Palatogenesis: morphogenetic and molecular mechanisms of secondary palate development

Cleft Palate

The primary function of the palate is to separate the nasal and oral cavities and facilitate the production of normal speech. The velar levator veli palatini (LVP) muscular sling is the palate speech motor. In the cleft palate, the LVP muscles are aberrantly sagittally oriented, which prevents their normal cranial, posterior, and lateral pull on the soft palate, resulting in velopharyngeal incompetence. Palatoplasty techniques enlist the same 3 principles: closure of the nasal mucosa, reorientation and repair of the LVP muscle sling, and closure of the oral mucosa. The primary outcome measures for palatoplasty are speech quality and palatal integrity.

The development of orofacial complex in bats: Implications for orofacial clefting

Orofacial morphology in mammals plays a critical role in essential life functions such as feeding and communication, which are influenced by the shapes of these anatomical structures. Bats are known to exhibit highly diversified orofacial morphotypes within their clade, reflecting their varied diets and echolocation behaviors. The presence of bony discontinuities between the premaxilla and maxilla or among the premaxillae is a notable feature of bat orofacial morphology, observed in certain lineages. It is suggested that these unique orofacial morphotypes, not generally found in other mammals, have evolved in relation to dietary adaptations rather than merely for echolocation mode. Until now, the developmental background of the bony discontinuities in the bat orofacial complex has been insufficiently investigated. Here, we present a comparative study of the chondrocranium and epithelial organs in the orofacial complex of three bat species: Cynopterus sphinx, Rhinolophus malayanus, and Vespertilio sinensis. Our observations indicate that the preceding morphogenesis of orofacial cartilage and epithelial structures is remarkably different among these three species. In C. sphinx and V. sinensis, the region forming from the regression of the palatine process of the premaxilla was filled with orofacial cartilage and epithelial structures. We also found that the clefted morphology observed in R. malayanus and V. sinensis was formed via contrastingly divergent developmental processes. Midline clefts among Yangochiroptera have been previously categorized to represent a uniform morphotype, but our study highlights that attributing midline clefts into a singular category should be revisited, advocating for a nuanced categorization of cleft morphology based on their morphogenetic patterns. Further research on the bat orofacial complex may enhance our understanding of bat evolutionary diversification and offer insights into the developmental mechanisms of human cleft palate.

Prenatal growth patterns of the upper jaw complex with implications for laryngeal echolocation in bats

Craniofacial morphology is extremely diversified within bat phylogeny, however growth and development of the palate in bats remains unstudied. The formation of both midline and bilateral orofacial clefts in laryngeally echolocating bats, morphologically similar to the syndromic and non-syndromic cleft palate in humans, are not well understood. Developmental series of prenatal samples (n = 128) and adults (n = 10) of eight bat species (two pteropodids, four rhinolophoids, and two yangochiropterans), and two non-bat mammals (Mus musculus and Erinaceus amurensis), were CT-scanned and cranial bones forming the upper jaw complex were three-dimensionally visualised to assess whether differences in palate development can be observed across bat phylogeny. Volumetric data of bones composing the upper jaw complex were measured to quantify palate growth. The premaxilla is relatively reduced in bats compared to other mammals and its shape is heterogeneous depending on the presence and type of orofacial cleft across bat phylogeny. The palatine process of premaxillary bones is lacking in pteropodids and yangochiropterans, whereas the premaxilla is a mobile structure which is only in contact caudally with the maxilla by a fibrous membrane or suture in rhinolophoids. In all bats, maxillary bones progressively extend caudally and palatine bones, in some cases split into three branches, extend caudally so that they are completely fused to another one medially prior to the birth. Ossification of the vomer and fusion of the maxillary and palatine bones occur earlier in rhinolophoids than in pteropodids and yangochiropterans. The vomer ossifies bilaterally from two different ossification centres in yangochiropterans, which is uncommon in other bats and non-bat mammals. Analysis of ontogenetic allometric trajectories of the upper jaw complex revealed faster development of maxillary, vomer, and palatine bones in yangochiropterans compared to other bats, especially rhinolophoids. Ancestral state reconstruction revealed that yangochiropterans have a higher magnitude of change in ossification rate compared to other bats and E. amurensis a lower magnitude compared to M. musculus and bats. This study provides new evidence of heterochronic shifts in craniofacial development and growth across bat phylogeny that can improve understanding of the developmental differences characterising nasal and oral emission strategies.

Glycolysis regulates palatal mesenchyme proliferation through Pten-Glut1 axis via Pten classical and non-classical pathways

Abnormal embryonic development leads to the formation of cleft palate (CP) which is difficult to be detected by genetic screening and needs sequent treatment from infants to adults. There are no interceptive treatment about CP until now. Germline deletion of phosphatase and tensin homolog (Pten) was related to embryonic malformation and regulated tumor cell proliferation through glycolysis. However, the role of Pten in CP and the relationship between CP, Pten, and glycolysis are unknown. In our research, we constructed Pten knockdown models in vitro and in vivo. Our results provided preliminary evidence that blocking Pten by its inhibitor such as VO-OHpic might be an effective interceptive treatment in early period of palate development when pregnant mother expose in harmful environment during the early period of palate development to reducing CP occurring which was related with the crosstalk between Pten, and glycolysis in the process.

5'tiRNA-35-GlyTCC-3 and 5'tiRNA-33-CysGCA-11 target BMP6, CUL1 and SPR of non-syndromic cleft palate

BACKGROUND

tsRNAs are novel small non-coding RNAs that play important regulatory roles in gene expression, translation, transcription, and epigenetic modification through proteins or mRNAs and may be therapeutic targets for certain diseases. The etiology of non-syndromic cleft palate-only is complex and the pathogenesis is poorly understood, non-coding RNAs play important roles in its development.

METHODS

The tsRNAs of patients with simple cleft palate were compared with healthy individuals using small RNA microarray, bioinformatic analysis, quantitative real-time transcription polymerase chain reaction, and the effects measured using immunohistochemical staining.

RESULTS

Seventy-nine tsRNAs were upregulated and fifty-four tsRNAs were downregulated in patients with simple cleft palate compared with healthy individuals, among which the expression of 5'tiRNA-35-GlyTCC-3 and 5'tiRNA-33-CysGCA-11 was markedly different and was involved in key signaling pathways related to the development of the palate, such as the cell cycle, cAMP signaling pathway, BMP signal transduction, folate biosynthesis, and other key signaling pathways that determine anatomical structure occurrence, regulate gene expression during development, influence epigenetics, and other biological processes, its target genes include BMP6, CUL1 and SPR.

CONCLUSION

5'tiRNA-35-GlyTCC-3 and 5'tiRNA-33-CysGCA-11 are closely associated with non-syndromic cleft palate development and are expected to be potential new targets for diagnosis and treatment.

Novel insights into palatal shelf elevation dynamics in normal mouse embryos

Development of the embryonic palate requires that the palatal shelves (PS), which extend from maxillary processes, to grow bilaterally and vertically alongside the tongue. This growth continues until embryonic day (E) 13.5, after which the PS elevate above the tongue and adhere, completing the process by E14.5. Current models indicate that this elevation process involves a complex vertical-to-horizontal PS reorientation. While earlier studies have implied that reorientation occurs rapidly, the precise timing has not been resolved. Time-restricted pregnancies with a 1-h resolution showed that in 97% of C57BL/6J embryos, the PS were unelevated at E14.0. However, 6 h later, at E14.25, the PS had completed elevation in 80% of embryos, indicating that the PS elevate in a rapid and constrained timeframe. Interestingly, all E14.25 embryos with unelevated PS (20%) were female, suggesting sex differences in C57BL/6J PS elevation. In FVB/NJ embryos, the elevation window started earlier (E13.875-E14.25), and without any sex differences. An intermediate stage with unilateral PS elevation was frequently observed. Magnetic resonance imaging (MRI) of various stages showed that PS elevation began with posterior bilateral bulges, which then progressed laterally and anteriorly over time. During elevation, we observed increased cell proliferation in the PS lingual region. Within the bulge, cell orientation was tilted towards the tongue, and actomyosin activity was increased, which together may participate in horizontal projection of the bulge. Thus, our data reveal novel insights into rapid dynamic changes during PS elevation, and lay the foundation for future studies of normal and abnormal palatogenesis.

