Sonic hedgehog regulation of Foxf2 promotes cranial neural crest mesenchyme proliferation and is disrupted in cleft lip morphogenesis

Foxk1 promotes bone formation through inducing aerobic glycolysis

Transcription factor Foxk1 can regulate cell proliferation, differentiation, metabolism, and promote skeletal muscle regeneration and cardiogenesis. However, the roles of Foxk1 in bone formation is unknown. Here, we found that Foxk1 expression decreased in the bone tissue of aged mice and osteoporosis patients. Knockdown of Foxk1 in primary murine calvarial osteoblasts suppressed osteoblast differentiation and proliferation. Conditional knockout of Foxk1 in preosteoblasts and mature osteoblasts in mice exhibited decreased bone mass and mechanical strength due to reduced bone formation. Mechanistically, we identified Foxk1 targeted the promoter region of many genes of glycolytic enzyme by CUT&Tag analysis. Lacking of Foxk1 in primary murine calvarial osteoblasts resulted in reducing aerobic glycolysis. Inhibition of glycolysis by 2DG hindered osteoblast differentiation and proliferation induced by Foxk1 overexpression. Finally, specific overexpression of Foxk1 in preosteoblasts, driven by a preosteoblast specific osterix promoter, increased bone mass and bone mechanical strength of aged mice, which could be suppressed by inhibiting glycolysis. In summary, these findings reveal that Foxk1 plays a vital role in the osteoblast metabolism regulation and bone formation stimulation, offering a promising approach for preventing age-related bone loss.

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.

The presence and distribution of various genes in postnatal CLP-affected palatine tissue

BACKGROUND

Worldwide cleft lip with or without a cleft palate (CL/P) is the most common craniofacial birth defect. Apart from changes in facial appearance, additionally affected individuals often suffer from various associated comorbidities requiring complex multidisciplinary treatment with overall high expenses. Understanding the complete pathogenetic mechanisms of CL/P might aid in developing new preventative strategies and therapeutic approaches, help with genetic counselling, and improve quality of life. Many genes have been associated with the development of orofacial clefts; however, the majority require further research. Based on the role of PAX7, PAX9, SHH, SOX3, WNT3A, and WNT9B in orofacial development, the intention was to use chromogenic in situ hybridization to detect the six genes in postnatal CLP-affected palatine tissue and compare their distribution within the tissue samples.

RESULTS

Statistically significant differences in the distribution of PAX7, PAX9, WNT3A, and WNT9B were observed. In total, 19 pairs of moderate to very strong positive correlations were noted.

CONCLUSIONS

Changes in the cleft-affected palatine epithelium primarily seem to be associated with the PAX7 gene; however, PAX9, WNT3A, WNT9B, and SOX3 role seems to be more limited. Whilst connective tissue changes seem to depend on PAX7 only, SHH seems to participate individually and indistinctly. Numerous positive correlations reflect the complicating interactions of the pathways and their components in the orofacial cleft morphopathogenesis.

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.

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

Orofacial clefts (OFCs) are the most common craniofacial birth defects and are often categorized into two etiologically distinct groups: cleft lip with or without cleft palate (CL/P) and isolated cleft palate (CP). CP is highly heritable, but there are still relatively few established genetic risk factors associated with its occurrence compared to CL/P. Historically, CP has been studied as a single phenotype despite manifesting across a spectrum of defects involving the hard and/or soft palate. We performed GWAS using transmission disequilibrium tests using 435 case-parent trios to evaluate broad risks for any cleft palate (ACP, n=435), as well as 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 in craniofacial tissue of human embryos, as well as in the 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 (ORs) for each of the 20 loci were most similar across all three groups for SNPs associated with the ACP group, but more distinct when comparing SNPs associated with either the CSP or CHP groups. We also found nominal evidence of replication (p<0.05) for 22 SNPs previously associated with cleft palate (including CL/P). Interestingly, most SNPs associated with CL/P cases were found to convey the opposite effect in those replicated in our dataset for CP only. Ours is the first 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.

Frem1 activity is regulated by Sonic hedgehog signaling in the cranial neural crest mesenchyme during midfacial morphogenesis

BACKGROUND

Frem1 has been linked to human face shape variation, dysmorphology, and malformation, but little is known about its regulation and biological role in facial development.

RESULTS

During midfacial morphogenesis in mice, we observed Frem1 expression in the embryonic growth centers that form the median upper lip, nose, and palate. Expansive spatial gradients of Frem1 expression in the cranial neural crest cell (cNCC) mesenchyme of these tissues suggested transcriptional regulation by a secreted morphogen. Accordingly, Frem1 expression paralleled that of the conserved Sonic Hedgehog (Shh) target gene Gli1 in the cNCC mesenchyme. Suggesting direct transcriptional regulation by Shh signaling, we found that Frem1 expression is induced by SHH ligand stimulation or downstream pathway activation in cNCCs and observed GLI transcription factor binding at the Frem1 transcriptional start site during midfacial morphogenesis. Finally, we found that FREM1 is sufficient to induce cNCC proliferation in a concentration-dependent manner and that Shh pathway antagonism reduces Frem1 expression during pathogenesis of midfacial hypoplasia.

CONCLUSIONS

By demonstrating that the Shh signaling pathway regulates Frem1 expression in cNCCs, these findings provide novel insight into the mechanisms underlying variation in midfacial morphogenesis.

High-throughput detection of craniofacial defects in fluorescent zebrafish

Losses and malformations of cranial neural crest cell (cNCC) derivatives are a hallmark of several common brain and face malformations. Nevertheless, the etiology of these cNCC defects remains unknown for many cases, suggesting a complex basis involving interactions between genetic and/or environmental factors. However, the sheer number of possible factors (thousands of genes and hundreds of thousands of toxicants) has hindered identification of specific interactions. Here, we develop a high-throughput analysis that will enable faster identification of multifactorial interactions in the genesis of craniofacial defects. Zebrafish embryos expressing a fluorescent marker of cNCCs (fli1:EGFP) were exposed to a pathway inhibitor standard or environmental toxicant, and resulting changes in fluorescence were measured in high-throughput using a fluorescent microplate reader to approximate cNCC losses. Embryos exposed to the environmental Hedgehog pathway inhibitor piperonyl butoxide (PBO), a Hedgehog pathway inhibitor standard, or alcohol (ethanol) exhibited reduced fli1:EGFP fluorescence at one day post fertilization, which corresponded with craniofacial defects at five days post fertilization. Combining PBO and alcohol in a co-exposure paradigm synergistically reduced fluorescence, demonstrating a multifactorial interaction. Using pathway reporter transgenics, we show that the plate reader assay is sensitive at detecting alterations in Hedgehog signaling, a critical regulator of craniofacial development. We go on to demonstrate that this technique readily detects defects in other important cell types, namely neurons. Together, these findings demonstrate this novel in vivo platform can predict developmental abnormalities and multifactorial interactions in high-throughput.

Revisiting the embryogenesis of lip and palate development

Clefts of the lip and palate (CLP), the major causes of congenital facial malformation globally, result from failure of fusion of the facial processes during embryogenesis. With a prevalence of 1 in 500-2500 live births, CLP causes major morbidity throughout life as a result of problems with facial appearance, feeding, speaking, obstructive apnoea, hearing and social adjustment and requires complex, multi-disciplinary care at considerable cost to healthcare systems worldwide. Long-term outcomes for affected individuals include increased mortality compared with their unaffected siblings. The frequent occurrence and major healthcare burden imposed by CLP highlight the importance of dissecting the molecular mechanisms driving facial development. Identification of the genetic mutations underlying syndromic forms of CLP, where CLP occurs in association with non-cleft clinical features, allied to developmental studies using appropriate animal models is central to our understanding of the molecular events underlying development of the lip and palate and, ultimately, how these are disturbed in CLP.

