The genetics of auricular development and malformation: new findings in model systems driving future directions for microtia research

Decreased Tiam1-mediated Rac1 activation is responsible for impaired directional persistence of chondrocyte migration in microtia

The human auricle has a complex structure, and microtia is a congenital malformation characterized by decreased size and loss of elaborate structure in the affected ear with a high incidence. Our previous studies suggest that inadequate cell migration is the primary cytological basis for the pathogenesis of microtia, however, the underlying mechanism is unclear. Here, we further demonstrate that microtia chondrocytes show a decreased directional persistence during cell migration. Directional persistence can define a leading edge associated with oriented movement, and any mistakes would affect cell function and tissue morphology. By the screening of motility-related genes and subsequent confirmations, active Rac1 (Rac1-GTP) is identified to be critical for the impaired directional persistence of microtia chondrocytes migration. Moreover, Rho guanine nucleotide exchange factors (GEFs) and Rho GTPase-activating proteins (GAPs) are detected, and overexpression of Tiam1 significantly upregulates the level of Rac1-GTP and improves directional migration in microtia chondrocytes. Consistently, decreased expression patterns of Tiam1 and active Rac1 are found in microtia mouse models, Bmp5se/J and Prkralear-3J/GrsrJ. Collectively, our results provide new insights into microtia development and therapeutic strategies of tissue engineering for microtia patients.

A Consolidated Understanding of the Contribution of Redox Dysregulation in the Development of Hearing Impairment

The etiology of hearing impairment is multifactorial, with contributions from both genetic and environmental factors. Although genetic studies have yielded valuable insights into the development and function of the auditory system, the contribution of gene products and their interaction with alternate environmental factors for the maintenance and development of auditory function requires further elaboration. In this review, we provide an overview of the current knowledge on the role of redox dysregulation as the converging factor between genetic and environmental factor-dependent development of hearing loss, with a focus on understanding the interaction of oxidative stress with the physical components of the peripheral auditory system in auditory disfunction. The potential involvement of molecular factors linked to auditory function in driving redox imbalance is an important promoter of the development of hearing loss over time.

"Microtia, Branchial Cleft Fistula, and Tetralogy of Fallot: A Possible Association"

When searching over associations between congenital ear abnormalities, especially microtia and affiliated deformities like cleft lip or palate and congenital heart diseases, some clinical analysis and genetic theories are found. A 10-year-old boy sent to the plastic surgery hospital was puzzled by a congenital anterior auricular fistula with fluid trace for more than 9 years. The preoperative diagnoses were branchial cleft fistula and congenital left ear deformity with postoperation of TOF. By browsing over studies on genetic concerns and clinical performance, it may be attributed to a possible association between microtia, branchial cleft fistula, and tetralogy of Fallot, though whose fundamental mechanisms remain concerned.

BMP signaling maintains auricular chondrocyte identity and prevents microtia development by inhibiting protein kinase A

Elastic cartilage constitutes a major component of the external ear, which functions to guide sound to the middle and inner ears. Defects in auricle development cause congenital microtia, which affects hearing and appearance in patients. Mutations in several genes have been implicated in microtia development, yet, the pathogenesis of this disorder remains incompletely understood. Here, we show that Prrx1 genetically marks auricular chondrocytes in adult mice. Interestingly, BMP-Smad1/5/9 signaling in chondrocytes is increasingly activated from the proximal to distal segments of the ear, which is associated with a decrease in chondrocyte regenerative activity. Ablation of Bmpr1a in auricular chondrocytes led to chondrocyte atrophy and microtia development at the distal part. Transcriptome analysis revealed that Bmpr1a deficiency caused a switch from the chondrogenic program to the osteogenic program, accompanied by enhanced protein kinase A activation, likely through increased expression of Adcy5/8. Inhibition of PKA blocked chondrocyte-to-osteoblast transformation and microtia development. Moreover, analysis of single-cell RNA-seq of human microtia samples uncovered enriched gene expression in the PKA pathway and chondrocyte-to-osteoblast transformation process. These findings suggest that auricle cartilage is actively maintained by BMP signaling, which maintains chondrocyte identity by suppressing osteogenic differentiation.

Clinical report and genetic analysis of a Chinese neonate with craniofacial microsomia caused by a splicing variant of the splicing factor 3b subunit 2 gene

BACKGROUND

Craniofacial microsomia (CFM) is a common congenital malformation with unknown pathogenesis. Although few cases have been reported, it is suggested that variants of the SF3B2 gene may lead to CFM. We herein report the case of a neonate with CFM exhibiting rare features of airway obstruction.

METHODS

Trio whole-exome sequencing and Sanger validation were performed on the proband and her parents. Candidate gene mutations were analyzed using the Genome Aggregation Database (gnomAD) for normal frequency distributions. The Human Splicing Finder (HSF) and Rare Disease Data Center (RDDC) RNA splicer algorithms predicted the variant's harmfulness, verified by a Minigene assay.

RESULTS

The proband had a heterozygous SF3B2 variant, NM_006842.3:c.777+1G>A. The patient's father also carried this variant and exhibited facial abnormalities. The variant was not in gnomAD, and HSF and RDDC RNA splicers indicated donor site disruption. The minigene assay suggested that two mRNA products were produced, leading to a premature termination codon.

CONCLUSION

For this family, the pathogenesis of CFM may have been caused by an SF3B2 splicing variant. Affected family members exhibited varying degrees of malformation, indicating that CFM has phenotypic heterogeneity. This finding expands the phenotype and variant spectrum of SF3B2, enriches neonatal CFM research, and provides a possible guide to genetic counseling.