Molecular Regulation of Palatogenesis and Clefting: An Integrative Analysis of Genetic, Epigenetic Networks, and Environmental Interactions

Palatogenesis is a complex developmental process requiring temporospatially coordinated cellular and molecular events. The following review focuses on genetic, epigenetic, and environmental aspects directing palatal formation and their implication in orofacial clefting genesis. Essential for palatal shelf development and elevation (TGF-β, BMP, FGF, and WNT), the subsequent processes of fusion (SHH) and proliferation, migration, differentiation, and apoptosis of neural crest-derived cells are controlled through signaling pathways. Interruptions to these processes may result in the birth defect cleft lip and/or palate (CL/P), which happens in approximately 1 in every 700 live births worldwide. Recent progress has emphasized epigenetic regulations via the class of non-coding RNAs with microRNAs based on critically important biological processes, such as proliferation, apoptosis, and epithelial-mesenchymal transition. These environmental risks (maternal smoking, alcohol, retinoic acid, and folate deficiency) interact with genetic and epigenetic factors during palatogenesis, while teratogens like dexamethasone and TCDD inhibit palatal fusion. In orofacial cleft, genetic, epigenetic, and environmental impact on the complex epidemiology. This is an extensive review, offering current perspectives on gene-environment interactions, as well as non-coding RNAs, in palatogenesis and emphasizing open questions regarding these interactions in palatal development.

Transcriptional factor ISL1 regulates palate development by tuning the SHH cascade

Cleft palate is one of the most common birth defects in humans, and palate morphogenesis depends on epithelial-mesenchymal interaction. In this study, we report that ablation of Isl1 in the epithelium leads to complete cleft palate. A significant reduction in mesenchymal cell proliferation was detected in the Isl1Pitx2Cre mutant palates, but there was no significant difference in apoptosis between wild-type and mutant embryos. Fewer rugae structures were observed in Isl1Pitx2Cre mutant embryos. Shh, Sox2, Foxe1, Foxd2, and Msx1 expression was downregulated in the developing palate in Isl1 mutant embryos. We found that ISL1 can directly regulate Shh expression in palatal epithelial cells, suggesting a critical role for ISL1 in epithelial-mesenchymal interactions during palate development. Remarkably, cleft palate defects due to Isl1 deletion were rescued by a conditional transgenic allele (Tg-pmes-Ihh), confirming the genetic integration of Hedgehog signaling. Our findings indicate that ISL1 controls palatal shelf morphogenesis by modulating epithelial-mesenchymal communication via SHH signaling.

MLL4 regulates postnatal palate growth and midpalatal suture development

MLL4, also known as KMT2D, is a histone methyltransferase that acts as an important epigenetic regulator in various organogenesis programs. Mutations in the MLL4 gene are the major cause of Kabuki syndrome, a human developmental disorder that involves craniofacial birth defects, including anomalies in the palate. This study aimed to investigate the role of MLL4 and the underlying mechanisms in the development and growth of the palate. We generated a novel conditional knockout (cKO) mouse model with tissue-specific deletion of Mll4 in the palatal mesenchyme. Using micro-computed tomography (CT), histological analysis, cell mechanism assays, and gene expression profiling, we examined palate development and growth in the Mll4-cKO mice. Gross craniofacial examination at adult stages revealed mild midfacial hypoplasia and midline defects of the palate in Mll4-cKO mice, including a widened midpalatal suture and disrupted midline rugae pattern. Micro-CT-based time-course skeletal analysis during postnatal palatogenesis through adulthood demonstrated a transverse growth deficit in overall palate width in Mll4-cKO mice. Whole-mount and histological staining at perinatal stages identified that the midline defects in the Mll4-cKO mice emerged as early as 1 day prior to birth, presenting as a widened midpalatal suture, accompanied by increased cell apoptosis in the suture mesenchyme. Genome-wide mRNA expression analysis of the midpalatal suture tissue revealed that MLL4 is essential for the timely expression of major cartilage development genes, such as Col2a1 and Acan, at birth. Immunofluorescence staining for osteochondral differentiation markers demonstrated a marked decrease in the chondrogenic marker COL2A1, while the expression of the osteogenic marker RUNX2 remained unchanged, in the Mll4-cKO midpalatal suture. Additionally, SOX9, a master regulator of chondrogenesis, exhibited a significant decrease in protein expression. Indeed, time-course histological analysis during postnatal palate growth revealed retardation in the development of the suture cartilage in Mll4-cKO mice. Taken together, our results demonstrate that MLL4 is essential for orchestrating key cellular and molecular events that ensure proper midpalatal suture development and palate growth.

PRMT1-methylated MSX1 phase separates to control palate development

Little is known about the regulation and function of phase separation in craniofacial developmental disorders. MSX1 mutations are associated with human cleft palate, the most common craniofacial birth defect. Here, we show that MSX1 phase separation is a vertebrate-conserved mechanism underlying embryonic palatal fusion. Notably, MSX1 phase separation is triggered by its intrinsically disordered protein region (IDR) and regulated by PRMT1-catalyzed methylation, specifically asymmetric dimethylation of arginine in the MSX1 IDR including R150 and R157. Hypomethylated MSX1 due to methylation site mutations and PRMT1 deficiency consistently leads to abnormal MSX1 phase separation to form less dynamic gel-like condensates, resulting in proliferation defects of embryonic palatal mesenchymal cells and cleft palate. Besides, high frequency mutations in the MSX1 IDR, especially R157S, have been identified in humans with cleft palate. Overall, we reveal the function and regulatory pathway of MSX1 phase separation as a conserved mechanism underlying cleft palate, providing a proof-of-concept example of a phenotype-associated phase separation mechanism associated with craniofacial developmental disorders.

Palatal segment contributions to midfacial anterior-posterior growth

Anterior-posterior (A-P) elongation of the palate is a critical aspect of integrated midfacial morphogenesis. Reciprocal epithelial-mesenchymal interactions drive secondary palate elongation that is coupled to the periodic formation of signaling centers within the rugae growth zone (RGZ). However, the relationship between RGZ-driven morphogenetic processes, the differentiative dynamics of underlying palatal bone mesenchymal precursors, and the segmental organization of the upper jaw has remained enigmatic. A detailed ontogenetic study of these relationships is important because palatal segment growth is a critical aspect of normal midfacial growth, can produce dysmorphology when altered, and is a likely basis for evolutionary differences in upper jaw morphology. We completed a combined whole mount gene expression and morphometric analysis of normal murine palatal segment growth dynamics and resulting upper jaw morphology. Our results demonstrated that the first formed palatal ruga (ruga 1), found just posterior to the RGZ, maintained an association with important nasal, neurovascular and palatal structures throughout early midfacial development. This suggested that these features are positioned at a proximal source of embryonic midfacial directional growth. Our detailed characterization of midfacial morphogenesis revealed a one-to-one relationship between palatal segments and upper jaw bones during the earliest stages of palatal elongation. Growth of the maxillary anlage within the anterior secondary palate is uniquely coupled to RGZ-driven morphogenesis. This may help drive the unequaled proportional elongation of the anterior secondary palate segment prior to palatal shelf fusion. Our results also demonstrated that the future maxillary-palatine suture, approximated by the position of ruga 1 and consistently associated with the palatine anlage, formed predominantly via the posterior differentiation of the maxilla within the expanding anterior secondary palate. Our ontogenetic analysis provides a novel and detailed picture of the earliest spatiotemporal dynamics of intramembranous midfacial skeletal specification and differentiation within the context of the surrounding palatal segment A-P elongation and associated rugae formation.

Association of selected gene variants with nonsyndromic orofacial clefts in Kuwait

INTRODUCTION AND OBJECTIVES

Non-syndromic orofacial clefts (NSOFCs) are complex congenital abnormalities involving both environmental and genetic factors involved in orofacial development. This study aimed to investigate the genetic association of specific genetic variants at different CYRIA gene loci with the development of NSOFCs in Kuwait.

METHODS

Four genetic variants (rs7552, rs3758249, rs3821949, and rs3917201) at four selected gene loci (CYRIA, FOXE1, MSX1, and TGFB3) were genotyped in a total of 240 DNA samples (patients (n = 114) and random controls (n = 126)) employing TaqMan® allele discrimination assay. For each variant and its genotype, the frequencies were determined and tested for Hardy-Weinberg Equilibrium. Genotype frequencies was compared between patients and controls using Pearson's test. Logistic regression analyses were employed to test for the associations of the four selected variants with the occurrence of NSOFCSs.

RESULTS

Significant differences in the distribution of genotypes between cases and controls, rs7552, rs3821949, and rs3917201 were found to have a positive association with NSOFCs. After adjusting for gender, the GG genotype of the rs7552 variant, the AG genotype of the rs3821949 variant, and the CC genotype of the rs3917201 variant showed nearly a two-fold increased risk of NSOFC (p < 0.05).

