Normal Craniofacial Development Research Articles

Ash1 l loss-of-function results in structural birth defects and altered cortical development

Abstract The histone methyltransferase ASH1L plays a crucial role in regulating gene expression across various organ systems during development, yet its role in brain development remains largely unexplored. Over 130 individuals with autism harbour heterozygous loss-of-function ASH1L variants, and population studies confirm it as a high-risk autism gene. Previous studies on Ash1 l deficient mice have reported autistic-like behaviours and provided insights into the underlying neuropathophysiology. In this study, we used mice with a cre-inducible deletion of Ash1 l exon 4, which results in a frame shift and premature stop codon (p.V1693Afs*2). Our investigation evaluated the impact of Ash1 l loss-of-function on survival and craniofacial skeletal development. Using a tamoxifen-inducible cre strain, we targeted Ash1 l knockout early in cortical development (Emx1-Cre-ERT2; e10.5). Immunohistochemistry was utilized to assess cortical lamination, while EdU incorporation aided in birthdating cortical neurons. Additionally, single-cell RNA sequencing was employed to compare cortical cell populations and identify genes with differential expression. At e18.5, the proportion of homozygous Ash1 l germline knockout embryos appeared normal; however, no live Ash1 l null pups were present at birth (e18.5: n = 77, P = 0.90; p0: n = 41, P = 0.00095). Notably, Ash1l-/- exhibited shortened nasal bones (n = 31, P = 0.017). In the cortical-specific knockout model, SATB2 neurons showed increased numbers (n = 6/genotype, P = 0.0001) and were distributed through the cortical plate. Birthdating revealed generation of ectopically placed deep layer neurons that express SATB2 (e13.5 injection: n = 4/genotype, P = 0.0126). Single cell RNA sequencing revealed significant differences in gene expression between control and mutant upper layer neurons, leading to distinct clustering. Pseudotime analysis indicated that the mutant cluster followed an altered cell differentiation trajectory. This study underscores the essential role of Ash1 l in postnatal survival and normal craniofacial development. In the cortex, ASH1L exerts broad effects on gene expression and is indispensable for determining the fate of upper layer cortical neurons. These findings provide valuable insights into the potential mechanisms of ASH1L neuropathology, shedding light on its significance in neurodevelopmental disorders like autism.

Zmym4 is required for early cranial gene expression and craniofacial cartilage formation.

Introduction: The Six1 transcription factor plays important roles in the development of cranial sensory organs, and point mutations underlie craniofacial birth defects. Because Six1's transcriptional activity can be modulated by interacting proteins, we previously screened for candidate interactors and identified zinc-finger MYM-containing protein 4 (Zmym4) by its inclusion of a few domains with a bona fide cofactor, Sine oculis binding protein (Sobp). Although Zmym4 has been implicated in regulating early brain development and certain cancers, its role in craniofacial development has not previously been described. Methods: We used co-immunoprecipitation and luciferase-reporter assays in cultured cells to test interactions between Zmym4 and Six1. We used knock-down and overexpression of Zmym4 in embryos to test for its effects on early ectodermal gene expression, neural crest migration and craniofacial cartilage formation. Results: We found no evidence that Zmym4 physically or transcriptionally interacts with Six1 in cultured cells. Nonetheless, knockdown of endogenous Zmym4 in embryos resulted in altered early cranial gene expression, including those expressed in the neural border, neural plate, neural crest and preplacodal ectoderm. Experimentally increasing Zmym4 levels had minor effects on neural border or neural plate genes, but altered the expression of neural crest and preplacodal genes. At larval stages, genes expressed in the otic vesicle and branchial arches showed reduced expression in Zmym4 morphants. Although we did not detect defects in neural crest migration into the branchial arches, loss of Zmym4 resulted in aberrant morphology of several craniofacial cartilages. Discussion: Although Zmym4 does not appear to function as a Six1 transcriptional cofactor, it plays an important role in regulating the expression of embryonic cranial genes in tissues critical for normal craniofacial development.

