Cleft lip and palate genetics and application in early embryological development

Potential of Viruses as Environmental Etiological Factors for Non-Syndromic Orofacial Clefts

In this study, we analyzed the potential of viral infections in the species Homo sapiens as environmental causes of orofacial clefts (OFCs). A scoring system was adapted for qualitatively assessing the potential of viruses to cause cleft lip and/or palate (CL/P). This assessment considered factors such as information from the literature, nucleotide and amino acid similarities, and the presence of Endogenous Viral Elements (EVEs). The analysis involved various algorithm packages within Basic Local Alignment Search Tool 2.13.0 software and databases from the National Center for Biotechnology Information and the International Committee on Taxonomy of Viruses. Twenty significant viral species using different biosynthesis strategies were identified: Human coronavirus NL63, Rio Negro virus, Alphatorquevirus homin9, Brisavirus, Cosavirus B, Torque teno mini virus 4, Bocaparvovirus primate2, Human coronavirus HKU1, Monkeypox virus, Mammarenavirus machupoense, Volepox virus, Souris mammarenavirus, Gammapapillomavirus 7, Betainfluenzavirus influenzae, Lymphocytic choriomeningitis mammarenavirus, Ledantevirus kern, Gammainfluenzavirus influenzae, Betapolyomavirus hominis, Vesiculovirus perinet, and Cytomegalovirus humanbeta5. The evident viral etiological potential in relation to CL/P varies depending on the Baltimore class to which the viral species belongs. Given the multifactorial nature of CL/P, this relationship appears to be dynamic.

Exploring the Molecular Mechanism of lncRNA-miRNA-mRNA Networks in Non-Syndromic Cleft Lip with or without Cleft Palate

Background

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common craniofacial birth defect. Growing evidence has demonstrated the competing endogenous RNA (ceRNA) hypothesis has played a role in the pathogenesis of NSCL/P. Here, we identified the important lncRNAs in NSCL/P and constructed a ceRNA regulatory network to predict their underlying functional mechanism.

Methods

Total RNA isolated from the peripheral blood samples were analyzed by the Human Clariom D Affymetrix platform and differentially expressed genes (DEGs) were identified. Using the limma package in R software, DEGs in the expression profile of GSE42589 were identified from Gene Expression Omnibus (GEO) database. Co-differentially expressed lncRNAs (co-DElncRNAs) were used to predict the microRNAs that may bind to them. Co-differentially expressed mRNAs (co-DEmRNAs) were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The hub genes were screened using the cytohubba plug-in in Cytoscape. A ceRNA network was built to investigate the molecular mechanism underlying the etiology of NSCL/P. The expression levels of lncRNAs, miRNAs, and mRNAs in the network were assessed by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

We found 116 DElncRNAs and 2955 DEmRNAs from the GSE42589 dataset, and 2626 DElncRNAs and 2771 DEmRNAs from the Human Clariom D gene chip. A network of co-DEmRNAs containing 3712 edges and 621 nodes were identified by PPI analysis. A ceRNA regulatory network comprising lncRNA USP17L6P, hsa-miR-449c-5p, and MYC was established. qRT-PCR results revealed significantly lower expression levels of lncRNA USP17L6P and c-Myc in NSCL/P tissues, while the expression level of hsa-miR-449c-5p was higher as compared to control samples (p < 0.05).

Conclusion

The identified lncRNAs and the established ceRNA regulatory network provide novel insight into the pathogenesis of NSCL/P, therefore hold great promise in NSCL/P management in clinical practice.

The effect of facemask in patients with unilateral cleft lip and palate: a systematic review and meta-analysis

BACKGROUND

Patients with cleft lip and palate usually present a Class III skeletal pattern. Facemask (FM) is one of the conventional orthodontic treatment modalities used to address the skeletal discrepancy in cleft patients.

OBJECTIVE

To investigate the potential effectiveness of FM in unilateral cleft lip and palate (UCLP) patients.