A Neural Crest-specific Overexpression Mouse Model Reveals the Transcriptional Regulatory Effects of Dlx2 During Maxillary Process Development

Craniofacial morphogenesis is a complex process that requires precise regulation of cell proliferation, migration, and differentiation. Perturbations of this process cause a series of craniofacial deformities. Dlx2 is a critical transcription factor that regulates the development of the first branchial arch. However, the transcriptional regulatory functions of Dlx2 during craniofacial development have been poorly understood due to the lack of animal models in which the Dlx2 level can be precisely modulated. In this study, we constructed a Rosa26 site-directed Dlx2 gene knock-in mouse model Rosa26 ^{CAG-LSL-Dlx2-3xFlag} for conditionally overexpressing Dlx2. By breeding with wnt1 ^cre mice, we obtained wnt1 ^cre ; Rosa26 ^Dlx2/- mice, in which Dlx2 is overexpressed in neural crest lineage at approximately three times the endogenous level. The wnt1 ^cre ; Rosa26 ^Dlx2/- mice exhibited consistent phenotypes that include cleft palate across generations and individual animals. Using this model, we demonstrated that Dlx2 caused cleft palate by affecting maxillary growth and uplift in the early-stage development of maxillary prominences. By performing bulk RNA-sequencing, we demonstrated that Dlx2 overexpression induced significant changes in many genes associated with critical developmental pathways. In summary, our novel mouse model provides a reliable and consistent system for investigating Dlx2 functions during development and for elucidating the gene regulatory networks underlying craniofacial development.

16p12.1 Deletion Orthologs are Expressed in Motile Neural Crest Cells and are Important for Regulating Craniofacial Development in Xenopus laevis

Copy number variants (CNVs) associated with neurodevelopmental disorders are characterized by extensive phenotypic heterogeneity. In particular, one CNV was identified in a subset of children clinically diagnosed with intellectual disabilities (ID) that results in a hemizygous deletion of multiple genes at chromosome 16p12.1. In addition to ID, individuals with this deletion display a variety of symptoms including microcephaly, seizures, cardiac defects, and growth retardation. Moreover, patients also manifest severe craniofacial abnormalities, such as micrognathia, cartilage malformation of the ears and nose, and facial asymmetries; however, the function of the genes within the 16p12.1 region have not been studied in the context of vertebrate craniofacial development. The craniofacial tissues affected in patients with this deletion all derive from the same embryonic precursor, the cranial neural crest, leading to the hypothesis that one or more of the 16p12.1 genes may be involved in regulating neural crest cell (NCC)-related processes. To examine this, we characterized the developmental role of the 16p12.1-affected gene orthologs, polr3e, mosmo, uqcrc2, and cdr2, during craniofacial morphogenesis in the vertebrate model system, Xenopus laevis. While the currently-known cellular functions of these genes are diverse, we find that they share similar expression patterns along the neural tube, pharyngeal arches, and later craniofacial structures. As these genes show co-expression in the pharyngeal arches where NCCs reside, we sought to elucidate the effect of individual gene depletion on craniofacial development and NCC migration. We find that reduction of several 16p12.1 genes significantly disrupts craniofacial and cartilage formation, pharyngeal arch migration, as well as NCC specification and motility. Thus, we have determined that some of these genes play an essential role during vertebrate craniofacial patterning by regulating specific processes during NCC development, which may be an underlying mechanism contributing to the craniofacial defects associated with the 16p12.1 deletion.

Orofacial Cleft and Mandibular Prognathism-Human Genetics and Animal Models

Many complex molecular interactions are involved in the process of craniofacial development. Consequently, the network is sensitive to genetic mutations that may result in congenital malformations of varying severity. The most common birth anomalies within the head and neck are orofacial clefts (OFCs) and prognathism. Orofacial clefts are disorders with a range of phenotypes such as the cleft of the lip with or without cleft palate and isolated form of cleft palate with unilateral and bilateral variations. They may occur as an isolated abnormality (nonsyndromic-NSCLP) or coexist with syndromic disorders. Another cause of malformations, prognathism or skeletal class III malocclusion, is characterized by the disproportionate overgrowth of the mandible with or without the hypoplasia of maxilla. Both syndromes may be caused by the presence of environmental factors, but the majority of them are hereditary. Several mutations are linked to those phenotypes. In this review, we summarize the current knowledge regarding the genetics of those phenotypes and describe genotype-phenotype correlations. We then present the animal models used to study these defects.

The Pleiotropic Intricacies of Hedgehog Signaling: From Craniofacial Patterning to Carcinogenesis

Hedgehog signaling was discovered more than 40 years ago in experiments demonstrating that it is a fundamental mediator of limb development. Since that time, it has been shown to be important in development, homeostasis, and disease. The hedgehog pathway proceeds through a pathway highly conserved throughout animals beginning with the extracellular diffusion of hedgehog ligands, proceeding through an intracellular signaling cascade, and ending with the activation of specific target genes. A vast amount of research has been done elucidating hedgehog signaling mechanisms and regulation. This research has found a complex system of genetics and signaling that helps determine how organisms develop and function. This review provides an overview of what is known about hedgehog genetics and signaling, followed by an in-depth discussion of the role of hedgehog signaling in craniofacial development and carcinogenesis.

FAT4 identified as a potential modifier of orofacial cleft laterality

Orofacial clefts (OFCs) are common (1 in 700 births) congenital malformations that include a cleft lip (CL) and cleft lip and palate (CLP). These OFC subtypes are also heterogeneous themselves, with the CL occurring on the left, right, or both sides of the upper lip. Unilateral CL and CLP have a 2:1 bias towards left-sided clefts, suggesting a nonrandom process. Here, we performed a study of left- and right-sided clefts within the CL and CLP subtypes to better understand the genetic factors controlling cleft laterality. We conducted genome-wide modifier analyses by comparing cases that had right unilateral CL (RCL; N = 130), left unilateral CL (LCL; N = 216), right unilateral CLP (RCLP; N = 416), or left unilateral CLP (LCLP; N = 638), and identified a candidate region on 4q28, 400 kb downstream from FAT4, that approached genome-wide significance for LCL versus RCL (p = 8.4 × 10^-8 ). Consistent with its potential involvement as a genetic modifier of CL, we found that Fat4 exhibits a specific domain of expression in the mesenchyme of the medial nasal processes that form the median upper lip. Overall, these results suggest that the epidemiological similarities in left- to right-sided clefts in CL and CLP are not reflected in the genetic association results.

Symmetry and fluctuation of cell movements in neural crest-derived facial mesenchyme

In the face, symmetry is established when bilateral streams of neural crest cells leave the neural tube at the same time, follow identical migration routes and then give rise to the facial prominences. However, developmental instability exists, particularly surrounding the steps of lip fusion. The causes of instability are unknown but inability to cope with developmental fluctuations are a likely cause of congenital malformations, such as non-syndromic orofacial clefts. Here, we tracked cell movements over time in the frontonasal mass, which forms the facial midline and participates in lip fusion, using live-cell imaging of chick embryos. Our mathematical examination of cell velocity vectors uncovered temporal fluctuations in several parameters, including order/disorder, symmetry/asymmetry and divergence/convergence. We found that treatment with a Rho GTPase inhibitor completely disrupted the temporal fluctuations in all measures and blocked morphogenesis. Thus, we discovered that genetic control of symmetry extends to mesenchymal cell movements and that these movements are of the type that could be perturbed in asymmetrical malformations, such as non-syndromic cleft lip.