Severe Unilateral Microtia with Aural Atresia, Hair White Patch, Stereotypes in a Young Boy with De novo 16p13.11 Deletion: Reasons for a New Genotype-Phenotype Correlation

Background  Microtia is an uncommon congenital malformation ranging from mild anatomic structural abnormalities to partial or complete absence of the ear leading to hearing impairment. Congenital microtia may present as a single malformation (isolated microtia) or sometimes associated with other congenital anomalies involving various organs. Microtia has been classified in three degrees according to the complexity of the auricular malformation and to anotia referred to the total absence of the ear. Genetic role in causing auricular malformation has been widely demonstrated, and genotype-phenotype correlation has been reported in cases of syndromic microtia. Case Presentation  We report here a young patient with a third degree of scale classification and aural atresia. The patient showed unspecific facial dysmorphism, speech delay, precocious teething, hair white patch, and stereotypic anomalous movements. Genetic analysis displayed a de novo 16p13.11 deletion. Conclusion  Microtia with aural atresia is an uncommon and severe birth defect, which affects functional and esthetic aspects, often associated with other malformations. As traumatic this disorder may be for the parents, the microtia and aural atresia are treatable, thanks to the improving and evolving surgical techniques. Based on the genetic analysis and the clinical features observed in the present case, a genotype-phenotype correlation has been proposed.

Current Status of Auricular Reconstruction Strategy Development

Microtia has severe physical and psychological impacts on patients, and auricular reconstruction offers improved esthetics and function, alleviating psychological issues. Microtia is a congenital disease caused by a multifactorial interaction of environmental and genetic factors, with complex clinical manifestations. Classification assessment aids in determining treatment strategies. Auricular reconstruction is the primary treatment for severe microtia, focusing on the selection of auricular scaffold materials, the construction of auricular morphology, and skin and soft tissue scaffold coverage. Autologous rib cartilage and synthetic materials are both used as scaffold materials for auricular reconstruction, each with advantages and disadvantages. Methods for achieving skin and soft tissue scaffold coverage have been developed to include nonexpansion and expansion techniques. In recent years, the application of digital auxiliary technology such as finite element analysis has helped optimize surgical outcomes and reduce complications. Tissue-engineered cartilage scaffolds and 3-dimensional bioprinting technology have rapidly advanced in the field of ear reconstruction. This article discusses the prevalence and classification of microtia, the selection of auricular scaffolds, the evolution of surgical methods, and the current applications of digital auxiliary technology in ear reconstruction, with the aim of providing clinical physicians with a reference for individualized ear reconstruction surgery. The focus of this work is on the current applications and challenges of tissue engineering and 3-dimensional bioprinting technology in the field of ear reconstruction, as well as future prospects.

Conductive Hearing Loss in Children

A variety of congenital and acquired disorders result in pediatric conductive hearing loss. Malformations of the external auditory canal are invariably associated with malformations of the middle ear space and ossicles. Isolated ossicular malformations are uncommon. Syndromes associated with external and middle ear malformations are frequently associated with abnormal development of first and second pharyngeal arch derivatives. Chronic inflammatory disorders include cholesteatoma, cholesterol granuloma, and tympanosclerosis.

Management Strategy of Local Subcutaneous Effusion After Auricle Reconstruction

OBJECTIVES

Microtia is a severe congenital malformation of the external ear, and auricular reconstruction is still a challenge for plastic surgeons because of the complicated procedures and rare conditions. This study aimed to describe the location of subcutaneous effusion after auricular reconstruction and explore the clinical efficacy of the indwelling needle puncture drainage method in the treatment of local subcutaneous effusion.

METHODS

From January 2017 to December 2019, 1240 patients (1296 affected sides) who underwent auricular reconstruction using autogenous cartilage framework in the Plastic Surgery Hospital of Chinese Academy of Medical Science and Peking Union Medical College were selected. The local subcutaneous effusion occurred within 5 days after the drainage tube was removed, and the indwelling needle was used for puncture and drainage in the postoperative treatment.

RESULTS

A total of 55 patients had subcutaneous effusion after the operation, including 24 cases with Nagata's method and 31 cases with the expanded single-flap method. One patient showed no obvious reduction after puncture and drainage by indwelling needle and improved after the secondary operation. Two patients had slight cartilage absorption. The remaining patients had good results.

CONCLUSIONS

The method of the indwelling needle for puncture and drainage is easy to operate. The problem of local subcutaneous effusion after auricular reconstruction can be solved and good efficacy can be obtained.

Evaluation of loci to predict ear morphology using two SNaPshot assays

Human ear morphology prediction with SNP-based genotypes is growing in forensic DNA phenotyping and is scarcely explored in Pakistan as a part of EVCs (externally visible characteristics). The ear morphology prediction assays with 21 SNPs were assessed for their potential utility in forensic identification of population. The SNaPshot™ multiplex chemistries, capillary electrophoresis methods and GeneMapper™ software were used for obtaining genotypic data. A total of 33 ear phenotypes were categorized with digital photographs of 300 volunteers. SHEsis software was applied to make LD plot. Ordinal and multinomial logistic regression was implemented for association testing. Multinomial logistic regression was executed to construct the prediction model in 90% training and 10% testing subjects. Several influential SNPs for ear phenotypic variation were found in association testing. The model based on genetic markers predicted ear phenotypes with moderate to good predictive accuracies demonstrated with the area under curve (AUC), sensitivity and specificity of predicted phenotypes. As an additional EVC, the estimated ear phenotypic profiles have the possibility of determining the human ear morphology differences in unknown biological samples found in crimes that do not result in a criminal database hit. Furthermore, this can help in facial reconstruction and act as an investigational lead.