SEARCH METHODS

Search without restrictions except language in seven databases since inception and hand searching until January 2019 was conducted. Detailed search strategies were developed for each database which were based on the PubMed strategy and adapted accordingly.

SELECTION CRITERIA

Controlled studies assessing the effect of FM in UCLP patients were to be included.

DATA COLLECTION AND ANALYSIS

After retrieval and selection of the studies, data extraction was performed. Both angular and linear cephalometric measurements were collected. Weighted mean differences (WMDs) and 95% confidence intervals (CΙs) between treated and untreated UCLP patients concerning the pre- and post-treatment angular measurements of each group were calculated using a random-effects meta-analysis model. The risk of bias in individual studies was assessed using the ROBINS-I tool.

RESULTS

From nine eligible studies, five were included in the meta-analysis investigating the use of FM in patients and controls with UCLP (with and without maxillary expansion). Statistically significant differences were evident for SNA/S-N-ss, SNB/S-N-sm, ANB/ss-N-sm, and SN-MP. FM was found to induce an increase of SNA (WMD = 2.12 degrees, 95% CI: 1.58 to 2.66), ANB (WMD = 4.17 degrees, 95% CI: 3.60 to 4.74), and SN-MP angles (WMD = 2.60 degrees, 95% CI: 1.10 to 4.10) and a decrease of SNB angle (WMD = -1.94 degrees, 95% CI: -2.48 to -1.40) in UCLP patients. Low to moderate heterogeneity was observed.

LIMITATIONS

They emerge due to risk of bias, exclusion of non-English papers and methodological characteristics of the included papers.

CONCLUSIONS

According to the available data, FM seems to improve the sagittal skeletal relationships in UCLP patients, increasing the SNA and ANB angles and decreasing the SNB angle. Moreover, in the vertical dimension, FM increases the SN-MP angle. Regarding dental measurements, there are controversial results. More high-quality studies need to be conducted in order to further clarify the impact of FM on UCLP patients.

REGISTRATION NUMBER

PROSPERO: CRD42019131619.

Orofacial clefts embryology, classification, epidemiology, and genetics

Orofacial clefts (OFCs) rank as the second most common congenital birth defect in the United States after Down syndrome and are the most common head and neck congenital malformations. They are classified as cleft lip with or without cleft palate (CL/P) and cleft palate only (CPO). OFCs have significant psychological and socio-economic impact on patients and their families and require a multidisciplinary approach for management and counseling. A complex interaction between genetic and environmental factors contributes to the incidence and clinical presentation of OFCs. In this comprehensive review, the embryology, classification, epidemiology and etiology of clefts are thoroughly discussed and a "state-of-the-art" snapshot of the recent advances in the genetics of OFCs is presented.

Cellular and developmental basis of orofacial clefts

During craniofacial development, defective growth and fusion of the upper lip and/or palate can cause orofacial clefts (OFCs), which are among the most common structural birth defects in humans. The developmental basis of OFCs includes morphogenesis of the upper lip, primary palate, secondary palate, and other orofacial structures, each consisting of diverse cell types originating from all three germ layers: the ectoderm, mesoderm, and endoderm. Cranial neural crest cells and orofacial epithelial cells are two major cell types that interact with various cell lineages and play key roles in orofacial development. The cellular basis of OFCs involves defective execution in any one or several of the following processes: neural crest induction, epithelial-mesenchymal transition, migration, proliferation, differentiation, apoptosis, primary cilia formation and its signaling transduction, epithelial seam formation and disappearance, periderm formation and peeling, convergence and extrusion of palatal epithelial seam cells, cell adhesion, cytoskeleton dynamics, and extracellular matrix function. The latest cellular and developmental findings may provide a basis for better understanding of the underlying genetic, epigenetic, environmental, and molecular mechanisms of OFCs.