This article has an associated ‘The people behind the papers’ interview.

Highlighted Article: Live imaging of the chick embryo face followed by mathematical analysis of mesenchymal cell tracks captures novel fluctuations between states of order/disorder as well as symmetry/asymmetry, revealing developmental instabilities that are part of normal morphogenesis.

Cleft Candidate Genes and Their Products in Human Unilateral Cleft Lip Tissue

Cleft lip and palate are common congenital pathologies that affect the human population worldwide. The formation of cleft lip is associated with multiple genes and their coded proteins, which regulate the development of craniofacial region, but the exact role of these factors is not always clear. The use of morphological studies for evaluation of human cleft-affected tissue has been limited because of insufficiency of available pathological material. The aim of this study was to detect and compare the immunohistochemical expression of cleft candidate gene coded proteins (DLX4, MSX2, HOXB3, SHH, PAX7, SOX3, WNT3A, and FOXE1) in the non-syndromic unilateral cleft lip patient tissue and control group tissue. A semiquantitative counting method was used to evaluate the tissue in biotin-streptavidin-stained slides. Statistically significant differences between the patient and control groups were found for the number of immunoreactive structures for SHH (p = 0.019) and FOXE1 (p = 0.011) in the connective tissue and SOX3 (p = 0.012) in the epithelium. Multiple statistically significant very strong and strong correlations were found between the immunoreactives in cleft-affected tissue. These significant differences and various correlations indicate that multiple morphopathogenetic pathways are possibly involved in unilateral cleft lip pathogenesis. Therefore, we further discuss these possible interactions.

The regulatory roles and mechanisms of the transcription factor FOXF2 in human diseases

Many studies have focused on the relationship between transcription factors and a variety of common pathological conditions, such as diabetes, stroke, and cancer. It has been found that abnormal transcription factor regulation can lead to aberrant expression of downstream genes, which contributes to the occurrence and development of many diseases. The forkhead box (FOX) transcription factor family is encoded by the FOX gene, which mediates gene transcription and follow-up functions during physiological and pathological processes. FOXF2, a member of the FOX transcription family, is expressed in various organs and tissues while maintaining their normal structural and functional development during the embryonic and adult stages. Multiple regulatory pathways that regulate FOXF2 may also be controlled by FOXF2. Abnormal FOXF2 expression induced by uncontrollable regulatory signals mediate the progression of human diseases by interfering with the cell cycle, proliferation, differentiation, invasion, and metastasis. FOXF2 manipulates downstream pathways and targets as both a pro-oncogenic and anti-oncogenic factor across different types of cancer, suggesting it may be a new potential clinical marker or therapeutic target for cancer. However, FOXF2’s biological functions and specific roles in cancer development remain unclear. In this study, we provide an overview of FOXF2’s structure, function, and regulatory mechanisms in the physiological and pathological conditions of human body. We also discussed the possible reasons why FOXF2 performs the opposite function in the same types of cancer.

A Microphysiological Approach to Evaluate Effectors of Intercellular Hedgehog Signaling in Development

Paracrine signaling in the tissue microenvironment is a central mediator of morphogenesis, and modeling this dynamic intercellular activity in vitro is critical to understanding normal and abnormal development. For example, Sonic Hedgehog (Shh) signaling is a conserved mechanism involved in multiple developmental processes and strongly linked to human birth defects including orofacial clefts of the lip and palate. SHH ligand produced, processed, and secreted from the epithelial ectoderm is shuttled through the extracellular matrix where it binds mesenchymal receptors, establishing a gradient of transcriptional response that drives orofacial morphogenesis. In humans, complex interactions of genetic predispositions and environmental insults acting on diverse molecular targets are thought to underlie orofacial cleft etiology. Consequently, there is a need for tractable in vitro approaches that model this complex cellular and environmental interplay and are sensitive to disruption across the multistep signaling cascade. We developed a microplate-based device that supports an epithelium directly overlaid onto an extracellular matrix-embedded mesenchyme, mimicking the basic tissue architecture of developing orofacial tissues. SHH ligand produced from the epithelium generated a gradient of SHH-driven transcription in the adjacent mesenchyme, recapitulating the gradient of pathway activity observed in vivo. Shh pathway activation was antagonized by small molecule inhibitors of epithelial secretory, extracellular matrix transport, and mesenchymal sensing targets, supporting the use of this approach in high-content chemical screening of the complete Shh pathway. Together, these findings demonstrate a novel and practical microphysiological model with broad utility for investigating epithelial-mesenchymal interactions and environmental signaling disruptions in development.

The Special Developmental Biology of Craniofacial Tissues Enables the Understanding of Oral and Maxillofacial Physiology and Diseases

Maxillofacial hard tissues have several differences compared to bones of other localizations of the human body. These could be due to the different embryological development of the jaw bones compared to the extracranial skeleton. In particular, the immigration of neuroectodermally differentiated cells of the cranial neural crest (CNC) plays an important role. These cells differ from the mesenchymal structures of the extracranial skeleton. In the ontogenesis of the jaw bones, the development via the intermediate stage of the pharyngeal arches is another special developmental feature. The aim of this review was to illustrate how the development of maxillofacial hard tissues occurs via the cranial neural crest and pharyngeal arches, and what significance this could have for relevant pathologies in maxillofacial surgery, dentistry and orthodontic therapy. The pathogenesis of various growth anomalies and certain syndromes will also be discussed.

Differentiation of Brain Pericyte-Like Cells from Human Pluripotent Stem Cell-Derived Neural Crest

Brain pericytes regulate diverse aspects of neurovascular development and function, including blood-brain barrier (BBB) induction and maintenance. Primary brain pericytes have been widely employed in coculture-based in vitro models of the BBB, and a method to generate brain pericytes from human pluripotent stem cells (hPSCs) could provide a renewable, genetically tractable source of cells for BBB modeling and studying pericyte roles in development and disease. Here, we describe a protocol to differentiate hPSCs to NG2+ PDGFRβ+ αSMAlow brain pericyte-like cells in 22-25 days through a p75-NGFR+ HNK-1+ neural crest intermediate, which mimics the developmental origin of forebrain pericytes. The resulting brain pericyte-like cells have molecular and functional attributes of brain pericytes. We also provide protocols for maintenance, cryopreservation, and recovery of the neural crest intermediate, and for molecular and functional characterization of the resulting cells. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Differentiation of hPSCs to neural crest Basic Protocol 2: Differentiation of neural crest to brain pericyte-like cells Support Protocol 1: Flow cytometry analysis of neural crest cells Support Protocol 2: Maintenance, cryopreservation, and recovery of neural crest cells Support Protocol 3: Molecular characterization of brain pericyte-like cells Support Protocol 4: Cord formation assay with endothelial cells and brain pericyte-like cells.

si-SNHG5-FOXF2 inhibits TGF-β1-induced fibrosis in human primary endometrial stromal cells by the Wnt/β-catenin signalling pathway

Background

Intrauterine adhesions (IUAs) are manifestations of endometrial fibrosis characterized by inflammation and fibrinogen aggregation in the extracellular matrix (ECM). The available therapeutic interventions for IUA are insufficiently effective in the clinical setting for postoperative adhesion recurrence and infertility problems. In this study, we investigated whether si-SNHG5-FOXF2 can serve as a molecular mechanism for the inhibition of IUA fibrosis ex vivo.

