A review of FGF signaling in palate development

The molecular mechanisms of glycosaminoglycan biosynthesis regulating chondrogenesis and endochondral ossification

Disorders of chondrocyte differentiation and endochondral osteogenesis are major underlying factors in skeletal developmental disorders, including tibial dysplasia (TD), osteoarthritis (OA), chondrodysplasia (ACH), and multiple epiphyseal dysplasia (MED). Understanding the cellular and molecular pathogenesis of these disorders is crucial for addressing orthopedic diseases resulting from impaired glycosaminoglycan synthesis. Glycosaminoglycan is a broad term that refers to the glycan component of proteoglycan macromolecules. It is an essential component of the cartilage extracellular matrix and plays a vital role in various biological processes, including gene transcription, signal transduction, and chondrocyte differentiation. Recent studies have demonstrated that glycosaminoglycan biosynthesis plays a regulatory role in chondrocyte differentiation and endochondral osteogenesis by modulating various growth factors and signaling molecules. For instance, glycosaminoglycan is involved in mediating pathways such as Wnt, TGF-β, FGF, Ihh-PTHrP, and O-GlcNAc glycosylation, interacting with transcription factors SOX9, BMPs, TGF-β, and Runx2 to regulate chondrocyte differentiation and endochondral osteogenesis. To propose innovative approaches for addressing orthopedic diseases caused by impaired glycosaminoglycan biosynthesis, we conducted a comprehensive review of the molecular mechanisms underlying chondrocyte glycosaminoglycan biosynthesis, which regulates chondrocyte differentiation and endochondral osteogenesis. Our analysis considers the role of genes, glycoproteins, and associated signaling pathways during chondrogenesis and endochondral ossification.

Integrative analysis of transcriptome dynamics during human craniofacial development identifies candidate disease genes

Craniofacial disorders arise in early pregnancy and are one of the most common congenital defects. To fully understand how craniofacial disorders arise, it is essential to characterize gene expression during the patterning of the craniofacial region. To address this, we performed bulk and single-cell RNA-seq on human craniofacial tissue from 4-8 weeks post conception. Comparisons to dozens of other human tissues revealed 239 genes most strongly expressed during craniofacial development. Craniofacial-biased developmental enhancers were enriched +/- 400 kb surrounding these craniofacial-biased genes. Gene co-expression analysis revealed that regulatory hubs are enriched for known disease causing genes and are resistant to mutation in the normal healthy population. Combining transcriptomic and epigenomic data we identified 539 genes likely to contribute to craniofacial disorders. While most have not been previously implicated in craniofacial disorders, we demonstrate this set of genes has increased levels of de novo mutations in orofacial clefting patients warranting further study.

MiRNA-470-5p suppresses epithelial-mesenchymal transition of embryonic palatal shelf epithelial cells by targeting Fgfr1 during palatogenesis

MicroRNAs (miRNAs) have been identified as crucial modulators of gene expression and to play a role in palatogenesis. The aim of this study was to explore the potential role and regulatory mechanisms of miRNAs during palatogenesis. RNA-sequencing was performed to compare the RNA expression profiles of mouse embryonic palatal shelf (MEPS) tissue between an all-trans retinoic acid (ATRA)-induced group and control group, followed by reverse transcription-quantitative polymerase chain reaction for validation, demonstrating upregulated expression of miRNA-470-5p and downregulated expression of Fgfr1 in the ATRA-induced group. The specific binding sites of miRNA-470-5p that potentially govern Fgfr1 expression were predicted by miRanda and TargetScan. The relationship between miRNA-470-5p and Fgfr1 was validated in HEK293T cells by luciferase reporter assays, confirming that miR-470-5p acts directly on the Fgfr1 3'-untranslated region. Fgfr1 mRNA and FGFR1 protein levels were markedly downregulated in MEPS epithelial cells over-expressing miRNA-470-5p. Functional experiments in vitro with CCK-8, cell colony formation, and 5-ethynyl-2'-deoxyuridine (EdU) staining assays revealed that upregulated miRNA-470-5p expression could inhibit the epithelial-mesenchymal transition (EMT) of MEPS epithelial cells by targeting Fgfr1. These findings provide a new molecular mechanism of cleft palate formation, which can inform the development of new treatment and/or prevention targets.

