Cranial Neural Crest Research Articles

Depolarization induces calcium-dependent BMP4 release from mouse embryonic palate mesenchymal cells.

Bone Morphogenetic Protein (BMP) signaling is essential for craniofacial development, though little is known about the mechanisms that govern BMP secretion. We show that depolarization induces calcium-dependent BMP4 release from mouse embryonic palate mesenchyme. We show endogenous transient changes in intracellular calcium occur in cranial neural crest cells, the cells from which embryonic palate mesenchyme derives. Waves of transient changes in intracellular calcium suggest that these cells are electrically coupled and may temporally coordinate BMP release. These transient changes in intracellular calcium persist in palate mesenchyme cells from embryonic day 9.5 to 13.5 mice. Disruption of a potassium channel called Kcnj2 significantly decreases the amplitude of calcium transients and the ability of cells to secrete BMP. Kcnj2 knockout mice have cleft palate and reduced BMP signaling. Our data suggest that temporal control of developmental cues is regulated by ion channels, depolarization, and intracellular calcium for mammalian craniofacial morphogenesis.

The bone Gla protein osteocalcin is expressed in cranial neural crest cells.

Osteocalcin is a small protein abundant in the bone extracellular-matrix, that serves as a marker for mature osteoblasts. To become activated, osteocalcin undergoes a specific post-translational carboxylation. Osteocalcin is expressed at advanced stages of embryogenesis and after birth, when bone formation takes place. Neural crest cells (NCCs) are a unique cell population that evolves during early stages of development. While initially NCCs populate the dorsal neural-tube, later they undergo epithelial-to-mesenchymal-transition and migrate throughout the embryo in highly-regulated manner. NCCs give rise to multiple cell types including neurons and glia of the peripheral nervous system, chromaffin cells and skin melanocytes. Remarkably, in the head region, NCCs give rise to cartilage and bone. Here we report that osteocalcin is detected in cranial NCCs. Analysis of chick embryos at stages of cranial NCC migration revealed that osteocalcin mRNA and protein is expressed in pre-migratory and migratory NCCs in-vivo and ex-vivo. Addition of warfarin, an inhibitor of osteocalcin carboxylation, onto neural-tube explants, reduced the amount of NCC migration. These results provide the first evidence of osteocalcin presence in cranial NCCs, much before they give rise to craniofacial skeleton, and propose its possible involvement in the regulation of NCC migration.

Alcohol induces p53-mediated apoptosis in neural crest by stimulating an AMPK-mediated suppression of TORC1, S6K, and ribosomal biogenesis

Prenatal alcohol exposure is a leading cause of permanent neurodevelopmental disability and can feature distinctive craniofacial deficits that partly originate from the apoptotic deletion of craniofacial progenitors, a stem cell lineage called the neural crest (NC). We recently demonstrated that alcohol causes nucleolar stress in NC through its suppression of ribosome biogenesis (RBG) and this suppression is causative in their p53/MDM2-mediated apoptosis. Here, we show that this nucleolar stress originates from alcohol’s activation of AMPK, which suppresses TORC1 and the p70/S6K-mediated stimulation of RBG. Alcohol-exposed cells of the pluripotent, primary cranial NC line O9-1 were evaluated with respect to their S6K, TORC1, and AMPK activity. The functional impact of these signals with respect to RBG, p53, and apoptosis were assessed using gain-of-function constructs and small molecule mediators. Alcohol rapidly (<2hr) increased pAMPK, pTSC2, and pRaptor, and reduced both total and pS6K in NC cells. These changes persisted for at least 12hr to 18hr following alcohol exposure. Attenuation of these signals via gain- or loss-of-function approaches that targeted AMPK, S6K, or TORC1 prevented alcohol’s suppression of rRNA synthesis and the induction of p53-stimulated apoptosis. We conclude that alcohol induces ribosome dysbiogenesis and activates their p53/MDM2-mediated apoptosis via its activation of pAMPK, which in turn activates TSC2 and Raptor to suppress the TORC1/S6K-mediated promotion of ribosome biogenesis. This represents a novel mechanism underlying alcohol’s neurotoxicity and is consistent with findings that TORC1/S6K networks are critical for cranial NC survival.

