TBX22 mutation associated with cleft lip/palate, hypodontia, and limb anomaly

Novel Candidate Genes for Non-Syndromic Tooth Agenesis Identified Using Targeted Next-Generation Sequencing

Non-syndromic tooth agenesis (ns-TA) is one of the most common dental anomalies characterized by the congenital absence of at least one permanent tooth (excluding third molars). Regarding the essential role of genetic factors in ns-TA aetiology, the present study aimed to identify novel pathogenic variants underlying hypodontia and oligodontia. In a group of 65 ns-TA patients and 127 healthy individuals from the genetically homogenous Polish population, the coding sequences of 423 candidate genes were screened using targeted next-generation sequencing. Pathogenic and likely pathogenic variants were identified in 37 (56.92%) patients, including eight nucleotide alternations of genes not previously implicated in ns-TA (CHD7, CREBBP, EVC, LEF1, ROR2, TBX22 and TP63). However, since only single variants were detected, future research is required to confirm and fully understand their role in the aetiology of ns-TA. Additionally, our results support the importance of already known ns-TA candidate genes (AXIN2, EDA, EDAR, IRF6, LAMA3, LRP6, MSX1, PAX9 and WNT10A) and provide additional evidence that ns-TA might be an oligogenic condition involving the cumulative effect of rare variants in two or more distinct genes.

Spatiotemporal MicroRNA-Gene Expression Network Related to Orofacial Clefts

Craniofacial structures change dynamically in morphology during development through the coordinated regulation of various cellular molecules. However, it remains unclear how these complex mechanisms are regulated in a spatiotemporal manner. Here we applied natural cubic splines to model gene and microRNA (miRNA) expression from embryonic day (E) 10.5 to E14.5 in the proximal and distal regions of the maxillary processes to identify spatiotemporal patterns of gene and miRNA expression, followed by constructing corresponding regulatory networks. Three major groups of differentially expressed genes (DEGs) were identified, including 3,927 temporal, 314 spatial, and 494 spatiotemporal DEGs. Unsupervised clustering further resolved these spatiotemporal DEGs into 8 clusters with distinct expression patterns. Interestingly, we found 2 clusters of differentially expressed miRNAs: 1 had 80 miRNAs monotonically decreasing and the other had 97 increasing across developmental stages. To evaluate the phenotypic relevance of these DEGs during craniofacial development, we integrated data from the CleftGeneDB database and constructed the regulatory networks of genes related to orofacial clefts. Our analysis revealed 2 hub miRNAs, mmu-miR-325-3p and mmu-miR-384-5p, that repressed cleft-related genes Adamts3, Runx2, Fgfr2, Acvr1, and Edn2, while their expression increased over time. On the contrary, 2 hub miRNAs, mmu-miR-218-5p and mmu-miR-338-5p, repressed cleft-related genes Pbx2, Ermp1, Snai1, Tbx2, and Bmi1, while their expression decreased over time. Our experiments indicated that these miRNA mimics significantly inhibited cell proliferation in mouse embryonic palatal mesenchymal (MEPM) cells and O9-1 cells through the regulation of genes associated with cleft palate and validated the role of our regulatory networks in orofacial clefts. To facilitate interactive exploration of these data, we developed a user-friendly web tool to visualize the gene and miRNA expression patterns across developmental stages, as well as the regulatory networks (https://fyan.shinyapps.io/facebase_shiny/). Taken together, our results provide a valuable resource that serves as a reference map for future research in craniofacial development.

Exploring the interaction between FGF Genes and T-box genes among chinese nonsyndromic cleft lip with or without cleft palate case-parent trios

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is a common birth defect. Genetic variants causing syndromic orofacial clefts can also contribute to the etiology of NSCL/P. The purpose of the present study was to explore gene-gene (G × G) interaction using common single nucleotide polymorphic (SNP) markers in fibroblast growth factor (FGF) family and its receptors and T-box genes, which were associated with syndromic orofacial clefts. Our study was conducted in 806 Chinese NSCL/P case-parent trios drawn from an international consortium. A total of 252 SNPs in FGF8, FGF10, FGFR1, FGFR2, and TBX5 passed the quality control criteria and were included in the analysis. The interactions between SNPs in different genes were assessed using Cordell's method, which fitted a conditional logistic regression model. The analysis was performed using the R-package trio (Version 3.8.0). Bonferroni correction was used to adjust for multiple comparisons, and the overall significance threshold was set as P = 1.98 × 10^-4 (0.05/252). Conditional logistic regression revealed the most significant interaction between rs2330542 in FGF10 and rs1946295 in TBX5, which remained significant (P = 9.63 × 10^-6 ) after Bonferroni correction. The relative risk of allele C in rs2330542 (FGF10) was 1.02 (95%CI 0.81-1.28), while the relative risk was 1.42 (95%CI 1.03-1.97) when the exposure was a combination of allele C in rs2330542 and allele A in rs1946295 (TBX5). Our findings confirmed the importance of considering G × G interaction when exploring the genetic risk factors of NSCL/P. Further investigations are warranted to validate the potential interaction and reveal the biological function of FGF10/FGFR2/TBX5. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

