Genome-wide association study identifies multiple susceptibility loci for craniofacial microsomia

FBLN2 is associated with Goldenhar syndrome and is essential for cranial neural crest cell development

Goldenhar syndrome, a rare craniofacial malformation, is characterized by developmental anomalies in the first and second pharyngeal arches. Its etiology is considered to be heterogenous, including both genetic and environmental factors that remain largely unknown. To further elucidate the genetic cause in a five-generation Goldenhar syndrome pedigree and exploit the whole-exome sequencing (WES) data of this pedigree, we generated collapsed haplotype pattern markers based on WES and employed rare variant nonparametric linkage analysis. FBLN2 was identified as a candidate gene via analysis of WES data across the significant linkage region. A fbln2 knockout zebrafish line was established by CRISPR/Cas9 to examine the gene's role in craniofacial cartilage development. fbln2 was expressed specifically in the mandible during the zebrafish early development, while fbln2 knockout zebrafish exhibited craniofacial malformations with abnormal chondrocyte morphologies. Functional studies revealed that fbln2 knockout caused abnormal chondrogenic differentiation, apoptosis, and proliferation of cranial neural crest cells (CNCCs), and downregulated the bone morphogenic protein (BMP) signaling pathway in the zebrafish model. This study demonstrates the role of FBLN2 in CNCC development and BMP pathway regulation, and highlights FBLN2 as a candidate gene for Goldenhar syndrome, which may have implications for the selection of potential screening targets and the development of treatments for conditions like microtia-atresia.

Insights into Craniofacial Development and Anomalies: Exploring Fgf Signaling in Zebrafish Models

PURPOSE OF REVIEW

To illustrate the value of using zebrafish to understand the role of the Fgf signaling pathway during craniofacial skeletal development under normal and pathological conditions.

RECENT FINDINGS

Recent data obtained from studies on zebrafish have demonstrated the genetic redundancy of Fgf signaling pathway and have identified new molecular partners of this signaling during the early stages of craniofacial skeletal development. Studies on zebrafish models demonstrate the involvement of the Fgf signaling pathway at every stage of craniofacial development. They particularly emphasize the central role of Fgf signaling pathway during the early stages of the development, which significantly impacts the formation of the various structures making up the craniofacial skeleton. This partly explains the craniofacial abnormalities observed in disorders associated with FGF signaling. Future research efforts should focus on investigating zebrafish Fgf signaling during more advanced stages, notably by establishing zebrafish models expressing mutations responsible for diseases such as craniosynostoses.

Genotype-phenotype associations in microtia: a systematic review

BACKGROUND

Microtia is a congenital ear malformation that can occur as isolated microtia or as part of a syndrome. The etiology is currently poorly understood, although there is strong evidence that genetics has a role in the occurrence of microtia. This systematic review aimed to determine the genes involved and the abnormalities in microtia patients' head and neck regions.

METHODS

We used seven search engines to search all known literature on the genetic and phenotypic variables associated with the development or outcome of microtia. The identified publications were screened and selected based on inclusion and exclusion criteria and assessed for methodological quality using the Joanna Briggs Institute (JBI) critical appraisal tools. We found 40 papers in this systematic review with phenotypic data in microtia involving 1459 patients and 30 articles containing genetic data involved in microtia.

RESULT

The most common accompanying phenotype of all microtia patients was external ear canal atresia, while the most common head and neck abnormalities were the auricular, mental, and oral regions. The most common syndrome found was craniofacial microsomia syndrome. In the syndromic microtia group, the most common genes were TCOF1 (43.75%), SIX2 (4.69%), and HSPA9 (4.69%), while in the non-syndromic microtia group, the most frequently found gene was GSC exon 2 (25%), FANCB (16.67%), HOXA2 (8.33%), GSC exon 3 (8.33%), MARS1 (8.33%), and CDT1 (8.33%).

CONCLUSIONS

Our systematic review shows some genes involved in the microtia development, including TCOF1, SIX2, HSPA9, GSC exon 2, FANCB, HOXA2, GSC exon 3, MARS1, and CDT1 genes. We also reveal a genotype-phenotype association in microtia. In addition, further studies with more complete and comprehensive data are needed, including patients with complete data on syndromes, phenotypes, and genotypes.

Profiling of Long Non-Coding RNAs in Auricular Cartilage of Patients with Isolated Microtia

Introduction: Microtia is the second most common maxillofacial birth defect worldwide. However, the involvement of long non-coding RNAs (lncRNAs) in isolated microtia is not well understood. This study aimed at identifying lncRNAs that regulate the expression of genes associated with isolated microtia. Methods: We used our microarray data to analyze the expression pattern of lncRNA in the auricular cartilage tissues from 10 patients diagnosed with isolated microtia, alongside 15 control subjects. Five lncRNAs were chosen for validation using real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Results: We identified 4651 differentially expressed lncRNAs in the auricular cartilage from patients with isolated microtia. By Gene Ontology/Kyoto Encyclopedia of Genes and Genomes pathway (GO/KEGG) analysis, we identified 27 differentially expressed genes enriched in pathways associated with microtia. In addition, we predicted 9 differentially expressed genes as potential cis-acting targets of 12 differentially expressed lncRNAs. Our findings by qRT-PCR demonstrate significantly elevated expression levels of ZFAS1 and DAB1-AS1, whereas ADIRF-AS1, HOTAIRM1, and EPB41L4A-AS1 exhibited significantly reduced expression levels in the auricular cartilage tissues of patients with isolated microtia. Conclusions: Our study sheds light on the potential involvement of lncRNAs in microtia and provides a basis for further investigation into their functional roles and underlying mechanisms.