Rare variant modifier analysis identifies variants in SEC24D associated with orofacial cleft subtypes.

As one of the most common structural birth defects, orofacial clefts (OFCs) have been studied for decades, and recent studies have demonstrated that there are genetic differences between the different phenotypic presentations of OFCs. However, the contribution of rare genetic variation genome-wide to different subtypes of OFCs has been understudied, with most studies focusing on common genetic variation or rare variation within targeted regions of the genome. Therefore, we used whole-genome sequencing data from the Gabriella Miller Kids First Pediatric Research Program to conduct a gene-based burden analysis to test for genetic modifiers of cleft lip (CL) vs cleft lip and palate (CLP). We found that there was a significantly increased burden of rare variants in SEC24D in CL cases compared to CLP cases (p = 6.86 [Formula: see text] 10-7). Of the 15 variants within SEC24D, 53.3% were synonymous, but overlapped a known craniofacial enhancer. We then tested whether these variants could alter predicted transcription factor binding sites (TFBS), and found that the rare alleles destroyed binding sites for 9 transcription factors (TFs), including Pax1 (p = 0.0009), and created binding sites for 23 TFs, including Pax6 (p = 6.12 [Formula: see text] 10-5) and Pax9 (p = 0.0001), which are known to be involved in normal craniofacial development, suggesting a potential mechanism by which these synonymous variants could have a functional impact. Overall, this study indicates that rare genetic variation may contribute to the phenotypic heterogeneity of OFCs and suggests that regulatory variation may also contribute and warrant further investigation in future studies of genetic variants controlling risk to OFC.

RA-induced prominence-specific response resulted in distinctive regulation of Wnt and osteogenesis.

Proper retinoic acid (RA) signaling is essential for normal craniofacial development. Both excessive RA and RA deficiency in early embryonic stage may lead to a variety of craniofacial malformations, for example, cleft palate, which have been investigated extensively. Dysregulated Wnt and Shh signaling were shown to underlie the pathogenesis of RA-induced craniofacial defects. In our present study, we showed a spatiotemporal-specific effect of RA signaling in regulating early development of facial prominences. Although inhibited Wnt activities was observed in E12.5/E13.5 mouse palatal shelves, early exposure of excessive RA induced Wnt signaling and Wnt-related gene expression in E11.5/E12.5 mouse embryonic frontonasal/maxillary processes. A conserved regulatory network of miR-484-Fzd5 was identified to play critical roles in RA-regulated craniofacial development using RNA-seq. In addition, subsequent osteogenic/chondrogenic differentiation were differentially regulated in discrete mouse embryonic facial prominences in response to early RA induction, demonstrated using both in vitro and in vivo analyses.

Early screening and treatment methods of pediatric sleep-disordered breathing(SDB) in dental office

Pediatric sleep-disordered breathing(SDB) is a common sleep disorder in children caused by obstruction of upper airway during sleep. It is often unrecognized early in life and causes various complications, including abnormal craniofacial growth and oral muscle dysfunctions. Dentist can play a significant role in managing SDB by early screening SDB risk factors and timely referring for diagnosis. SDB risk factors can be easily screened in dental office through medical history, sleep history, physical factors, sleep questionnaire, and cephalometric x-ray. In case of abnormal craniofacial development, rapid maxillary expansion, oral appliances, and myofunctional therapy can be used to reduce SDB symptoms and restore normal craniofacial development and muscular tones. Understanding continuous interaction between oral-facial muscle tone, maxillary-mandibular growth and development of SDB is important in managing pediatric SDB. The ultimate goal of pediatric SDB treatment is to change mouth breathing to nasal breathing, and a multidisciplinary approach in medicine and dentistry is necessary.

