matched for dental anomalies in primary and/or permanent teeth were included without language restrictions. Eligible studies were scored as "A"-low risk of bias, "B"-moderate risk of bias, or "C"-high risk of bias and poor quality. Fixed and random effects models were used to aggregate individual odds ratios (OR) and to derive pooled estimates and 95% confidence intervals.

RESULTS

Six studies fulfilled our selection criteria and were included in the meta-analysis. Three distinct subgroup analyses were carried out in terms of dental anomalies. In the tooth agenesis meta-analysis, a random effects model was used because of heterogeneity and showed a significant association between tooth agenesis and oral clefts (OR  =  12.31; 95% confidence interval [CI]  =  3.75 to 40.36). In the remaining analyses, the fixed effects model revealed a positive association between supernumerary (OR  =  4.99; 95% CI, 2.58 to 9.64) and crown morphologic abnormalities (OR  =  5.69; 95% CI, 3.96 to 8.19) with oral clefts. Most included studies were of low to moderate quality.

CONCLUSION

Although general limitations in study design were observed, the evidence suggests that a higher number of dental anomalies in the permanent dentition are noted in individuals born with oral clefts.

No evidence for a role of CRISPLD2 in non-syndromic cleft lip with or without cleft palate in an Italian population

Non-syndromic cleft lip with or without cleft palate (NSCLP) is a malformation with variable phenotypes, resulting from a mixture of genetic and environmental factors. Some studies have supported a role for the 16q24 region and its candidate gene, CRISPLD2, in clefting. A replication study is necessary to confirm these findings. The aim of the present study was to test, by genetic linkage and association analyses, whether the candidate gene, CRISPLD2, represents a risk factor for NSCLP. The analysis of 39 multigenerational families provided formal exclusion of a linkage between NSCLP and the CRISPLD2 locus under different genetic models and non-parametric analyses. The family-based study of 239 unrelated probands and their parents revealed no association between any particular allele or haplotype and NSCLP. Therefore, the present investigation did not support the hypothesis of the involvement of CRISPLD2 in NSCLP malformation, at least with regard to the Italian population.

Genetics of nonsyndromic orofacial clefts

With an average worldwide prevalence of approximately 1.2/1000 live births, orofacial clefts are the most common craniofacial birth defects in humans. Like other complex disorders, these birth defects are thought to result from the complex interplay of multiple genes and environmental factors. Significant progress in the identification of underlying genes and pathways has benefited from large populations available for study, increased international collaboration, rapid advances in genotyping technology, and major improvements in analytic approaches. Here we review recent advances in genetic epidemiological approaches to complex traits and their applications to studies of nonsyndromic orofacial clefts. Our main aim is to bring together a discussion of new and previously identified candidate genes to create a more cohesive picture of interacting pathways that shape the human craniofacial region. In future directions, we highlight the need to search for copy number variants that affect gene dosage and rare variants that are possibly associated with a higher disease penetrance. In addition, sequencing of protein-coding regions in candidate genes and screening for genetic variation in noncoding regulatory elements will help advance this important area of research.

The clf2 gene has an epigenetic role in the multifactorial etiology of cleft lip and palate in the A/WySn mouse strain

BACKGROUND

The A/WySn mouse strain with 15 to 20% penetrance of cleft lip and palate (CLP) is an animal model for human multifactorial CLP. The CLP is due to two unlinked genes that interact epistatically, Wnt9b(clf1) and clf2, plus a maternal effect. The Wnt9b(clf1) mutation is an IAP transposon insertion. The clf2 gene, with unknown function, was located in a 13.6 Mb region of chromosome 13 containing 145 genes.

METHODS

To reduce the clf2 candidate region, 1146 mice segregating for A/WySn and C57BL/6J alleles at clf2 were screened for recombinants by simple sequence-length polymorphism haplotypes; recombinants' testcross progeny were typed for CLP and simple-sequence length polymorphisms. To identify the function of clf2, the effect of clf2 genotype on risk of CLP was tested in Wnt9b(null/null) knockouts and in compound mutants (Wnt9b(clf1/null) ), and the methylation of the IAP at Wnt9b was assayed in the Wnt9b(clf1/null) mutants by combined bisulfite restriction analysis.

RESULTS

The location of clf2 was redefined to 3.0 Mb between Cntnap3 and AK029746 containing 48 genes, of which 30 are Zfp genes. The clf2 genotype had no detectable effect on Wnt9b(null/null) embryos, but strongly affected risk of CLP and methylation of the IAP in Wnt9b(clf1/null) embryos. CLP was associated with low levels of methylation of the IAP.

CONCLUSIONS

The clf2 gene is the first identified polymorphism that affects the epigenetic methylation and silencing of IAP retrotransposons. This CLP model raises the question of whether parallel epigenetic factors are involved in risk and environmental sensitivity of human CLP.

Genome-wide and interaction linkage scan for nonsyndromic cleft lip with or without cleft palate in two multiplex families in Shenyang, China

OBJECTIVES

To identify the loci involved in nonsyndromic cleft lip with or without cleft palate (NSCL/P) in Northern Chinese people in Shenyang by using genomewide and interaction linkage scan.