Pharmacological Inhibition of the Spliceosome SF3b Complex by Pladienolide-B Elicits Craniofacial Developmental Defects in Mouse and Zebrafish.

Mutations in genes encoding spliceosome components result in craniofacial structural defects in humans, referred to as spliceosomopathies. The SF3b complex is a crucial unit of the spliceosome, but model organisms generated through genetic modification of the complex do not perfectly mimic the phenotype of spliceosomopathies. Since the phenotypes are suggested to be determined by the extent of spliceosome dysfunction, an alternative experimental system that can seamlessly control SF3b function is needed. To establish another experimental system for model organisms elucidating relationship between spliceosome function and human diseases, we administered Pladienolide-B (PB), a SF3b complex inhibitor, to mouse and zebrafish embryos and assessed resulting phenotypes. PB-treated mouse embryos exhibited neural tube defect and exencephaly, accompanied by apoptosis and reduced cell proliferation in the neural tube, but normal structure in the midface and jaw. PB administration to heterozygous knockout mice of Sf3b4, a gene coding for a SF3b component, influenced the formation of cranial neural crest cells (CNCCs). Despite challenges in continuous PB administration and a high death rate in mice, PB was stably administered to zebrafish embryos, resulting in prolonged survival. Brain, cranial nerve, retina, midface, and jaw development were affected, mimicking spliceosomopathy phenotypes. Additionally, alterations in cell proliferation, cell death, and migration of CNCCs were detected. We demonstrated that zebrafish treated with PB exhibited phenotypes similar to those observed in human spliceosomopathies. This experimental system may serve as a valuable research tool for understanding spliceosome function and human diseases.

Insights into the molecular characteristics of embryonic cranial neural crest cells and their derived mesenchymal cell pools

Neural crest cells (NCCs) are central to vertebrate embryonic development, giving rise to diverse cell types with unique migratory and differentiation capacities. This study examines the molecular characteristics of cranial neural crest cell (CNCC)-derived mesenchymal cells, specifically those from teeth which in deer show continuous but limited growth, and antlers, which exhibit remarkable regenerative capabilities. Here, through single-cell RNA sequencing analysis, we uncover shared gene expression profiles between adult antlerogenic and dental mesenchymal cells, indicating common developmental pathways. We identify a striking resemblance in transcriptomic features between antlerogenic progenitor cells and dental pulp mesenchymal cells. Comparative analysis of CNCC-derived and non-CNCC-derived mesenchymal cell pools across species reveals core signature genes associated with CNCCs and their derivatives, delineating essential connections between CNCCs and CNCC-derived adult mesenchymal pools. Furthermore, whole-genome DNA methylation analysis unveils hypomethylation of CNCC derivate signature genes in regenerative antlerogenic periosteum, implying a role in maintaining multipotency. These findings offer crucial insights into the developmental biology and regenerative potential of CNCC-derived mesenchymal cells, laying a foundation for innovative therapeutic strategies in tissue regeneration.

Alcohol induces p53-mediated apoptosis in neural crest by stimulating an AMPK-mediated suppression of TORC1, S6K, and ribosomal biogenesis.

Prenatal alcohol exposure is a leading cause of permanent neurodevelopmental disability and can feature distinctive craniofacial deficits that partly originate from the apoptotic deletion of craniofacial progenitors, a stem cell lineage called the neural crest (NC). We recently demonstrated that alcohol causes nucleolar stress in NC through its suppression of ribosome biogenesis (RBG) and this suppression is causative in their p53/MDM2-mediated apoptosis. Here, we show that this nucleolar stress originates from alcohol's activation of AMPK, which suppresses TORC1 and the p70/S6K-mediated stimulation of RBG. Alcohol-exposed cells of the pluripotent, primary cranial NC line O9-1 were evaluated with respect to their S6K, TORC1, and AMPK activity. The functional impact of these signals with respect to RBG, p53, and apoptosis were assessed using gain-of-function constructs and small molecule mediators. Alcohol rapidly (<2hr) increased pAMPK, pTSC2, and pRaptor, and reduced both total and pS6K in NC cells. These changes persisted for at least 12hr to 18hr following alcohol exposure. Attenuation of these signals via gain- or loss-of-function approaches that targeted AMPK, S6K, or TORC1 prevented alcohol's suppression of rRNA synthesis and the induction of p53-stimulated apoptosis. We conclude that alcohol induces ribosome dysbiogenesis and activates their p53/MDM2-mediated apoptosis via its activation of pAMPK, which in turn activates TSC2 and Raptor to suppress the TORC1/S6K-mediated promotion of ribosome biogenesis. This represents a novel mechanism underlying alcohol's neurotoxicity and is consistent with findings that TORC1/S6K networks are critical for cranial NC survival.