Evaluating the Anatomical Traits of Lip on Three-Dimensional Computed Tomography Images

BACKGROUND

Lips and mouth are the most recognizable parts of the lower face. The morphometry of the facial organs is important for the balance of the face. Besides congenital anomalies occur on the lips, some kinds of deformities might be seen because of trauma or carcinoma. In this respect, lips are in the study of plastic surgery, maxillofacial surgery and orthodontics. Lip morphology also takes an important role in forensic facial reconstruction (facial approximation).

MATERIALS AND METHODS

Twenty parameters on the soft tissue and 12 parameters on the hard tissue were measured on three dimensional (3D) computed tomography (CT) images belonging 50 individuals (25 female, mean age 35.40 ± 9.97; 25 male, mean age 34.32 ± 11.06).

RESULTS

Statistical significance was observed on 4 parameters measured at soft tissue and 6 parameters measured in hard tissue. Statistical significance was not seen between the measurements taken bilaterally. Fourteen equations were developed in order to estimate the lip morphometry using the morphometric traits of hard tissue.

CONCLUSION

We hope that the results of current study will be useful at surgery and forensic sciences.

Differences in the Tensor Veli Palatini Muscle and Hearing Status in Children With and Without 22q11.2 Deletion Syndrome

PURPOSE

To investigate the dimensions of the tensor veli palatini (TVP) muscle using high image resolution 3-dimensional magnetic resonance imaging (MRI) of the soft palate among children with normal velopharyngeal and craniofacial anatomy and to compare values to individuals with a diagnosis of 22q11.2 deletion syndrome (22q11DS). We also sought to determine whether there is a relationship between hypoplasia of the TVP and severity of middle ear dysfunction and hearing loss.

METHODS

Three-dimensional MRI were used to collect and analyze data obtained across 53 children between 4 and 12 years of age, including 40 children with normal velopharyngeal and craniofacial anatomy and 13 children with a diagnosis of 22q11.2 DS. Tensor veli palatini muscle length, thickness, and volume as well as bihamular distance were compared among participant groups.

RESULTS

A Welch's t-test revealed that the TVP in participants with 22q11DS is significantly shorter (P = .005, 17.3 vs 19.0 mm), thinner (P < .001, 1.1 vs 1.8 mm), and less voluminous (P < .001, 457.5 vs 667.3 mm³) than participants without 22q11DS. Participants with 22q11DS also had a greater (P = .006, 27.7 vs 24.7 mm) bihamular distance than participants without 22q11DS. There was an inverse relationship between TVP abnormalities noted above and the severity of audiologic and otologic histories.

CONCLUSION

The TVP muscle is substantially reduced in volume, length, and thickness in children with 22q11DS. These findings serve as preliminary support for the association of patient hearing and otologic severity and TVP dysmorphology.

Modeling human craniofacial disorders in Xenopus

PURPOSE OF REVIEW

Craniofacial disorders are among the most common human birth defects and present an enormous health care and social burden. The development of animal models has been instrumental to investigate fundamental questions in craniofacial biology and this knowledge is critical to understand the etiology and pathogenesis of these disorders.

RECENT FINDINGS

The vast majority of craniofacial disorders arise from abnormal development of the neural crest, a multipotent and migratory cell population. Therefore, defining the pathogenesis of these conditions starts with a deep understanding of the mechanisms that preside over neural crest formation and its role in craniofacial development.

SUMMARY

This review discusses several studies using Xenopus embryos to model human craniofacial conditions, and emphasizes the strength of this system to inform important biological processes as they relate to human craniofacial development and disease.