Transcriptome analyses of murine right and left maxilla-mandibular complex

OBJECTIVE

The objective of the study was to investigate differential gene expression between murine right and left maxilla-mandibular (MxMn) complexes.

SETTING AND SAMPLE POPULATION

Wild-type (WT) C57BL/6 embryonic (E) day 14.5 (n = 3) and 18.5 (n = 3) murine embryos.

METHODS

The E14.5 and 18.5 embryos were harvested and hemi-sectioned the MxMn complexes into right and left halves in the mid-sagittal plane. We isolated total RNA using Trizol reagent and further purified using the RNA-easy kit (QIAGEN). We confirmed equal expression of house-keeping genes in right and left halves using RT-PCR and then performed paired-end whole mRNA sequencing in LC Sciences (Houston, TX) followed by differential transcript analyses (>1 or <-1 log fold change; p < .05; q < .05; and FPKM >0.5 in 2/3 samples). The Mouse Genome Informatics and Online Mendelian Inheritance in Man databases as well as gnomAD constraint scores were used to prioritize differentially expressed transcripts.

RESULTS

There were 19 upregulated and 19 downregulated transcripts at E14.5 and 8 upregulated and 17 downregulated transcripts at E18.5 time-points. These differentially expressed transcripts were statistically significant and shown to be associated with craniofacial phenotypes in mouse models. These transcripts also have significant gnomAD constraint scores and are enriched in biological processes critical for embryogenesis.

CONCLUSIONS

We identified significant differential expression of transcripts between E14.5 and 18.5 murine right and left MxMn complexes. These findings when extrapolated to humans, they may provide a biological basis for facial asymmetry. Further experiments are required to validate these findings in murine models with craniofacial asymmetry.

Hemifacial microsomia is linked to a rare homozygous variant V162I in FRK and validated in zebrafish

OBJECTIVES

Hemifacial microsomia (HFM) is a common birth defect involving the first and second branchial arch derivatives. Although several chromosomal abnormalities and causal gene variants have been identified, genetic etiologies in a majority of cases with HFM remain unknown. This study aimed to identify genetic mutations in affected individuals with HFM.

METHODS

Whole-exome sequencing and bioinformatics analysis were performed for 16 affected individuals and their family members. Sanger sequencing was applied for confirmation of selected mutations. Zebrafish embryos were used for in situ hybridization of candidate gene, microinjection with antisense morpholino, and cartilage staining.

RESULTS

A homozygous missense mutation (c.484G > A; p.V162I) in the FRK gene was identified in an 18-year-old girl with HFM and dental abnormalities. Heterozygous mutation of this mutation was identified in her parents, who are first cousins in a consanguineous family. FRK is highly expressed in the Meckel's cartilage during embryonic development in mouse and zebrafish. Knockdown of frk in zebrafish showed a lower length and width ratio of Meckel's cartilage, abnormal mandibular jaw joint, and disorganized ceratobranchial cartilage and bone.

CONCLUSIONS

We identified a recessive variant in the FRK gene as a novel candidate gene for a patient with HFM and mandibular hypoplasia and revealed its effects on craniofacial and embryonic development in zebrafish.

The etiology, clinical features, and treatment options of hemifacial microsomia

The second most frequent craniomaxillofacial congenital deformity is hemifacial microsomia (HFM). Patients often accompany short mandible, ear dysplasia, facial nerve, and soft tissue dysplasia. The etiology of HFM is not fully understood. To organize the possible up-to-date information on the etiology, craniofacial phenotypes, and therapeutic alternatives in order to fully comprehend the HFM. Reviewing the potential causes, exploring the clinical features of HFM and summarizing the available treatment options. Vascular malformation, Meckel's cartilage abnormalities, and cranial neural crest cells (CNCCs) abnormalities are three potential etiology hypotheses. The commonly used clinical classification for HFM is OMENS, OMENS-plus, and SAT. Other craniofacial anomalies, like dental defects, and zygomatic deformities, are still not precisely documented in the classification. Patients with moderate phenotypes may not need any treatment from infancy through adulthood. However, patients with severe HFM require to undergo multiple surgeries to address facial asymmetries, such as mandibular distraction osteogenesis (MDO), autologous costochondral rib graft (CCG), orthodontic and orthognathic treatment, and facial soft tissue reconstruction. It is anticipated that etiology research will examine the pathogenic mechanism of HFM. A precise treatment for HFM may be possible with thoroughly documented phenotypes and a pathogenic diagnosis.

Evaluation of Research Diagnostic Criteria in Craniofacial Microsomia

Characteristics of patients with craniofacial microsomia (CFM) vary in type and severity. The diagnosis is based on phenotypical assessment and no consensus on standardized clinical diagnostic criteria is available. The use of diagnostic criteria could improve research and communication among patients and healthcare professionals. Two sets of phenotypic criteria for research were independently developed and based on multidisciplinary consensus: the FACIAL and ICHOM criteria. This study aimed to assess the sensitivity of both criteria with an existing global multicenter database of patients with CFM and study the characteristics of patients that do not meet the criteria. A total of 730 patients with CFM from were included. Characteristics of the patients were extracted, and severity was graded using the O.M.E.N.S. and Pruzansky-Kaban classification. The sensitivity of the FACIAL and ICHOM was respectively 99.6% and 94.4%. The Cohen's kappa of 0.38 indicated a fair agreement between both criteria. Patients that did not fulfill the FACIAL criteria had facial asymmetry without additional features. It can be concluded that the FACIAL and ICHOM criteria are accurate criteria to describe patients with CFM. Both criteria could be useful for future studies on CFM to create comparable and reproducible outcomes.