TGF-β signaling in the cranial neural crest affects late-stage mandibular bone resorption and length.

Malocclusions are common craniofacial malformations that cause quality of life and health problems if left untreated. Unfortunately, the current treatment for severe skeletal malocclusion is invasive surgery. Developing improved therapeutic options requires a deeper understanding of the cellular mechanisms responsible for determining jaw bone length. We have recently shown that neural crest mesenchyme (NCM) can alter jaw length by controlling the recruitment and function of mesoderm-derived osteoclasts. Transforming growth factor beta (TGF-β) signaling is critical to craniofacial development by directing bone resorption and formation, and heterozygous mutations in the TGF-β type I receptor (TGFBR1) are associated with micrognathia in humans. To identify the role of TGF-β signaling in NCM in controlling osteoclasts during mandibular development, the mandibles of mouse embryos deficient in the gene encoding Tgfbr1, specifically in NCM, were analyzed. Our laboratory and others have demonstrated that Tgfbr1 fl/fl ;Wnt1-Cre mice display significantly shorter mandibles with no condylar, coronoid, or angular processes. We hypothesize that TGF-β signaling in NCM can also direct late bone remodeling and further regulate late embryonic jaw bone length. Interestingly, analysis of mandibular bone based on micro-computed tomography and Masson's trichrome revealed no significant difference in bone quality between the Tgfbr1 fl/fl ;Wnt1-Cre mice and controls, as measured by the bone perimeter/bone area, trabecular rod-like diameter, number and separation, and gene expression of collagen type 1 alpha 1 (Col1α1) and matrix metalloproteinase 13 (Mmp13). Although there was not a difference in localization of bone resorption within the mandible indicated by tartrate-resistant acid phosphatase (TRAP) staining, Tgfbr1 fl/fl ;Wnt1-Cre mice had approximately three-fold less osteoclast number and perimeter than controls. Gene expression of receptor activator of nuclear factor kappa-β (Rank) and Mmp9, markers of osteoclasts and their activity, also showed a three-fold decrease in Tgfbr1 fl/fl ;Wnt1-Cre mandibles. Evaluation of osteoblast-to-osteoclast signaling revealed no significant difference between Tgfbr1 fl/fl ;Wnt1-Cre mandibles and controls, leaving the specific mechanism unresolved. Finally, pharmacological inhibition of Tgfbr1 signaling during the initiation of bone mineralization and resorption significantly shortened jaw length in embryos. We conclude that TGF-β signaling in NCM decreases mesoderm-derived osteoclast number, that TGF-β signaling in NCM impacts jaw length late in development, and that this osteoblast-to-osteoclast communication may be occurring through an undescribed mechanism.

Delivery of a Jagged1-PEG-MAL hydrogel with pediatric human bone cells regenerates critically sized craniofacial bone defects