Auricular fistula: a review of its clinical manifestations, genetics, and treatments

Auricular fistula is a common congenital auricular malformation, characterized as a small opening in the skin and a subcutaneous cyst. It can be classified in different ways according to positions of pits and directions of fistula tracts. The term preauricular fistula and variant type of preauricular fistula (postauricular fistula) are used. Auricular fistula prevalence varies in countries and populations, and its actual prevalence is presently unknown. The most accepted and widely cited theory of auricular fistula etiopathogenesis is an incorrect or incomplete fusion of six auricular hillocks that are mesenchymal proliferations. Auricular fistula can occur either sporadically or genetically. The pattern in inherited cases is thought to be incomplete autosomal dominant, with variable expressions, reduced penetrance, and inapparent gender differences. Auricular fistula has several forms and is reported as being a component of many syndromes. In the field of genetics, currently, there is no related review to comprehensively summarize the genetic basis of auricular fistula and related disorders. This article provides a comprehensive review of auricular fistula, especially congenital preauricular fistula, which accounts for the majority of auricular fistula, by summarizing the clinical manifestations, histological and embryological development, genetics, examinations, and treatments, as well as syndromes with auricular fistula.

Neural crest cells give rise to non-myogenic mesenchymal tissue in the adult murid ear pinna

Despite being a major target of reconstructive surgery, development of the external ear pinna remains poorly studied. As a craniofacial organ highly accessible to manipulation and highly conserved among mammals, the ear pinna represents a valuable model for the study of appendage development and wound healing in the craniofacial complex. Here we provide a cellular characterization of late gestational and postnatal ear pinna development in Mus musculus and Acomys cahirinus and demonstrate that ear pinna development is largely conserved between these species. Using Wnt1-cre;ROSAmT/mG mice we find that connective tissue fibroblasts, elastic cartilage, dermal papilla cells, dermal sheath cells, vasculature, and adipocytes in the adult pinna are derived from cranial crest. In contrast, we find that skeletal muscle and hair follicles are not derived from neural crest cells. Cellular analysis using the naturally occurring short ear mouse mutant shows that elastic cartilage does not develop properly in distal pinna due to impaired chondroprogenitor proliferation. Interestingly, while chondroprogenitors develop in a mostly continuous sheet, the boundaries of cartilage loss in the short ear mutant strongly correlate with locations of vasculature-conveying foramen. Concomitant with loss of elastic cartilage we report increased numbers of adipocytes, but this seems to be a state acquired in adulthood rather than a developmental abnormality. In addition, chondrogenesis remains impaired in the adult mid-distal ear pinna of these mutants. Together these data establish a developmental basis for the study of the ear pinna with intriguing insights into the development of elastic cartilage.

Inheritance analysis and family history for microtia: A hospital-based study in China

OBJECTIVES

Microtia is a congenital anomaly of the outer ear. Although genetic and environmental factors could play a role, no consensus has been established on the pathogenesis and cause of this condition. In this study, we surveyed the frequency and pattern of family history in patients with microtia in a Chinese specialty clinic population.

METHODS

We evaluated data from 672 patients (mean age = 9.2, male-to-female ratio = 2.6:1) with microtia admitted to the Department of Auricular Reconstruction at the Plastic Surgery Hospital of Peking Union Medical College from December 2014 to February 2016. Family history of congenital ear anomalies across three generations was recorded. Pearson chi-square test or Fisher exact test was used to test the associations between the characteristics of microtia and hereditary features.

RESULTS

A family history of auricle anomalies was identified in 202 patients (30.1%), of whom, 95 families showed vertical transmission, 14 families skipped a generation, and 120 families showed family aggregations. The incidence of family history varied with grades of microtia (P = 0.001). Patients with preauricular tags or pits (38.3%) had a higher familial incidence of microtia than those with simple microtia (24.1%) (P < 0.001).

CONCLUSION

Patients with a lower grade of microtia demonstrated a higher incidence of family history. Patients with microtia had significantly more relatives with preauricular tags or pits. Microtia and preauricular tags or pits are different manifestations of the same defect, and their significant concurrency among relatives suggests that a considerable proportion of microtia is inherited and could recur with varying degrees of severity in other family members.

The spontaneous mouse mutant low set ears (Lse) is caused by tandem duplication of Fgf3 and Fgf4

The external ear develops from an organized convergence of ventrally migrating neural crest cells into the first and second branchial arches. Defects in external ear position are often symptomatic of complex syndromes such as Apert, Treacher-Collins, and Crouzon Syndrome. The low set ears (Lse) spontaneous mouse mutant is characterized by the dominant inheritance of a ventrally shifted external ear position and an abnormal external auditory meatus (EAM). We identified the causative mutation as a 148 Kb tandem duplication on Chromosome 7, which includes the entire coding sequences of Fgf3 and Fgf4. Duplications of FGF3 and FGF4 occur in 11q duplication syndrome in humans and are associated with craniofacial anomalies, among other features. Intercrosses of Lse-affected mice revealed perinatal lethality in homozygotes, and Lse/Lse embryos display additional phenotypes including polydactyly, abnormal eye morphology, and cleft secondary palate. The duplication results in increased Fgf3 and Fgf4 expression in the branchial arches and additional discrete domains in the developing embryo. This ectopic overexpression resulted in functional FGF signaling, demonstrated by increased Spry2 and Etv5 expression in overlapping domains of the developing arches. Finally, a genetic interaction between Fgf3/4 overexpression and Twist1, a regulator of skull suture development, resulted in perinatal lethality, cleft palate, and polydactyly in compound heterozygotes. These data indicate a role for Fgf3 and Fgf4 in external ear and palate development and provide a novel mouse model for further interrogation of the biological consequences of human FGF3/4 duplication.