Germline modifiers of the tumor immune microenvironment implicate drivers of cancer risk and immunotherapy response

With the continued promise of immunotherapy for treating cancer, understanding how host genetics contributes to the tumor immune microenvironment (TIME) is essential to tailoring cancer screening and treatment strategies. Here, we study 1084 eQTLs affecting the TIME found through analysis of The Cancer Genome Atlas and literature curation. These TIME eQTLs are enriched in areas of active transcription, and associate with gene expression in specific immune cell subsets, such as macrophages and dendritic cells. Polygenic score models built with TIME eQTLs reproducibly stratify cancer risk, survival and immune checkpoint blockade (ICB) response across independent cohorts. To assess whether an eQTL-informed approach could reveal potential cancer immunotherapy targets, we inhibit CTSS, a gene implicated by cancer risk and ICB response-associated polygenic models; CTSS inhibition results in slowed tumor growth and extended survival in vivo. These results validate the potential of integrating germline variation and TIME characteristics for uncovering potential targets for immunotherapy.

FOXI3 pathogenic variants cause one form of craniofacial microsomia

Craniofacial microsomia (CFM; also known as Goldenhar syndrome), is a craniofacial developmental disorder of variable expressivity and severity with a recognizable set of abnormalities. These birth defects are associated with structures derived from the first and second pharyngeal arches, can occur unilaterally and include ear dysplasia, microtia, preauricular tags and pits, facial asymmetry and other malformations. The inheritance pattern is controversial, and the molecular etiology of this syndrome is largely unknown. A total of 670 patients belonging to unrelated pedigrees with European and Chinese ancestry with CFM, are investigated. We identify 18 likely pathogenic variants in 21 probands (3.1%) in FOXI3. Biochemical experiments on transcriptional activity and subcellular localization of the likely pathogenic FOXI3 variants, and knock-in mouse studies strongly support the involvement of FOXI3 in CFM. Our findings indicate autosomal dominant inheritance with reduced penetrance, and/or autosomal recessive inheritance. The phenotypic expression of the FOXI3 variants is variable. The penetrance of the likely pathogenic variants in the seemingly dominant form is reduced, since a considerable number of such variants in affected individuals were inherited from non-affected parents. Here we provide suggestive evidence that common variation in the FOXI3 allele in trans with the pathogenic variant could modify the phenotypic severity and accounts for the incomplete penetrance.

COMMD10 Is Essential for Neural Plate Development during Embryogenesis

The COMMD (copper metabolism MURR1 domain containing) family includes ten structurally conserved proteins (COMMD1 to COMMD10) in eukaryotic multicellular organisms that are involved in a diverse array of cellular and physiological processes, including endosomal trafficking, copper homeostasis, and cholesterol metabolism, among others. To understand the role of COMMD10 in embryonic development, we used Commd10Tg(Vav1-icre)A2Kio/J mice, where the Vav1-cre transgene is integrated into an intron of the Commd10 gene, creating a functional knockout of Commd10 in homozygous mice. Breeding heterozygous mice produced no COMMD10-deficient (Commd10Null) offspring, suggesting that COMMD10 is required for embryogenesis. Analysis of Commd10Null embryos demonstrated that they displayed stalled development by embryonic day 8.5 (E8.5). Transcriptome analysis revealed that numerous neural crest-specific gene markers had lower expression in mutant versus wild-type (WT) embryos. Specifically, Commd10Null embryos displayed significantly lower expression levels of a number of transcription factors, including a major regulator of the neural crest, Sox10. Moreover, several cytokines/growth factors involved in early embryonic neurogenesis were also lower in mutant embryos. On the other hand, Commd10Null embryos demonstrated higher expression of genes involved in tissue remodeling and regression processes. Taken together, our findings show that Commd10Null embryos die by day E8.5 due to COMMD10-dependent neural crest failure, revealing a new and critical role for COMMD10 in neural development.

Exploration of Novel Genetic Evidence and Clinical Significance Into Hemifacial Microsomia Pathogenesis

The authors browsed through past genetic findings in hemifacial microsomia along with our previously identified mutations in ITGB4 and PDE4DIP from whole genome sequencing of hemifacial microsomia patients. Wondering whether these genes influence mandibular bone modeling by regulation on osteogenesis, the authors approached mechanisms of hemifacial microsomia through this investigation into gene knockdown effects in vitro. MC3T3E1 cells were divided into 5 groups: the negative control group without osteogenesis induction or siRNA, the positive control group with only osteogenesis induction, and 3 gene silenced groups with both osteogenesis induction and siRNA. Validation of transfection was through fluorescence microscopy and quantitative real-time Polymerase chain reaction on knockdown efficiency. Changes in expression levels of the 3 genes during osteogenesis and impact of Itgb4 and Pde4dip knockdown on osteogenesis were examined by quantitative real-time Polymerase chain reaction, alkaline phosphatase, and alizarin red staining. Elevation of osteogenic genes Alpl, Col1a1, Bglap, Spp1, and Runx2 verified successful osteogenesis. Both genes were upregulated under osteogenic induction, while they had different trends over time. Intracellular fluorophores under microscope validated successful transfection and si-m-Itgb4_003, si-m-Pde4dip_002 had satisfactory knockdown effects. During osteogenesis, Pde4dip knockdown enhanced Spp1 expression (1.95±0.13 folds, P =0.045). The authors speculated that these genes may have different involvements in osteogenesis. Stimulated expression of Spp1 by Pde4dip knockdown may suggest that Pde4dip inhibits osteogenesis.