The impact of developmental genes in non-syndromic cleft lip and/or palate

Non-syndromic cleft lip and/or palate (NSCL/P) is a congenital malformation with a prevalence of 1:700 births. It has a multifactorial etiology. Human craniofacial development takes place during the first 10 weeks of pregnancy. Normal craniofacial development arises from the convergence and fusion of the facial and palatal processes and involves interactions between genes that regulate cell growth, proliferation, differentiation, epithelial-to-mesenchymal transition, and apoptosis. Whole genome/exome analysis, and also genome-wide association studies give us to chance to identify the genetic factors which contribute to the development of NSCL/P. After detecting a cleft lip and/or palate on ultrasonography without associated anomalies, the patient should be evaluated in collaboration with a clinical geneticist, taking into account the many genes and environmental factors involved in NSCL/P etiopathogenesis, and a roadmap for possible genetic diagnosis should be drawn.

Inhibition of the 3-hydroxy-3-methyl-glutaryl-CoA reductase diminishes the survival and size of chondrocytes during orofacial morphogenesis in zebrafish.

The 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR) is the enzyme controlling the rate-limiting step in the synthesis of cholesterol, sterols, and isoprenoids in the mevalonate biosynthetic pathway. Impaired function of HMGCR in zebrafish produces craniofacial malformations and orofacial cleft, mainly affecting the post-migratory neural crest cells with little earlier effect. Here we investigate morphogenetic and cellular mechanisms underlying the generation of these malformations. The morphology of chondrocytes in the lower jaw and the proliferation/apoptosis in the ethmoid plate were analysed in hmgcr1b mutants and in embryos treated with atorvastatin. In the ceratohyal of treated embryos, we measured the number and dimensions of chondrocytes. In the ethmoid plate, we performed proliferation and apoptosis assays to quantify the number of cells undergoing each process in both hmgcr1b mutants and pharmacologically treated embryos. All embryos were imaged using confocal microscopy and processed to obtain maximum intensity z-projection. The shortening of the ceratohyal is produced by a moderate reduction in the number of cells combined with isometric shrinkage of the chondrocytes. At the same time, the shortening of the ethmoid plate is due to a combination of a slightly diminished proliferation with massive abnormal apoptosis at the proliferation front. HMGCR function is necessary for the normal survival and morphology of chondrocytes during condensation and chondrogenesis in the developing palate and jaw. Further studies are required to establish the pathways through which HMGCR acts on apoptosis, proliferation, and cell size during normal craniofacial development.

To Check the Reliability of Various Cephalometric Parameters used for Predicting the Type of Malocclusions and Growth Patterns.

Background:There are many different types of malocclusions that may result from the sagittal, vertical, or transverse deviations in normal craniofacial development. When it comes to orthodontic problems, malocclusions in the sagittal plane may have a considerable impact on a person's self-esteem as well as their ability to speak and eat properly. Sagittal anomalies in the skeletal, dental, and soft tissue systems may now be accurately diagnosed using a universally accepted standard lateral cephalogram (SLCE).Methods and Materials:The principal investigator manually traced the cephalograms, identified skeletal landmarks, and measured the following data. The ANB angle (normal range: 0° to 4°) is the angle framed by the point A, Nasion, and B. Estimated oppositely from point A and B on the functional occlusal plane, with Wits evaluation: AO-to-BO direct distance. AB plane angle : the angle formed by the AB and the Npog plane (normal range = -9° to 0°). Beta angle: the angle framed by the A-CB and AB lines, with a typical range of 27° to 35°. W angle: this is the angle created by the opposite line from M to the S-G line and the M-G line, with a typical range of 51 to 55 degrees. The angle of convexity: the angle between N-point A and A-Pog. (Normal range: -8.5 to 10 degree)Results:We utilised Pearson correlation to see how well the different skeletal studies correlated with one another. Wits and the ANB angle of convexity exhibited an excellent relationship with each other, with r = 0.831 and Downs angle of convexity (both r = 0.823 and P = 0.01) being statistically significant. This study used Kappa statistics to assess the degree of agreement between several cephalometric diagnostic criteria. The agreement between the ANB and final groups was strong (k = 0.802, P = 0.01).Conclusion:There was a strong link between all of the cephalometric measures. The cephalometric landmark and valid indication was determined to be the most dependable in evaluating malocclusion and development pattern.