Whole genome sequencing analysis of four patients: Are de novo copy number variations in non-coding region responsible for microtia with lung hypoplasia?

BACKGROUND

Microtia is a congenital malformation of the out ear, occurring either as an isolated defect or part of a specific pattern of multiple congenital anomalies. The etiology of microtia is poorly understood. Four patients with microtia and lung hypoplasia were reported by our team in a previous article. The purpose of this study was to identify the underlying genetic basis, mainly focusing on de novo copy number variations (CNVs) embedded in the noncoding region, in the four subjects.

METHODS

DNA samples from all four patients and their unaffected parents were extracted for whole-genome sequencing on the Illumina platform. All variants were obtained through data quality control, variant calling and bioinformatics analysis. De novo strategy was used to prioritize the variants, and candidate variants were verified by PCR amplification combined with Sanger sequencing and visual inspection of bam file.

RESULTS

Whole gene sequencing following bioinformatics analysis showed no potential de novo pathogenic variants in the coding region. Nonetheless, four de novo CNVs in the non-coding region, intronic or intergenic, were identified in each subject, ranging in size from 10 Kb to 12.5 Kb, and all are deletions. Case 1 had a de novo deletion of 10 Kb on chromosome10q22.3, located in the intronic region of the LRMDA gene. The other three cases all had a de novo deletion in intergenic regions, located on chromosome 20q11.21, 7q31.1 and 13q12.13, respectively.

CONCLUSIONS

This study reported multiple long-lived cases of microtia with pulmonary hypoplasia and provided genome-wide genetic analysis focusing on de novo mutations. Whether the de novo CNVs identified are responsible for the rare phenotypes remains an open question. However, the results of our study provided a new perspective that the unsolved etiology of microtia might involve in non-coding sequences, which have long been ignored.

Functional Pathway and Process Enrichment Analysis of Genes Associated With Morphological Abnormalities of the Outer Ear

Congenital anomalies of the outer ear are common birth defects, including a variety of congenital deformities or malformations ranging from mild structural anomalies to total absence of the ear. Despite its high incidence and detrimental impact on patients, the etiology of outer ear abnormalities remains poorly understood. The goal of this study was to summarize the related genes and improve our understanding of the genetic etiology of morphological abnormalities of the outer ear. Human Phenotype Ontology (HPO) database, Mouse Genome Informatics (MGI) database, and PubMed search engine were used to acquire the genes associated with abnormal human or mouse outer ear. Metascape was employed on the genes above to conduct functional annotation, pathway and process enrichment analysis, protein-protein interaction network analysis, and MCODE component analysis. After a comprehensive review of the databases and literature, we identified 394 human genes and 148 mouse genes that have been associated with abnormal phenotypes of the outer ear, and we identified several biological pathways for human and mouse respectively. Especially, the analysis of common genes shared by human and mouse emphasized the importance of certain genes ( PAX6 , PBX1 , HOXA1 , HOXA2 , TBX1 , TBX15 , PRRX1 , and HMX1 ) in the embryonic development of the external ear. Through our analysis of genes associated with morphological abnormalities of the outer ear, the authors have shown that embryonic development pathways take important roles in the morphogenesis of abnormal external ear and highlighted some potential genetic drivers.

Auricular prosthesis positioning using virtual planning in combination with additive manufacturing

INTRODUCTION

This study focused on deformed or missing auricles and their replacement with silicone prostheses which are retained by craniofacial implants. Surgeons find it difficult to accurately place the implants in relation to the missing auricle in theatre. The aim of this study was to develop patient-specific devices using additive manufacturing technologies and associated software to indicate the positions of implants and to correctly orientate the prostheses relative to the positions of the implants.

MATERIAL AND METHODS

The morphology of the patient was determined using Computed-Tomography (CT) scanning and the opposite auricle was mirrored in the virtual environment through specialized software from Materialise. A positioning guide for placing the implants was developed, together with an orientation guide that orientates the prosthesis accurately in relation to the implants. The orientation guide is a new development in the field of maxillofacial prosthetics and has not been attempted before. The guides are produced in nylon through laser sintering additive manufacturing.

RESULTS

The accuracy of implant placements was determined and the results showed relatively accurate positioning using the guides.

DISCUSSION

Implant placement showed some deviation which can largely be attributed to improper use of the guide by the surgeon during the marking of implant positions. The orientation guide can however somewhat compensate for this to still achieve aesthetically pleasing results. Using the guides significantly reduces risk, time and cost in placing the implants and producing auricular silicone prostheses.

Damaging variants in FOXI3 cause microtia and craniofacial microsomia

PURPOSE

Craniofacial microsomia (CFM) represents a spectrum of craniofacial malformations, ranging from isolated microtia with or without aural atresia to underdevelopment of the mandible, maxilla, orbit, facial soft tissue, and/or facial nerve. The genetic causes of CFM remain largely unknown.

METHODS

We performed genome sequencing and linkage analysis in patients and families with microtia and CFM of unknown genetic etiology. The functional consequences of damaging missense variants were evaluated through expression of wild-type and mutant proteins in vitro.

RESULTS

We studied a 5-generation kindred with microtia, identifying a missense variant in FOXI3 (p.Arg236Trp) as the cause of disease (logarithm of the odds = 3.33). We subsequently identified 6 individuals from 3 additional kindreds with microtia-CFM spectrum phenotypes harboring damaging variants in FOXI3, a regulator of ectodermal and neural crest development. Missense variants in the nuclear localization sequence were identified in cases with isolated microtia with aural atresia and found to affect subcellular localization of FOXI3. Loss of function variants were found in patients with microtia and mandibular hypoplasia (CFM), suggesting dosage sensitivity of FOXI3.