Gene expression profiling analysis contributes to understanding the association between non-syndromic cleft lip and palate, and cancer

The present study aimed to investigate the molecular mechanisms underlying non-syndromic cleft lip, with or without cleft palate (NSCL/P), and the association between this disease and cancer. The GSE42589 data set was downloaded from the Gene Expression Omnibus database, and contained seven dental pulp stem cell samples from children with NSCL/P in the exfoliation period, and six controls. Differentially expressed genes (DEGs) were screened using the RankProd method, and their potential functions were revealed by pathway enrichment analysis and construction of a pathway interaction network. Subsequently, cancer genes were obtained from six cancer databases, and the cancer-associated protein-protein interaction network for the DEGs was visualized using Cytoscape. In total, 452 upregulated and 1,288 downregulated DEGs were screened. The upregulated DEGs were significantly enriched in the arachidonic acid metabolism pathway, including PTGDS, CYP4F2 and PLA2G16; and transforming growth factor (TGF)-β signaling pathway, including SMAD3 and TGFB2. The downregulated DEGs were distinctly involved in the pathways of DNA replication, including MCM2 and POLA1; cell cycle, including CDK1 and STAG1; and viral carcinogenesis, including PIK3CA and HIST1H2BF. Furthermore, the pathways of cell cycle and viral carcinogenesis, with higher degrees of interaction were found to interact with other pathways, including DNA replication, transcriptional misregulation in cancer, and the TGF-β signaling pathway. Additionally, TP53, CDK1, SMAD3, PIK3R1 and CASP3, with higher degrees, interacted with the cancer genes. In conclusion, the DEGs for NSCL/P were implicated predominantly in the TGF-β signaling pathway, the cell cycle and in viral carcinogenesis. The TP53, CDK1, SMAD3, PIK3R1 and CASP3 genes were found to be associated, not only with NSCL/P, but also with cancer. These results may contribute to a better understanding of the molecular mechanisms of NSCL/P.

Methylated microRNA genes of the developing murine palate

Environmental factors contribute to the etiology of cleft palate (CP). Environmental factors can also affect gene expression via alterations in DNA methylation suggesting a possible mechanism for the induction of CP. Identification of genes methylated during development of the secondary palate provides the basis for examination of the means by which environmental factors may adversely influence palatal ontogeny. We previously characterized the methylome of the developing murine secondary palate focusing primarily on protein- encoding genes. We now extend this study to include methylated microRNA (miRNA) genes. A total of 42 miRNA genes were found to be stably methylated in developing murine palatal tissue. Twenty eight of these were localized within host genes. Gene methylation was confirmed by pyrosequencing of selected miRNA genes. Integration of methylated miRNA gene and expression datasets identified 62 miRNAs, 69% of which were non-expressed. For a majority of genes (83%), upstream CpG islands (CGIs) were highly methylated suggesting down-regulation of CGI-associated promoters. DAVID and IPA analyses indicated that both expressed and non-expressed miRNAs target identical signaling pathways and biological processes associated with palatogenesis. Furthermore, these analyses also identified novel signaling pathways whose roles in palatogenesis remain to be elucidated. In summary, we identify methylated miRNA genes in the developing murine secondary palate, correlate miRNA gene methylation with expression of their cognate miRNA transcripts, and identify pathways and biological processes potentially mediated by these miRNAs.

Skeletal malocclusion: a developmental disorder with a life-long morbidity

The likelihood of birth defects in orofacial tissues is high due to the structural and developmental complexity of the face and the susceptibility to intrinsic and extrinsic perturbations. Skeletal malocclusion is caused by the distortion of the proper mandibular and/or maxillary growth during fetal development. Patients with skeletal malocclusion may suffer from dental deformities, bruxism, teeth crowding, trismus, mastication difficulties, breathing obstruction and digestion disturbance if the problem is left untreated. In this review, we focused on skeletal malocclusion that affects 27.9% of the US population with different severity levels. We summarized the prevalence of class I, II and III of malocclusion in different ethnic groups and discussed the most frequent medical disorders associated with skeletal malocclusion. Dental anomalies that lead to malocclusion such as tooth agenesis, crowding, missing teeth and abnormal tooth size are not addressed in this review. We propose a modified version of malocclusion classification for research purposes to exhibit a clear distinction between skeletal vs. dental malocclusion in comparison to Angle’s classification. In addition, we performed a cross-sectional analysis on orthodontic (malocclusion) data through the BigMouth Dental Data Repository to calculate potential association between malocclusion with other medical conditions. In conclusion, this review emphasizes the need to identify genetic and environmental factors that cause or contribute risk to skeletal malocclusion and the possible association with other medical conditions to improve assessment, prognosis and therapeutic approaches.