Evaluation of effects of removable functional orthodontic apparatus on the upper airway size by cephalometric films

ObjectiveRespiration is a vital functional process that has effects on normal craniofacial development. Since the upper airway formations and dentofacial structures are adjacent to each other, the interaction between them is possible. The aim of this study is to evaluate the effects of removable functional appliances used in the treatment of patients with mandibular and maxillary growth retardation-stenosis in Class I, Class II, and Class III malocclusion on the upper airway. Materials and methodsThirty two patients were studied in the study. The patients were divided into 4 groups according to treatment modalities. Maxillary expansion device group (Group A), Twinblock-Monoblock group (Group B), Face mask group (Group C), and Chincup group (Group D). The upper airway size in the lateral cephalometric images of the patients before orthodontic treatment with removable functional appliances (T0) and the upper airway size in the lateral cephalometric images taken after the end of the orthodontic treatment with the removable functional appliances (T1) were retrospectively compared. ResultMost upper airway size increased after orthodontic treatment (T1) in the individuals who received orthodontic treatment with A, B, C, and D type removable functional appliances compared to pre-treatment (T0). When the changes in upper airway size pre-treatment (T0) and post-treatment (T1) were compared, the change in upper airway size according to treatment groups was found to be statistically different (p <0.05). ConclusionSince a large part of the upper airway is located in the craniofacial complex, orthodontists also examine the airway for diagnosis and planning and can regulate the airway in case of occlusion that has occurred or may occur. This puts orthodontists in an important place to intervene when complications occur or may develop in the upper airway. By determining the effects of removable functional appliances on the airways, airway problems that may be experienced at an early age can be prevented.

Pharyngeal endoderm expression of nanos1 is dispensable for craniofacial development

Nanos proteins are essential for developing primordial germ cells (PGCs) in both invertebrates and vertebrates. In invertebrates, also contribute to the patterning of the anterior-posterior axis of the embryo and the neural development. In vertebrates, however, besides the role of Nanos proteins in PGC development, the biological functions of the proteins in normal development have not yet been identified. Here, we analyzed the expression and function of nanos1 during craniofacial development in zebrafish. nanos1 was expressed in the pharyngeal endoderm and endodermal pouches essential for the development of facial skeletons and endocrine glands in the vertebrate head. However, no craniofacial defects, such as abnormal pouches, hypoplasia of the thymus, malformed facial skeletons, have been found in nanos1 knockout animals. The normal craniofacial development of nanos1 knockout animals is unlikely a consequence of the genetic redundancy of Nanos1 with Nanos2 or Nanos3 or a result of the genetic compensation for the loss of Nanos1 by Nanos2 or Nanos3 because the expression of nanos2 and nanos3 was rarely seen in the pharyngeal endoderm and endodermal pouches in wild-type and nanos1 mutant animals during craniofacial development. Our findings suggest that nanos1 expression in the pharyngeal endoderm might be dispensable for craniofacial development in zebrafish.

CDON gene contributes to pituitary stalk interruption syndrome associated with unilateral facial and abducens nerve palsy

The relationship between congenital defects of the brain and facial anomalies was proven. The Hedgehog signaling pathway plays a fundamental role in normal craniofacial development in humans. Mutations in the sonic hedgehog (SHH) signaling gene CDON have been recently reported in patients with holoprosencephaly and with pituitary stalk interruption syndrome (PSIS). This study’s aim was an elucidation of an 18-year-old patient presenting PSIS, multiple pituitary hormone deficiency, and congenital unilateral facial and abducens nerve palsy. Additionally, bilateral sensorineural hearing loss, dominating at the right site, was diagnosed. From the second year of life, growth deceleration was observed, and from the age of eight, anterior pituitary hormone deficiencies were gradually confirmed and substituted. At the MRI, characteristic triad for PSIS (anterior pituitary hypoplasia, interrupted pituitary stalk and ectopic posterior lobe) was diagnosed. We performed a comprehensive genomic screening, including microarrays for structural rearrangements and whole-exome sequencing for a monogenic defect. A novel heterozygous missense variant in the CDON gene (c.1814G > T; p.Gly605Val) was identified. The variant was inherited from the mother, who, besides short stature, did not show any disease symptoms. The variant was absent in control databases and 100 healthy subjects originating from the same population. We report a novel variant in the CDON gene associated with PSIS and congenital cranial nerve palsy. The variant revealed autosomal dominant inheritance with incomplete penetrance in concordance with previous studies reporting CDON defects.