Current treatments for congenital and acquired craniofacial (CF) bone abnormalities are limited and costly. Conventional methods involve surgical correction, short-term stabilization, and long-term bone grafting, which may include problematic allografts and limited autografts. While bone morphogenetic protein 2 (BMP2) has been used for bone regeneration, it can cause bone overgrowth and life-threatening inflammation. Bone marrow-derived mesenchymal stem cell therapies, though promising, are not Food and Drug Administration approved and are resource intensive. Thus, there is a need for effective, affordable, and less side-effect-prone bone regenerative therapies. Previous research demonstrated that JAGGED1 induces osteoblast commitment in murine cranial neural crest cells through a NOTCH-dependent non-canonical pathway involving JAK2–STAT5. We hypothesize that delivery of JAGGED1 and induction of its downstream NOTCH non-canonical signaling in pediatric human osteoblasts constitutes an effective bone regenerative treatment. Delivering pediatric human bone-derived osteoblast-like cells to an in vivo murine bone loss model of a critically sized cranial defect, we identified that JAGGED1 promotes human pediatric osteoblast commitment and bone formation through p70 S6K phosphorylation. This approach highlights the potential of JAGGED1 and its downstream activators as innovative treatments for pediatric CF bone loss.

Delivery of a Jagged1-PEG-MAL hydrogel with pediatric human bone cells regenerates critically sized craniofacial bone defects.

Current treatments for congenital and acquired craniofacial (CF) bone abnormalities are limited and costly. Conventional methods involve surgical correction, short-term stabilization, and long-term bone grafting, which may include problematic allografts and limited autografts. While bone morphogenetic protein 2 (BMP2) has been used for bone regeneration, it can cause bone overgrowth and life-threatening inflammation. Bone marrow-derived mesenchymal stem cell therapies, though promising, are not Food and Drug Administration approved and are resource intensive. Thus, there is a need for effective, affordable, and less side-effect-prone bone regenerative therapies. Previous research demonstrated that JAGGED1 induces osteoblast commitment in murine cranial neural crest cells through a NOTCH-dependent non-canonical pathway involving JAK2-STAT5. We hypothesize that delivery of JAGGED1 and induction of its downstream NOTCH non-canonical signaling in pediatric human osteoblasts constitutes an effective bone regenerative treatment. Delivering pediatric human bone-derived osteoblast-like cells to an in vivo murine bone loss model of a critically sized cranial defect, we identified that JAGGED1 promotes human pediatric osteoblast commitment and bone formation through p70 S6K phosphorylation. This approach highlights the potential of JAGGED1 and its downstream activators as innovative treatments for pediatric CF bone loss.

Cleft Palate Induced by Augmented Fibroblast Growth Factor-9 Signaling in Cranial Neural Crest Cells in Mice.

Although enhanced fibroblast growth factor (FGF) signaling has been demonstrated to be crucial in many cases of syndromic cleft palate caused by tongue malposition in humans, animal models that recapitulate this phenotype are limited, and the precise mechanisms remain elusive. Mutations in FGF9 with the effect of either loss- or gain-of-function effects have been identified to be associated with cleft palate in humans. Here, we generated a mouse model with a transgenic Fgf9 allele specifically activated in cranial neural crest cells, aiming to elucidate the gain-of-function effects of Fgf9 in palatogenesis. We observed cleft palate with 100% penetrance in mutant mice. Further analysis demonstrated that no inherent defects in the morphogenic competence of palatal shelves could be found, but a passively lifted tongue prevented the elevation of palatal shelves, leading to the cleft palate. This tongue malposition was induced by posterior spatial confinement that was exerted by temporomandibular joint (TMJ) dysplasia characterized by a reduction in Sox9+ progenitors within the condyle and a structural decrease in the posterior dimension of the lower jaw. Our findings highlight the critical role of excessive FGF signaling in disrupting spatial coordination during palate development and suggest a potential association between palatal shelf elevation and early TMJ development.

Single-cell transcriptomic resolution of osteogenesis during craniofacial morphogenesis

Craniofacial morphogenesis depends on complex cell fate decisions during the differentiation of post-migratory cranial neural crest cells. Molecular mechanisms of cell differentiation of mesenchymal cells to developing bones, cartilage, teeth, tongue, and other craniofacial tissues are still poorly understood. We performed single-cell transcriptomic analysis of craniofacial mesenchymal cells derived from cranial NCCs in mouse embryo. Using FACS sorting of Wnt1-Cre2 progeny, we carefully mapped the cell heterogeneity in the craniofacial region during the initial stages of cartilage and bone formation. Transcriptomic data and in vivo validations identified molecular determinants of major cell populations involved in the development of lower and upper jaw, teeth, tongue, dermis, or periocular mesenchyme. Single-cell transcriptomic analysis of Meis2-deficient mice revealed critical gene expression differences, including increased osteogenic and cell adhesion markers. This leads to affected mesenchymal cell differentiation and increased ossification, resulting in impaired bone, cartilage, and tongue formation.