Predicting Modifiers of Genotype-Phenotype Correlations in Craniofacial Development

Most human birth defects are phenotypically variable even when they share a common genetic basis. Our understanding of the mechanisms of this variation is limited, but they are thought to be due to complex gene-environment interactions. Loss of the transcription factor Gata3 associates with the highly variable human birth defects HDR syndrome and microsomia, and can lead to disruption of the neural crest-derived facial skeleton. We have demonstrated that zebrafish gata3 mutants model the variability seen in humans, with genetic background and candidate pathways modifying the resulting phenotype. In this study, we sought to use an unbiased bioinformatic approach to identify environmental modifiers of gata3 mutant craniofacial phenotypes. The LINCs L1000 dataset identifies chemicals that generate differential gene expression that either positively or negatively correlates with an input gene list. These chemicals are predicted to worsen or lessen the mutant phenotype, respectively. We performed RNA-seq on neural crest cells isolated from zebrafish across control, Gata3 loss-of-function, and Gata3 rescue groups. Differential expression analyses revealed 551 potential targets of gata3. We queried the LINCs database with the 100 most upregulated and 100 most downregulated genes. We tested the top eight available chemicals predicted to worsen the mutant phenotype and the top eight predicted to lessen the phenotype. Of these, we found that vinblastine, a microtubule inhibitor, and clofibric acid, a PPAR-alpha agonist, did indeed worsen the gata3 phenotype. The Topoisomerase II and RNA-pol II inhibitors daunorubicin and triptolide, respectively, lessened the phenotype. GO analysis identified Wnt signaling and RNA polymerase function as being enriched in our RNA-seq data, consistent with the mechanism of action of some of the chemicals. Our study illustrates multiple potential pathways for Gata3 function, and demonstrates a systematic, unbiased process to identify modifiers of genotype-phenotype correlations.

GATA3 mediates nonclassical β-catenin signaling in skeletal cell fate determination and ectopic chondrogenesis

Skeletal precursors are mesenchymal in origin and can give rise to distinct sublineages. Their lineage commitment is modulated by various signaling pathways. The importance of Wnt signaling in skeletal lineage commitment has been implicated by the study of β-catenin-deficient mouse models. Ectopic chondrogenesis caused by the loss of β-catenin leads to a long-standing belief in canonical Wnt signaling that determines skeletal cell fate. As β-catenin has other functions, it remains unclear whether skeletogenic lineage commitment is solely orchestrated by canonical Wnt signaling. The study of the Wnt secretion regulator Gpr177/Wntless also raises concerns about current knowledge. Here, we show that skeletal cell fate is determined by β-catenin but independent of LEF/TCF transcription. Genomic and bioinformatic analyses further identify GATA3 as a mediator for the alternative signaling effects. GATA3 alone is sufficient to promote ectopic cartilage formation, demonstrating its essential role in mediating nonclassical β-catenin signaling in skeletogenic lineage specification.

Extending the PAX1 spectrum: a dominantly inherited variant causes oculo-auriculo-vertebral syndrome

Oculo-auriculo-vertebral syndrome (OAVS) is a clinically heterogeneous disorder, with both genetic and environmental contributors. Multiple genes have been associated with OAVS and common molecular pathways, such as retinoic acid and the PAX-SIX-EYA-DACH (PSED) network, are being implicated in the disease pathophysiology. Biallelic homozygous nonsense or hypomorphic missense mutations in PAX1 cause otofaciocervical syndrome type 2 (OTFCS2), a similar but more severe multi-system disorder that can be accompanied by severe combined immunodeficiency due to thymic aplasia. Here we have identified a multi-generational family with mild features of OAVS segregating a heterozygous frameshift in PAX1. The four base duplication is expected to result in nonsense-mediated decay, and therefore cause a null allele. While there was full penetrance of the variant, expressivity of facial and ear features were variable. Our findings indicate there can be monoallelic and biallelic disorders associated with PAX1, and further implicate the PSED network in OAVS.

Whole exome sequencing of high-risk neuroblastoma identifies novel non-synonymous variants

Neuroblastoma (NBL), one of the main death-causing cancers in children, is known for its remarkable genetic heterogeneity and varied patient outcome spanning from spontaneous regression to widespread disease. Specific copy number variations and single gene rearrangements have been proven to be associated with biological behavior and prognosis; however, there is still an unmet need to enlarge the existing armamentarium of prognostic and therapeutic targets. We performed whole exome sequencing (WES) of samples from 18 primary tumors and six relapse samples originating from 18 NBL patients. Our cohort consists of 16 high-risk, one intermediate, and one very low risk patient. The obtained results confirmed known mutational hotspots in ALK and revealed other non-synonymous variants of NBL-related genes (TP53, DMD, ROS, LMO3, PRUNE2, ERBB3, and PHOX2B) and of genes cardinal for other cancers (KRAS, PIK3CA, and FLT3). Beyond, GOSeq analysis determined genes involved in biological adhesion, neurological cell-cell adhesion, JNK cascade, and immune response of cell surface signaling pathways. We were able to identify novel coding variants present in more than one patient in nine biologically relevant genes for NBL, including TMEM14B, TTN, FLG, RHBG, SHROOM3, UTRN, HLA-DRB1, OR6C68, and XIRP2. Our results may provide novel information about genes and signaling pathways relevant for the pathogenesis and clinical course in high-risk NBL.

Mutated KLF4(K409Q) in meningioma binds STRs and activates FGF3 gene expression

Krüppel-like factor 4 (KLF4) is a transcription factor that has been proven necessary for both induction and maintenance of pluripotency and self-renewal. Whole-genome sequencing defined a unique mutation in KLF4 (KLF4K409Q) in human meningiomas. However, the molecular mechanism of this tumor-specific KLF4 mutation is unknown. Using genome-wide high-throughput and focused quantitative transcriptional approaches in human cell lines, primary meningeal cells, and meningioma tumor tissue, we found that a change in the evolutionarily conserved DNA-binding domain of KLF4 alters its DNA recognition preference, resulting in a shift in downstream transcriptional activity. In the KLF4K409Q-specific targets, the normally silent fibroblast growth factor 3 (FGF3) is activated. We demonstrated a neomorphic function of KLF4K409Q in stimulating FGF3 transcription through binding to its promoter and in using short tandem repeats (STRs) located within the locus as enhancers.