Diabetes, Oxidative Stress, and DNA Damage Modulate Cranial Neural Crest Cell Development and the Phenotype Variability of Craniofacial Disorders.

Craniofacial malformations are among the most common birth defects in humans and they often have significant detrimental functional, aesthetic, and social consequences. To date, more than 700 distinct craniofacial disorders have been described. However, the genetic, environmental, and developmental origins of most of these conditions remain to be determined. This gap in our knowledge is hampered in part by the tremendous phenotypic diversity evident in craniofacial syndromes but is also due to our limited understanding of the signals and mechanisms governing normal craniofacial development and variation. The principles of Mendelian inheritance have uncovered the etiology of relatively few complex craniofacial traits and consequently, the variability of craniofacial syndromes and phenotypes both within families and between families is often attributed to variable gene expression and incomplete penetrance. However, it is becoming increasingly apparent that phenotypic variation is often the result of combinatorial genetic and non-genetic factors. Major non-genetic factors include environmental effectors such as pregestational maternal diabetes, which is well-known to increase the risk of craniofacial birth defects. The hyperglycemia characteristic of diabetes causes oxidative stress which in turn can result in genotoxic stress, DNA damage, metabolic alterations, and subsequently perturbed embryogenesis. In this review we explore the importance of gene-environment associations involving diabetes, oxidative stress, and DNA damage during cranial neural crest cell development, which may underpin the phenotypic variability observed in specific craniofacial syndromes.

Effects of EPHB receptors on facial morphology: non‐additive interactions during mouse facial development

EPHRIN-B1 mutations underlie craniofrontonasal syndrome (CFNS), and signaling interactions between EPHRIN-B1 ligand and the EPHB1, EPHB2, and EPHB3 receptors are presumed to be critical for normal craniofacial development. However, our understanding of the relative and spatial contribution of each receptor to facial morphogenesis remains incomplete. Here, we expand upon previous work by providing a detailed morphometric analysis of an E14.5 allelic seriesof Ephb1, Ephb2, and Ephb3 null mouse mutants. We assess the impact of individual receptor loss on facial morphology and compare observed facial shapes with those predicted by an additive genetic model. We found that Ephb1, Ephb2, and Ephb3 as well as facial size contribute significantly to facial shape. Predicted Principal Components (PC) scores of facial shape variation suggest a minimal global effect of Ephb1, with moderate effects of Ephb2 and Ephb3 on facial morphology. Observed scores for Ephb2 and Ephb3 homozygous single nulls align closely with predicted additive genetic scores, intermediate between controls and triple homozygous nulls. Compared to controls, triple homozygous nulls have wider orbits, inferiorly displaced nasals, and rostrally placed ear pinnae, suggesting an overall wider but shorter face. Ephb2 and Ephb3 mutants exhibit different facial shape effects, with Ephb2 homozygous nulls having infero-laterally oriented orbits and less severe shape changes in the rest of the face. Predicted and observed PC scores for Ephb1/Ephb2 double nulls are similar to Ephb2 single nulls, and Ephb2/Ephb3 double nulls are similar to triple homozygous nulls. While facial shape variation across our sample is primarily explained by additive genetic effects, there is also a non-additive Ephb1 effect that may be influencing facial shape and size. Predicted additive genetic PC scores place Ephb1 homozygous nulls close to controls, and Ephb1/Ephb3 homozygous double nulls close to Ephb3 homozygous nulls. These genotypes instead deviate from additive genetic predictions by having a relatively wider and shorter face, and overall smaller facial size. In sum, we have identified major additive genetic effects of Ephb1, Ephb2, and Ephb3 on facial shape development, as well as a more subtle non-additive effect of Ephb1. We also describe specific morphologies associated with individual or compound loss of EPHB receptors and find overlapping and distinct facial shape effects of each. More broadly, this work helps identify signaling interactions that may occur between EPHRIN-B1 and EPHB1, EPHB2, and EPHB3 receptorsand the role each plays during normal craniofacial development and CFNS.