The primary cilia: Orchestrating cranial neural crest cell development

Primary cilia (hereafter “cilia”) are microtubule-based antenna-like organelles projecting from the surface of vertebrate cells. Cilia can serve as cellular antennae controlling cell growth and differentiation. Absent or dysfunctional cilia frequently lead to craniofacial anomalies known as craniofacial ciliopathies. However, the detailed pathological mechanisms of craniofacial ciliopathies remain unclear. This perspective discusses our current understanding of the role of cilia in cranial neural crest cells. We also describe potential mechanisms of ciliogenesis in cranial neural crest cells, which may contribute to unraveling the complex pathogenesis of craniofacial ciliopathies.

Conditional heterozygous loss of kit receptor tyrosine kinase in neural crest cell lineage is associated with midline cleft lip and bifid nose deformity

ObjectivesThe receptor tyrosine kinase Kit is expressed in cells derived from the trunk neural crest (NC), such as melanocytes; however, its role in cranial NC cell development is not fully understood. MethodsWe investigated the effects of the heterozygous loss of Kit in NC cells during embryonic development by mating Kit2lox/+ mice with Wnt1-Cre mice to produce Wnt1-Cre; Kit2lox/+ embryos. In addition, Wnt1-Cre mice were mated with Rosa26R-yellow fluorescent protein (YFP) mice to visualize the tissue regions expressing Cre recombinase. Histological studies of the craniofacial regions of these mice were performed using samples from embryonic day (E) 12.5 and postnatal day (P) 1. Cellular apoptosis and proliferation were both analyzed through the immunostaining of tissue sections collected on E13.5 and E14.5 using anti-cleaved caspase 3 (CC3) to detect apoptosis and anti-Ki67 to detect proliferation. Cells from YFP-positive tissue regions of the facial areas of Wnt1-Cre; Kit+/+; Rosa26R–YFP embryos and Wnt1-Cre; Kit2lox/+; Rosa26R–YFP embryos collected on E12.5 and E15.5 were cultured and evaluated for cell proliferation. ResultsCompared with control littermates, Wnt1-Cre; Kit2lox/+ embryos exhibited midline cleft lip and bifid nose deformities. Substantial early (P1) postnatal lethality was observed in Wnt1-Cre; Kit2lox/+ mice, with none surviving to 3 weeks of age. YFP-positive cells from the maxillary regions of Wnt1-Cre; Kit2lox/+; Rosa26R–YFP embryos exhibited defective cell growth and self-renewal in vitro. ConclusionConditional heterozygous loss of Kit in Wnt1-Cre; Kit2lox/+ embryos is associated with craniofacial dysplasia and exhibit defective NC development in vitro and in vivo.

Alternative Balance between Transcriptional and Epigenetic Regulation during Developmental Proliferation of Human Cranial Neural Crest Cells.

Cranial neural crest cells are implicated in multiple transcriptional events at the different stages of differentiation during development. The alteration of some transcription factors expressed during neural crest development, like PAX7, could be implicated in the etiology of face malformation in murine models. Epigenetic regulation has been shown to be an important mechanistic actor in the control of timing and the level of gene expression at different stages of neural crest development. During this work, we investigated the interconnection between epigenetics and transcription factors across a diversity of human development cranial neural crest cells. Across a diversity of neural cells from human developing cranial tissues, in accordance with their proliferation stage, an alternative balance of regulation between transcription factors and epigenetic factors was identified.

PDGFRα signaling regulates Srsf3 transcript binding to affect PI3K signaling and endosomal trafficking.