An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations

Microtia is a congenital malformation that encompasses mild hypoplasia to complete loss of the external ear, or pinna. Although the contribution of genetic variation and environmental factors to microtia remains elusive, Amerindigenous populations have the highest reported incidence. Here, using both transmission disequilibrium tests and association studies in microtia trios (parents and affected child) and microtia cohorts enrolled in Latin America, we map an ∼10-kb microtia locus (odds ratio = 4.7; P = 6.78e-18) to the intergenic region between Roundabout 1 (ROBO1) and Roundabout 2 (ROBO2) (chr3: 78546526 to 78555137). While alleles at the microtia locus significantly increase the risk of microtia, their penetrance is low (<1%). We demonstrate that the microtia locus contains a polymorphic complex repeat element that is expanded in affected individuals. The locus is located near a chromatin loop region that regulates ROBO1 and ROBO2 expression in induced pluripotent stem cell–derived neural crest cells. Furthermore, we use single nuclear RNA sequencing to demonstrate ROBO1 and ROBO2 expression in both fibroblasts and chondrocytes of the mature human pinna. Because the microtia allele is enriched in Amerindigenous populations and is shared by some East Asian subjects with craniofacial malformations, we propose that both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas and that the high incidence of microtia among Amerindigenous populations reflects the population bottleneck that occurred during the migration out of Eurasia.

GATA3 is essential for separating patterning domains during facial morphogenesis

Neural crest cells (NCCs) within the mandibular and maxillary prominences of the first pharyngeal arch are initially competent to respond to signals from either region. However, mechanisms that are only partially understood establish developmental tissue boundaries to ensure spatially correct patterning. In the 'hinge and caps' model of facial development, signals from both ventral prominences (the caps) pattern the adjacent tissues whereas the intervening region, referred to as the maxillomandibular junction (the hinge), maintains separation of the mandibular and maxillary domains. One cap signal is GATA3, a member of the GATA family of zinc-finger transcription factors with a distinct expression pattern in the ventral-most part of the mandibular and maxillary portions of the first arch. Here, we show that disruption of Gata3 in mouse embryos leads to craniofacial microsomia and syngnathia (bony fusion of the upper and lower jaws) that results from changes in BMP4 and FGF8 gene regulatory networks within NCCs near the maxillomandibular junction. GATA3 is thus a crucial component in establishing the network of factors that functionally separate the upper and lower jaws during development.

Natural genetic variation in Drosophila melanogaster reveals genes associated with Coxiella burnetii infection

The gram-negative bacterium Coxiella burnetii is the causative agent of Query (Q) fever in humans and coxiellosis in livestock. Host genetics are associated with C. burnetii pathogenesis both in humans and animals; however, it remains unknown if specific genes are associated with severity of infection. We employed the Drosophila Genetics Reference Panel to perform a genome-wide association study to identify host genetic variants that affect host survival to C. burnetii infection. The genome-wide association study identified 64 unique variants (P < 10⁻⁵) associated with 25 candidate genes. We examined the role each candidate gene contributes to host survival during C. burnetii infection using flies carrying a null mutation or RNAi knockdown of each candidate. We validated 15 of the 25 candidate genes using at least one method. This is the first report establishing involvement of many of these genes or their homologs with C. burnetii susceptibility in any system. Among the validated genes, FER and tara play roles in the JAK/STAT, JNK, and decapentaplegic/TGF-β signaling pathways which are components of known innate immune responses to C. burnetii infection. CG42673 and DIP-ε play roles in bacterial infection and synaptic signaling but have no previous association with C. burnetii pathogenesis. Furthermore, since the mammalian ortholog of CG13404 (PLGRKT) is an important regulator of macrophage function, CG13404 could play a role in host susceptibility to C. burnetii through hemocyte regulation. These insights provide a foundation for further investigation regarding the genetics of C. burnetii susceptibility across a wide variety of hosts.

A high level of KLF12 causes folic acid-resistant neural tube defects by activating the Shh signalling pathway in mice

Although adequate periconceptional folic acid (FA) supplementation has reduced the occurrence of pregnancies affected by neural tube defects (NTDs), the mechanisms underlying FA-resistant NTDs are poorly understood, and thus NTDs still remain a global public health concern. A high level of Krüppel-like factor 12 (KLF12) exerts deleterious effects on heath in most cases, but evidence for its roles in development has not been published. We observed KLF12-overexpressing mice showed disturbed neural tube development. KLF12-overexpressing foetuses died in utero at approximately 10.5 days post coitus, with 100% presenting cranial NTDs. Neither FA nor formate promoted normal neural tube closure in mutant foetuses. The RNA-seq results showed that a high level of KLF12 caused NTDs in mice via overactivating the sonic hedgehog (Shh) signalling pathway, leading to the upregulation of patched 1, GLI-Krüppel family member GLI1, hedgehog-interacting protein, etc., while FA metabolism-related enzymes did not express differently. PF-5274857, an antagonist of the Shh signalling pathway, significantly promoted dorsolateral hinge point formation and partially rescued the NTDs. The regulatory hierarchy between a high level of KLF12 and FA-resistant NTDs might provide new insights into the diagnosis and treatment of unexplained NTDs in the future.