Wnt Signaling Drives Correlated Changes in Facial Morphology and Brain Shape.

Canonical Wnt signaling plays multiple roles critical to normal craniofacial development while its dysregulation is known to be involved in structural birth defects of the face. However, when and how Wnt signaling influences phenotypic variation, including those associated with disease, remains unclear. One potential mechanism is via Wnt signaling’s role in the patterning of an early facial signaling center, the frontonasal ectodermal zone (FEZ), and its subsequent regulation of early facial morphogenesis. For example, Wnt signaling may directly alter the shape and/or magnitude of expression of the sonic hedgehog (SHH) domain in the FEZ. To test this idea, we used a replication-competent avian sarcoma retrovirus (RCAS) encoding Wnt3a to modulate its expression in the facial mesenchyme. We then quantified and compared ontogenetic changes in treated to untreated embryos in the three-dimensional (3D) shape of both the SHH expression domain of the FEZ, and the morphology of the facial primordia and brain using iodine-contrast microcomputed tomography imaging and 3D geometric morphometrics (3DGM). We found that increased Wnt3a expression in early stages of head development produces correlated variation in shape between both structural and signaling levels of analysis. In addition, altered Wnt3a activation disrupted the integration between the forebrain and other neural tube derivatives. These results show that activation of Wnt signaling influences facial shape through its impact on the forebrain and SHH expression in the FEZ, and highlights the close relationship between morphogenesis of the forebrain and midface.

Genetic And Environmental Factors Involved In The Development Of Oral Malformations Such As Cleft Lip/Palate In Non-Syndromic Patients And Open Bite Malocclusion

Among the most common malformations observed in the oral cavity are cleft lip/palate and malocclusions, being this last one considered by the World Health Organization, the third public health problem.Malocclusions include the anterior open bite, a change in the vertical plane, that can be of two types: dental anterior open bite and skeletal anterior open bite. Cleft lip and cleft palate are the most common congenital malformations at birth. These malformations result from a failure in the normal craniofacial development process, which requires the coordination of a complex series of events. From the embryological point of view, the cleft lip/palate is a consequence of the failure of the first superior branchial arch to complete fusion with the frontonasal process during pregnancy.All these malformations result from the interaction of both genetic and environmental factors. Among the environmental factors involved in the development of malocclusions are deleterious habits, mouth breathing and trauma. Several genes involved in the development of facial bones, muscles and teeth are also responsible for the development of malocclusions. In the same way, clefts development is a multifactorial trait where multiple genes are involved as well as environmental factor like alcohol consumption, tobacco, exposure to pesticides or toxic solvents, in a complex interaction.All these factors may jeopardize the normal functioning of the stomatognathic system and the consequent quality of life of the patient. The purpose of this study was to review the literature concerning the genetic and environmental aspects involved in the development of these malformations.