FGF signaling in cranial suture development and related diseases

Suture mesenchymal stem cells (SMSCs) are a heterogeneous stem cell population with the ability to self-renew and differentiate into multiple cell lineages. The cranial suture provides a niche for SMSCs to maintain suture patency, allowing for cranial bone repair and regeneration. In addition, the cranial suture functions as an intramembranous bone growth site during craniofacial bone development. Defects in suture development have been implicated in various congenital diseases, such as sutural agenesis and craniosynostosis. However, it remains largely unknown how intricate signaling pathways orchestrate suture and SMSC function in craniofacial bone development, homeostasis, repair and diseases. Studies in patients with syndromic craniosynostosis identified fibroblast growth factor (FGF) signaling as an important signaling pathway that regulates cranial vault development. A series of in vitro and in vivo studies have since revealed the critical roles of FGF signaling in SMSCs, cranial suture and cranial skeleton development, and the pathogenesis of related diseases. Here, we summarize the characteristics of cranial sutures and SMSCs, and the important functions of the FGF signaling pathway in SMSC and cranial suture development as well as diseases caused by suture dysfunction. We also discuss emerging current and future studies of signaling regulation in SMSCs.

Retinoic acid effects on in vitro palatal fusion and WNT signaling

Retinoic acid is the main active vitamin A derivate and a key regulator of embryonic development. Excess of retinoic acid can disturb palate development in mice leading to cleft palate. WNT signaling is one of the main pathways in palate development. We evaluated the effects of retinoic acid on palate fusion and WNT signaling in in vitro explant cultures. Unfused palates from E13.5 mouse embryos were cultured for 4 days with 0.5 μM, 2 μM or without retinoic acid. Apoptosis, proliferation, WNT signaling and bone formation were analyzed by histology and quantitative PCR. Retinoic acid treatment with 0.5 and 2.0 μM reduced palate fusion from 84% (SD 6.8%) in the controls to 56% (SD 26%) and 16% (SD 19%), respectively. Additionally, 2 μM retinoic acid treatment increased Axin2 expression. Retinoic acid also increased the proliferation marker Pcna as well as the number of Ki-67-positive cells in the palate epithelium. At the same time, the WNT inhibitors Dkk1, Dkk3, Wif1 and Sfrp1 were downregulated at least two-fold. Retinoic acid also down-regulated Alpl and Col1a2 gene expression. Alkaline phosphatase (ALP) activity was notably reduced in the osteogenic areas of the retinoic acid- treated palates. Our data suggest that retinoic acid impairs palate fusion and bone formation by upregulation of WNT signaling.

FGF9 Promotes Expression of HAS2 in Palatal Elevation via the Wnt/β-Catenin/TCF7L2 Pathway

Background: Fgf9 mutation was found in cleft palate patients. Our previous study indicated that Fgf9 promotes timely elevation of palate by regulating hyaluronic acid (HA) accumulation at embryonic day 13.5 (E13.5). HA is synthesized by hyaluronic acid synthases (HAS) isoforms 1, 2, or 3. However, how FGF9 regulates HA in palatogenesis is still unclear. Methods: Using Ddx4-Cre mice, we generated the Fgf9^−/− mouse model (with exon 2 deletion). Immunohistochemistry was used to detect the location and expression of HAS2 in WT and the Fgf9^−/− palate at E13.5. We also predicted the association between Fgf9 and Has2 within the developing palate by performing a bioinformatics analysis. The expression of β-catenin, HAS2, and TCF7L2 were verified by Western blotting after knockout of Fgf9. Rescue experiments were performed by ELISA in vitro. Results: Fgf9^−/− mice exhibited 100% penetrance of the cleft palate. A knockout of Fgf9 confirmed that HAS2 and TCF7L2 expression was positively correlated with FGF9. TCF7L2 binds to the Has2 promoter, exhibiting the high specificity predicted by JASPAR. Additionally, increased HA expression by BML-284, TCF-dependent agonist, was blocked in Fgf9^−/− palate because of the significant decline in TCF7L2 expression. Conclusions: FGF9 promotes HAS2 expression via Wnt/β-catenin/TCF7L2 pathway with TCF7L2 activating transcription of Has2 in the palate.