Methods

FOXF2, TGF-β1 and collagen expression levels were measured by microarray sequencing analysis in three normal endometrium groups and six IUA patients. We induced primary human endometrial stromal cells (HESCs) into myofibroblasts (MFs) to develop an IUA cell model with various concentrations of TGF-β1 at various times. Downstream target genes of FOXF2 were screened by chromatin immunoprecipitation combined with whole-genome high-throughput sequencing (ChIP-seq). We investigated ECM formation, cell proliferation and Wnt/β-catenin signalling pathway-related proteins in primary HESCs with FOXF2 downregulation by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting (WB), immunohistochemistry (IHC), flow cytometry, ethylenediurea (EdU) and CCK8 assays. We identified long noncoding RNAs (lncRNA) SNHG5 as the upstream regulatory gene of FOXF2 through RNA immunoprecipitation (RIP), RNA pulldown and fluorescence in situ hybridization (FISH). Finally, we examined FOXF2 expression, ECM formation, cell proliferation and Wnt/β-catenin signalling pathway-related proteins in primary HESCs upon FOXF2 downregulation.

Results

FOXF2 was highly expressed in the endometrium of patients with IUA. Treatment of primary HESCs with 10 ng/ml TGF-β1 for 72 h was found to be most effective for developing an IUA cell model. FOXF2 regulated multiple downstream target genes, including collagen, vimentin (VIM) and cyclin D2/DK4, by ChIP-seq and ChIP-PCR. FOXF2 downregulation inhibited TGF-β1-mediated primary HESC fibrosis, including ECM formation, cell proliferation and Wnt/β-catenin signalling pathway-related protein expression. We identified lncRNA SNHG5 as an upstream gene that directly regulates FOXF2 by RIP-seq, qRT-PCR, WB and FISH. SNHG5 downregulation suppressed FOXF2 expression in the IUA cell model, resulting in synergistic repression of the Wnt/β-catenin pathway, thereby altering TGF-β1-mediated ECM aggregation in endometrial stromal cells ex vivo.

Conclusions

Regulation of the Wnt/β-catenin signalling pathway and ECM formation by si-SNHG5-FOXF2 effectively inhibited the profibrotic effect of TGF-β1 on primary HESCs. This finding can provide a molecular basis for antagonizing TGF-β1-mediated fibrosis in primary HESCs.

Genetics and signaling mechanisms of orofacial clefts

Craniofacial development involves several complex tissue movements including several fusion processes to form the frontonasal and maxillary structures, including the upper lip and palate. Each of these movements are controlled by many different factors that are tightly regulated by several integral morphogenetic signaling pathways. Subject to both genetic and environmental influences, interruption at nearly any stage can disrupt lip, nasal, or palate fusion and result in a cleft. Here, we discuss many of the genetic risk factors that may contribute to the presentation of orofacial clefts in patients, and several of the key signaling pathways and underlying cellular mechanisms that control lip and palate formation, as identified primarily through investigating equivalent processes in animal models, are examined.

Sonic Hedgehog Signaling in Cranial Neural Crest Cells Regulates Microvascular Morphogenesis in Facial Development

Sonic hedgehog (Shh) pathway disruption causes craniofacial malformations including orofacial clefts (OFCs) of the lip and palate. In normal craniofacial morphogenesis, Shh signals to multipotent cranial neural crest cells (cNCCs) and was recently discovered to regulate the angiogenic transcriptome, including expression markers of perivascular cells and pericytes. The mural cells of microvasculature, pericytes in the brain and face differentiate from cNCCs, but their role in facial development is not known. Here, we examined microvascular morphogenesis in a mouse model of Shh pathway antagonist-induced cleft lip and the impact of cNCC-specific Shh pathway activation in a cNCC-endothelial cell co-culture system. During cleft pathogenesis in vivo, disrupted microvascular morphogenesis localized with attenuated tissue outgrowth in the medial nasal processes that form the upper lip. In vitro, we found that human umbilical vein endothelial cell (HUVEC) cord formation was not affected by direct Shh pathway perturbation. However, in a co-culture system in which cNCCs directly interact with endothelial cells, cNCC-autonomous Shh pathway activity significantly prolonged endothelial cord network stability. Taken together, these findings support the premise that Shh pathway activation in cNCCs promotes pericyte-like function and microvascular stability. In addition to suggesting a previously unrecognized role for Shh signaling in facial development, these studies also identify perivascular differentiation and microvascular morphogenesis as new focuses for understanding normal and abnormal craniofacial development.

Multifactorial Genetic and Environmental Hedgehog Pathway Disruption Sensitizes Embryos to Alcohol-Induced Craniofacial Defects

BACKGROUND

Prenatal alcohol exposure (PAE) is perhaps the most common environmental cause of human birth defects. These exposures cause a range of structural and neurological defects, including facial dysmorphologies, collectively known as fetal alcohol spectrum disorders (FASD). While PAE causes FASD, phenotypic outcomes vary widely. It is thought that multifactorial genetic and environmental interactions modify the effects of PAE. However, little is known of the nature of these modifiers. Disruption of the Hedgehog (Hh) signaling pathway has been suggested as a modifier of ethanol teratogenicity. In addition to regulating the morphogenesis of craniofacial tissues commonly disrupted in FASD, a core member of the Hh pathway, Smoothened, is susceptible to modulation by structurally diverse chemicals. These include environmentally prevalent teratogens like piperonyl butoxide (PBO), a synergist found in thousands of pesticide formulations.

METHODS

Here, we characterize multifactorial genetic and environmental interactions using a zebrafish model of craniofacial development.

RESULTS

We show that loss of a single allele of shha sensitized embryos to both alcohol- and PBO-induced facial defects. Co-exposure of PBO and alcohol synergized to cause more frequent and severe defects. The effects of this co-exposure were even more profound in the genetically susceptible shha heterozygotes.

CONCLUSIONS

Together, these findings shed light on the multifactorial basis of alcohol-induced craniofacial defects. In addition to further implicating genetic disruption of the Hh pathway in alcohol teratogenicity, our findings suggest that co-exposure to environmental chemicals that perturb Hh signaling may be important variables in FASD and related craniofacial disorders.

Prognostic Value of the FOXK Family Expression in Patients with Locally Advanced Rectal Cancer Following Neoadjuvant Chemoradiotherapy

Purpose

To assess the role of the expression levels of FOXK family members, FOXK1 and FOXK2, in predicting response to neo-chemoradiotherapy (NCRT) and prognosis in locally advanced rectal cancer (LARC).

Methods

A total of 256 LARC patients who underwent NCRT and radical resection between 2011 and 2017 were enrolled in the present study. The patients were divided into a training dataset (n=169, 2011–2015) and a validation dataset (n=87, 2016–2017). Tumor tissues were collected before NCRT and post-surgery and were used for immunohistochemical analysis.

Results

Oncomine database analysis revealed that FOXK1 and FOXK2 were overexpressed in most cancers especially in colorectal cancer. Additionally, overexpression of FOXK1 and FOXK2 was associated with poorer prognosis by the R2 database. In both our training and validation datasets, the expression of FOXK1 and FOXK2 was lower in the pathological complete response (pCR) group compared with the non-pCR group (P<0.05). Cox regression analysis demonstrated that pathological N stage (HR=1.810, 95% CI 1.159–2.827, P=0.009), FOXK1 expression (HR=5.831, 95% CI 2.925–11.625, P<0.001), and FOXK2 expression (HR=2.390, 95% CI 11.272–4.491, P=0.007) were independent predictors of disease-free survival (DFS). Based on the Cox multivariate analysis, we constructed a risk score model that served as a prognostic biomarker and had a powerful ability to predict pCR in LARC patients upon NCRT in both training and validation groups.