Congenital lateral cleft palate with unilateral craniofacial microsomia and lateral ankyloglossia

Craniofacial microsomia is a group of anomalies that occur due to developmental defects in the first and second branchial arches during the embryological period. The disease has various craniofacial and extracraniofacial presentation patterns. Lateral cleft palate is distinct from the most common palate clefts because it is located lateral to the uvula. The presence of a lateral cleft palate has been very rarely reported in the literature, and the aetiopathogenesis of the disease is still not well understood. We aimed to report a case of the coexistence of lateral cleft palate and craniofacial microsomia and discuss the aetiopathogenesis of these diseases.

Unmasking familial CPX by WES and identification of novel clinical signs

Mutations in the T-Box transcription factor gene TBX22 are found in X-linked Cleft Palate with or without Ankyloglossia syndrome (CPX syndrome). In addition to X-linked inheritance, ankyloglossia, present in the majority of CPX patients, is an important diagnostic marker, but it is frequently missed or unreported, as it is a "minor" feature. Other described anomalies include cleft lip, micro and/or hypodontia, and features of CHARGE syndrome. We conducted whole exome sequencing (WES) on 22 individuals from 17 "a priori" non-syndromic cleft lip and/or cleft palate (CL/P) families. We filtered the data for heterozygous pathogenic variants within a set of predefined candidate genes. Two canonical splice-site mutations were found in TBX22. Detailed re-phenotyping of the two probands and their families unravelled orofacial features previously not associated with the CPX phenotypic spectrum: choanal atresia, Pierre-Robin sequence, and overgrowths on the posterior edge of the hard palate, on each side of the palatal midline. This study emphasizes the importance of WES analysis in familial CLP cases, combined with deep (reverse) phenotyping in "a priori" non-syndromic clefts.

Tooth agenesis and orofacial clefting: genetic brothers in arms?

Tooth agenesis and orofacial clefts represent the most common developmental anomalies and their co-occurrence is often reported in patients as well in animal models. The aim of the present systematic review is to thoroughly investigate the current literature (PubMed, EMBASE) to identify the genes and genomic loci contributing to syndromic or non-syndromic co-occurrence of tooth agenesis and orofacial clefts, to gain insight into the molecular mechanisms underlying their dual involvement in the development of teeth and facial primordia. Altogether, 84 articles including phenotype and genotype description provided 9 genomic loci and 26 gene candidates underlying the co-occurrence of the two congenital defects: MSX1, PAX9, IRF6, TP63, KMT2D, KDM6A, SATB2, TBX22, TGFα, TGFβ3, TGFβR1, TGFβR2, FGF8, FGFR1, KISS1R, WNT3, WNT5A, CDH1, CHD7, AXIN2, TWIST1, BCOR, OFD1, PTCH1, PITX2, and PVRL1. The molecular pathways, cellular functions, tissue-specific expression and disease association were investigated using publicly accessible databases (EntrezGene, UniProt, OMIM). The Gene Ontology terms of the biological processes mediated by the candidate genes were used to cluster them using the GOTermMapper (Lewis-Sigler Institute, Princeton University), speculating on six super-clusters: (a) anatomical development, (b) cell division, growth and motility, (c) cell metabolism and catabolism, (d) cell transport, (e) cell structure organization and (f) organ/system-specific processes. This review aims to increase the knowledge on the mechanisms underlying the co-occurrence of tooth agenesis and orofacial clefts, to pave the way for improving targeted (prenatal) molecular diagnosis and finally to reflect on therapeutic or ultimately preventive strategies for these disabling conditions in the future.

A 5.8 Mb interstitial deletion on chromosome Xq21.1 in a boy with intellectual disability, cleft palate, hearing impairment and combined growth hormone deficiency

Background

Deletions of the long arm of chromosome X in males are a rare cause of X-linked intellectual disability. Here we describe a patient with an interstitial deletion of the Xq21.1 chromosome.

Case presentation

In a 15 year boy, showing intellectual disability, short stature, hearing loss and dysmorphic facial features, a deletion at Xq21.1 was identified by array-CGH. This maternally inherited 5.8 Mb rearrangement encompasses 14 genes, including BRWD3 (involved in X-linked intellectual disability), TBX22 (a gene whose alterations have been related to the presence of cleft palate), POU3F4 (mutated in X-linked deafness) and ITM2A (a gene involved in cartilage development).

Conclusion

Correlation between the clinical findings and the function of gene mapping within the deleted region confirms the causative role of this microrearrangement in our patient and provides new insight into a gene possibly involved in short stature.