Illustrated review of the embryology and development of the facial region, part 3: an overview of the molecular interactions responsible for facial development

SUMMARY

Parts 1 and 2 of this review discussed the complex morphogenesis of the face. However, the molecular processes that drive the morphology of the face were not addressed. Part 3 of this review will present an overview of the genes and their products that have been implicated in the developing face.

Susceptibility to DNA damage as a molecular mechanism for non-syndromic cleft lip and palate

Non-syndromic cleft lip/palate (NSCL/P) is a complex, frequent congenital malformation, determined by the interplay between genetic and environmental factors during embryonic development. Previous findings have appointed an aetiological overlap between NSCL/P and cancer, and alterations in similar biological pathways may underpin both conditions. Here, using a combination of transcriptomic profiling and functional approaches, we report that NSCL/P dental pulp stem cells exhibit dysregulation of a co-expressed gene network mainly associated with DNA double-strand break repair and cell cycle control (p = 2.88×10(-2)-5.02×10(-9)). This network included important genes for these cellular processes, such as BRCA1, RAD51, and MSH2, which are predicted to be regulated by transcription factor E2F1. Functional assays support these findings, revealing that NSCL/P cells accumulate DNA double-strand breaks upon exposure to H2O2. Furthermore, we show that E2f1, Brca1 and Rad51 are co-expressed in the developing embryonic orofacial primordia, and may act as a molecular hub playing a role in lip and palate morphogenesis. In conclusion, we show for the first time that cellular defences against DNA damage may take part in determining the susceptibility to NSCL/P. These results are in accordance with the hypothesis of aetiological overlap between this malformation and cancer, and suggest a new pathogenic mechanism for the disease.

Role of SOX9 in the Etiology of Pierre-Robin Syndrome

Objective(s : Cleft lip/palate are common congenital anomalies, affecting approximately 2/1000 live births. Pierre Robin Sequence is a subgroup of the cleft palate population. Chromosomal abnormalities near the SOX9 gene disrupt the regulation of this gene and prevent the SOX9 protein from properly controlling the development of facial structures, which leads to isolated PRS. The present study was conducted to identify the role of the SOX9 gene in the etiology of Pierre robin syndrome and to study the association of SOX9 and PRS in regulating morphogenesis of the face in individuals with Cleft lip/Palate using the PCR technique and GTG banding.

MATERIALS AND METHODS

Molecular and cytogenetic analysis was performed in 27 subjects with cleft lip/palate and 13 age matched controls. DNA was isolated and PCR was performed for the amplification of the gene of interest and the products were run on a 2% Agarose gel and the band patterns were analyzed. The chromosomal abnormalities were analyzed from the cultured lymphocytes after GTG banding.

RESULT

Out of 27 patients screened, deletion of the SOX9 gene was observed in 1 case for exon1 and in 2 cases for exon2. The cytogenetic analysis showed no structural or numerical abnormalities and all the patients showed normal karyotype.

CONCLUSION

The results of molecular methods showed a positive association suggesting that the SOX9 gene is of particular importance, but the cytogenetic study didn't seem to show a stronger association suggesting that, this method would not identify disease genes acting via other mechanisms of genetic dominance and also due to the fact that Cleft lip / palate has a multifactorial inheritance.

Developmental profiles of the murine palatal methylome

BACKGROUND

Environmental factors contribute to the etiology of cleft palate (CP). Identification of genes that are methylated during development of the secondary palate will contribute to a better understanding of the gene-environment link contributing to CP.