Conclusion

Expression levels of FOXK family members were associated with chemoradiotherapy resistance and prognosis of LARC patients following NCRT and were used to construct a risk score model that is a promising biomarker for LARC.

A Mutation in VWA1, Encoding von Willebrand Factor A Domain-Containing Protein 1, Is Associated With Hemifacial Microsomia

Background

Hemifacial microsomia (HFM) is a type of rare congenital syndrome caused by developmental disorders of the first and second pharyngeal arches that occurs in one out of 5,600 live births. There are significant gaps in our knowledge of the pathogenic genes underlying this syndrome.

Methods

Whole exome sequencing (WES) was performed on five patients, one asymptomatic carrier, and two marry-in members of a five-generation pedigree. Structure of WARP (product of VWA1) was predicted using the Phyre2 web portal. In situ hybridization and vwa1-knockdown/knockout studies in zebrafish using morpholino and CRISPR/Cas9 techniques were performed. Cartilage staining and immunofluorescence were carried out.

Results

Through WES and a set of filtration, we identified a c.G905A:p.R302Q point mutation in a novel candidate pathogenic gene, VWA1. The Phyre2 web portal predicted alterations in secondary and tertiary structures of WARP, indicating changes in its function as well. Predictions of protein-to-protein interactions in five pathways related to craniofacial development revealed possible interactions with four proteins in the FGF pathway. Knockdown/knockout studies of the zebrafish revealed deformities of pharyngeal cartilage. A decrease of the proliferation of cranial neural crest cells (CNCCs) and alteration of the structure of pharyngeal chondrocytes were observed in the morphants as well.

Conclusion

Our data suggest that a mutation in VWA1 is functionally linked to HFM through suppression of CNCC proliferation and disruption of the organization of pharyngeal chondrocytes.

Neurogenesis From Neural Crest Cells: Molecular Mechanisms in the Formation of Cranial Nerves and Ganglia

The neural crest (NC) is a transient multipotent cell population that originates in the dorsal neural tube. Cells of the NC are highly migratory, as they travel considerable distances through the body to reach their final sites. Derivatives of the NC are neurons and glia of the peripheral nervous system (PNS) and the enteric nervous system as well as non-neural cells. Different signaling pathways triggered by Bone Morphogenetic Proteins (BMPs), Fibroblast Growth Factors (FGFs), Wnt proteins, Notch ligands, retinoic acid (RA), and Receptor Tyrosine Kinases (RTKs) participate in the processes of induction, specification, cell migration and neural differentiation of the NC. A specific set of signaling pathways and transcription factors are initially expressed in the neural plate border and then in the NC cell precursors to the formation of cranial nerves. The molecular mechanisms of control during embryonic development have been gradually elucidated, pointing to an important role of transcriptional regulators when neural differentiation occurs. However, some of these proteins have an important participation in malformations of the cranial portion and their mutation results in aberrant neurogenesis. This review aims to give an overview of the role of cell signaling and of the function of transcription factors involved in the specification of ganglia precursors and neurogenesis to form the NC-derived cranial nerves during organogenesis.

The novel ciliogenesis regulator DYRK2 governs Hedgehog signaling during mouse embryogenesis

Mammalian Hedgehog (Hh) signaling plays key roles in embryogenesis and uniquely requires primary cilia. Functional analyses of several ciliogenesis-related genes led to the discovery of the developmental diseases known as ciliopathies. Hence, identification of mammalian factors that regulate ciliogenesis can provide insight into the molecular mechanisms of embryogenesis and ciliopathy. Here, we demonstrate that DYRK2 acts as a novel mammalian ciliogenesis-related protein kinase. Loss of Dyrk2 in mice causes suppression of Hh signaling and results in skeletal abnormalities during in vivo embryogenesis. Deletion of Dyrk2 induces abnormal ciliary morphology and trafficking of Hh pathway components. Mechanistically, transcriptome analyses demonstrate down-regulation of Aurka and other disassembly genes following Dyrk2 deletion. Taken together, the present study demonstrates for the first time that DYRK2 controls ciliogenesis and is necessary for Hh signaling during mammalian development.

FOXF2 acts as a crucial molecule in tumours and embryonic development

As a key member of the forkhead box transcription factors, forkhead box F2 (FOXF2) serves as a transcriptional regulator and regulates downstream gene expression in embryonic development, metabolism and in some common diseases, such as stroke and gastroparesis. Recent studies have shown that aberrant expression of FOXF2 is associated with a variety of tumorigenic processes, such as proliferation, invasion and metastasis. The role of FOXF2 in the development of many different organs has been confirmed by studies and has been speculated about in case reports. We focus on the mechanisms and signal pathways of tumour development initiated by aberrant expression of FOXF2, and we summarize the diseases and signal pathways caused by aberrant expression of FOXF2 in embryogenesis. This article highlights the differences in the role of FOXF2 in different tumours and demonstrates that multiple factors can regulate FOXF2 levels. In addition, FOXF2 is considered a biomarker for the diagnosis or prognosis of various tumours. Therefore, regulating the level of FOXF2 is an ideal treatment for tumours. FOXF2 could also affect the expression of some organ-specific genes to modulate organogenesis and could serve as a biomarker for specific differentiated cells. Finally, we present prospects for the continued research focus of FOXF2.

Cleft lip and cleft palate in Esrp1 knockout mice is associated with alterations in epithelial-mesenchymal crosstalk

Cleft lip is one of the most common human birth defects. However, there remain a limited number of mouse models of cleft lip that can be leveraged to characterize the genes and mechanisms that cause this disorder. Crosstalk between epithelial and mesenchymal cells underlies formation of the face and palate, but the basic molecular events mediating this crosstalk remain poorly understood. We previously demonstrated that mice lacking the epithelial-specific splicing factor Esrp1 have fully penetrant bilateral cleft lip and palate. In this study, we further investigated the mechanisms leading to cleft lip as well as cleft palate in both existing and new Esrp1 mutant mouse models. These studies included a detailed transcriptomic analysis of changes in ectoderm and mesenchyme in Esrp1-/- embryos during face formation. We identified altered expression of genes previously implicated in cleft lip and/or palate, including components of multiple signaling pathways. These findings provide the foundation for detailed investigations using Esrp1 mutant disease models to examine gene regulatory networks and pathways that are essential for normal face and palate development - the disruption of which leads to orofacial clefting in human patients.

SHH Signaling Pathway Drives Pediatric Bone Sarcoma Progression

Primary bone tumors can be divided into two classes, benign and malignant. Among the latter group, osteosarcoma and Ewing sarcoma are the most prevalent malignant primary bone tumors in children and adolescents. Despite intensive efforts to improve treatments, almost 40% of patients succumb to the disease. Specifically, the clinical outcome for metastatic osteosarcoma or Ewing sarcoma remains poor; less than 30% of patients who present metastases will survive 5 years after initial diagnosis. One common and specific point of these bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Over the past years, considerable interest in the Sonic Hedgehog (SHH) pathway has taken place within the cancer research community. The activation of this SHH cascade can be done through different ways and, schematically, two pathways can be described, the canonical and the non-canonical. This review discusses the current knowledge about the involvement of the SHH signaling pathway in skeletal development, pediatric bone sarcoma progression and the related therapeutic options that may be possible for these tumors.