CONCLUSION

This study reports significant findings on the contribution and modest effect of CYRIA rs7552, MSX1 rs3821949, and TGFB3 rs3917201 in the development of NSOFCs. Our findings provide further evidence on the molecular mechanism and the role of the selected genes in NSOFCs.

Comprehensive three-dimensional microCT and signaling analysis reveal the teratogenic effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on craniofacial bone development in mice

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in utero can result in osteogenic defect during palatogenesis, but the effects on other craniofacial bones and underlying mechanisms remain to be characterized. By treating pregnant mice with TCDD (40 μg/kg) at the vital craniofacial patterning stages (embryonic day 8.5, 10.5 and 12.5), and scanning and reconstructing the skulls at embryonic day 18.5 using microCT, we found that TCDD exposure at the earlier and later patterning stages induced variable craniofacial malformations, including premature fusion of metopic and coronal sutures, truncated palatal processes of maxillary and palatine bones, as well as opening oriented pterygoid processes. Further in vitro determination of the underlying mechanisms using human fetal palatal mesenchymal cells (hFPMCs) revealed that TCDD suppressed a wide variety of osteogenic genes responsible for osteoblast commitment and bone matrix synthesis and mineralization, through activating aryl hydrocarbon receptor (AhR) signaling and subsequently inhibiting estrogen signaling. The attenuation of AhR signaling significantly blocked the osteogenic toxicity, and partly restored the expressing level of estrogen receptor α (ERα). Additional treatment with ERα agonist (PPT) significantly relieved the activation of AhR and rescued the impairment of osteogenesis caused by TCDD. Together, our findings demonstrated that TCDD was teratogenic in numerous cranial neural crest cell-derived craniofacial bone development, and disrupted multiple genes for osteogenic differentiation via the TCDD-mediated AhR/ ERα signaling cross-talk.

The role of sonic hedgehog signaling in the oropharyngeal epithelium during jaw development

Sonic hedgehog (Shh) is expressed in the oropharyngeal epithelium, including the frontonasal ectodermal zone (FEZ), which is defined as the boundary between Shh and Fgf8 expression domains in the frontonasal epithelium. To investigate the role of SHH signaling from the oropharyngeal epithelium, we generated mice in which Shh expression is specifically deleted in the oropharyngeal epithelium (Isl1-Cre; Shhf/f). In the mutant mouse, Shh expression was excised in the oropharyngeal epithelium as well as FEZ and ventral forebrain, consistent with the expression pattern of Isl1. Isl1-Cre; Shhf/f mice exhibited a complete loss of lower jaw components and a malformed upper jaw with defects in the cranial base and secondary palate. Massive cell death was observed in the mandibular process at embryonic day (E) 9.5 and E10.5, while mild cell death was observed in the lambdoidal region (the fusion area in the maxillary, lateral nasal, and medial nasal processes) at E10.5. An RNA-seq analysis revealed that Satb2, a gene involved in cell survival during jaw formation, was downregulated in the lambdoidal region in Isl1-Cre; Shhf/f mice. These results suggest that Shh expression in the FEZ is required for cell survival and skeletogenesis in the lambdoidal region during the development of the upper jaw and that the developmental control governed by SHH signaling is different between upper and lower jaws.

The mechanism of all-trans retinoic acid-induced cleft palate may be related to the novel ENSMUST00000159153-miR-137-5p-Wnt7a and ENSMUST000000236086-miR-34b-3p-EphA10/TRPM2 ceRNA crosstalk

Cleft palate is the most prevalent congenital condition. Cleft palate is brought on by an exogenous chemical called all-trans retinoic acid (atRA). In order to indirectly control gene expression, long chain non-coding RNAs (lncRNAs) act as competitive endogenous RNA (ceRNA) sponges. Its exact mode of action in cleft palate has not yet been determined. The purpose of this study was to determine whether lncRNAs and miRNAs regulated palatal fusion genes during the formation of cleft palate and to offer a possible course for cleft palate target gene therapy. In this work, we created a cleft palate model using atRA, conducted RNA sequencing (RNA-seq) to identify the genes that differed between the atRA-treated group and the control group, and built the lncRNA-miRNA-mRNA ceRNA network based on the projected ceRNA. The results were confirmed using a quantitative real-time polymerase chain reaction (qRT-PCR). ENSMUST00000159153-miR-137-5p-Wnt7a and ENSMUST000000236086-miR-34b-3p-EphA10/TRPM2 may be the main causes of atRA-induced cleft palate, according to the results.

MLL4 regulates postnatal palate growth and midpalatal suture development

MLL4, also known as KMT2D, is a histone methyltransferase that acts as an important epigenetic regulator in various organogenesis programs. Mutations in the MLL4 gene are the major cause of Kabuki syndrome, a human developmental disorder that involves craniofacial birth defects, including anomalies in the palate. This study aimed to investigate the role of MLL4 and the underlying mechanisms in the development and growth of the palate. We generated a novel conditional knockout (cKO) mouse model with tissue-specific deletion of Mll4 in the palatal mesenchyme. Using micro-computed tomography (CT), histological analysis, cell mechanism assays, and gene expression profiling, we examined palate development and growth in the Mll4-cKO mice. Gross craniofacial examination at adult stages revealed mild midfacial hypoplasia and midline defects of the palate in Mll4-cKO mice, including a widened midpalatal suture and disrupted midline rugae pattern. Micro-CT-based time-course skeletal analysis during postnatal palatogenesis through adulthood demonstrated a transverse growth deficit in overall palate width in Mll4-cKO mice. Whole-mount and histological staining at perinatal stages identified that the midline defects in the Mll4-cKO mice emerged as early as one day prior to birth, presenting as a widened midpalatal suture, accompanied by increased cell apoptosis in the suture mesenchyme. Genome-wide mRNA expression analysis of the midpalatal suture tissue revealed that MLL4 is essential for the timely expression of major cartilage development genes, such as Col2a1 and Acan, at birth.Immunofluorescence staining for osteochondral differentiation markers demonstrated a marked decrease in the chondrogenic marker COL2A1, while the expression of the osteogenic marker RUNX2 remained unchanged, in the Mll4-cKO midpalatal suture. Additionally, SOX9, a master regulator of chondrogenesis, exhibited a significant decrease in protein expression. Indeed, time-course histological analysis during postnatal palate growth revealed retardation in the development of the suture cartilage in Mll4-cKO mice. Taken together, our results demonstrate that MLL4 is essential for orchestrating key cellular and molecular events that ensure proper midpalatal suture development and palate growth.

Palatal segment contributions to midfacial anterior-posterior growth

Anterior-posterior (A-P) elongation of the palate is a critical aspect of integrated midfacial morphogenesis. Reciprocal epithelial-mesenchymal interactions drive secondary palate elongation that is coupled to the periodic formation of signaling centers within the rugae growth zone (RGZ). However, the relationship between RGZ-driven morphogenetic processes, the differentiative dynamics of underlying palatal bone mesenchymal precursors, and the segmental organization of the upper jaw has remained enigmatic. A detailed ontogenetic study of these relationships is important because palatal segment growth is a critical aspect of normal midfacial growth, can produce dysmorphology when altered, and is a likely basis for evolutionary differences in upper jaw morphology. We completed a combined whole mount gene expression and morphometric analysis of normal murine palatal segment growth dynamics and resulting upper jaw morphology. Our results demonstrated that the first formed palatal ruga (ruga 1), found just posterior to the RGZ, maintained an association with important nasal, neurovascular and palatal structures throughout early midfacial development. This suggested that these features are positioned at a proximal source of embryonic midfacial directional growth. Our detailed characterization of midfacial morphogenesis revealed a one-to-one relationship between palatal segments and upper jaw bones during the earliest stages of palatal elongation. Growth of the maxillary anlage within the anterior secondary palate is uniquely coupled to RGZ-driven morphogenesis. This may help drive the unequaled proportional elongation of the anterior secondary palate segment prior to palatal shelf fusion. Our results also demonstrated that the future maxillary-palatine suture, approximated by the position of ruga 1 and consistently associated with the palatine anlage, formed predominantly via the posterior differentiation of the maxilla within the expanding anterior secondary palate. Our ontogenetic analysis provides a novel and detailed picture of the earliest spatiotemporal dynamics of intramembranous midfacial skeletal specification and differentiation within the context of the surrounding palatal segment AP elongation and associated rugae formation.