METHODS

Genomic DNA fragments from secondary palate tissue from gestational days (GDs) 12 to 14 were subjected to Selective Enrichment of Methylated DNA (SEMD) and used to probe NimbleGen 2.1M mouse promoter arrays. Input (control) and SEMD samples were labeled with Cy3 and Cy5, respectively, and used for array hybridization (three arrays per GD). Data were analyzed using the Bioconductor package Ringo. Gene methylation was verified by pyrosequencing analysis and expression by quantitative real-time PCR.

RESULTS

A total of 5577 methylated genes were identified during palate development: (1) 74% of genes were methylated on all three GDs; (2) CpG islands accounted for only 30% of methylated regions of interest (MRIs); (3) location of MRIs was more often observed in gene bodies (73%) than in promoters; (4) evaluation of MRIs on GDs 12-14 revealed no significant differentially methylated regions; (5) DAVID analysis of MRIs revealed that the cadherin and Wnt signaling pathways, as well as pathways involved in proteoglycan synthesis, were significantly enriched for methylated genes.

CONCLUSIONS

Our prior studies identified differentially expressed mRNAs and microRNAs in the developing palate. The current study complements these studies by identifying genes whose expression may be altered as a result of DNA methylation.

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.

Specific inactivation of Twist1 in the mandibular arch neural crest cells affects the development of the ramus and reveals interactions with hand2

BACKGROUND

The basic helix-loop-helix (bHLH) transcription factor Twist1 fulfills an essential function in neural crest cell formation, migration, and survival and is associated with the craniosynostic Saethre-Chotzen syndrome in humans. However, its functions during mandibular development, when it may interact with other bHLH transcription factors like Hand2, are unknown because mice homozygous for the Twist1 null mutation die in early embryogenesis. To determine the role of Twist1 during mandibular development, we used the Hand2-Cre transgene to conditionally inactivate the gene in the neural crest cells populating the mandibular pharyngeal arch.

RESULTS

The mutant mice exhibited a spectrum of craniofacial anomalies, including mandibular hypoplasia, altered middle ear development, and cleft palate. It appears that Twist1 is essential for the survival of the neural crest cells involved in the development of the mandibular ramal elements. Twist1 plays a role in molar development and cusp formation by participating in the reciprocal signaling needed for the formation of the enamel knot. This gene is also needed to control the ossification of the mandible, a redundant role shared with Hand2.

CONCLUSION

Twist1, along with Hand2, is essential for the proximodistal patterning and development of the mandible and ossification.

Fibroblast growth factor 9 (FGF9)-pituitary homeobox 2 (PITX2) pathway mediates transforming growth factor β (TGFβ) signaling to regulate cell proliferation in palatal mesenchyme during mouse palatogenesis

Cleft palate represents one of the most common congenital birth defects. Transforming growth factor β (TGFβ) signaling plays crucial functions in regulating craniofacial development, and loss of TGFβ receptor type II in cranial neural crest cells leads to craniofacial malformations, including cleft palate in mice (Tgfbr2(fl/fl);Wnt1-Cre mice). Here we have identified candidate target genes of TGFβ signaling during palatal formation. These target genes were selected based on combining results from gene expression profiles of embryonic day 14.5 palates from Tgfbr2(fl/fl);Wnt1-Cre mice and previously identified cleft palate phenotypes in genetically engineered mouse models. We found that fibroblast growth factor 9 (Fgf9) and transcription factor pituitary homeobox 2 (Pitx2) expressions are significantly down-regulated in the palate of Tgfbr2(fl/fl);Wnt1-Cre mice, and Fgf9 and Pitx2 loss of function mutations result in cleft palate in mice. Pitx2 expression is down-regulated by siRNA knockdown of Fgf9, suggesting that Fgf9 is upstream of Pitx2. We detected decreased expression of both cyclins D1 and D3 in the palates of Tgfbr2(fl/fl);Wnt1-Cre mice, consistent with the defect in cell proliferation. Significantly, exogenous FGF9 restores expression of cyclins D1 and D3 in a Pitx2-dependent manner and rescues the cell proliferation defect in the palatal mesenchyme of Tgfbr2(fl/fl);Wnt1-Cre mice. Our study indicates that a TGFβ-FGF9-PITX2 signaling cascade regulates cranial neural crest cell proliferation during palate formation.