Characterizing the Craniofacial Morphological Changes in Neural Crest Cell Specific Conditional Connexin‐43 Knock‐Out Mice

The craniofacial skeleton is an intricate structure that forms through complex cell‐cell interactions across neural crest and mesoderm derived cell populations. Proper cell‐cell communication during the migration and differentiation of cranial neural crest cells is critical for normal craniofacial development and this intercellular communication is thought to be facilitated through gap junctions – membrane channels composed of connexin proteins. In particular, connexin‐43 (Cx43) has been shown to be expressed in pre‐migratory and migratory cranial neural crest cells and plays a role in neural crest epithelial‐to‐mesenchyme transition. Additionally, within the skull, neural crest‐derived regions show the greatest morphological changes in mice wherein Cx43 has been globally ablated providing further evidence that Cx43 is important for proper neural crest function and ultimately proper development of the skull. To date, there have been no studies that have directly looked at the role of Cx43 in cranial neural crest cells in a mouse model. Thus, we have developed a neural crest‐specific Cx43 knockout mouse to address this gap in knowledge. In this study we (1) verify that Cx43 ablation is limited to neural crest cell and (2) characterize and compare craniofacial size and shape among wildtype, heterozygous and homozygous knockout mice.Heterozygous Wnt1‐Cre2 recombinase mice were bred with homozygous floxed Cx43 mice to create offspring which were bred to express the genotype, Wnt1‐Cre2/+:Cx43fl/+. These mice were bred to create: control mice (Wnt‐1Cre2/+:Cx43+/+), heterozygous conditional knock‐outs (Wnt1‐Cre2/+:Cx43fl/fl) and homozygous conditional knock‐outs (Wnt1‐Cre2+/+:Cx43fl/fl). To verify the knockout, paraffin embedded sagittal sections of embryonic and post‐natal mouse hearts and skulls were tagged with Wnt1 and Cx43 antibodies. RT‐PCR, and Western blotting were performed on neural crest and mesoderm derived newborn skull bones, to verify the expression levels of Cx43 mRNA and protein respectively. Newborn skulls from each genotype were imaged using high resolution micro‐CT and these images were used to quantify and compare skull morphology among genotypes using statistical analyses of shape.We have confirmed that Cx43 ablation is limited to neural crest cells in our mice. Analyses of skull shape comparisons among genotypes is ongoing with our initial findings indicating that mice homozygous for the knockout demonstrate overt changes to skull morphology, heterozygous mouse skulls are qualitatively similar to control mouse skulls. We predict that statistical analyses will uncover that only the bones derived from neural crest cells will display morphological differences among genotypes.Our study addresses a fundamental gap of the role connexin‐43 plays in cranial neural crest function and subsequent development of much of the skull.Support or Funding InformationFunding: Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant (R5211A02)

Sfrp4 Expression in Thyroxine Treated Calvarial Cells: A Novel Target

Evidence suggests alterations of thyroid hormone levels can disrupt normal craniofacial development. Most data suggest the major targets of thyroid hormones to be the Htra1/Igf1 pathway. Recent discovery by our group suggests involvement of targets of the WNT pathway, specifically overexpression of antagonist Sfrp4 in the presence of excess thyroid hormone. Here we aimed to model these interactions in vitro to determine if thyroid hormone directly drives Sfrp4 expression in cells relevant to craniofacial development. Affymetrix transcriptional profiling found Sfrp4 to be overexpressed in cranial suture derived cells stimulated with thyroxine in vitro. Bioinformatics interrogation of the SFRP4 promoter identified multiple putative binding sites for thyroid hormone receptors. Experimentation with several cell lines demonstrated that thyroxine treatment induced Sfrp4 expression. However, protein levels did not correlate with induction of gene expression, demonstrating that Sfrp4 mRNA and protein levels are not tightly coupled. Transcriptional and protein analyses demonstrate thyroid hormone receptor binding to the proximal promoter of the target gene Sfrp4. Interestingly functional analysis of stem cells, fibroblasts, or primary culture cells after thyroxine stimulation for alkaline phosphatase activity shows only pre‐osteoblasts are pushed to become positive after thyroid hormone stimulation, suggesting cell type susceptibility. Finally, we added recombinant SFRP4 to pre‐osteoblasts in combination with thyroxine treatment and observed a significant decrease in alkaline phosphatase positivity, suggesting SFRP4 may be a key regulatory molecule that prevents thyroxine driven osteogenesis. The implications for this relationship indicate SFRP4 as a potential diagnostic or therapeutic target for hyperostotic craniofacial disorders.Support or Funding InformationThe authors would like to thank Xing Ming Shi for isolation of the bone marrow mesenchymal cells. The following funding sources were used for this study a grant from the Cleft Palate Foundation, NIH/NIDCR R03DE023350A, 5T32DE017551, and F31DE026684, NIH/NCATS UL1 TR000062, NIH/NIGM P30GM103331, GM103342 and GM103499, and MUSC’s Office of the Vice President for Research.