Epithelial-mesenchymal crosstalk: the scriptwriter of craniofacial morphogenesis

Epithelial-mesenchymal interactions (EMI) are fundamental mechanisms in regulating development and organogenesis. Here we summarized the signaling mechanisms involved in EMI in the major developmental events during craniofacial morphogenesis, including neural crest cell induction, facial primordial growth as well as fusion processes. Regional specificity/polarity are demonstrated in the expression of most signaling molecules that usually act in a mutually synergistic/antagonistic manner. The underlying mechanisms of pathogenesis due to disrupted EMI was also discussed in this review.

Compromised actin dynamics underlie the orofacial cleft in Baraitser-Winter Cerebrofrontofacial syndrome with a variant in ACTB

Craniofacial anomalies encompassing the orofacial cleft are associated with > 30% of systemic congenital malformations. Baraitser-Winter Cerebrofrontofacial syndrome (BWCFF) is a rare genetic disorder attributed to variants in the actin beta (ACTB) or actin gamma genes that are correlated with a range of craniofacial abnormalities, including cleft lip and/or palate. The underlying pathological mechanism of BWCFF remains elusive, and it is necessary to investigate the etiology of orofacial clefts in patients with BWCFF. In this study, we identified a missense variant (c.1043C > T: p.S348L) in the ACTB gene of a patient with BWCFF and concomitant cleft lip and palate. Furthermore, we performed functional assessments of this variant using various disease models such as the MDCK cell line and Xenopus laevis. These models revealed a compromised capacity of mutated ACTB to localize to the epithelial junction, consequently affecting the behavior of epithelial cells. Additionally, we discovered that the mutated ACTB exhibited an impaired ability to bind PROFILIN1, a critical factor in actin polymerization. This defective ability may contribute to the molecular etiology of aberrant epithelial cell adhesion and migration, resulting in orofacial cleft formation in BWCFF.

Multiple roles for retinoid signaling in craniofacial development

Retinoic acid (RA) signaling plays multiple essential roles in development of the head and face. Animal models with mutations in genes involved in RA signaling have enabled understanding of craniofacial morphogenic processes that are regulated by the retinoid pathway. During craniofacial morphogenesis RA signaling is active in spatially restricted domains defined by the expression of genes involved in RA production and RA breakdown. The spatial distribution of RA signaling changes with progressive development, corresponding to a multiplicity of craniofacial developmental processes that are regulated by RA. One important role of RA signaling occurs in the hindbrain. There RA contributes to specification of the anterior-posterior (AP) axis of the developing CNS and to the neural crest cells (NCC) which form the bones and nerves of the face and pharyngeal region. In the optic vesicles and frontonasal process RA orchestrates development of the midface, eyes, and nasal airway. Additional roles for RA in craniofacial development include regulation of submandibular salivary gland development and maintaining patency in the sutures of the cranial vault.

Reflecting the human lip in vitro: Cleft lip skin and mucosa keratinocytes keep their identities

OBJECTIVES

Cell models have shown great promise as tools for research, potentially providing intriguing alternatives to animal models. However, the original tissue characteristics must be maintained in culture, a fact that is often assumed, but seldom assessed. We aimed to follow the retention of the original tissue identities of cleft lip-derived skin and mucosa keratinocytes in vitro.

METHODS

Cleft lip-derived keratinocytes were isolated from discarded tissue along the cleft margins during cheiloplasty. Cell identities were assessed by immunohistochemistry and quantitative real-time PCR for tissue-specific markers and compared with native lip tissue. Moreover, keratinocytes were regularly analyzed for the retention of the original tissue characteristics by the aforementioned methods as well as by differentiation assays.

RESULTS

The various anatomical zones of the human lip could be distinguished using a panel of differentiation and functional-based markers. Using these markers, retention of the original tissue identities could be followed and confirmed in the corresponding primary keratinocytes in culture.

CONCLUSIONS

Our findings promote patient-derived cells retaining their original identities as astonishing and clinically relevant in vitro tools. Such cells allow a better molecular understanding of various lip-associated pathologies as well as their modeling in vitro, including but not restricted to orofacial clefts.

Expression analysis of genes including Zfhx4 in mice and zebrafish reveals a temporospatial conserved molecular basis underlying craniofacial development

BACKGROUND

Embryonic craniofacial development involves several cellular and molecular events that are evolutionarily conserved among vertebrates. Vertebrate models such as mice and zebrafish have been used to investigate the molecular and cellular etiologies underlying human craniofacial disorders, including orofacial clefts. However, the molecular mechanisms underlying embryonic development in these two species are unknown. Therefore, elucidating the shared mechanisms of craniofacial development between disease models is crucial to understanding the underlying mechanisms of phenotypes in individual species.

RESULTS

We selected mice and zebrafish as model organisms to compare various events during embryonic craniofacial development. We identified genes (Sox9, Zfhx3 and 4, Cjun, and Six1) exhibiting similar temporal expression patterns between these species through comprehensive and stage-matched gene expression analyses. Expression analysis revealed similar gene expression in hypothetically corresponding tissues, such as the mice palate and zebrafish ethmoid plate. Furthermore, loss-of-function analysis of Zfhx4/zfhx4, a causative gene of human craniofacial anomalies including orofacial cleft, in both species resulted in deformed skeletal elements such as the palatine and ethmoid plate in mice and zebrafish, respectively.

CONCLUSIONS

These results demonstrate that these disease models share common molecular mechanisms, highlighting their usefulness in modeling craniofacial defects in humans.

2,3,7,8-Tetrachlorodibenzo-p-Dioxin Suppresses Mesenchymal Cell Proliferation and Migration Through miR-214-3p in Cleft Palate

OBJECTIVE

The aetiology of CL/P is complicated, with both genetic and environmental factors. This study aimed to investigate the association between TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) exposure and changes in the expression of miR-214-3p in the context of cleft palate.

DESIGN

In this study, we established a fetal mouse cleft palate model using TCDD and differentially expressed miRNAs were analysed by microarray analysis and verified by qRT-PCR. Finally, we demonstrated the effects of TCDD and microRNAs on the proliferation and migration of mesenchymal cells by using CCK8, EDU, Transwell, and wound-healing assays.

RESULTS

Our findings revealed significant upregulation of miRNAs such as miR-214-3p, miR-296-5p, and miR-33-5p in the TCDD intervention group, while miRNAs like miR-92a-3p, miR-126a-3p, and miR-411-5p were significantly downregulated. Notably, qRT-PCR testing confirmed a significant difference in miR-214-3P expression. Further investigations involved the overexpression of miR-214-3p, reducing cell proliferation and migration in primary mouse embryonic palatal mesenchymal (MEPM) cells.

CONCLUSIONS

These results are consistent with the finding that TCDD suppresses palatal mesenchymal cell proliferation and migration through miR-214-3p. In conclusion, miR-214-3p probably plays a role in TCDD-induced cleft palates in mice.

Identification of novel genes regulating the development of the palate

The International Mouse Phenotyping Consortium (IMPC) has generated thousands of knockout mouse lines, many of which exhibit embryonic or perinatal lethality. Using micro-computed tomography (micro-CT), the IMPC has created and publicly released 3D image datasets of embryos from these lethal and subviable lines. In this study, we leveraged this dataset to screen homozygous null mutants for anomalies in secondary palate development. We analyzed optical sections from 2,987 embryos at embryonic days E15.5 and E18.5, representing 484 homozygous mutant lines. Our analysis identified 45 novel genes implicated in palatogenesis. Gene set enrichment analysis highlighted biological processes and pathways relevant to palate development and uncovered 18 genes jointly regulating the development of the eye and the palate. These findings present a valuable resource for further research, offer novel insights into the molecular mechanisms underlying palatogenesis, and provide important context for understanding the etiology of rare human congenital disorders involving simultaneous malformations of the palate and other organs, including the eyes, ears, kidneys, and lungs.

A WAP-Based Concept Acquisition Teaching Model in Cleft Lip and Palate Phenotype and Embryonic Development: Functionality and Usability Study

OBJECTIVE

Taking advantage of the broad coverage of Wireless Application Protocol (WAP), we developed a Content Management System (CMS)-programmed mobile learning application. This application can help the undergraduate to obtain a comprehensive understanding of concepts in Cleft lip and palate Phenotype, and Embryonic development (CPE). The present study aims to evaluate the feasibility and efficacy of the concept acquisition teaching model on the basis of WAP in a practical undergraduate course of CPE.

DESIGN

The concept acquisition teaching model based on WAP was programmed by CMS, covering definitions of various cleft lip and palate, the mechanisms underlying the phenotypes, practical medical cases, as well as corresponding tests after learning.

SETTING

The CPE concept acquisition teaching model was distributed to a total of 524 undergraduate students and 46 tutors participated in CPE teaching from seven highly ranked schools of stomatology in China since April 2022.