CONCLUSION

Damaging variants in FOXI3 are the second most frequent genetic cause of CFM, causing 1% of all cases, including 13% of familial cases in our cohort.

In vitro elastic cartilage reconstruction using human auricular perichondrial chondroprogenitor cell-derived micro 3D spheroids

Morphologically stable scaffold-free elastic cartilage tissue is crucial for treating external ear abnormalities. However, establishing adequate mechanical strength is challenging, owing to the difficulty of achieving chondrogenic differentiation in vitro; thus, cartilage reconstruction is a complex task. Auricular perichondrial chondroprogenitor cells exhibit high proliferation potential and can be obtained with minimal invasion. Therefore, these cells are an ideal resource for elastic cartilage reconstruction. In this study, we aimed to develop a novel in vitro scaffold-free method for elastic cartilage reconstruction, using human auricular perichondrial chondroprogenitor cells. Inducing chondrogenesis by using microscopic spheroids similar to auricular hillocks significantly increased the chondrogenic potential. The size and elasticity of the tissue were maintained after craniofacial transplantation in immunodeficient mice, suggesting that the reconstructed tissue was morphologically stable. Our novel tissue reconstruction method may facilitate the development of future treatments for external ear abnormalities.

The Enigmatic Etiology of Oculo-Auriculo-Vertebral Spectrum (OAVS): An Exploratory Gene Variant Interaction Approach in Candidate Genes

The clinical diagnosis of oculo-auriculo-vertebral spectrum (OAVS) is established when microtia is present in association with hemifacial hypoplasia (HH) and/or ocular, vertebral, and/or renal malformations. Genetic and non-genetic factors have been associated with microtia/OAVS. Although the etiology remains unknown in most patients, some cases may have an autosomal dominant, autosomal recessive, or multifactorial inheritance. Among the possible genetic factors, gene−gene interactions may play important roles in the etiology of complex diseases, but the literature lacks related reports in OAVS patients. Therefore, we performed a gene−variant interaction analysis within five microtia/OAVS candidate genes (HOXA2, TCOF1, SALL1, EYA1 and TBX1) in 49 unrelated OAVS Mexican patients (25 familial and 24 sporadic cases). A statistically significant intergenic interaction (p-value < 0.001) was identified between variants p.(Pro1099Arg) TCOF1 (rs1136103) and p.(Leu858=) SALL1 (rs1965024). This intergenic interaction may suggest that the products of these genes could participate in pathways related to craniofacial alterations, such as the retinoic acid (RA) pathway. The absence of clearly pathogenic variants in any of the analyzed genes does not support a monogenic etiology for microtia/OAVS involving these genes in our patients. Our findings could suggest that in addition to high-throughput genomic approaches, future gene−gene interaction analyses could contribute to improving our understanding of the etiology of microtia/OAVS.

Predicting the Risk of Microtia From Prenatal Factors: A Hospital-Based Case-Control Study

Background

Although a wide range of risk factors for microtia were identified, the limitation of these studies, however, is that risk factors were not estimated in comparison with one another or from different domains. Our study aimed to uncover which factors should be prioritized for the prevention and intervention of non-syndromic microtia via tranditonal and meachine-learning statistical methods.

Methods

293 pairs of 1:1 matched non-syndromic microtia cases and controls who visited Shanghai Ninth People's Hospital were enrolled in the current study during 2017-2019. Thirty-nine risk factors across four domains were measured (i.e., parental sociodemographic characteristics, maternal pregnancy history, parental health conditions and lifestyles, and parental environmental and occupational exposures). Lasso regression model and multivariate conditional logistic regression model were performed to identify the leading predictors of microtia across the four domains. The area under the curve (AUC) was used to calculate the predictive probabilities.

Results

Eight predictors were identified by the lasso regression, including abnormal pregnancy history, genital system infection, teratogenic drugs usage, folic acid supplementation, paternal chronic conditions history, parental exposure to indoor decoration, paternal occupational exposure to noise and maternal acute respiratory infection. The additional predictors identified by the multivariate conditional logistic regression model were maternal age and maternal occupational exposure to heavy metal. Predictors selected from the conditional logistic regression and lasso regression both yielded AUCs (95% CIs) of 0.83 (0.79-0.86).

Conclusion

The findings from this study suggest some factors across multiple domains are key drivers of non-syndromic microtia regardless of the applied statistical methods. These factors could be used to generate hypotheses for further observational and clinical studies on microtia and guide the prevention and intervention strategies for microtia.

Ipsilateral hemifacial microsomia with dextrocardia and pulmonary hypoplasia: A case report

BACKGROUND

Hemifacial microsomia (HFM) is a rare congenital malformation characterized by a combination of various anomalies, including the face, ears, eyes, and vertebrae. Prenatal diagnosis for HFM is possible, and quite accurate ultrasound can detect obvious defects. The etiology is still unknown, although some hypotheses have been proposed, including gene mutation, chromosome anomaly, and environmental risk factors. However, there are few reports of pulmonary hypoplasia and dextrocardia in HFM.

CASE SUMMARY

A 2-year-old boy presented to the ear reconstruction department of our hospital complaining of deviation of the face to the right side and auricular anomaly. Physical examination revealed facial asymmetry, preauricular skin tags, and concha-type microtia with stricture of the external auditory canal on the right side. Head magnetic resonance imaging showed bilateral semicircular canal dysplasia and bilateral internal auditory canals stenosis. Audiometric examination showed bilateral severe sensorineural hearing loss. Chest radiography and computed tomography showed dextrocardia and right pulmonary hypoplasia.