Evaluation of the Multiple Tissue Factors in the Cartilage of Primary and Secondary Rhinoplasty in Cleft Lip and Palate Patients

Cleft lip and palate (CLP) is one of the craniofacial defects. The objective of this study was to identify the differences in appearance between the tissue factors in cartilage of CLP patients after primary and secondary rhinoplasty. Immunohistochemistry was performed with MMP-2, MMP-8, MMP-9, TIMP-2, IL-1α, IL-10, bFGF, and TGFβ1. The quantification of the structures was performed using a semi-quantitative census method. MMP-2, -9, IL-1a, and bFGF demonstrated higher number of positive cells in patients, while the number of MMP-8, IL-1a, -10 and TGFβ1 cells was higher or equal in the control subjects. The only statistically significant difference between CLP-operated patients was found in the TIMP-2 group, where the primary CLP patient group had a higher number of TIMP-2 positive chondrocytes than the secondary CLP patient group (U = 53.5; p = 0.021). The median value of the primary CLP group was ++ number of TIMP-2 positive chondrocytes compared to +++ in the secondary CLP group. No statistically significant difference was found between primary and secondary rhinoplasty patients for other tissue factors. Commonly, the rich expression of different tissue factors suggests a stimulation of higher elasticity in cleft affected cartilage. The statistically significant TIMP-2 elevation in primary operated cartilage indicates an impact of the selective tissue remodeling for hard tissue.

Cleft Palate in Apert Syndrome

Apert syndrome is a rare genetic disorder characterized by craniosynostosis, midface retrusion, and limb anomalies. Cleft palate occurs in a subset of Apert syndrome patients. Although the genetic causes underlying Apert syndrome have been identified, the downstream signaling pathways and cellular mechanisms responsible for cleft palate are still elusive. To find clues for the pathogenic mechanisms of palatal defects in Apert syndrome, we review the clinical characteristics of the palate in cases of Apert syndrome, the palatal phenotypes in mouse models, and the potential signaling mechanisms involved in palatal defects. In Apert syndrome patients, cleft of the soft palate is more frequent than of the hard palate. The length of the hard palate is decreased. Cleft palate is associated most commonly with the S252W variant of FGFR2. In addition to cleft palate, high-arched palate, lateral palatal swelling, or bifid uvula are common in Apert syndrome patients. Mouse models of Apert syndrome display palatal defects, providing valuable tools to understand the underlying mechanisms. The mutations in FGFR2 causing Apert syndrome may change a signaling network in epithelial–mesenchymal interactions during palatogenesis. Understanding the pathogenic mechanisms of palatal defects in Apert syndrome may shed light on potential novel therapeutic solutions.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

The role of fibroblast growth factor 8 in cartilage development and disease

Fibroblast growth factor 8 (FGF‐8), also known as androgen‐induced growth factor (AIGF), is presumed to be a potent mitogenic cytokine that plays important roles in early embryonic development, brain formation and limb development. In the bone environment, FGF‐8 produced or received by chondrocyte precursor cells binds to fibroblast growth factor receptor (FGFR), causing different levels of activation of downstream signalling pathways, such as phospholipase C gamma (PLCγ)/Ca²⁺, RAS/mitogen‐activated protein kinase‐extracellular regulated protein kinases (RAS/MAPK‐MEK‐ERK), and Wnt‐β‐catenin‐Axin2 signalling, and ultimately controlling chondrocyte proliferation, differentiation, cell survival and migration. However, the molecular mechanism of FGF‐8 in normal or pathological cartilage remains unclear, and thus, FGF‐8 represents a novel exploratory target for studies of chondrocyte development and cartilage disease progression. In this review, studies assessing the relationship between FGF‐8 and chondrocytes that have been published in the past 5 years are systematically summarized to determine the probable mechanism and physiological effect of FGF‐8 on chondrocytes. Based on the existing research results, a therapeutic regimen targeting FGF‐8 is proposed to explore the possibility of treating chondrocyte‐related diseases.

Exosomes-a potential indicator and mediator of cleft lip and palate: a narrative review

Objective

This article summarizes the recent literature on noncoding ribonucleic acids (ncRNAs) in relation to cleft lip with or without palate and exosomes and their usage in craniofacial diseases.