PARTICIPANTS

524 undergraduate students and 46 tutors from seven highly ranked schools of stomatology in China.

INTERVENTIONS

The CPE concept acquisition teaching model.

MAIN OUTCOME MEASURES

The effectiveness of the CPE teaching model.

RESULTS

The response rate to the survey was 100%. The grading of the questionnaires indicated that the students were satisfied with the usability, practicality, and outcome, whereas the tutors were more positive with the contents, cooperation, and outcome.

CONCLUSIONS

The present study demonstrated the feasibility and efficacy of the WAP-based concept acquisition teaching model of CPE and a high level of satisfaction among undergraduate students and tutors who major in Stomatology.

Dyrk1a is required for craniofacial development in Xenopus laevis

Loss of function variations in the dual specificity tyrosine-phosphorylation-regulated kinase 1 A (DYRK1A) gene are associated with craniofacial malformations in humans. Here we characterized the effects of deficient DYRK1A in craniofacial development using a developmental model, Xenopus laevis. Dyrk1a mRNA and protein were expressed throughout the developing head and both were enriched in the branchial arches which contribute to the face and jaw. Consistently, reduced Dyrk1a function, using dyrk1a morpholinos and pharmacological inhibitors, resulted in orofacial malformations including hypotelorism, altered mouth shape, slanted eyes, and narrower face accompanied by smaller jaw cartilage and muscle. Inhibition of Dyrk1a function resulted in misexpression of key craniofacial regulators including transcription factors and members of the retinoic acid signaling pathway. Two such regulators, sox9 and pax3 are required for neural crest development and their decreased expression corresponds with smaller neural crest domains within the branchial arches. Finally, we determined that the smaller size of the faces, jaw elements and neural crest domains in embryos deficient in Dyrk1a could be explained by increased cell death and decreased proliferation. This study is the first to provide insight into why craniofacial birth defects might arise in humans with variants of DYRK1A.

Unveiling the Impact of Maternal Hyperthermia in the Late First Trimester: A Case Report of Anterior Esthetic Rehabilitation Utilizing Heterodontic Biologic Posts

The perinatal maternal environment is important for the normal development of the fetus. Epigenetic modifications that influence developmental control genes and signalling pathways for proper fetal development have been associated with maternal illnesses brought on by viruses, bacteria, or even parasitic protozoa. It is crucial to provide details on the onset, length, and timing of the mother's fever because these factors may influence the kind of certain abnormalities. Although fever is a primarily benign disease, it has been linked to negative health outcomes in children and has occasionally resulted in a substantial referral to critical care. This case report presents a 15-year-old female patient with repaired cleft palate and tetralogy of Fallot (TOF) who approached for esthetic rehabilitation of lower anterior teeth. The teeth (31, 32, 43) were tender on percussion. Radiographic evaluation showed the presence of periapical radiolucency. The root canal procedure was performed under local anaesthesia, and the supernumerary maxillary teeth were extracted. After cleaning and disinfecting, these teeth were used as biologic posts with respect to 32 and 33. A follow-up examination was performed after 12 months. The results of this case indicate that using autologous heterodontic biologic posts can lead to a favourable outcome.

Soft Palate Dysplasia: Properties and Surgical Techniques

BACKGROUND

The authors aimed to report a hitherto undescribed class of patients with the obvious phenotype of a novel soft palate dysplasia (SPD) combining unilateral soft palate hypoplasia with a fully developed uvula. The authors also aimed to investigate and evaluate the corresponding surgical approaches.

METHODS

Twelve patients were clinically diagnosed with SPD. Clinical examination, including radiographic tests, was performed to characterize the congenital deformity. The effectiveness of velopharyngeal closure and speech were tested preoperatively and postoperatively.

RESULTS

SPD was featured with velopharyngeal insufficiency, food regurgitation, and speech disorders. It was commonly manifested as structural deformities of the soft palate, tongue palatine arch, pharyngeal palatine arch, and pterygomandibular fold, but with complete uvula shape. According to radiographic analysis, in five patients, the lateral pterygoid processes were poorly developed, and other malformations were present. Velopharyngoplasty based on the unilateral posterior pharyngeal flap can well restore the velopharyngeal closure and speech intelligibility without respiration obstruction.

CONCLUSIONS

SPD is characterized as congenital velopharyngeal insufficiency manifested as a primary soft palate defect. It is highly associated with other physical deformities but independent of conventionally known syndromes. The cause may be an abnormal development of the pterygoid process. Unilateral velopharyngoplasty based on the posterior pharyngeal flap is a great technique to repair SPD.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Histology Atlas of the Developing Mouse Respiratory System From Prenatal Day 9.0 Through Postnatal Day 30

Respiratory diseases are one of the leading causes of death and disability around the world. Mice are commonly used as models of human respiratory disease. Phenotypic analysis of mice with spontaneous, congenital, inherited, or treatment-related respiratory tract abnormalities requires investigators to discriminate normal anatomic features of the respiratory system from those that have been altered by disease. Many publications describe individual aspects of normal respiratory tract development, primarily focusing on morphogenesis of the trachea and lung. However, a single reference providing detailed low- and high-magnification, high-resolution images of routine hematoxylin and eosin (H&E)-stained sections depicting all major structures of the entire developing murine respiratory system does not exist. The purpose of this atlas is to correct this deficiency by establishing one concise reference of high-resolution color photomicrographs from whole-slide scans of H&E-stained tissue sections. The atlas has detailed descriptions and well-annotated images of the developing mouse upper and lower respiratory tracts emphasizing embryonic days (E) 9.0 to 18.5 and major early postnatal events. The selected images illustrate the main structures and events at key developmental stages and thus should help investigators both confirm the chronological age of mouse embryos and distinguish normal morphology as well as structural (cellular and organ) abnormalities.

Tendon-associated gene expression precedes osteogenesis in mid-palatal suture establishment

Orthodontic maxillary expansion relies on intrinsic mid-palatal suture mechanobiology to induce guided osteogenesis, yet establishment of the mid-palatal suture within the continuous secondary palate and causes of maxillary insufficiency remain poorly understood. In contrast, advances in cranial suture research hold promise to improve surgical repair of prematurely fused cranial sutures in craniosynostosis to potentially restore the obliterated signaling environment and ensure continual success of the intervention. We hypothesized that mid-palatal suture establishment is governed by shared principles with calvarial sutures and involves functional linkage between expanding primary ossification centres with the midline mesenchyme. We characterized establishment of the mid-palatal suture from late embryonic to early postnatal timepoints. Suture establishment was visualized using histological techniques and multimodal transcriptomics. We identified that mid-palatal suture formation depends on a spatiotemporally controlled signalling milieu in which tendon-associated genes play a significant role. We mapped relationships between extracellular matrix-encoding gene expression, tenocyte markers, and novel suture patency candidate genes. We identified similar expression patterns in FaceBase-deposited scRNA-seq datasets from cranial sutures. These findings demonstrate shared biological principles for suture establishment, providing further avenues for future development and understanding of maxillofacial interventions.

LAMA5: A new pathogenic gene for non-syndromic cleft lip with or without cleft palate

BACKGROUND

This study aimed to investigate the effect of LAMA5 on palatal development in mice.

METHODS

The palatine process of C57BL/6 J fetal mice on the embryonic day 13.5 (E13.5) was cultured in vitro via the rotating culture method. The LAMA5-shRNA adenovirus vector was constructed, then transfected into the palatal process of E13.5 for 48 h in vitro. A fluorescence microscope was used to visualize the fusion of palates. The expression of LAMA5 was also detected. The expression of ki67, cyclin D1, caspase 3, E-cadherin, vimentin and SHH signaling pathway-related signaling factors in the blank control group, the negative control group, and the LAMA5 interference group were detected after virus transfection.

RESULTS

The bilateral palates in the LAMA5 interference group were not fused after virus transfection. PCR and WB showed that the mRNA and protein expressions of LAMA5 were decreased in the LAMA5 interference group. Furthermore, the mRNA and protein expressions of ki67, cyclin D1 and gli1 were decreased in the LAMA5 interference group, while the mRNA and protein expressions of caspase 3 were increased. However, the mRNA and protein expression of E-cadherin, vimentin, Shh and ptch1 did not significantly change in the LAMA5 interference group.

CONCLUSIONS

LAMA5 silencing causes cleft palate by inhibiting the proliferation of mouse palatal cells and promoting apoptosis, which may not be involved in EMT. LAMA5 silencing can also cause cleft palate by interfering with the SHH signaling pathway.