Signaling through the platelet-derived growth factor receptor alpha (PDGFRα) plays a critical role in craniofacial development, as mutations in PDGFRA are associated with cleft lip/palate in humans and Pdgfra mutant mouse models display varying degrees of facial clefting. Phosphatidylinositol 3-kinase (PI3K)/Akt is the primary effector of PDGFRα signaling during skeletal development in the mouse. We previously demonstrated that Akt phosphorylates the RNA-binding protein serine/arginine-rich splicing factor 3 (Srsf3) downstream of PI3K-mediated PDGFRα signaling in mouse embryonic palatal mesenchyme (MEPM) cells, leading to its nuclear translocation. We further showed that ablation of Srsf3 in the murine neural crest lineage results in severe midline facial clefting, due to defects in proliferation and survival of cranial neural crest cells, and widespread alternative RNA splicing (AS) changes. Here, we sought to determine the molecular mechanisms by which Srsf3 activity is regulated downstream of PDGFRα signaling to control AS of transcripts necessary for craniofacial development. We demonstrated via enhanced UV-crosslinking and immunoprecipitation (eCLIP) of MEPM cells that PDGF-AA stimulation leads to preferential binding of Srsf3 to exons and loss of binding to canonical Srsf3 CA-rich motifs. Through the analysis of complementary RNA-seq data, we showed that Srsf3 activity results in the preferential inclusion of exons with increased GC content and lower intron to exon length ratio. Moreover, we found that the subset of transcripts that are bound by Srsf3 and undergo AS upon PDGFRα signaling commonly encode regulators of PI3K signaling and early endosomal trafficking. Functional validation studies further confirmed that Srsf3 activity downstream of PDGFRα signaling leads to retention of the receptor in early endosomes and increases in downstream PI3K-mediated Akt signaling. Taken together, our findings reveal that growth factor-mediated phosphorylation of an RNA-binding protein underlies gene expression regulation necessary for mammalian craniofacial development.

Emerging biological functions of Twist1 in cell differentiation.

Twist1 is required for embryonic development and expresses after birth in mesenchymal stem cells derived from mesoderm, where it governs mesenchymal cell development. As a well-known regulator of epithelial-mesenchymal transition or embryonic organogenesis, Twist1 is important in a variety of developmental systems, including mesoderm formation, neurogenesis, myogenesis, cranial neural crest cell migration, and differentiation. In this review, we first highlight the physiological significance of Twist1 in cell differentiation, including osteogenic, chondrogenic, and myogenic differentiation, and then detail its probable molecular processes and signaling pathways. On this premise, we summarize the significance of Twist1 in distinct developmental disorders and diseases to provide a reference for studies on cell differentiation/development-related diseases.

Keratin 8/18a.1 Expression Influences Embryonic Neural Crest Cell Dynamics and Contributes to Postnatal Corneal Regeneration in Zebrafish.

A complete understanding of neural crest cell mechanodynamics during ocular development will provide insight into postnatal neural crest cell contributions to ophthalmic abnormalities in adult tissues and inform regenerative strategies toward injury repair. Herein, single-cell RNA sequencing in zebrafish during early eye development revealed keratin intermediate filament genes krt8 and krt18a.1 as additional factors expressed during anterior segment development. In situ hybridization and immunofluorescence microscopy confirmed krt8 and krt18a.1 expression in the early neural plate border and migrating cranial neural crest cells. Morpholino oligonucleotide (MO)-mediated knockdown of K8 and K18a.1 markedly disrupted the migration of neural crest cell subpopulations and decreased neural crest cell marker gene expression in the craniofacial region and eye at 48 h postfertilization (hpf), resulting in severe phenotypic defects reminiscent of neurocristopathies. Interestingly, the expression of K18a.1, but not K8, is regulated by retinoic acid (RA) during early-stage development. Further, both keratin proteins were detected during postnatal corneal regeneration in adult zebrafish. Altogether, we demonstrated that both K8 and K18a.1 contribute to the early development and postnatal repair of neural crest cell-derived ocular tissues.