Background

Cleft lip with or without cleft palate (CL/P) is a common congenital malformation with genetic and environmental risk factors that affects numerous children and families. Surgical procedures can correct deformations; however, residual sequelae remain after surgery. Studies exploring the pathogenesis of CL/P are crucial for its early diagnosis and treatment and can inform treatment strategy decisions, etiology searches, and treatment during pregnancy. Recently, research has shown that most disease-related genes are ncRNAs, which are important transcripts in the human transcriptome. ncRNAs include microRNAs, long noncoding RNAs, and circular RNAs. These ncRNAs play essential roles in various pathophysiological processes, including cell proliferation, migration, apoptosis, and epithelial-mesenchymal transition. Previous studies on protein-coding genes have identified a number of genes related to CL/P; however, the pathogenesis of CL/P has not yet been thoroughly explained. Exosomes are vehicles that transfer various bioactive molecules between cells and represent a new method of intercellular communication. Research has shown that exosomes are related to some craniofacial diseases.

Methods

We searched the PubMed database for recently published English-language articles using the following keywords: “cleft lip with or without palate,” “noncoding RNA,” “exosomes,” and “craniofacial diseases”. We then reviewed the retrieved articles.

Conclusions

As exosomes serve as cellular communicators and the palate consists of epithelial and mesenchymal cells, communication between the two cell types may affect its formation. Thus, exosomes could represent a new indicator and mediator of CL/P.

Genome-wide Gene-by-Sex Interaction Studies Identify Novel Nonsyndromic Orofacial Clefts Risk Locus

Risk loci identified through genome-wide association studies have explained about 25% of the phenotypic variations in nonsyndromic orofacial clefts (nsOFCs) on the liability scale. Despite the notable sex differences in the incidences of the different cleft types, investigation of loci for sex-specific effects has been understudied. To explore the sex-specific effects in genetic etiology of nsOFCs, we conducted a genome-wide gene × sex (GxSex) interaction study in a sub-Saharan African orofacial cleft cohort. The sample included 1,019 nonsyndromic orofacial cleft cases (814 cleft lip with or without cleft palate and 205 cleft palate only) and 2,159 controls recruited from 3 sites (Ethiopia, Ghana, and Nigeria). An additive logistic model was used to examine the joint effects of the genotype and GxSex interaction. Furthermore, we examined loci with suggestive significance (P < 1E-5) in the additive model for the effect of the GxSex interaction only. We identified a novel risk locus on chromosome 8p22 with genome-wide significant joint and GxSex interaction effects (rs2720555, p_2df = 1.16E-08, p_GxSex = 1.49E-09, odds ratio [OR] = 0.44, 95% CI = 0.34 to 0.57). For males, the risk of cleft lip with or without cleft palate at this locus decreases with additional copies of the minor allele (p < 0.0001, OR = 0.60, 95% CI = 0.48 to 0.74), but the effect is reversed for females (p = 0.0004, OR = 1.36, 95% CI = 1.15 to 1.60). We replicated the female-specific effect of this locus in an independent cohort (p = 0.037, OR = 1.30, 95% CI = 1.02 to 1.65), but no significant effect was found for the males (p = 0.29, OR = 0.86, 95% CI = 0.65 to 1.14). This locus is in topologically associating domain with craniofacially expressed and enriched genes during embryonic development. Rare coding mutations of some of these genes were identified in nsOFC cohorts through whole exome sequencing analysis. Our study is additional proof that genome-wide GxSex interaction analysis provides an opportunity for novel findings of loci and genes that contribute to the risk of nsOFCs.

The Association of Aberrant Expression of FGF1 and mTOR-S6K1 in Colorectal Cancer

Colorectal cancer (CRC) is one of the most frequent malignant neoplasms worldwide, and the effect of treatments is limited. Fibroblast growth factor 1 (FGF1) has been involved in a wide variety of several malignant diseases and takes part in the tumorigenesis of CRC. However, the function and mechanism of FGF1 in CRC remains elusive. In this study, the results indicated that FGF1 is elevated in CRC tissues and linked with poor prognosis (P < 0.001). In subgroup analysis of FGF1 in CRC, regardless of any clinic-factors except gender, high level FGF1 expression was associated with markedly shorter survival (P < 0.05). In addition, the expression of p-S6K1 and FGF1 was not associated in normal tissue (P = 0.781), but their expression was closely related in tumor tissue (P = 0.010). The oncogenic role of FGF1 was determined using in vitro and in vivo functional assays. FGF1 depletion inhibited the proliferation and migration of CRC cells in vitro and vivo. FGF1 was also significantly correlated with mTOR-S6K1 pathway on the gene and protein levels (P < 0.05). In conclusion, FGF1 acts as a tumor activator in CRC, and against FGF1 may provide a new visual field on treating CRC, especially for mTORC1-targeted resistant patients.

