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.status: publishe

Deletions and loss-of-function variants in TP63 associated with orofacial clefting

We aimed to identify novel deletions and variants of TP63 associated with orofacial clefting (OFC). Copy number variants were assessed in three OFC families using microarray analysis. Subsequently, we analyzed TP63 in a cohort of 1072 individuals affected with OFC and 706 population-based controls using molecular inversion probes (MIPs). We identified partial deletions of TP63 in individuals from three families affected with OFC. In the OFC cohort, we identified several TP63 variants predicting to cause loss-of-function alleles, including a frameshift variant c.569_576del (p.(Ala190Aspfs*5)) and a nonsense variant c.997C>T (p.(Gln333*)) that introduces a premature stop codon in the DNA-binding domain. In addition, we identified the first missense variants in the oligomerization domain c.1213G>A (p.(Val405Met)), which occurred in individuals with OFC. This variant was shown to abrogate oligomerization of mutant p63 protein into oligomeric complexes, and therefore likely represents a loss-of-function allele rather than a dominant-negative. All of these variants were inherited from an unaffected parent, suggesting reduced penetrance of such loss-of-function alleles. Our data indicate that loss-of-function alleles in TP63 can also give rise to OFC as the main phenotype. We have uncovered the dosage-dependent functions of p63, which were previously rejected

Deletions and loss-of-function variants in TP63 associated with orofacial clefting

We aimed to identify novel deletions and variants of TP63 associated with orofacial clefting (OFC). Copy number variants were assessed in three OFC families using microarray analysis. Subsequently, we analyzed TP63 in a cohort of 1072 individuals affected with OFC and 706 population-based controls using molecular inversion probes (MIPs). We identified partial deletions of TP63 in individuals from three families affected with OFC. In the OFC cohort, we identified several TP63 variants predicting to cause loss-of-function alleles, including a frameshift variant c.569_576del (p.(Ala190Aspfs*5)) and a nonsense variant c.997C>T (p.(Gln333*)) that introduces a premature stop codon in the DNA-binding domain. In addition, we identified the first missense variants in the oligomerization domain c.1213G>A (p.(Val405Met)), which occurred in individuals with OFC. This variant was shown to abrogate oligomerization of mutant p63 protein into oligomeric complexes, and therefore likely represents a loss-of-function allele rather than a dominant-negative. All of these variants were inherited from an unaffected parent, suggesting reduced penetrance of such loss-of-function alleles. Our data indicate that loss-of-function alleles in TP63 can also give rise to OFC as the main phenotype. We have uncovered the dosage-dependent functions of p63, which were previously rejected.status: publishe

Novel IRF6 Mutations Detected in Orofacial Cleft Patients by Targeted Massively Parallel Sequencing

Common variants in interferon regulatory factor 6 (IRF6) have been associated with nonsyndromic cleft lip with or without cleft palate (NSCL/P) as well as with tooth agenesis (TA). These variants contribute a small risk towards the 2 congenital conditions and explain only a small percentage of heritability. On the other hand, many IRF6 mutations are known to be a monogenic cause of disease for syndromic orofacial clefting (OFC). We hypothesize that IRF6 mutations in some rare instances could also cause nonsyndromic OFC. To find novel rare variants in IRF6 responsible for nonsyndromic OFC and TA, we performed targeted multiplex sequencing using molecular inversion probes (MIPs) in 1,072 OFC patients, 67 TA patients, and 706 controls. We identified 3 potentially pathogenic de novo mutations in OFC patients. In addition, 3 rare missense variants were identified, for which pathogenicity could not unequivocally be shown, as all variants were either inherited from an unaffected parent or the parental DNA was not available. Retrospective investigation of the patients with these variants revealed the presence of lip pits in one of the patients with a de novo mutation suggesting a Van der Woude syndrome (VWS) phenotype, whereas, in other patients, no lip pits were identified.status: publishe

Novel mutations in LRP6 highlight the role of WNT signaling in tooth agenesis

We aimed to identify a novel genetic cause of tooth agenesis (TA) and/or orofacial clefting (OFC) by combining whole-exome sequencing (WES) and targeted resequencing in a large cohort of TA and OFC patients.status: publishe

Novel mutations in LRP6 highlight the role of WNT signaling in tooth agenesis

Purpose:We aimed to identify a novel genetic cause of tooth agenesis (TA) and/or orofacial clefting (OFC) by combining whole-exome sequencing (WES) and targeted resequencing in a large cohort of TA and OFC patients.Methods:WES was performed in two unrelated patients: one with severe TA and OFC and another with severe TA only. After deleterious mutations were identified in a gene encoding low-density lipoprotein receptor-related protein 6 (LRP6), all its exons were resequenced with molecular inversion probes in 67 patients with TA, 1,072 patients with OFC, and 706 controls.Results:We identified a frameshift (c.4594delG, p.Cys1532fs) and a canonical splice-site mutation (c.3398-2A>C, p.?) in LRP6, respectively, in the patient with TA and OFC and in the patient with severe TA only. The targeted resequencing showed significant enrichment of unique LRP6 variants in TA patients but not in nonsyndromic OFC patients. Of the five variants in patients with TA, two affected the canonical splice site and three were missense variants; all variants segregated with the dominant phenotype, and in one case the missense mutation occurred de novo.Conclusion:Mutations in LRP6 cause TA in humans

Deletions and loss-of-function variants in TP63 associated with orofacial clefting

We aimed to identify novel deletions and variants of TP63 associated with orofacial clefting (OFC). Copy number variants were assessed in three OFC families using microarray analysis. Subsequently, we analyzed TP63 in a cohort of 1072 individuals affected with OFC and 706 population-based controls using molecular inversion probes (MIPs). We identified partial deletions of TP63 in individuals from three families affected with OFC. In the OFC cohort, we identified several TP63 variants predicting to cause loss-of-function alleles, including a frameshift variant c.569_576del (p.(Ala190Aspfs*5)) and a nonsense variant c.997C>T (p.(Gln333*)) that introduces a premature stop codon in the DNA-binding domain. In addition, we identified the first missense variants in the oligomerization domain c.1213G>A (p.(Val405Met)), which occurred in individuals with OFC. This variant was shown to abrogate oligomerization of mutant p63 protein into oligomeric complexes, and therefore likely represents a loss-of-function allele rather than a dominant-negative. All of these variants were inherited from an unaffected parent, suggesting reduced penetrance of such loss-of-function alleles. Our data indicate that loss-of-function alleles in TP63 can also give rise to OFC as the main phenotype. We have uncovered the dosage-dependent functions of p63, which were previously rejected