Palm and finger print characteristics in nonfamilial cleft lip and palate patients and their parents

The aim of this study was to investigate if Iranian individuals with nonfamilial cleft lip and palate (CLP) and their unaffected parents display more dermatoglyphic asymmetry than the normal population.The study group included 55 patients with nonfamilial CLP and their unaffected parents (38 fathers and 47 mothers). The control group included 60 healthy children and their parents (37 fathers and 50 mothers). Total ridge counts of each finger (TRC), atd angles, a-b ridge counts, and finger print pattern types of all participants were recorded. Asymmetry between the right and left hands of each individual was determined. Dissimilarity between pattern types on homologous fingers was compared using chi-square test. Asymmetry of other parameters was statistically analyzed using the Mann-Whitney U test.There were no significant differences between the groups in terms of their asymmetry of atd angle, a-b ridge count, and pattern dissimilarity score. However, significant differences in mean TRC between CLP patients and control children were found for the right ring digit (P = 0.023), right little digit (P = 0.032), and left index digit (P = 0.005). Also, there were significant differences among CLP patients and control children (P = 0.022) as well as unaffected fathers of CLP patients and their control group (P = 0.020) in terms of type of finger print pattern.No enhanced fluctuating asymmetry was found in most of the dermatoglyphic traits in the population studied, which indicated a low degree of developmental instability of the sporadic cases of cleft deformity.

Identification of a novel heterozygous truncation mutation in exon 1 of ARHGAP29 in an Indian subject with nonsyndromic cleft lip with cleft palate

Objective:

Mutations in exon 1 of ARHGAP29, a RhoA specific GTPase have been identified in North American and Filipino subjects with nonsyndromic cleft palate and cleft lip with or without cleft palate. Since the genetic status of ARHGAP29 in Indian subjects with nonsyndromic oral clefts is not known, we designed the present study to investigate the occurrence of the above mutations in them.

Materials and Methods:

Total genomic DNA extracted from peripheral blood of 60 subjects with nonsyndromic cleft palate and cleft lip with or without cleft palate, and equal number of control healthy subjects were amplified with primers flanking exon 1 of ARHGAP29 gene and subjected to direct sequencing.

Results:

Sequencing analysis identified a nonsense mutation in exon 1 of ARHGAP29 that caused substitution of lysine to stop codon at codon position 32 in a subject with nonsyndromic cleft lip with cleft palate. The mutation, however, occurred in heterozygous condition. None of the other subjects carried mutation in this region.

Conclusion:

The study has thus identified a rare but novel truncation mutation in ARHGAP29 gene for the first time in nonsyndromic oral clefts.

WNT10A mutations also associated with agenesis of the maxillary permanent canines, a separate entity

Agenesis or isolated hypodontia of the maxillary permanent canines is a very rare dental anomaly. We report on nine unrelated Thai patients with this condition. Three of them had one affected parent. Three heterozygous missense mutations (p.Arg171Cys; p.Gly213Ser; and IVS2+1G>A) were identified in WNT10A in six patients. The p.Gly213Cys mutation was found in four patients. One of the patients who had p.Gly213Ser mutation also had peg-shaped (microdontia of the) maxillary lateral incisors with dens invaginatus. The mothers of two patients who carried the same mutation as their affected sons (p.Gly213Ser and p.Arg171Cys) had microdontia of the maxillary permanent lateral incisor. Our study has demonstrated for the first time that agenesis of the maxillary permanent canines is a distinct entity, associated with mutations in WNT10A. Inheritance appears to be autosomal dominant. Agenesis of the maxillary permanent canines may accompany by microdontia of the maxillary permanent lateral incisors and dens invaginatus of the maxillary permanent lateral incisors. Mutations could not be identified in the coding exons of WNT10A in three patients. They might be located outside the coding exons, including the promoter regions. However, it is likely that agenesis of the maxillary permanent canines is a heterogeneous disorder.

Regulation of organogenesis and stem cell properties by T-box transcription factors

T-box transcription factors containing the common DNA-binding domain T-box contribute to the organization of multiple tissues in vertebrates and invertebrates. In mammals, 17 T-box genes are divided into five subfamilies depending on their amino acid homology. The proper distribution and expression of individual T-box transcription factors in different tissues enable regulation of the proliferation and differentiation of tissue-specific stem cells and progenitor cells in a suitable time schedule for tissue organization. Consequently, uncontrollable expressions of T-box genes induce abnormal tissue organization, and eventually cause various diseases with malformation and malfunction of tissues and organs. Furthermore, some T-box transcription factors are essential for maintaining embryonic stem cell pluripotency, improving the quality of induced pluripotent stem cells, and inducing cell-lineage conversion of differentiated cells. These lines of evidence indicate fundamental roles of T-box transcription factors in tissue organization and stem cell properties, and suggest that these transcription factors will be useful for developing therapeutic approaches in regenerative medicine.