Spatial Multiomics Reveal the Role of Wnt Modulator, Dkk2, in Palatogenesis

Multiple genetic and environmental etiologies contribute to the pathogenesis of cleft palate, which constitutes the most common among the inherited disorders of the craniofacial complex. Insights into the molecular mechanisms regulating osteogenic differentiation and patterning in the palate during embryogenesis are limited and needed for the development of innovative diagnostics and cures. This study utilized the Pax9-/- mouse model with a consistent phenotype of cleft secondary palate to investigate the role of Pax9 in the process of palatal osteogenesis. While prior research had identified upregulation of Wnt pathway modulators Dkk1 and Dkk2 in Pax9-/- palate mesenchyme, limitations of spatial resolution and technology restricted a more robust analysis. Here, data from single-nucleus transcriptomics and chromatin accessibility assays validated by in situ highly multiplex targeted single-cell spatial profiling technology suggest a distinct relationship between Pax9+ and osteogenic populations. Loss of Pax9 results in spatially restricted osteogenic domains bounded by Dkk2, which normally interfaces with Pax9 in the mesenchyme. These results suggest that Pax9-dependent Wnt signaling modulators influence osteogenic programming during palate formation, potentially contributing to the observed cleft palate phenotype.

Role of TGF-β3 in modulating inflammatory responses and wound healing processes in ischemic ulcers in atherosclerotic patients

Ischemic ulcers pose a multifaceted clinical dilemma for patients with atherosclerosis, frequently compounded by suboptimal wound healing mechanisms. The dual function of Transforming Growth Factor Beta 3 (TGF-β3) in ischemic ulcer healing is not fully comprehended, despite its involvement in modulating inflammatory responses and tissue regeneration. The main aim of this investigation was to clarify the functions and mechanisms by which TGF-β3 regulates inflammatory responses and promotes wound healing in patients with ischemic ulcers who have atherosclerosis. Between August 2022 and November 2023, this cross-sectional investigation was conducted on 428 patients diagnosed with atherosclerotic ischemic ulcers in Haikou, China. The expression and function of TGF-β3 were examined throughout the different stages of wound healing, including inflammation, proliferation and remodelling. In addition to documenting patient demographics and ulcer characteristics, an analysis was conducted on biopsy samples to determine the expression of TGF-β3, pro-inflammatory and anti-inflammatory markers. A subset of patients were administered topical TGF-β3 in order to evaluate its therapeutic effects. The expression pattern of TGF-β3 was found to be stage-dependent and significant, exhibiting increased levels during the phase of inflammation and reduced activity in subsequent phases. TGF-β3 levels were found to be greater in ulcers that were larger and deeper, especially in inflammatory phase. TGF-β3 applied topically induced discernible enhancement in ulcer healing parameters, such as reduction in ulcer depth and size. The therapeutic significance of TGF-β3 was emphasised due to its twofold function of regulating the inflammatory environment and facilitating the regeneration of damaged tissues. Ischemic ulcer lesion healing is significantly influenced by TGF-β3, which functions as an anti-inflammatory and pro-inflammatory mediator. Its correlation with ulcer characteristics and stages of healing suggests that it may have utility as a targeted therapeutic agent.

Single-cell multiomics decodes regulatory programs for mouse secondary palate development

Perturbations in gene regulation during palatogenesis can lead to cleft palate, which is among the most common congenital birth defects. Here, we perform single-cell multiome sequencing and profile chromatin accessibility and gene expression simultaneously within the same cells (n = 36,154) isolated from mouse secondary palate across embryonic days (E) 12.5, E13.5, E14.0, and E14.5. We construct five trajectories representing continuous differentiation of cranial neural crest-derived multipotent cells into distinct lineages. By linking open chromatin signals to gene expression changes, we characterize the underlying lineage-determining transcription factors. In silico perturbation analysis identifies transcription factors SHOX2 and MEOX2 as important regulators of the development of the anterior and posterior palate, respectively. In conclusion, our study charts epigenetic and transcriptional dynamics in palatogenesis, serving as a valuable resource for further cleft palate research.

Advancing the assessment of pacifier effects with a novel computational method

BACKGROUND

Numerous studies have demonstrated a high likelihood of malocclusions resulting from non-nutritive sucking. Consequently, quantifying the impact of pacifiers can potentially aid in preventing the development or exacerbation of malocclusions and guide the design of improved performance pacifiers.

METHODS

This work proposes and assesses a computational methodology that can effectively gather crucial information and provide more precise data regarding the consequences of non-nutritive pacifier sucking. The computational framework utilized is based on solids4Foam [1, 2], a collection of numerical solvers developed within the OpenFOAM® computational library [3]. The computational model focuses on the palate of a six-month-old baby and incorporates various components such as palate tissues, pacifier and tongue, and considers the negative intraoral pressure generated and the tongue displacement. Different models were tested, each offering varying levels of detail in representing the palate structure. These models range from a simplified approach, with one tissue, to a more intricate representation, involving up to five different tissues, offering a more comprehensive palate model compared to existing literature.

RESULTS

The analysis of results involved examining the distribution of stress on the palate surface, as well as the displacement and forces exerted on the dental crowns. By comparing the obtained results, it was possible to evaluate the precision of the approaches previously described in the literature. The findings revealed that the predictions were less accurate when using the simplified model with a single tissue for the palate, which is the most common approach proposed in the literature. In contrast, the results demonstrated that the palate model with the most intricate structure, incorporating five different tissues, yielded distinct outcomes compared to all other combinations.

CONCLUSIONS

The computational methodology proposed, employing the most detailed palate model, has demonstrated its effectiveness and necessity in obtaining accurate data on the impact of non-nutritive sucking habits, which are recognized as a primary contributor to the development of dental malocclusions. In the future, this approach could be extended to conduct similar studies encompassing diverse pacifier designs, sizes, and age groups. This would foster the design of innovative pacifiers that mitigate the adverse effects of non-nutritive sucking on orofacial structures.

Dyrk1a is required for craniofacial development in Xenopus laevis

Loss of function mutations in the dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) gene are associated with craniofacial malformations in humans. Here we characterized the effects of deficient DYRK1A in craniofacial development using a developmental model, Xenopus laevis . Dyrk1a mRNA and protein was expressed throughout the developing head and was enriched in the branchial arches which contribute to the face and jaw. Consistently, reduced Dyrk1a function, using dyrk1a morpholinos and pharmacological inhibitors, resulted in orofacial malformations including hypotelorism, altered mouth shape, slanted eyes, and narrower face accompanied by smaller jaw cartilage and muscle. Inhibition of Dyrk1a function resulted in misexpression of key craniofacial regulators including transcription factors and members of the retinoic acid signaling pathway. Two such regulators, sox9 and pax3 are required for neural crest development and their decreased expression corresponds with smaller neural crest domains within the branchial arches. Finally, we determined that the smaller size of the faces, jaw elements and neural crest domains in embryos deficient in Dyrk1a could be explained by increased cell death and decreased proliferation. This study is the first to provide insight into why craniofacial birth defects might arise in humans with DYRK1A mutations.

Sidedness in Unilateral Orofacial Clefts: A Systematic Scoping Review

OBJECTIVE

An overview of the literature relating to the sidedness of unilateral cleft lip with or without cleft palate to map current knowledge on the cause and impact of directional asymmetry.

DESIGN

Scoping review with a systematic search of Medline and Embase from inception to May 2023.

PATIENTS, PARTICIPANTS

Humans born with a left or right unilateral cleft lip with or without a cleft palate.

MAIN OUTCOME MEASURES

Cleft sidedness as a co-occurrence, an outcome or an exposure.

RESULTS

Forty studies were eligible for inclusion and confirmed the predilection for the occurrence of left sided cleft lips; 12 studies reported cleft sidedness co-occurring with another phenotype, 11 studies report sidedness as an outcome and 17 studies as an exposure. Phenotypes which were reported to co-occur with either left or right sided clefts included congenital dental anomalies, handedness and additional congenital anomalies. Variables investigated as a potential cause of left or right sided clefts as an outcome included chromosomal anomalies, genetic variants and environmental factors. Outcomes investigated in relation to cleft sidedness as an exposure included facial anatomical features, facial growth, educational attainment, functional and psychological characteristics. More studies showed worse outcomes in right sided clefts versus left sided clefts than vice versa, although studies were inconsistent, and a quality assessment was not performed.

CONCLUSIONS

The field of cleft sidedness research is expanding and there are promising early findings to differentiate cause and outcome by sidedness of the cleft.