Whole-Exome Sequencing Reveals Rare Germline Mutations in Patients With Hemifacial Microsomia

Hemifacial microsomia (HFM) is a rare congenital disease characterized by a spectrum of craniomaxillofacial malformations, including unilateral hypoplasia of the mandible and surrounding structures. Genetic predisposition for HFM is evident but the causative genes have not been fully understood. Thus, in the present study, we used whole-exome sequencing to screen 52 patients with HFM for rare germline mutations. We revealed 3,341 rare germline mutations in this patient cohort, including those in 13 genes previously shown to be associated with HFM. Among these HFM-related genes, NID2 was most frequently mutated (in 3/52 patients). PED4DIP, which has not been previously associated with HFM, exhibited rare variants most frequently (in 7/52 patients). Pathway enrichment analysis of genes that were mutated in >2 patients predicted the "laminin interactions" pathway to be most significantly disrupted, predominantly by mutations in ITGB4, NID2, or LAMA5. In summary, this study is the first to identify rare germline mutations in HFM. The likely disruptions in the signaling pathways due to the mutations reported here may be considered potential causes of HFM.

Variation in phenotypes from a Bmp-Gata3 genetic pathway is modulated by Shh signaling

We sought to understand how perturbation of signaling pathways and their targets generates variable phenotypes. In humans, GATA3 associates with highly variable defects, such as HDR syndrome, microsomia and choanal atresia. We previously characterized a zebrafish point mutation in gata3 with highly variable craniofacial defects to the posterior palate. This variability could be due to residual Gata3 function, however, we observe the same phenotypic variability in gata3 null mutants. Using hsp:GATA3-GFP transgenics, we demonstrate that Gata3 function is required between 24 and 30 hpf. At this time maxillary neural crest cells fated to generate the palate express gata3. Transplantation experiments show that neural crest cells require Gata3 function for palatal development. Via a candidate approach, we determined if Bmp signaling was upstream of gata3 and if this pathway explained the mutant's phenotypic variation. Using BRE:d2EGFP transgenics, we demonstrate that maxillary neural crest cells are Bmp responsive by 24 hpf. We find that gata3 expression in maxillary neural crest requires Bmp signaling and that blocking Bmp signaling, in hsp:DN-Bmpr1a-GFP embryos, can phenocopy gata3 mutants. Palatal defects are rescued in hsp:DN-Bmpr1a-GFP;hsp:GATA3-GFP double transgenic embryos, collectively demonstrating that gata3 is downstream of Bmp signaling. However, Bmp attenuation does not alter phenotypic variability in gata3 loss-of-function embryos, implicating a different pathway. Due to phenotypes observed in hypomorphic shha mutants, the Sonic Hedgehog (Shh) pathway was a promising candidate for this pathway. Small molecule activators and inhibitors of the Shh pathway lessen and exacerbate, respectively, the phenotypic severity of gata3 mutants. Importantly, inhibition of Shh can cause gata3 haploinsufficiency, as observed in humans. We find that gata3 mutants in a less expressive genetic background have a compensatory upregulation of Shh signaling. These results demonstrate that the level of Shh signaling can modulate the phenotypes observed in gata3 mutants.

Changes in the Transcriptome and Proteome of Cartilage in Microtia

ABSTRACT

Congenital microtia is a severe physiological defect and is among the most common craniofacial defects. It is characterized by severe auricle dysplasia, external auditory canal atresia or stenosis, and middle ear malformation, though inner ear development is mostly normal with some hearing occurring through bone conduction. Auricular reconstruction is the only treatment for congenital microtia. In this study, the authors integrated messenger ribonucleic acid and mass spectrometry data of cartilage obtained from the affected and unaffected sides of 16 unilateral microtia patients who had undergone ear reconstruction surgery. The authors next performed functional analyses to investigate differences in the proteome of the affected and unaffected ears to elicit molecular pathways involved in microtia pathogenesis. The authors collected 16 pairs samples. Proteomic and transcriptomic analyses identified 47 genes that were differentially expressed in affected and unaffected cartilage. Integrated pathway analysis implicated the involvement of genes related to cell adhesion, extracellular matrix organization, and cell migration in disease progression. Through the integration of gene and protein expression data in human primary chondrocytes, the authors identified molecular markers of microtia progression that were replicated across independent datasets and that have translational potential.

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.

Functional Diversification of SRSF Protein Kinase to Control Ubiquitin-Dependent Neurodevelopmental Signaling

Conserved protein kinases with core cellular functions have been frequently redeployed during metazoan evolution to regulate specialized developmental processes. The Ser/Arg (SR)-rich splicing factor (SRSF) protein kinase (SRPK), which is implicated in splicing regulation, is one such conserved eukaryotic kinase. Surprisingly, we show that SRPK has acquired the capacity to control a neurodevelopmental ubiquitin signaling pathway. In mammalian embryonic stem cells and cultured neurons, SRPK phosphorylates Ser-Arg motifs in RNF12/RLIM, a key developmental E3 ubiquitin ligase that is mutated in an intellectual disability syndrome. Processive phosphorylation by SRPK stimulates RNF12-dependent ubiquitylation of nuclear transcription factor substrates, thereby acting to restrain a neural gene expression program that is aberrantly expressed in intellectual disability. SRPK family genes are also mutated in intellectual disability disorders, and patient-derived SRPK point mutations impair RNF12 phosphorylation. Our data reveal unappreciated functional diversification of SRPK to regulate ubiquitin signaling that ensures correct regulation of neurodevelopmental gene expression.

A novel nonsense substitution identified in the AMIGO2 gene in an Occulo-Auriculo-Vertebral spectrum patient

OBJECTIVE

Craniofacial microsmia is the second most common congenital disorder with mostly unilateral defects of ear, temporomandibular joint, mandible, and muscles of facial expression and mastication. The objective of this study was to identify, if there were any, de novo germline or somatic variants in a patient with Occulo-Auriculo-Vertebral Spectrum (OAVS) using whole-exome sequencing.

SETTINGS AND SAMPLE POPULATION

Trio/Family-based study of an OAVS proband.