CONCLUSION

This case presented a rare finding and an unusual association of 3 malformations, ipsilateral HFM, pulmonary agenesis, and dextrocardia.

Proposed clinical approach and imaging studies in families with oculo-auriculo-vertebral spectrum to assess variable expressivity

A diagnosis of oculo-auriculo-vertebral spectrum (OAVS) is established when microtia is present in association with hemifacial hypoplasia (HH) and/or ocular, vertebral, and/or renal malformations. There is no consensus on which imaging studies should be used to rule out variable expressivity and distinguish "sporadic" from "familial" patients. This observational and descriptive study was performed in a Mexican population of 51 patients (32 males, 19 females, 0-18 years old) with microtia/OAVS, and their available parents. A clinical history, genealogy, and physical examination were obtained from all included patients, as were a computed tomography (CT) scan of the ear, audiological evaluation, orthopantomography, complete spine radiography, and renal ultrasound. The same approach was completed in their available parents (51 mothers and 40 fathers), excluding the CT scan and audiological evaluation. By genealogy, 53% of patients were classified as "sporadic"; of the "familial" patients, at least 79.1% had suggestion of a multifactorial inheritance. In the available parents, orthopantomography, complete spine X-ray, and renal ultrasound identified the following OAVS-related manifestations: HH (16.2%, n = 14/86), vertebral alterations (10.9%, n = 10/91), and renal anomalies (2.2%, n = 2/90). Our evaluation of the parents allowed three patients to be reclassified from "sporadic" to "familial" (5.8%, n = 3/51). Our proposed clinical and imaging approach allowed the identification of variable expressivity that more clearly distinguished between "sporadic" and "familial" OAVS patients, which is of utmost importance in providing proper genetic counseling to these families.

The genes for sensory perception of sound should be considered in gene diagnosis of congenital sensorineural hearing loss and microtia

Congenital sensorineural hearing loss (CSHL) and microtia are development-related diseases, sharing some factors and affecting children's hearing. However, genetic tests only focus on CSHL. We try to identify the common molecular mechanism of CSHL and microtia as candidates combining gene diagnosis biomarkers. Whole-exon sequencing (WES), Sanger sequencing, qPCR, and bioinformatics analyses were performed in microtia family (F1), family two, whose proband suffered from microtia and CSHL (F2), five microtia, and four CSHL individuals, respectively. We found that 40% microtia and 40% CSHL relevant genes were detected in F1 and a sharing pathway: the sensory perception of sound was identified. Moreover, the copy number variation in proband F2 was identified in one gene of the sharing pathway: EYA1. Meanwhile, two variants of BUB3 were identified in F1 data. BUB3 is related to development, dog ear type, direct and indirect interaction with microtia, and CSHL relevant genes. Notably, although the allele frequency of two variants of BUB3 showed significant differences between microtia and CSHL, the special microtia-relevant genotype also could be detected in one CSHL sample. These results suggest that the sensory perception of sound and the development of relevant pathways may be the common pathways of microtia and CSHL. Genes of these pathways can be used as candidates combining gene diagnosis biomarkers.

Haploinsufficiency of SF3B2 causes craniofacial microsomia

Craniofacial microsomia (CFM) is the second most common congenital facial anomaly, yet its genetic etiology remains unknown. We perform whole-exome or genome sequencing of 146 kindreds with sporadic (n = 138) or familial (n = 8) CFM, identifying a highly significant burden of loss of function variants in SF3B2 (P = 3.8 × 10^-10), a component of the U2 small nuclear ribonucleoprotein complex, in probands. We describe twenty individuals from seven kindreds harboring de novo or transmitted haploinsufficient variants in SF3B2. Probands display mandibular hypoplasia, microtia, facial and preauricular tags, epibulbar dermoids, lateral oral clefts in addition to skeletal and cardiac abnormalities. Targeted morpholino knockdown of SF3B2 in Xenopus results in disruption of cranial neural crest precursor formation and subsequent craniofacial cartilage defects, supporting a link between spliceosome mutations and impaired neural crest development in congenital craniofacial disease. The results establish haploinsufficient variants in SF3B2 as the most prevalent genetic cause of CFM, explaining ~3% of sporadic and ~25% of familial cases.

Heterogeneity of Accompanying Phenotypes and Genomic Variants Involved in Microtia

OBJECTIVES

The symptoms associated with microtia are ever-changing and not to stick to 1 pattern. The symptoms associated with microtia are constantly changing and are not set in stone. The aim of this article was to describe the various phenotypes from multiple systems found in microtitis patients included in the DatabasE of genomiC varIation and Phenotype in Humans using Ensembl Resources database, and to analyze possible pathogenic mutations.

METHODS

DatabasE of genomiC varIation and Phenotype in Humans using Ensembl Resources is an interactive web-based database, which incorporates a suite of tools designed to aid the interpretation of genomic variants. The term "microtia" was used as the search term, and the data extracted from the DatabasE of genomiC varIation and Phenotype in Humans using Ensembl Resources for this study was updated until October 2020. Pearson chi-squared test was used to test associations between types of genomic variants and the pathogenicity of variants.

RESULTS

Of the 386 cases enrolled in the study, 99% (n = 382) had 1 or more associated abnormalities. The most frequently detected abnormalities were those of the face and neck (n = 362 [93.8% of all cases]); musculoskeletal system (n = 337 [87.3%]); and nervous system (n = 334 [86.5%]), followed by abnormalities of limbs (n = 252 [65.3%]); the eye (n = 212 [54.9%]); and the integument (n = 200 [51.8%]). Besides, a total of 479 genomic variants were determined, including sequence variants and copy number variants (loss and gain). The pathogenicity of loss-type variants was significantly higher among other types (P < 0.001). Twelve sharing variants had more than 5 repeats, and the repeated fragments were concentrated on chromosome 3, 7, 9, 10, 11, 15, 17, 18, and 22.