Temporospatial sonic hedgehog signalling is essential for neural crest-dependent patterning of the intrinsic tongue musculature

The tongue is a highly specialised muscular organ with a complex anatomy required for normal function. We have utilised multiple genetic approaches to investigate local temporospatial requirements for sonic hedgehog (SHH) signalling during tongue development. Mice lacking a Shh cis-enhancer, MFCS4 (ShhMFCS4/-), with reduced SHH in dorsal tongue epithelium have perturbed lingual septum tendon formation and disrupted intrinsic muscle patterning, with these defects reproduced following global Shh deletion from E10.5 in pCag-CreERTM; Shhflox/flox embryos. SHH responsiveness was diminished in local cranial neural crest cell (CNCC) populations in both mutants, with SHH targeting these cells through the primary cilium. CNCC-specific deletion of orofaciodigital syndrome 1 (Ofd1), which encodes a ciliary protein, in Wnt1-Cre; Ofdfl/Y mice led to a complete loss of normal myotube arrangement and hypoglossia. In contrast, mesoderm-specific deletion of Ofd1 in Mesp1-Cre; Ofdfl/Y embryos resulted in normal intrinsic muscle arrangement. Collectively, these findings suggest key temporospatial requirements for local SHH signalling in tongue development (specifically, lingual tendon differentiation and intrinsic muscle patterning through signalling to CNCCs) and provide further mechanistic insight into the tongue anomalies seen in patients with disrupted hedgehog signalling.

Pilot GWAS of caries in African-Americans shows genetic heterogeneity

BACKGROUND

Dental caries is the most common chronic disease in the US and disproportionately affects racial/ethnic minorities. Caries is heritable, and though genetic heterogeneity exists between ancestries for a substantial portion of loci associated with complex disease, a genome-wide association study (GWAS) of caries specifically in African Americans has not been performed previously.

METHODS

We performed exploratory GWAS of dental caries in 109 African American adults (age > 18) and 96 children (age 3-12) from the Center for Oral Health Research in Appalachia (COHRA1 cohort). Caries phenotypes (DMFS, DMFT, dft, and dfs indices) assessed by dental exams were tested for association with 5 million genotyped or imputed single nucleotide polymorphisms (SNPs), separately in the two age groups. The GWAS was performed using linear regression with adjustment for age, sex, and two principal components of ancestry. A maximum of 1 million adaptive permutations were run to determine empirical significance.

RESULTS

No loci met the threshold for genome-wide significance, though some of the strongest signals were near genes previously implicated in caries such as antimicrobial peptide DEFB1 (rs2515501; p = 4.54 × 10- 6) and TUFT1 (rs11805632; p = 5.15 × 10- 6). Effect estimates of lead SNPs at suggestive loci were compared between African Americans and Caucasians (adults N = 918; children N = 983). Significant (p < 5 × 10- 8) genetic heterogeneity for caries risk was found between racial groups for 50% of the suggestive loci in children, and 12-18% of the suggestive loci in adults.

CONCLUSIONS

The genetic heterogeneity results suggest that there may be differences in the contributions of genetic variants to caries across racial groups, and highlight the critical need for the inclusion of minorities in subsequent and larger genetic studies of caries in order to meet the goals of precision medicine and to reduce oral health disparities.

Cohesin complex-associated holoprosencephaly

Marked by incomplete division of the embryonic forebrain, holoprosencephaly is one of the most common human developmental disorders. Despite decades of phenotype-driven research, 80-90% of aneuploidy-negative holoprosencephaly individuals with a probable genetic aetiology do not have a genetic diagnosis. Here we report holoprosencephaly associated with variants in the two X-linked cohesin complex genes, STAG2 and SMC1A, with loss-of-function variants in 10 individuals and a missense variant in one. Additionally, we report four individuals with variants in the cohesin complex genes that are not X-linked, SMC3 and RAD21. Using whole mount in situ hybridization, we show that STAG2 and SMC1A are expressed in the prosencephalic neural folds during primary neurulation in the mouse, consistent with forebrain morphogenesis and holoprosencephaly pathogenesis. Finally, we found that shRNA knockdown of STAG2 and SMC1A causes aberrant expression of HPE-associated genes ZIC2, GLI2, SMAD3 and FGFR1 in human neural stem cells. These findings show the cohesin complex as an important regulator of median forebrain development and X-linked inheritance patterns in holoprosencephaly.

FOXF2 is required for cochlear development in humans and mice

Molecular mechanisms governing the development of the human cochlea remain largely unknown. Through genome sequencing, we identified a homozygous FOXF2 variant c.325A>T (p.I109F) in a child with profound sensorineural hearing loss (SNHL) associated with incomplete partition type I anomaly of the cochlea. This variant is not found in public databases or in over 1000 ethnicity-matched control individuals. I109 is a highly conserved residue in the forkhead box (Fox) domain of FOXF2, a member of the Fox protein family of transcription factors that regulate the expression of genes involved in embryogenic development as well as adult life. Our in vitro studies show that the half-life of mutant FOXF2 is reduced compared to that of wild type. Foxf2 is expressed in the cochlea of developing and adult mice. The mouse knockout of Foxf2 shows shortened and malformed cochleae, in addition to altered shape of hair cells with innervation and planar cell polarity defects. Expressions of Eya1 and Pax3, genes essential for cochlear development, are reduced in the cochleae of Foxf2 knockout mice. We conclude that FOXF2 plays a major role in cochlear development and its dysfunction leads to SNHL and developmental anomalies of the cochlea in humans and mice.

FOXK transcription factors: Regulation and critical role in cancer

Growing evidence suggests that alterations of gene expression including expression and activities of transcription factors are closely associated with carcinogenesis. Forkhead Box Class K (FOXK) proteins, FOXK1 and FOXK2, are a family of evolutionarily conserved transcriptional factors, which have recently been recognized as key transcriptional regulators involved in many types of cancer. Members of the FOXK family mediate a wide spectrum of biological processes, including cell proliferation, differentiation, apoptosis, autophagy, cell cycle progression, DNA damage and tumorigenesis. Therefore, the deregulation of FOXKs can affect the cell fate and they promote tumorigenesis as well as cancer progression. The mechanisms of FOXKs regulation including post-translational modifications (PTMs), microRNAs (miRNAs) and protein-protein interactions are well demonstrated. However, the detailed mechanisms of FOXKs activation and deregulation in cancer progression are still inconclusive. In this review, we summarize the regulatory mechanisms of FOXKs expression and activity, and their role in the development and progression of cancer. We have discussed whether FOXKs act as tumor suppressors/oncoproteins in tumor cells and their therapeutic applications in malignant diseases are also discussed. This review may assist in designing experimental studies involving FOXKs and it would strength the therapeutic potential of FOXKs as targets for cancers.

A CCR4-NOT Transcription Complex, Subunit 1, CNOT1, Variant Associated with Holoprosencephaly

Holoprosencephaly is the incomplete separation of the forebrain during embryogenesis. Both genetic and environmental etiologies have been determined for holoprosencephaly; however, a genetic etiology is not found in most cases. In this report, we present two unrelated individuals with semilobar holoprosencephaly who have the identical de novo missense variant in the gene CCR4-NOT transcription complex, subunit 1 (CNOT1). The variant (c.1603C>T [p.Arg535Cys]) is predicted to be deleterious and is not present in public databases. CNOT1 has not been previously associated with holoprosencephaly or other brain malformations. In situ hybridization analyses of mouse embryos show that Cnot1 is expressed in the prosencephalic neural folds at gestational day 8.25 during the critical period for subsequent forebrain division. Combining human and mouse data, we show that CNOT1 is associated with incomplete forebrain division.