MicroRNAs in Small Extracellular Vesicles from Amniotic Fluid and Maternal Plasma Associated with Fetal Palate Development in Mice

Cleft palate (CP) is a common congenital birth defect. Cellular and morphological processes change dynamically during palatogenesis, and any disturbance in this process could result in CP. However, the molecular mechanisms steering this fundamental phase remain unclear. One study suggesting a role for miRNAs in palate development via maternal small extracellular vesicles (SEVs) drew our attention to their potential involvement in palatogenesis. In this study, we used an in vitro model to determine how SEVs derived from amniotic fluid (ASVs) and maternal plasma (MSVs) influence the biological behaviors of mouse embryonic palatal mesenchyme (MEPM) cells and medial edge epithelial (MEE) cells; we also compared time-dependent differential expression (DE) miRNAs in ASVs and MSVs with the DE mRNAs in palate tissue from E13.5 to E15.5 to study the dynamic co-regulation of miRNAs and mRNAs during palatogenesis in vivo. Our results demonstrate that some pivotal biological activities, such as MEPM proliferation, migration, osteogenesis, and MEE apoptosis, might be directed, in part, by stage-specific MSVs and ASVs. We further identified interconnected networks and key miRNAs such as miR-744-5p, miR-323-5p, and miR-3102-5p, offering a roadmap for mechanistic investigations and the identification of early CP biomarkers.

A Rare Case of Cleft Palate Associated With Tongue Hamartoma: A Case Report and Systematic Review

INTRODUCTION

Palate development involves a genetic regulation through a complex molecular mechanism that may be disrupted by environmental factors, resulting in impaired fusion and cleft palate formation. An encounter with a case of cleft palate due to dorsal tongue hamartoma prompted us to perform this systematic review.

OBJECTIVE

To review the clinical profile and management approach for a case with cleft palate and tongue hamartoma.

DESIGN

A systematic literature search was conducted using keywords related to cleft palate and tongue hamartoma in PubMed, Scopus, MEDLINE, and Scielo databases through December 2021, with no time or language restrictions.

PATIENTS, PARTICIPANTS

Studies reporting patients with cleft palate and tongue hamartoma were included.

MAIN OUTCOME MEASURE(S)

Information related to clinical profile, diagnostic tests, histopathology, management, and outcomes were extracted.

Fourteen relevant publications were identified with 16 cases reported so far. Among them, thirteen patients were females (81.25%), and 3 were males (18.75%). The age of presentation varied from birth to 19 years. Oral-facial-digital syndrome (type II) was the most commonly associated syndrome.

Congenital tongue hamartoma with cleft palate is a rare presentation, which can present as an isolated entity or part of a syndrome. Genetic evaluation is warranted, particularly for multiple hamartomatous lesions. The preferred treatment is immediate excision of hamartoma while following a standard timeline for palatoplasty.

Ezh2-dependent methylation in oral epithelia promotes secondary palatogenesis

BACKGROUND

In addition to genomic risk variants and environmental influences, increasing evidence suggests epigenetic modifications are important for orofacial development and their alterations can contribute to orofacial clefts. Ezh2 encodes a core catalytic component of the Polycomb repressive complex responsible for addition of methyl marks to Histone H3 as a mechanism of repressing target genes. The role of Ezh2 in orofacial clefts remains unknown.

AIMS

To investigate the epithelial role of Ezh2-dependent methylation in secondary palatogenesis.

METHODS

We used conditional gene-targeting methods to ablate Ezh2 in the surface ectoderm-derived oral epithelium of mouse embryos. We then performed single-cell RNA sequencing combined with immunofluorescence and RT-qPCR to investigate gene expression in conditional mutant palate. We also employed double knockout analyses of Ezh1 and Ezh2 to address if they have synergistic roles in palatogenesis.

RESULTS

We found that conditional inactivation of Ezh2 in oral epithelia results in partially penetrant cleft palate. Double knockout analyses revealed that another family member Ezh1 is dispensable in orofacial development, and it does not have synergistic roles with Ezh2 in palatogenesis. Histochemistry and single-cell RNA-seq analyses revealed dysregulation of cell cycle regulators in the palatal epithelia of Ezh2 mutant mouse embryos disrupts palatogenesis.

CONCLUSION

Ezh2-dependent histone H3K27 methylation represses expression of cell cycle regulator Cdkn1a and promotes proliferation in the epithelium of the developing palatal shelves. Loss of this regulation may perturb movement of the palatal shelves, causing a delay in palate elevation which may result in failure of the secondary palate to close altogether.

Cleft palate and minor metabolic disturbances in a mouse global Arl15 gene knockout

ARL15, a small GTPase protein, was linked to metabolic traits in association studies. We aimed to test the Arl15 gene as a functional candidate for metabolic traits in the mouse. CRISPR/Cas9 germline knockout (KO) of Arl15 showed that homozygotes were postnatal lethal and exhibited a complete cleft palate (CP). Also, decreased cell migration was observed from Arl15 KO mouse embryonic fibroblasts (MEFs). Metabolic phenotyping of heterozygotes showed that females had reduced fat mass on a chow diet from 14 weeks of age. Mild body composition phenotypes were also observed in heterozygous mice on a high-fat diet (HFD)/low-fat diet (LFD). Females on a HFD showed reduced body weight, gonadal fat depot weight and brown adipose tissue (BAT) weight. In contrast, in the LFD group, females showed increased bone mineral density (BMD), while males showed a trend toward reduced BMD. Clinical biochemistry analysis of plasma on HFD showed transient lower adiponectin at 20 weeks of age in females. Urinary and plasma Mg2+ concentrations were not significantly different. Our phenotyping data showed that Arl15 is essential for craniofacial development. Adult metabolic phenotyping revealed potential roles in brown adipose tissue and bone development.

Mesenchymal β-catenin signaling affects palatogenesis by regulating α-actinin-4 and F-actin

OBJECTIVE

Our previous research have found that mesenchymal β-catenin may be involved in palatal shelf (PS) elevation by regulating F-actin. Here, we further investigated the exact mechanism of β-catenin/F-actin in the PS mesenchyme to regulate palatal reorientation.

MATERIALS AND METHODS

(1) Firstly, Ctnnb1ex3f (β-catenin) mice were conditionally overexpressed in the palatal mesenchyme by crossing with the Sox9-creERT2 mice (induced by Tamoxifen injections); (2) Subsequently, histology and immunohistochemistry were used to characterize the variations of PS morphology and expression of key molecules associated with developmental process; (3) Finally, experiments in vivo and ex vivo were employed to identify the critical mechanisms in β-catenin silenced and overexpressed models.

RESULTS

We found that the Sox9CreER; Ctnnb1ex3f mice exhibited failed palatal elevation and visible cleft palate, and overexpression of β-catenin disturbed the F-actin responsible for cytoskeletal remodeling in palatal mesenchymal cells. qRT-PCR results showed mRNA levels of α-actinin4, a gene involved in F-actin cross-linking, were associated with knockdown or overexpression of β-catenin in ex vivo, respectively. Experiments in vivo revealed that mesenchymal specific inactivation or overexpression of β-catenin exhibited decreased or increased α-actinin-4 expression.

CONCLUSIONS

Mesenchymal β-catenin/F-actin plays an essential role in PS reorientation, which mediate α-actinin-4 to regulate F-actin cytoskeleton reorganization.

Identification of an adverse outcome pathway (AOP) for chemical-induced craniofacial anomalies using the transgenic zebrafish model

Craniofacial anomalies are one of the most frequent birth defects worldwide and are often caused by genetic and environmental factors such as pharmaceuticals and chemical agents. Although identifying adverse outcome pathways (AOPs) is a central issue for evaluating the teratogenicity, the AOP causing craniofacial anomalies has not been identified. Recently, zebrafish has gained interest as an emerging model for predicting teratogenicity because of high throughput, cost-effectiveness and availability of various tools for examining teratogenic mechanisms. Here, we established zebrafish sox10-EGFP reporter lines to visualize cranial neural crest cells (CNCCs) and have identified the AOPs for craniofacial anomalies. When we exposed the transgenic embryos to teratogens that were reported to cause craniofacial anomalies in mammals, CNCC migration and subsequent morphogenesis of the first pharyngeal arch were impaired at 24 hours post-fertilization. We also found that cell proliferation and apoptosis of the migratory CNCCs were disturbed, which would be key events of the AOP. From these results, we propose that our sox10-EGFP reporter lines serve as a valuable model for detecting craniofacial skeletal abnormalities, from early to late developmental stages. Given that the developmental process of CNCCs around this stage is highly conserved between zebrafish and mammals, our findings can be extrapolated to mammalian craniofacial development and thus help in predicting craniofacial anomalies in human.