ARID1A-BAF coordinates ZIC2 genomic occupancy for epithelial-to-mesenchymal transition in cranial neural crest specification

The BAF chromatin remodeler regulates lineage commitment including cranial neural crest cell (CNCC) specification. Variants in BAF subunits cause Coffin-Siris syndrome (CSS), a congenital disorder characterized by coarse craniofacial features and intellectual disability. Approximately 50% of individuals with CSS harbor variants in one of the mutually exclusive BAF subunits, ARID1A/ARID1B. While Arid1a deletion in mouse neural crest causes severe craniofacial phenotypes, little is known about the role of ARID1A in CNCC specification. Using CSS-patient-derived ARID1A+/- induced pluripotent stem cells to model CNCC specification, we discovered that ARID1A-haploinsufficiency impairs epithelial-to-mesenchymal transition (EMT), a process necessary for CNCC delamination and migration from the neural tube. Furthermore, wild-type ARID1A-BAF regulates enhancers associated with EMT genes. ARID1A-BAF binding at these enhancers is impaired in heterozygotes while binding at promoters is unaffected. At the sequence level, these EMT enhancers contain binding motifs for ZIC2, and ZIC2 binding at these sites is ARID1A-dependent. When excluded from EMT enhancers, ZIC2 relocates to neuronal enhancers, triggering aberrant neuronal gene activation. In mice, deletion of Zic2 impairs NCC delamination, while ZIC2 overexpression in chick embryos at post-migratory neural crest stages elicits ectopic delamination from the neural tube. These findings reveal an essential ARID1A-ZIC2 axis essential for EMT and CNCC delamination.

ADAM interact with large protein complexes to regulate Histone modification, gene expression and splicing.

Cranial neural crest (CNC) cells are key stem cells that contribute to most of the facial structures in all vertebrates. Previous work has shown that multiple ADAM (A Disintegrin And Metalloprotease) cell surface metalloproteases are essential for the induction and migration of the CNC in multiple vertebrate animal models. In Xenopus, we have shown that Adam13 associates with the transcription factor Arid3a to regulate gene expression. Here we show that Adam13 regulates gene expression by modulating Histone modifications globally in the CNC. Furthermore, we show that Arid3a binding to the tfap2a; promoter depends on the presence of Adam13. This association promotes the expression of one tfap2a; variant predominantly expressed in the CNC that uniquely activates the expression of calpain-8, a gene critical for CNC migration. This tfap2a; variant selectively associates with proteins involved with mRNA splicing, a function that is critically affected by the loss of Adam13 in the CNC. Our results suggest that ADAM metalloproteases may act as sensors of the environment that can modulate chromatin availability, leading to changes in gene expression and splicing.

Hemifacial microsomia – a review of the literature of current hypotheses of pathogenesis, and possible therapeutic methods

&lt;b&gt;Introduction:&lt;/b&gt; Hemifacial microsomia (HFM) is the second most common congenital craniofacial anomaly.&lt;b&gt;Aim:&lt;/b&gt; The aim of this study is to review data related to HFM.&lt;b&gt;Materials and methods:&lt;/b&gt; Materials for the review were selected based on an analysis of publications published in the last 10 years.&lt;b&gt;Results:&lt;/b&gt; There are three possible models of pathogenesis – vascular abnormalities, Meckel’s cartilage damage, and abnormal development of cranial neural crest cells – caused by genetic, maternal, and external factors. Symptoms results from disorders of structures originating from the first, and second branchial arches, most commonly resulting in mandibular hypoplasia, microtia or anotia, hypoplasia of the auditory ossicles, facial nerve paralysis, and soft tissue deficiency. The severity of the disorder varies greatly, depending on the number of structures involved, and the degree of penetration. The most common classification system (Orbit, Mandible, Ear, Nerve, Soft tissue; OMENS) has recently been proposed to assess the temporomandibular joint disc, and to assess disturbances originating from another structures. Other classifications such as FACIAL or ICHOM criteria have also been developed. The approach to treating each case should be individualized, primarily focusing on reconstructing the underdeveloped mandible, orthodontic treatment, creating the external ear, and filling soft tissue deficiencies.&lt;b&gt;Discussion:&lt;/b&gt; The complexity of the condition is noted, as well as the need for interdisciplinary patient care.&lt;b&gt;Conclusions:&lt;/b&gt; Through analysis of existing research, and clinical data, significant information regarding etiology, symptoms, possible classification systems, and therapeutic options has been gathered.