Identification of microRNAs and gene regulatory networks in cleft lip common in humans and mice

The etiology of cleft lip with/without cleft palate (CL/P), one of the most frequent craniofacial birth defects worldwide, is complicated by contributions of both genetic and environmental factors. Understanding the etiology of these conditions is essential for developing preventive strategies. This study thus aims to identify regulatory networks of microRNAs (miRNAs), transcriptional factors (TFs) and non-TF genes associated with cleft lip (CL) that are conserved in humans and mice. Notably, we found that miR-27b, miR-133b, miR-205, miR-376b and miR-376c were involved in the regulation of CL-associated gene expression in both humans and mice. Among the candidate miRNAs, the overexpression of miR-27b, miR-133b and miR-205, but not miR-376b and miR-376c, significantly inhibited cell proliferation through suppression of CL-associated genes (miR-27b suppressed PAX9 and RARA; miR-133b suppressed FGFR1, PAX7, and SUMO1; and miR-205 suppressed PAX9 and RARA) in cultured human and mouse lip mesenchymal cells. Taken together, our results suggest that elevated expression of miR-27b, miR-133b and miR-205 may play a crucial role in CL through the suppression of genes associated with CL.

The Fibroblast Growth Factor 9 (Fgf9) Participates in Palatogenesis by Promoting Palatal Growth and Elevation

Cleft palate, a common global congenital malformation, occurs due to disturbances in palatal growth, elevation, contact, and fusion during palatogenesis. The Fibroblast growth factor 9 (FGF9) mutation has been discovered in humans with cleft lip and palate. Fgf9 is expressed in both the epithelium and mesenchyme, with temporospatial diversity during palatogenesis. However, the specific role of Fgf9 in palatogenesis has not been extensively discussed. Herein, we used Ddx4-Cre mice to generate an Fgf9^–/– mouse model (with an Fgf9 exon 2 deletion) that exhibited a craniofacial syndrome involving a cleft palate and deficient mandibular size with 100% penetrance. A smaller palatal shelf size, delayed palatal elevation, and contact failure were investigated to be the intrinsic causes for cleft palate. Hyaluronic acid accumulation in the extracellular matrix (ECM) sharply decreased, while the cell density correspondingly increased in Fgf9^–/– mice. Additionally, significant decreases in cell proliferation were discovered in not only the palatal epithelium and mesenchyme but also among cells in Meckel’s cartilage and around the mandibular bone in Fgf9^–/– mice. Serial sections of embryonic heads dissected at embryonic day 14.5 (E14.5) were subjected to craniofacial morphometric measurement. This highlighted the reduced oral volume owing to abnormal tongue size and descent, and insufficient mandibular size, which disturbed palatal elevation in Fgf9^–/– mice. These results indicate that Fgf9 facilitates palatal growth and timely elevation by regulating cell proliferation and hyaluronic acid accumulation. Moreover, Fgf9 ensures that the palatal elevation process has adequate space by influencing tongue descent, tongue morphology, and mandibular growth.

Transcriptome Analysis of the Liver and Muscle Tissues of Black Carp (Mylopharyngodon piceus) of Different Growth Rates

In this study, we used RNA-seq to analyze the muscle and liver tissues of black carps (Mylopharyngodon piceus) of different growth rates from the same batch to evaluate their growth traits. We have two groups; they are the black carp group with fast-growth rate and the slow-growth rate. A total of 23,132 genes were enriched in the Gene Ontology analysis, and 285 related pathways were found in the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The KEGG pathway analysis showed significant differences in the expression of some genes involved in growth- and development-related metabolic pathways such as the FoxO signaling pathway, p53 signaling pathway, PI3K-Akt signaling pathway, apoptosis, TGF-β signaling pathway, and insulin signaling pathway. The numbers of differentially expressed genes in muscle and liver are 1913 and 1775. Nine of the differently expressed genes involved in the different growth traits and accuracy of the transcriptome data were validated using quantitative real-time PCR. We found that the expression levels of some growth-related genes were significantly higher in the fast-growth rate black carps than in the slow-growth rate black carps. The large number of transcriptome sequences obtained in this study has enriched the black carp gene resources, and the obtained differentially expressed genes and related pathway analysis provide valuable information for understanding the growth traits of the black carp.