MATERIALS AND METHODS

Children's Mercy Hospital Institutional Review Board approved this study and a request-to-rely was procured from the University of Missouri Kansas City IRB. Informed assent/consent was obtained for all family members prior to any research activities. The peripheral blood/affected side tissues from corrective surgery of the proband and peripheral blood samples from unaffected parents were collected. The isolated genomic DNA were enriched for exomes and sequenced on an Illlumina HiSeq 2500 instrument yielding paired-end 125 nucleotide reads (84X coverage). Gapped alignment to reference sequences (GRCh37.p5) was performed with BWA and the GATK and analysis completed using custom-developed software.

RESULTS

Analyses revealed that the proband carried a de novo germ line nonsense substitution (c.901C>T) in AMIGO2 gene, and missense substitutions in ZCCHC14 (c.1198C>T), and in SZT2 genes (c.2951C>T).

CONCLUSIONS

The nonsense substitution in AMIGO2 gene introduces a premature stop codon possibly rendering the gene non-functional via nonsense-mediated pathway decay-therefore considered a stronger candidate. Further functional studies are required to confirm whether loss-of-function variants in AMIGO2 can cause OAVS.

Thalidomide leads to mandible hypoplasia through inhibiting angiogenesis and secondary hemorrhage in the fetal craniofacial region in rabbits

The effect of thalidomide on mandibular development is unclear. In this study, thalidomide was delivered to pregnant rabbits from the 8th to 14th day of gestation. Then, embryos were harvested for examination on the 16th day (GD16), 20th day (GD20) and 24th day (GD24) of gestation. The results showed obvious hemorrhage and hematoma on one side of the craniofacial region in 50 % of the thalidomide-treated embryos and obvious hemorrhage and hematoma on both sides of the craniofacial region in 50 % of the thalidomide-treated embryos at GD16. Histological examination showed soft tissues and mandible defects on the affected side of the maxillofacial region. The expression of Vegf-α, Ki67 and Sox9 on the affected side was significantly down-regulated in comparison to their expression on the unaffected side at GD20. There was also an obvious defect in the affected mandible, and the density of the skull and mandible was decreased compared to the unaffected side or the control group at GD24. These findings demonstrated that thalidomide may lead to hemorrhage and hematoma in the craniofacial region by inhibiting angiogenesis, resulting in the abnormal development of cranial neural crest cells that are involved in the normal development of the mandible in rabbits.

Integrated DNA methylation and gene expression analysis identifies SLAMF7 as a key regulator of atherosclerosis

Atherosclerosis (AS) is a multifactorial disease. Exploration of DNA methylation in regulating gene transcription in a cell type- and stage-specific manner will shed light on understanding the biological processes associated with plaque stability. We identified 174 up-regulated genes with hypo-methylation in the promoter, and 86 down-regulated genes with hyper-methylation in the promoter, in AS vs. healthy controls. Among them, high expression of signaling lymphocytic activation molecule 7 (SLAM7) was examined in carotid plaque vs. intact tissue, in advanced plaque vs. early atherosclerotic tissue, and SLAMF7 protein expressed significantly higher in the unstable plaques than that in the stable plaques, especially in the CD68-positive macrophages. Depletion of SLAMF7 in plaque-derived macrophages induced a suppressed secretion of proinflammatory cytokines, and inhibited proliferation of vascular smooth muscle cells. These data provide emerging evidence that SLAMF7 could be a target of potential therapeutic intervention in carotid AS.

Hypoxia Signaling in Vascular Homeostasis

Hypoxia signaling in the vasculature controls vascular permeability, inflammation, vascular growth, and repair of vascular injury. In this review, we summarize recent insights in this burgeoning field and highlight the importance of studying the heterogeneity of hypoxia responses among individual patients, distinct vascular beds, and even individual vascular cells.

Etiology and Pathogenesis of Hemifacial Microsomia

Hemifacial microsomia (HFM) is a common congenital malformation of the craniofacial region. There are 3 possible pathogenic models of HFM—vascular abnormality and hemorrhage in the craniofacial region, damage to Meckel’s cartilage, and the abnormal development of cranial neural crest cells—and the most plausible hypothesis is the vascular abnormality and hemorrhage model. These 3 models are interrelated, and none of them is completely concordant with all the variable manifestations of HFM. External environmental factors (e.g., thalidomide, triazene, retinoic acid, and vasoactive medications), maternal intrinsic factors (e.g., maternal diabetes), and genetic factors (e.g., the recently reported mutations in OTX2, PLCD3, and MYT1) may lead to HFM through ≥1 of these pathogenic processes. Whole genome sequencing to identify additional pathogenic variants, biological functional studies to understand the exact molecular mechanisms, and additional animal model and clinical studies with large stratified samples to elucidate the pathogenesis of HFM will be necessary. Small-molecule drugs, as well as CRISPR/CAS9-based genetic interventions, for the prevention and treatment of HFM may also be a future research hotspot.

NKG2D gene variation and susceptibility to viral bronchiolitis in childhood

BACKGROUND

Genetic factors associated with bronchiolitis are inadequately characterized. We therefore inspected a selected subpopulation of our previous genome-wide association study (GWAS) of bronchiolitis for overlap with known quantitative trait loci (QTLs) to identify susceptibility loci that potentially affect mRNA and protein levels.

METHODS

GWAS included a Finnish-Swedish case-control population (n = 187), matched for age and site. We integrated GWAS variants (p < 10^-4) with QTL data. We subsequently verified allele-specific expression of identified QTLs by flow cytometry. Association of the resulting candidate loci with bronchiolitis was tested in three additional cohorts from Finland and Denmark (n = 1201).