Genome-wide chromatin accessibility and transcriptome profiling show minimal epigenome changes and coordinated transcriptional dysregulation of hedgehog signaling in Danforth's short tail mice

Danforth's short tail (Sd) mice provide an excellent model for investigating the underlying etiology of human caudal birth defects, which affect 1 in 10 000 live births. Sd animals exhibit aberrant axial skeleton, urogenital and gastrointestinal development similar to human caudal malformation syndromes including urorectal septum malformation, caudal regression, vertebral-anal-cardiac-tracheo-esophageal fistula-renal-limb (VACTERL) association and persistent cloaca. Previous studies have shown that the Sd mutation results from an endogenous retroviral (ERV) insertion upstream of the Ptf1a gene resulting in its ectopic expression at E9.5. Though the genetic lesion has been determined, the resulting epigenomic and transcriptomic changes driving the phenotype have not been investigated. Here, we performed ATAC-seq experiments on isolated E9.5 tailbud tissue, which revealed minimal changes in chromatin accessibility in Sd/Sd mutant embryos. Interestingly, chromatin changes were localized to a small interval adjacent to the Sd ERV insertion overlapping a known Ptf1a enhancer region, which is conserved in mice and humans. Furthermore, mRNA-seq experiments revealed increased transcription of Ptf1a target genes and, importantly, downregulation of hedgehog pathway genes. Reduced sonic hedgehog (SHH) signaling was confirmed by in situ hybridization and immunofluorescence suggesting that the Sd phenotype results, in part, from downregulated SHH signaling. Taken together, these data demonstrate substantial transcriptome changes in the Sd mouse, and indicate that the effect of the ERV insertion on Ptf1a expression may be mediated by increased chromatin accessibility at a conserved Ptf1a enhancer. We propose that human caudal dysgenesis disorders may result from dysregulation of hedgehog signaling pathways.

Wnt signaling in orofacial clefts: crosstalk, pathogenesis and models

Diverse signaling cues and attendant proteins work together during organogenesis, including craniofacial development. Lip and palate formation starts as early as the fourth week of gestation in humans or embryonic day 9.5 in mice. Disruptions in these early events may cause serious consequences, such as orofacial clefts, mainly cleft lip and/or cleft palate. Morphogenetic Wnt signaling, along with other signaling pathways and transcription regulation mechanisms, plays crucial roles during embryonic development, yet the signaling mechanisms and interactions in lip and palate formation and fusion remain poorly understood. Various Wnt signaling and related genes have been associated with orofacial clefts. This Review discusses the role of Wnt signaling and its crosstalk with cell adhesion molecules, transcription factors, epigenetic regulators and other morphogenetic signaling pathways, including the Bmp, Fgf, Tgfβ, Shh and retinoic acid pathways, in orofacial clefts in humans and animal models, which may provide a better understanding of these disorders and could be applied towards prevention and treatments.

Ultrastructural analysis of collagen fibril diameter distribution in cleft lip

OBJECTIVE

A preliminary study to determine collagen fibril diameter (CF-ED) distribution on medial and lateral sides of cleft lip (CL).

MATERIAL AND METHODS

Tissue samples from medial and lateral sides of CL were fixed in 2.5% glutaraldehyde and 1% osmium tetroxide and embedded in Araldite CY212 resin for transmission electron microscopy. The analysis of CF-ED was performed using the ImageJ program. To characterize the packaging of collagen fibrils (CFs) in the two tissues, we estimated the collagen number density (CF-ND) and fibril-area-fraction (FAF). Differences in measurements across the two sides were calculated using Wilcoxon signed-rank test.

RESULTS

The CF-ED was statistically significantly (p < 0.001) smaller on the medial side (45.69 ± 7.89 nm) than on the lateral side (54.18 ± 7.62 nm). The medial side had a higher CF-ND and a higher percentage of FAF than the lateral side.

CONCLUSION

Our finding of a smaller CF-ED and higher CF-ND and FAF for the medial side suggests possible differences in size and distribution of CFs between medial and lateral sides of CL. This finding provides knowledge toward underlying tissue biomechanics that may help reconstruction of perioral tissue scaffolds, ultimately resulting in better treatment of patients with oral clefts.

Gli2 is required for the induction and migration of Xenopus laevis neural crest

The neural crest (NC) is a multipotent migratory embryonic population that is formed during late gastrulation and gives rise to a wide array of derivatives, including cells from the peripheral nervous system (PNS), the craniofacial bones and cartilages, peripheral glial cells, and melanocyte cells, among others. In this work we analyzed the role of the Hedgehog signaling pathway effector gli2 in Xenopus NC. We provide evidence that the gli2 gene is expressed in the prospective, premigratory and migratory NC. The use of a specific morpholino against gli2 and the pharmacological specific inhibitor GANT61 in different experimental approaches allowed us to determine that gli2 is required for the induction and specification of NC cells as a transcriptional activator. Moreover, gli2 also acts by reducing apoptosis in the NC without affecting its cell proliferation status. We also demonstrated that gli2 is required cell-autonomously for NC migration, and for the formation of NC derivatives such as the craniofacial cartilages, melanocytes and the cranial ganglia. Altogether, our results showed that gli2 is a key transcriptional activator to accomplish the proper specification and development of Xenopus NC cells.

FGF8 and Shh promote the survival and maintenance of multipotent neural crest progenitors

The developmental mechanisms that control the building of the complex head of vertebrates and particularly, facial skeletogenesis, remain poorly known. Progenitor cells derived from the embryonic neural crest (NC) are the major constituents and players of facial tissue development. Deciphering the cellular and molecular machinery that controls NC cell (NCC) differentiation into bone, cartilage, fat and other mesenchymal tissues, is thus a main issue for understanding vertebrate facial variations. In this work, we investigated the effects of fibroblast growth factor 8 (FGF8) and Sonic Hedgehog (Shh), two signaling molecules essential for craniofacial development, on the in vitro differentiation and multipotentiality of mesencephalic NCCs (MNCCs) isolated from the quail embryo. Comparison of distinct temporal treatments with FGF8 and/or Shh showed that both promoted chondrogenesis of MNCCs by increasing the amount and size of cartilage nodules. Higher rates of chondrogenesis were observed when MNCCs were treated with FGF8 during the migration phase, thus mimicking the in vivo exposure of migrating NCCs to FGF8 secreted by the isthmic brain signaling center. An in vitro cell cloning assay revealed that, after concomitant treatment with FGF8 and Shh, about 80% of NC progenitors displayed chondrogenic potential, while in untreated cultures, only 18% exhibited this potential. In addition, colony analysis showed for the first time the existence of a highly multipotent progenitor able to clonally give rise to adipocytes in addition to other cephalic NC phenotypes (i.e. glial cells, neurons, melanocytes, smooth muscle cells and chondrocytes) (GNMFCA progenitor). This progenitor was observed only when clonal cultures were treated with both FGF8 and Shh. Several other types of multipotent cells, which generated four, five or six distinct phenotypes, accounted for 55% of the progenitors in FGF8 and Shh treated cultures, versus 13,5% in the untreated ones. Together, these data reveal an essential role for both FGF8 and Shh together in maintenance of MNCC multipotentiality by favoring the development of NC progenitors endowed with a broad array of mesectodermal potentials.

The multisystemic functions of FOXD1 in development and disease

Transcription factors (TFs) participate in a wide range of cellular processes due to their inherent function as essential regulatory proteins. Their dysfunction has been linked to numerous human diseases. The forkhead box (FOX) family of TFs belongs to the "winged helix" superfamily, consisting of proteins sharing a related winged helix-turn-helix DNA-binding motif. FOX genes have been extensively present during vertebrates and invertebrates' evolution, participating in numerous molecular cascades and biological functions, such as embryonic development and organogenesis, cell cycle regulation, metabolism control, stem cell niche maintenance, signal transduction, and many others. FOXD1, a forkhead TF, has been related to different key biological processes such as kidney and retina development and embryo implantation. FOXD1 dysfunction has been linked to different pathologies, thereby constituting a diagnostic biomarker and a promising target for future therapies. This paper aims to present, for the first time, a comprehensive review of FOXD1's role in mouse development and human disease. Molecular, structural, and functional aspects of FOXD1 are presented in light of physiological and pathogenic conditions, including its role in human disease aetiology, such as cancer and recurrent pregnancy loss. Taken together, the information given here should enable a better understanding of FOXD1 function for basic science researchers and clinicians.