Extracellular Matrix Composition and Remodeling: Current Perspectives on Secondary Palate Formation, Cleft Lip/Palate, and Palatal Reconstruction

Craniofacial development comprises a complex process in humans in which failures or disturbances frequently lead to congenital anomalies. Cleft lip with/without palate (CL/P) is a common congenital anomaly that occurs due to variations in craniofacial development genes, and may occur as part of a syndrome, or more commonly in isolated forms (non-syndromic). The etiology of CL/P is multifactorial with genes, environmental factors, and their potential interactions contributing to the condition. Rehabilitation of CL/P patients requires a multidisciplinary team to perform the multiple surgical, dental, and psychological interventions required throughout the patient's life. Despite progress, lip/palatal reconstruction is still a major treatment challenge. Genetic mutations and polymorphisms in several genes, including extracellular matrix (ECM) genes, soluble factors, and enzymes responsible for ECM remodeling (e.g., metalloproteinases), have been suggested to play a role in the etiology of CL/P; hence, these may be considered likely targets for the development of new preventive and/or therapeutic strategies. In this context, investigations are being conducted on new therapeutic approaches based on tissue bioengineering, associating stem cells with biomaterials, signaling molecules, and innovative technologies. In this review, we discuss the role of genes involved in ECM composition and remodeling during secondary palate formation and pathogenesis and genetic etiology of CL/P. We also discuss potential therapeutic approaches using bioactive molecules and principles of tissue bioengineering for state-of-the-art CL/P repair and palatal reconstruction.

Dynamic activation of Wnt, Fgf, and Hh signaling during soft palate development

The soft palate is a key component of the oropharyngeal complex that is critical for swallowing, breathing, hearing and speech. However, complete functional restoration in patients with cleft soft palate remains a challenging task. New insights into the molecular signaling network governing the development of soft palate will help to overcome these clinical challenges. In this study, we investigated whether key signaling pathways required for hard palate development are also involved in soft palate development in mice. We described the dynamic expression patterns of signaling molecules from well-known pathways, such as Wnt, Hh, and Fgf, during the development of the soft palate. We found that Wnt signaling is active throughout the development of soft palate myogenic sites, predominantly in cells of cranial neural crest (CNC) origin neighboring the myogenic cells, suggesting that Wnt signaling may play a significant role in CNC-myogenic cell-cell communication during myogenic differentiation in the soft palate. Hh signaling is abundantly active in early palatal epithelium, some myogenic cells, and the CNC-derived cells adjacent to the myogenic cells. Hh signaling gradually diminishes during the later stages of soft palate development, indicating its involvement mainly in early embryonic soft palate development. Fgf signaling is expressed most prominently in CNC-derived cells in the myogenic sites and persists until later stages of embryonic soft palate development. Collectively, our results highlight a network of Wnt, Hh, and Fgf signaling that may be involved in the development of the soft palate, particularly soft palate myogenesis. These findings provide a foundation for future studies on the functional significance of these signaling pathways individually and collectively in regulating soft palate development.

Craniofacial malformations and their association with brain development: the importance of a multidisciplinary approach for treatment

The craniofacial complex develops mainly in the first trimester of pregnancy, but its final shaping and the development of the teeth extend into the second and third trimesters. It is intimately connected with the development of the brain because of the crucial role the cranial neural crest cells play and the fact that many signals which control craniofacial development originate in the brain and vice versa. As a result, malformations of one organ may affect the development of the other. Similarly, there are developmental connections between the craniofacial complex and the teeth. Craniofacial anomalies are either isolated, resulting from abnormal development of the first two embryonic pharyngeal arches, or part of multiple malformation syndromes affecting many other organs. They may stem from gene mutations, chromosomal aberrations or from environmental causes induced by teratogens. The craniofacial morphologic changes are generally cosmetic, but they often interfere with important functions such as chewing, swallowing and respiration. In addition, they may cause hearing or visual impairment. In this review we discussed only a small number of craniofacial malformations and barely touched upon related anomalies of dentition. Following a brief description of the craniofacial development, we discussed oral clefts, craniofacial microsomia, teratogens that may interfere with craniofacial development resulting in different malformations, the genetically determined craniosynostoses syndromes and few other relatively common syndromes that, in addition to the craniofacial complex, also affect other organs. The understanding of these malformations is important in dentistry as dentists play an integral role in their diagnosis and multidisciplinary treatment.