CONCLUSIONS

Identification of the relation between phenotypes and genotypes will facilitate the uncovering of the mechanism of microtia and the study of potential therapeutic targets.

Evaluation of respiratory system anomalies associated with microtia in a Chinese specialty clinic population

BACKGROUND

Microtia is a congenital malformation of the external ear often with one or more associated congenital anomalies. The purpose of this study was to identify the characteristics and prevalence of respiratory anomalies in patients with microtia, and clarify the importance of this association in the perioperative period of patients' external ear reconstruction surgery.

METHODS

Data were collected from 923 microtia patients between August 2017 and December 2020 in the Department of Auricular Reconstruction at the Plastic Surgery Hospital of Peking Union Medical College. Co-occurring respiratory anomalies were detected using chest computed tomography plus three-dimensional reconstruction and Chest X-ray. Physical examination was performed to assess the severity and type of microtia by trained clinicians. Fisher's exact test was used to analyze the relation between laterality of pulmonary underdevelopment and microtia type.

RESULTS

Among the 923 participants enrolled in the study, we identified 21 cases (2.3%) having respiratory system anomalies, consisting of 6 cases with pulmonary underdevelopment (28.6% of all anomalies of respiratory system detected), 2 cases with tracheal bronchus (9.5%), 1 case with tracheal diverticula (4.8%), 11 cases with lung bullae(52.4%), and 1 case with pulmonary azygos lobe (4.8%). The laterality of pulmonary underdevelopment was related to the type of microtia (difference between types, p < 0.05), as patients with concha-type remnant ear had pulmonary underdevelopment ipsilaterally.

CONCLUSIONS

This study represents the first detailed and thematic study of a association featured by microtia and respiratory anomalies. Characteristics and prevalence of respiratory anomalies was observed in a Chinese clinical microtia population. Early diagnosis of associated respiratory malformations had practical clinical significance for microtia patients, plastic surgeons and anesthesiologists. Future studies are required to improve understanding of this association and its cause.

Reconstructive Options for Auricular Trauma

Given its prominent lateral position, the auricle is a common site of injury after blunt trauma. Auricular injuries can lead to both functional and aesthetic complications. A careful history and examination will help determine the mechanism of injury and identify factors that may influence repair. Auricular reconstruction is highly individualized and depends on the size, location, and nature of injury. Understanding the complex three-dimensional anatomy of the external ear is a necessity for appropriate reconstruction. This article reviews the reconstructive options for simple and complex auricular injuries based on the anatomical site and the intricate three-dimensional structures that form the auricle.

Congenital Aural Fistula Developing Between the Third and Fourth Hillocks of the Embryonal Helix and Presenting a Large Temporal Mass: A Case Report

This report aimed to introduce a very rare presentation of congenital aural fistula and its treatment. A 13-year-old girl presented with a mass on the right temporal region with protrusion of the helix. She noticed a mass a month previously, and the mass gradually swelled with pain. Pus discharged from the pit behind the helix. Mastoiditis was suspected; however, the tympanic membrane was normal. Magnetic resonance imaging revealed a cystic mass in the temporal region. The surgical removal of the mass was performed using a postauricular incision. The mass was cystic and had a stem connected to the pit. Insertion of a probe into the pit showed a connection to the mass. The mass was totally removed with the skin around the pit. Histologically, the cyst connected to the fistula and its lumen was covered with squamous cells. A diagnosis of a congenital aural fistula developed posterior to the helix was made. Considering its location, the fistula had been formed between the third and fourth hillocks of the embryonal helix. Aural fistula developed posteriorly is very rare, and it mimicked a temporal tumor or mastoiditis with a protruding auricle. Careful observation of the skin and consideration from developmental aspects are needed for an accurate diagnosis.

Whole-exome sequencing analysis in 10 families of sporadic microtia with thoracic deformities

Background

Microtia is a congenital malformation of the external ear and may occur as an isolated deformity or as part of a syndrome. Our previous study found a high correlation between microtia and thoracic deformities, thus, we propose that external ear and thorax development may be regulated by certain genes in common.

Methods

We performed exome sequencing on 10 families of sporadic microtia with thoracic abnormalities. We identified mutated genes under different models of inheritance, and checked them through Mouse Genome Informatics and association analysis.

Results

We identified 45 rare mutations, including 9 de novo mutations, 20 heterozygous mutations, 3 homozygous mutations, and 13 hemizygous mutations, of which 2 are likely to be causative. They are de novo missense variant in PHF5A and compound heterozygous mutations in CYP26B1, of which CYP26B1 mutation is highly likely pathogenic.

Conclusion

The results indicate that certain genes may affect both external ear and thorax development, and demonstrate the benefits of whole‐exome sequencing in identifying candidate genes of microtia. This study provides a new way for genetic exploration in microtia.