Developmental epigenetics of the murine secondary palate

Orofacial clefts occur with a frequency of 1 to 2 per 1000 live births. Cleft palate, which accounts for 30% of orofacial clefts, is caused by the failure of the secondary palatal processes--medially directed, oral projections of the paired embryonic maxillary processes--to fuse. Both gene mutations and environmental effects contribute to the complex etiology of this disorder. Although much progress has been made in identifying genes whose mutations are associated with cleft palate, little is known about the mechanisms by which the environment adversely influences gene expression during secondary palate development. An increasing body of evidence, however, implicates epigenetic processes as playing a role in adversely influencing orofacial development. Epigenetics refers to inherited changes in phenotype or gene expression caused by processes other than changes in the underlying DNA sequence. Such processes include, but are not limited to, DNA methylation, microRNA effects, and histone modifications that alter chromatin conformation. In this review, we describe our current understanding of the possible role epigenetics may play during development of the secondary palate. Specifically, we present the salient features of the embryonic palatal methylome and profile the expression of numerous microRNAs that regulate protein-encoding genes crucial to normal orofacial ontogeny.

The mechanism of TGF-β signaling during palate development

Cleft palate, a malformation of the secondary palate development, is one of the most common human congenital birth defects. Palate formation is a complex process resulting in the separation of the oral and nasal cavities that involves multiple events, including palatal growth, elevation, and fusion. Recent findings show that transforming growth factor beta (TGF-β) signaling plays crucial roles in regulating palate development in both the palatal epithelium and mesenchyme. Here, we highlight recent advances in our understanding of TGF-β signaling during palate development.

Asociación de labio y/o paladar hendido con variables de posición socioeconómica: un estudio de casos y controles

OBJETIVOS: determinar la asociación entre variables indicadoras de posición socioeconómica y la presencia de labio y/o paladar hendido no sindrómico (L/PH). MÉTODOS: se realizó un estudio de casos y controles en el que se incluyeron 110 casos con L/PH pareados por edad y sexo con 220 controles, seleccionados de la clínica del Hospital Niño DIF de Hidalgo, México. A través de un cuestionario se recogió una serie de variables relacionadas con la posición socio-económica. Utilizando el análisis de componentes principales (correlación policórica) se combinaron las variables relacionadas entre sí y se construyeron diversas variables indicadoras de posición socioeconómica; nivel socioeconómico (características de la vivienda), índice de bienestar (posesiones de bienes/ enseres del hogar), escolaridad de los padres (años de estudio), seguridad social (derechohabiencia), e indigenismo (hablar alguna lengua indígena por alguno de los padres). El análisis bivariado se realizó con regresión logística condicionada. RESULTADOS: el 90.9% de los pacientes presentó labio + paladar hendido al mismo tiempo, ya sea uni o bilateral. El tipo de defecto mas común fue el labio y paladar hendido izquierdo (33.6%). Resultaron asociadas a L/PH las variables: índice de bienestar (comparado con el peor quintil: 2do OR=0.46; p=0.030, 3er OR=0.39; p=0.015, 4to OR=0.30; p=0.002, 5to OR=0.27; p=0.001), nivel socioeconómico (comparado con el mejor tercil: 2do OR=0.46; p=0.004, 3er OR=0.18; p<0.001), escolaridad del padre (OR=0.86; p<0.001), y escolaridad de la madre (OR=0.84; p<0.001). CONCLUSIONES: este estudio demuestra la existencia de desigualdades socioeconómicas en salud bucal, observándose que los sujetos de menor posición socioeconómica presentan mayor riesgo de tener L/PH.