METHODS

Two multiplex families in Shenyang from North China were ascertained through probands with NSCL/P. Blood of every member was drawn for DNA extraction and analysis. Genotypes were available for 382 autosomal short tandem repeat (STR) markers from the ABI Prism Linkage Mapping Set version 2.5. Linkage between markers and NSCL/P was assessed by 2-point parametric LOD scores, multipoint-heterogeneity parametric LOD scores (HLODs), and multipoint nonparametric linkage score (NPL).

RESULTS

The initial scan suggested linkage on Chromosomes 1, 2, and 15. In subsequent fine mapping, 1q32-q42 showed a maximum multipoint LOD score of 1.9(empirical P=0.013) and an NPL score of 2.35 (empirical P=0.053). For 2p24-p25, the multipoint NPL increased to 2.94 (empirical P=0.007). 2-locus interaction analysis obtained a maximum NPL score of 3.73 (P=0.00078) and a maximum LOD score of 3 for Chromosome 1 (at 221 cM) and Chromosome 2 (at 29 cM).

CONCLUSION

Both parametric and nonparametric linkage scores greatly increased over the initial linkage scores on 1q32-q42, suggesting a susceptibility locus in this region. Nonparametric linkage gave a strong evidence for a candidate region on chromosome 2p24-p25. The superiority of 2-locus linkage scores compared to single-locus scores gave additional evidence for linkage on 1q32-q42 and 2p24-p25, and suggested that certain genes in the two regions may contribute to NCSL/P risks with interaction.

The function and regulation of TBX22 in avian frontonasal morphogenesis

The frontonasal mass gives rise to the facial midline and fuses with the maxillary prominence to form the upper lip. Here we focus on the regulation and function of TBX22, a repressor dynamically expressed in the frontonasal mass. Both FGF and Noggin (a BMP antagonist) strongly induce gTBX22, however, each has opposite effects on morphogenesis - Noggin inhibits whereas FGF stimulates growth. To determine whether TBX22 mediates these effects, we used retroviruses to locally increase expression levels. RCAS::hTBX22 decreased proliferation, reduced expression of MSX2 and DLX5 and caused cleft lip. Decreased levels of endogenous gTBX22 were also observed but were not the primary cause of the phenotype as determined in rescue experiments. Our data suggest that genetic or environmental insults such as those affecting the BMP pathway could lead to a gain-of-function of TBX22 and predispose an individual to cleft lip.

Genome scan, fine-mapping, and candidate gene analysis of non-syndromic cleft lip with or without cleft palate reveals phenotype-specific differences in linkage and association results

OBJECTIVES

Non-syndromic orofacial clefts, i.e. cleft lip (CL) and cleft palate (CP), are among the most common birth defects. The goal of this study was to identify genomic regions and genes for CL with or without CP (CL/P).

METHODS

We performed linkage analyses of a 10 cM genome scan in 820 multiplex CL/P families (6,565 individuals). Significant linkage results were followed by association analyses of 1,476 SNPs in candidate genes and regions, utilizing a weighted false discovery rate (wFDR) approach to control for multiple testing and incorporate the genome scan results.

RESULTS

Significant (multipoint HLOD >or=3.2) or genome-wide-significant (HLOD >or=4.02) linkage results were found for regions 1q32, 2p13, 3q27-28, 9q21, 12p11, 14q21-24 and 16q24. SNPs in IRF6 (1q32) and in or near FOXE1 (9q21) reached formal genome-wide wFDR-adjusted significance. Further, results were phenotype dependent in that the IRF6 region results were most significant for families in which affected individuals have CL alone, and the FOXE1 region results were most significant in families in which some or all of the affected individuals have CL with CP.

CONCLUSIONS

These results highlight the importance of careful phenotypic delineation in large samples of families for genetic analyses of complex, heterogeneous traits such as CL/P.

Dental agenesis: genetic and clinical perspectives

Dental agenesis is the most common developmental anomaly in humans and is frequently associated with several other oral abnormalities. Whereas the incidence of missing teeth may vary considerably depending on dentition, gender, and demographic or geographic profiles, distinct patterns of agenesis have been detected in the permanent dentition. These frequently involve the last teeth of a class to develop (I2, P2, M3) suggesting a possible link with evolutionary trends. Hypodontia can either occur as an isolated condition (non-syndromic hypodontia) involving one (80% of cases), a few (less than 10%) or many teeth (less than 1%), or can be associated with a systemic condition or syndrome (syndromic hypodontia), essentially reflecting the genetically and phenotypically heterogeneity of the condition. Based on our present knowledge of genes and transcription factors that are involved in tooth development, it is assumed that different phenotypic forms are caused by different genes involving different interacting molecular pathways, providing an explanation not only for the wide variety in agenesis patterns but also for associations of dental agenesis with other oral anomalies. At present, the list of genes involved in human non-syndromic hypodontia includes not only those encoding a signaling molecule (TGFA) and transcription factors (MSX1 and PAX9) that play critical roles during early craniofacial development, but also genes coding for a protein involved in canonical Wnt signaling (AXIN2), and a transmembrane receptor of fibroblast growth factors (FGFR1). Our objective was to review the current literature on the molecular mechanisms that are responsible for selective dental agenesis in humans and to present a detailed overview of syndromes with hypodontia and their causative genes. These new perspectives and future challenges in the field of identification of possible candidate genes involved in dental agenesis are discussed.