Mutations in P63 and IRF-6 Present with Overlapping Craniofacial Defects: A study from Lebanon

Interferon Regulatory Factor 6 (IRF-6) and p63 are two vital transcription factors implicated in normal craniofacial development. In this report, we present a family with Van Der Woude Syndrome (VWS) with a mutation in exon 9 of IRF-6 gene and a phenotypically overlapping case of Rapp-Hodgkin Syndrome (RHS) resulting from a mutation in the p63 gene. Members from both families presented with congenital lip pits and cleft lip/palate. The RHS case had additional ectodermal features that underscore the upstream nature of p63 in the complex p63-IRF-6 interactive pathway.

Genetics in Pediatric Dentistry

Genetics plays a very important role in normal craniofacial development, abnormal dental anomalies, and different dental diseases such as dental caries, periodontitis, and dental malocclusion. Even it has a great role in different oral cancers also. Very little importance is given for genetic screening and diagnosis of dental diseases. This article attempts to gather insight about different dental diseases and their genetic basis, the need for genetic screening and testing to avoid future problems.

Mouse models of human craniofacials spliceosomopathies: Are they neurocristopathies?

Splicing, the removal of introns from pre‐messenger RNA is an essential step for expression of most genes in multicellular organisms and for expanding the number of proteins coded by genomes. Recently, exome sequencing revealed that mutations in splicing factors and small nuclear ribonucleoprotein particles (snRNPs) which form core components of the spliceosome, are responsible for craniofacial malformations. Our group used in situ hybridization to examine expression of three core components of the spliceosome: Eftud2 – mutated in patients with mandibulofacial dysostosis, Guion‐Almeida type (MFDGA); SnrpB – responsible for Cerebrocostomandibular Syndrome (CMS); and Sf3b4 which is responsible for Nager syndrome. Herein, we report expression of Eftud2, Sf3b4 and SnrpB during craniofacial development. In addition, we used CRISPR/Cas9 to generate mice with deletion (Eftud2 del) and conditional mutation of exon 2 of Eftud2 (Eftud2 flox). At embryonic days (E) 7.5 and 8.5, Eftud2 was highly expressed in ectodermal and mesodermal components of the future craniofacial region, by E9.5 expression was also found in the body wall and developing heart. Eftud2 del heterozygous mice were viable and fertile, though these embryos showed reduced levels of Eftud2 mRNA and protein. In contrast, Eftud2 del homozygous mutant embryos arrest at E3.5 and failed to grow and hatch ex vivo. To examine the requirement for Eftud2 in neural crest cells, the Wnt1‐Cre2 transgenic line was used to delete exon 2 of Eftud2 specifically in that lineage. Eftud2 flox homozygous mutant embryos carrying the Wnt1‐Cre2 transgene displayed hypoplasia of the midbrain and pharyngeal arches starting at E9.5. By E11.5, most embryos also had an open neural tube and all embryos showed exencephaly at E14.5. Cartilage preparations revealed an absence of cartilage in the head, reduction/or absence of Meckel's cartilage, and abnormal inner ear development. Since deletion of exon 2 is predicted to generate a truncated protein with partial function, our data suggest that normal levels of Eftud2 is crucial in neural crest cells for normal craniofacial development. Future studies are focused on elucidating the molecular and transcriptional basis of MFDM using this mouse model.Support or Funding InformationCanadian Institute of Health Research (MOP#142452)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.