Identification of sonic hedgehog-regulated genes and biological processes in the cranial neural crest mesenchyme by comparative transcriptomics

Background

The evolutionarily conserved Sonic Hedgehog (Shh) signaling pathway is essential for embryogenesis and orofacial development. SHH ligand secreted from the surface ectoderm activates pathway activity in the underlying cranial neural crest cell (cNCC)-derived mesenchyme of the developing upper lip and palate. Disruption of Shh signaling causes orofacial clefts, but the biological action of Shh signaling and the full set of Shh target genes that mediate normal and abnormal orofacial morphogenesis have not been described.

Results

Using comparative transcriptional profiling, we have defined the Shh-regulated genes of the cNCC-derived mesenchyme. Enrichment analysis demonstrated that in cultured cNCCs, Shh-regulated genes are involved in smooth muscle and chondrocyte differentiation, as well as regulation of the Forkhead family of transcription factors, G1/S cell cycle transition, and angiogenesis. Next, this gene set from Shh-activated cNCCs in vitro was compared to the set of genes dysregulated in the facial primordia in vivo during the initial pathogenesis of Shh pathway inhibitor-induced orofacial clefting. Functional gene annotation enrichment analysis of the 112 Shh-regulated genes with concordant expression changes linked Shh signaling to interdependent and unique biological processes including mesenchyme development, cell adhesion, cell proliferation, cell migration, angiogenesis, perivascular cell markers, and orofacial clefting.

Conclusions

We defined the Shh-regulated transcriptome of the cNCC-derived mesenchyme by comparing the expression signatures of Shh-activated cNCCs in vitro to primordial midfacial tissues exposed to the Shh pathway inhibitor in vivo. In addition to improving our understanding of cNCC biology by determining the identity and possible roles of cNCC-specific Shh target genes, this study presents novel candidate genes whose examination in the context of human orofacial clefting etiology is warranted.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4885-5) contains supplementary material, which is available to authorized users.

Common basis for orofacial clefting and cortical interneuronopathy

Orofacial clefts (OFCs) of the lip and/or palate are among the most common human birth defects. Current treatment strategies focus on functional and cosmetic repair but even when this care is available, individuals born with OFCs are at high risk for persistent neurobehavioral problems. In addition to learning disabilities and reduced academic achievement, recent evidence associates OFCs with elevated risk for a constellation of psychiatric outcomes including anxiety disorders, autism spectrum disorder, and schizophrenia. The relationship between these outcomes and OFCs is poorly understood and controversial. Recent neuroimaging studies in humans and mice demonstrate subtle morphological brain abnormalities that co-occur with OFCs but specific molecular and cellular mechanisms have not been investigated. Here, we provide the first evidence directly linking OFC pathogenesis to abnormal development of GABAergic cortical interneurons (cINs). Lineage tracing revealed that the structures that form the upper lip and palate develop in molecular synchrony and spatiotemporal proximity to cINs, suggesting these populations may have shared sensitivity to genetic and/or teratogenic insult. Examination of cIN development in a mouse model of nonsyndromic OFCs revealed significant disruptions in cIN proliferation and migration, culminating in misspecification of the somatostatin-expressing subgroup. These findings reveal a unified developmental basis for orofacial clefting and disrupted cIN development, and may explain the significant overlap in neurobehavioral and psychiatric outcomes associated with OFCs and cIN dysfunction. This emerging mechanistic understanding for increased prevalence of adverse neurobehavioral outcomes in OFC patients is the entry-point for developing evidence-based therapies to improve patient outcomes.

Evaluating LINE-1 methylation in cleft lip tissues and its association with early pregnancy exposures

Aim: To pilot investigation of methylation of long interspersed nucleotide element-1 in lip tissues from infants with nonsyndromic cleft lip, and its association with maternal periconceptional exposures. Methods: The lateral and medial sides of the cleft lips of 23 affected infants were analyzed for long interspersed nucleotide element-1 methylation by bisulfite conversion and pyrosequencing. Results: The medial side showed 1.8% higher methylation compared with the lateral side; p = 0.031, particularly in male infants (2.7% difference; p = 0.011) or when the mothers did not take folic acid during periconceptional period (2.4% difference; p = 0.011). These results were not statistically significant when Bonferroni adjustment was used. Conclusion: The observed differences in DNA methylation, although nonsignificant after correction for multiple comparisons, suggest that differential regulation of the two sides may impact lip fusion and warrant larger-scale replication.

Coordinated d-cyclin/Foxd1 activation drives mitogenic activity of the Sonic Hedgehog signaling pathway

Sonic Hedgehog (Shh) signaling plays key regulatory roles in embryonic development and postnatal homeostasis and repair. Modulation of the Shh pathway is known to cause malformations and malignancies associated with dysregulated tissue growth. However, our understanding of the molecular mechanisms by which Shh regulates cellular proliferation is incomplete. Here, using mouse embryonic fibroblasts, we demonstrate that the Forkhead box gene Foxd1 is transcriptionally regulated by canonical Shh signaling and required for downstream proliferative activity. We show that Foxd1 deletion abrogates the proliferative response to SHH ligand while FOXD1 overexpression alone is sufficient to induce cellular proliferation. The proliferative response to both SHH ligand and FOXD1 overexpression was blocked by pharmacologic inhibition of cyclin-dependent kinase signaling. Time-course experiments revealed that Shh pathway activation of Foxd1 is followed by downregulation of Cdkn1c, which encodes a cyclin-dependent kinase inhibitor. Consistent with a direct transcriptional regulation mechanism, we found that FOXD1 reduces reporter activity of a Fox enhancer sequence in the second intron of Cdkn1c. Supporting the applicability of these findings to specific biological contexts, we show that Shh regulation of Foxd1 and Cdkn1c is recapitulated in cranial neural crest cells and provide evidence that this mechanism is operational during upper lip morphogenesis. These results reveal a novel Shh-Foxd1-Cdkn1c regulatory circuit that drives the mitogenic action of Shh signaling and may have broad implications in development and disease.

Muscle fiber diameter assessment in cleft lip using image processing

OBJECTIVE

To pilot investigation of muscle fiber diameter (MFD) on medial and lateral sides of the cleft in 18 infants with cleft lip with or without cleft palate (CL/P) using image processing.

MATERIAL AND METHODS

Formalin-fixed paraffin-embedded (FFPE) tissue samples from the medial and lateral sides of the cleft were analyzed for MFD using an image-processing program (ImageJ). For within-case comparison, a paired Student's t test was performed. For comparisons between classes, an unpaired t test was used.

RESULTS

Image processing enabled rapid measurement of MFD with majority of fibers showing diameter between 6 and 11 μm. There was no significant difference in mean MFD between the medial and lateral sides, or between CL and CLP. However, we found a significant difference on the medial side (p = .032) between males and females.

CONCLUSION

The image processing on FFPE tissues resulted in easy quantification of MFD with finding of a smaller MFD on the medial side in males suggesting possible differences in orbicularis oris (OO) muscle between the two sexes in CL that warrants replication using larger number of cases. Moreover, this finding can aid subclinical phenotyping and potentially in the restoration of the anatomy and function of the upper lip.