A functional variant alters binding of activating protein 1 regulating expression of FGF7 gene associated with chronic obstructive pulmonary disease

Background

Genome-wide association studies (GWASs) of a large cohort of subjects with chronic obstructive pulmonary disease (COPD) have successfully identified multiple risk genes, including fibroblast growth factor 7 (FGF7). However, the underlying molecular mechanism influencing function of FGF7 and risk of COPD remains further study.

Methods

In this study, we replicated the genetic association of variants near the FGF7 gene in 258 Chinese Han patients with COPD and 311 healthy controls. Additionally, we functionally evaluated a candidate causal variant upstream of the FGF7 gene.

Results

The most significant association was observed at rs12905203 (P = 5.9 × 10^− 3, odd ratio, OR = 1.516) that explains associations of previously reported variants at the FGF7 locus. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR) assays showed that the risk allele of the variant was bound to activator protein 1 transcription factors (c-Fos and c-Jun) with a significantly reduced affinity and associated with decreased mRNA expression of FGF7 in fibroblast cells at both resting and PMA/Ionomycin-stimulated conditions. Overexpression of c-Fos and c-Jun proteins or stimulation with PMA/Ionomycin significantly increases mRNA expression of FGF7 in fibroblast cells. Bioinformatic analysis showed that the variant overlaps with multiple genetic regulatory marks, suggesting the regulatory DNA element might function as an enhancer for the FGF7 gene. Luciferase enhancer activity assays demonstrated that the DNA sequences carrying the variant produce enhancer activity while the risk allele of the variant reduces its activity.

Conclusions

In this study, we demonstrated a consistent association of the FGF7 gene with COPD and mechanistically characterized a candidate functional variant upstream of the FGF7 gene. These data highlighted the important role of the risk variant and the FGF7 gene in influencing risk for COPD.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0761-7) contains supplementary material, which is available to authorized users.

Roles of FGF8 subfamily in embryogenesis and oral‑maxillofacial diseases (Review)

Fibroblast growth factors (FGFs) are diffusible polypeptides released by a variety of cell types. FGF8 subfamily members regulate embryonic development processes through controlling progenitor cell growth and differentiation, and are also functional in adults in tissue repair to maintain tissue homeostasis. FGF8 family members exhibit unique binding affinities with FGF receptors and tissue distribution patterns. Increasing evidence suggests that, by regulating multiple cellular signaling pathways, alterations in the FGF8 subfamily are involved in craniofacial development, odontogenesis, tongue development and salivary gland branching morphogenesis. Aberrant FGF signaling transduction, caused by mutations as well as abnormal expression or isoform splicing, plays an important role in the development of oral diseases. Targeting FGF8 subfamily members provides a new promising strategy for the treatment of oral diseases. The aim of this review was to summarize the aberrant regulations of FGF8 subfamily members and their potential implications in oral‑maxillofacial diseases.

TGF-β Signaling and the Epithelial-Mesenchymal Transition during Palatal Fusion

Signaling by transforming growth factor (TGF)-β plays an important role in development, including in palatogenesis. The dynamic morphological process of palatal fusion occurs to achieve separation of the nasal and oral cavities. Critically and specifically important in palatal fusion are the medial edge epithelial (MEE) cells, which are initially present at the palatal midline seam and over the course of the palate fusion process are lost from the seam, due to cell migration, epithelial-mesenchymal transition (EMT), and/or programed cell death. In order to define the role of TGF-β signaling during this process, several approaches have been utilized, including a small interfering RNA (siRNA) strategy targeting TGF-β receptors in an organ culture context, the use of genetically engineered mice, such as Wnt1-cre/R26R double transgenic mice, and a cell fate tracing through utilization of cell lineage markers. These approaches have permitted investigators to distinguish some specific traits of well-defined cell populations throughout the palatogenic events. In this paper, we summarize the current understanding on the role of TGF-β signaling, and specifically its association with MEE cell fate during palatal fusion. TGF-β is highly regulated both temporally and spatially, with TGF-β3 and Smad2 being the preferentially expressed signaling molecules in the critical cells of the fusion processes. Interestingly, the accessory receptor, TGF-β type 3 receptor, is also critical for palatal fusion, with evidence for its significance provided by Cre-lox systems and siRNA approaches. This suggests the high demand of ligand for this fine-tuned signaling process. We discuss the new insights in the fate of MEE cells in the midline epithelial seam (MES) during the palate fusion process, with a particular focus on the role of TGF-β signaling.