Retinoic acid delays murine palatal shelf elevation by inhibiting Wnt5a-mediated noncanonical Wnt signaling and downstream Cdc-42/F-actin remodeling in mesenchymal cells

BACKGROUND

Mammalian palatal shelves erupted from maxillary prominences undergo vertical extention, transient elevation, and horizontal growth to fuse. Previous studies in mice reported that the retinoic acid (RA) contributed to cleft palate in high incidence by delaying the elevating procedure, but little was known about the underlying biological mechanisms.

METHODS

In this study, hematoxylin-eosin and immunofluorescence staining were employed to evaluate the phenotypes and the expression of related markers in the RA-treated mice model. In situ hybridization and RT-qPCR were used to detect the expression of genes involved in Wnt signaling pathway. The palatal mesenchymal cells were cultured in vitro, and stimulated with RA or CASIN, and co-treated with Foxy5. Wnt5a and Ccd42 expression were evaluated by immunofluorescence staining. Phalloidin was used to label the microfilament cytoskeleton (F-actin) in cultured cells.

RESULTS

We revealed that RA resulted in 100% incidence of cleft palate in mouse embryos, and the expression of genes responsible for Wnt5a-mediated noncanonical Wnt signal transduction were specifically downregulated in mesenchymal palatal shelves. The in vitro study of palatal mesenchymal cells indicated that RA treatment disrupted the organized remodeling of cytoskeleton, an indicative structure of cell migration regulated by the small Rho GTPase Cdc42. Moreover, we showed that the suppression of cytoskeleton and cell migration induced by RA was partially restored using the small molecule Foxy-5-mediated activation of Wnt5A, and this restoration was attenuated by CASIN (a selective GTPase Cdc42 inhibitor) again.

CONCLUSIONS

These data identified a crucial mechanism for Wnt5a-mediated noncanonical Wnt signaling in acting downstream of Rho GTPase Cdc42 to regulate cytoskeletal remodeling and cell migration during the process of palate elevation. Our study provided a new explanation for the cause of cleft palate induced by RA.

Trio-based GWAS identifies novel associations and subtype-specific risk factors for cleft palate

Cleft palate (CP) is one of the most common craniofacial birth defects; however, there are relatively few established genetic risk factors associated with its occurrence despite high heritability. Historically, CP has been studied as a single phenotype, although it manifests across a spectrum of defects involving the hard and/or soft palate. We performed a genome-wide association study using transmission disequilibrium tests of 435 case-parent trios to evaluate broad risks for any cleft palate (ACP) (n = 435), and subtype-specific risks for any cleft soft palate (CSP), (n = 259) and any cleft hard palate (CHP) (n = 125). We identified a single genome-wide significant locus at 9q33.3 (lead SNP rs7035976, p = 4.24 × 10-8) associated with CHP. One gene at this locus, angiopoietin-like 2 (ANGPTL2), plays a role in osteoblast differentiation. It is expressed both in craniofacial tissue of human embryos and developing mouse palatal shelves. We found 19 additional loci reaching suggestive significance (p < 5 × 10-6), of which only one overlapped between groups (chromosome 17q24.2, ACP and CSP). Odds ratios for the 20 loci were most similar across all 3 groups for SNPs associated with the ACP group, but more distinct when comparing SNPs associated with either subtype. We also found nominal evidence of replication (p < 0.05) for 22 SNPs previously associated with orofacial clefts. Our study to evaluate CP risks in the context of its subtypes and we provide newly reported associations affecting the broad risk for CP as well as evidence of subtype-specific risks.

The roles of JAK2/STAT3 signaling in fusion of the secondary palate

Cleft palate has a multifactorial etiology. In palatal fusion, the contacting medial edge epithelium (MEE) forms the epithelial seam, which is subsequently removed with the reduction of p63. Failure in this process results in a cleft palate. We herein report the involvement of janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling in palatal fusion and that folic acid rescues the fusing defect by reactivating JAK2/STAT3. In closure of bilateral palatal shelves, STAT3 phosphorylation was activated at the fusing MEE and mesenchyme underlying the MEE. JAK2 inhibition by AG490 inhibited STAT3 phosphorylation and resulted in palatal fusion failure without removal of the epithelial seam, in which p63 and keratin 17 (K17) periderm markers were retained. Folic acid application restored STAT3 phosphorylation in AG490-treated palatal explants and rescued the fusion defect, in which the p63- and K17-positive epithelial seam were removed. The AG490-induced palatal defect was also rescued in p63 haploinsufficient explants. These findings suggest that JAK2/STAT3 signaling is involved in palatal fusion by suppressing p63 expression in MEE and that folate restores the fusion defect by reactivating JAK2/STAT3.

An improved multicellular human organoid model for the study of chemical effects on palatal fusion

BACKGROUND

Tissue fusion is a mechanism involved in the development of the heart, iris, genital tubercle, neural tube, and palate during embryogenesis. Failed fusion of the palatal shelves could result in cleft palate (CP), a common birth defect. Organotypic models constructed of human cells offer an opportunity to investigate developmental processes in the human. Previously, our laboratory developed an organoid model of the human palate that contains human mesenchyme and epithelial progenitor cells to study the effects of chemicals on fusion.

METHODS

Here, we developed an organoid model more representative of the embryonic palate that includes three cell types: mesenchyme, endothelial, and epithelial cells. We measured fusion by a decrease in epithelial cells at the contact point between the organoids and compared the effects of CP teratogens on fusion and toxicity in the previous and current organoid models. We further tested additional suspect teratogens in our new model.

RESULTS

We found that the three-cell-type model is more sensitive to fusion inhibition by valproic acid and inhibitors of FGF, BMP, and TGFβRI/II. In this new model, we tested other suspect CP teratogens and found that nocodazole, topiramate, and Y27632 inhibit fusion at concentrations that do not induce toxicity.

CONCLUSION

This sensitive human three-cell-type organotypic model accurately evaluates chemicals for cleft palate teratogenicity.

A potential osteogenic role for microRNA-181a-5p during palatogenesis

BACKGROUND

In a previous study, we found that the highly conserved hsa-miR-181a-5p is downregulated in palatal fibroblasts of non-syndromic cleft palate-only infants.

OBJECTIVES

To analyze the spatiotemporal expression pattern of mmu-miR-181a-5p during palatogenesis and identify possible mRNA targets and their involved molecular pathways.

MATERIAL AND METHODS

The expression of mmu-miR-181a-5p was analyzed in the developing palates of mouse embryos from E11 to E18 using qPCR and ISH. Mouse embryonic palatal mesenchyme cells from E13 were used to analyze mmu-miR-181a-5p expression during osteogenic differentiation. Differential mRNA expression and target identification were analyzed using whole transcriptome RNA sequencing after transfection with a mmu-miR-181a-5p mimic. Differentially expressed genes were linked with underlying pathways using gene set enrichment analysis.

RESULTS

The expression of mmm-miR-181a-5p in the palatal shelves increased from E15 and overlapped with palatal osteogenesis. During early osteogenic differentiation, mmu-miR-181a-5p was upregulated. Transient overexpression resulted in 49 upregulated mRNAs and 108 downregulated mRNAs (adjusted P-value < 0.05 and fold change > ± 1.2). Ossification (Stc1, Mmp13) and cell-cycle-related GO terms were significantly enriched for upregulated mRNAs. Analysis of possible mRNA targets indicated significant enrichment of Hippo signaling (Ywhag, Amot, Frmd6 and Serpine1) and GO terms related to cell migration and angiogenesis.

LIMITATIONS

Transient overexpression of mmu-miR-181a-5p in mouse embryonic palatal mesenchyme cells limited its analysis to early osteogenesis.

CONCLUSION

Mmu-miR-181-5p expression is increased in the developing palatal shelves in areas of bone formation and targets regulators of the Hippo signaling pathway.

Multimodal spatiotemporal transcriptomic resolution of embryonic palate osteogenesis

The terminal differentiation of osteoblasts and subsequent formation of bone marks an important phase in palate development that leads to the separation of the oral and nasal cavities. While the morphogenetic events preceding palatal osteogenesis are well explored, major gaps remain in our understanding of the molecular mechanisms driving the formation of this bony union of the fusing palate. Through bulk, single-nucleus, and spatially resolved RNA-sequencing analyses of the developing secondary palate, we identify a shift in transcriptional programming between embryonic days 14.5 and 15.5 pinpointing the onset of osteogenesis. We define spatially restricted expression patterns of key osteogenic marker genes that are differentially expressed between these developmental timepoints. Finally, we identify genes in the palate highly expressed by palate nasal epithelial cells, also enriched within palatal osteogenic mesenchymal cells. This investigation provides a relevant framework to advance palate-specific diagnostic and therapeutic biomarker discovery.