RESULTS

Bronchiolitis-susceptibility variant rs10772271 resided within QTLs previously associated with NKG2D (NK group 2, member D) mRNA and protein levels. Flow cytometric analysis confirmed the association with protein level in NK cells. The GWAS susceptibility allele (A) of rs10772271 (odds ratio [OR] = 2.34) corresponded with decreased NKG2D expression. The allele was nominally associated with bronchiolitis in one Finnish replicate (OR = 1.50), and the other showed directional consistency (OR = 1.43). No association was detected in Danish population CONCLUSIONS: The bronchiolitis GWAS susceptibility allele was linked to decreased NKG2D expression in the QTL data and in our expression analysis. We propose that reduced NKG2D expression predisposes infants to severe bronchiolitis.

Neural crest and the patterning of vertebrate craniofacial muscles

Patterning of craniofacial muscles overtly begins with the activation of lineage-specific markers at precise, evolutionarily conserved locations within prechordal, lateral, and both unsegmented and somitic paraxial mesoderm populations. Although these initial programming events occur without influence of neural crest cells, the subsequent movements and differentiation stages of most head muscles are neural crest-dependent. Incorporating both descriptive and experimental studies, this review examines each stage of myogenesis up through the formation of attachments to their skeletal partners. We present the similarities among developing muscle groups, including comparisons with trunk myogenesis, but emphasize the morphogenetic processes that are unique to each group and sometimes subsets of muscles within a group. These groups include branchial (pharyngeal) arches, which encompass both those with clear homologues in all vertebrate classes and those unique to one, for example, mammalian facial muscles, and also extraocular, laryngeal, tongue, and neck muscles. The presence of several distinct processes underlying neural crest:myoblast/myocyte interactions and behaviors is not surprising, given the wide range of both quantitative and qualitative variations in craniofacial muscle organization achieved during vertebrate evolution.

Whole-exome sequencing for monozygotic twins discordant for hemifacial microsomia

Hemifacial microsomia (HFM) is the second most common congenital craniofacial malformation. Although many sporadic and familial cases have been studied to explore the etiology and pathogenesis of HFM, no common understanding has been reached. We aimed to further probe into the etiology of HFM through studying monozygotic twins. Here, we report two cases of pairs of monozygotic twins discordant for HFM, and performed whole-exome sequencing (WES) and bioinformatics analysis to help determine the underlying molecular mechanisms. We identified 93 and 83, and 101 and 104 genes containing rare germline mutations in the twins of the two pairs, respectively. No positive gene candidates were found among the samples, and none of the analyses results revealed a clear intersection with previously reported gene candidates. The pathogenesis of HFM twin pairs does not appear to be related to single nucleotide variants or small insertions/deletions. Thus, HFM may be caused by structure variations, epigenetic alterations, and/or instability of short repeat sequences, which requires further investigation in a larger cohort with sequencing technology for verification.

Update on 13 Syndromes Affecting Craniofacial and Dental Structures

Care of individuals with syndromes affecting craniofacial and dental structures are mostly treated by an interdisciplinary team from early childhood on. In addition to medical and dental specialists that have a vivid interest in these syndromes and for whom these syndromes are of evident interest, experts of scientific background-like molecular and developmental geneticists, but also computational biologists and bioinformaticians-, become more frequently involved in the refined diagnostic and etiological processes of these patients. Early diagnosis is often crucial for the effective treatment of functional and developmental aspects. However, not all syndromes can be clinically identified early, especially in cases of absence of known family history. Moreover, the treatment of these patients is often complicated because of insufficient medical knowledge, and because of the dental and craniofacial developmental variations. The role of the team is crucial for the prevention, proper function, and craniofacial development which is often combined with orthognathic surgery. Although the existing literature does not provide considerable insight into this topic, this descriptive review aims to provide tools for the interdisciplinary team by giving an update on the genetics and general features, and the oral and craniofacial manifestations for early diagnosis. Clinical phenotyping together with genetic data and pathway information will ultimately pave the way for preventive strategies and therapeutic options in the future. This will improve the prognosis for better functional and aesthetic outcome for these patients and lead to a better quality of life, not only for the patients themselves but also for their families. The aim of this review is to promote interdisciplinary interaction and mutual understanding among all specialists involved in the diagnosis and therapeutic guidance of patients with these syndromal conditions in order to provide optimal personalized care in an integrated approach.

Mouth development

A mouth is present in all animals, and comprises an opening from the outside into the oral cavity and the beginnings of the digestive tract to allow eating. This review focuses on the earliest steps in mouth formation. In the first half, we conclude that the mouth arose once during evolution. In all animals, the mouth forms from ectoderm and endoderm. A direct association of oral ectoderm and digestive endoderm is present even in triploblastic animals, and in chordates, this region is known as the extreme anterior domain (EAD). Further support for a single origin of the mouth is a conserved set of genes that form a 'mouth gene program' including foxA and otx2. In the second half of this review, we discuss steps involved in vertebrate mouth formation, using the frog Xenopus as a model. The vertebrate mouth derives from oral ectoderm from the anterior neural ridge, pharyngeal endoderm and cranial neural crest (NC). Vertebrates form a mouth by breaking through the body covering in a precise sequence including specification of EAD ectoderm and endoderm as well as NC, formation of a 'pre-mouth array,' basement membrane dissolution, stomodeum formation, and buccopharyngeal membrane perforation. In Xenopus, the EAD is also a craniofacial organizer that guides NC, while reciprocally, the NC signals to the EAD to elicit its morphogenesis into a pre-mouth array. Human mouth anomalies are prevalent and are affected by genetic and environmental factors, with understanding guided in part by use of animal models. WIREs Dev Biol 2017, 6:e275. doi: 10.1002/wdev.275 For further resources related to this article, please visit the WIREs website.