An Essential Requirement for Fgf10 in Pinna Extension Sheds Light on Auricle Defects in LADD Syndrome

The pinna (or auricle) is part of the external ear, acting to capture and funnel sound toward the middle ear. The pinna is defective in a number of craniofacial syndromes, including Lacrimo-auriculo-dento-digital (LADD) syndrome, which is caused by mutations in FGF10 or its receptor FGFR2b. Here we study pinna defects in the Fgf10 knockout mouse. We show that Fgf10 is expressed in both the muscles and forming cartilage of the developing external ear, with loss of signaling leading to a failure in the normal extension of the pinna over the ear canal. Conditional knockout of Fgf10 in the neural crest fails to recapitulate this phenotype, suggesting that the defect is due to loss of Fgf10 from the muscles, or that this source of Fgf10 can compensate for loss in the forming cartilage. The defect in the Fgf10 null mouse is driven by a reduction in proliferation, rather than an increase in cell death, which can be partially phenocopied by inhibiting cell proliferation in explant culture. Overall, we highlight the mechanisms that could lead to the phenotype observed in LADD syndrome patients and potentially explain the formation of similar low-set and cup shaped ears observed in other syndromes.

Epidemiological Research of Microtia Combined With Congenital Heart Disease

Congenital heart disease (CHD) is one of the most common combined malformations of microtia. There is currently no specific study that investigates the relationship between microtia and CHD.

METHODS

This study collected microtia inpatients admitted from May 1, 2015 to July 31, 2016. The diagnosis of CHD was based on patient's symptoms, past history, and echocardiography. Pearson χ test was used to analyze the correlation between CHD and microtia.

RESULTS

A total of 30 cases (3.35%) were documented with CHD, including atrial septal defect (12/40.00%), ventricular septal defect (7/23.30%), patent ductus arteriosus (2/6.70%), complex congenital heart disease (3/10.00%), combined CHD (2/6.70%) and other malformations (4/13.30%). Analysis showed no statistically significant relation between CHD and the side of affected ear or gender.

CONCLUSIONS

The occurrence of CHD in microtia patients was higher than that in the general population. The relationship between them was explored mainly from the etiological perspective. Microtia and CHD were often combined in syndromes such as Goldenhar syndrome, 22q11 deletion syndrome, and CHARGE syndrome. Absence of genes or abnormal embryo development associated with these syndromes leads to the occurrence of both.

Whole-Exome Sequencing of Discordant Monozygotic Twin Families for Identification of Candidate Genes for Microtia-Atresia

Objective

We used data from twins and their families to probe the genetic factors contributing to microtia-atresia, in particular, early post-twinning variations that potentially account for the discordant phenotypes of monozygotic twin pairs.

Methods

Six families of monozygotic twins discordant for congenital microtia-atresia were recruited for study. The six patients shared a consistent clinical phenotype of unilateral microtia-atresia. Whole-exome sequencing (WES) was performed for all six twin pairs and their parents. Family segregation and multiple bioinformatics methods were applied to identify suspicious mutations in all families. Recurring mutations commonly detected in at least two families were highlighted. All variants were validated via Sanger sequencing. Gene Ontology (GO) analysis was performed to identify candidate gene sets and related pathways. Copy number variation (CNV), linkage analysis, association analysis and machine learning methods were additionally applied to isolate candidate mutations, and comparative genomics and structural modeling tools used to evaluate their potential roles in onset of microtia-atresia.

Results

Our analyses revealed 61 genes with suspected mutations associated with microtia-atresia. Five (HOXA4, MUC6, CHST15, TBX10, and AMER1) contained 7 de novo mutations that appeared in at least two families, which have been previously reported as pathogenic for other diseases. Among these, HOXA4 (c.920A>C, p.H307P) was determined as the most likely pathogenic variant for microtia-atresia. GO analysis revealed four gene sets involving 11 pathways potentially related to underlying pathogenesis of the disease. CNVs in three genes (UGT2B17, OVOS, and KATNAL2) were detected in at least two families. Linkage analysis disclosed 13 extra markers for the disease, of which two (FGFR1 and EYA1) were validated via machine learning analysis as plausible candidate genes for the disease.

Conclusion

Based on comprehensive genetic and bioinformatic analyses of WES data from six families of discordant monozygotic twins with microtia-atresia, we identified multiple candidate genes that may function in post-twinning onset of the disease. The collective findings provide novel insights into the pathogenesis of congenital microtia-atresia.

D-DEMØ, a distinct phenotype caused by ATP1A3 mutations

Objective

To describe a phenotype caused by ATP1A3 mutations, which manifests as dystonia, dysmorphism of the face, encephalopathy with developmental delay, brain MRI abnormalities always including cerebellar hypoplasia, no hemiplegia (Ø) (D-DEMØ), and neonatal onset.

Methods

Review and analysis of clinical and genetic data.

Results

Patients shared the above traits and had whole-exome sequencing that showed de novo variants of the ATP1A3 gene, predicted to be disease causing and occurring in regions of the protein critical for pump function. Patient 1 (c.1079C>G, p.Thr360Arg), an 8-year-old girl, presented on day 1 of life with episodic dystonia, complex partial seizures, and facial dysmorphism. MRI of the brain revealed cerebellar hypoplasia. Patient 2 (c.420G>T, p.Gln140His), an 18-year-old man, presented on day 1 of life with hypotonia, tremor, and facial dysmorphism. He later developed dystonia. MRI of the brain revealed cerebellar hypoplasia and, later, further cerebellar volume loss (atrophy). Patient 3 (c.974G>A, Gly325Asp), a 13-year-old girl, presented on day 1 of life with tremor, episodic dystonia, and facial dysmorphism. MRI of the brain showed severe cerebellar hypoplasia. Patient 4 (c.971A>G, p.Glu324Gly), a 14-year-old boy, presented on day 1 of life with tremor, hypotonia, dystonia, nystagmus, facial dysmorphism, and later seizures. MRI of the brain revealed moderate cerebellar hypoplasia.

Conclusions

D-DEMØ represents an ATP1A3-related phenotype, the observation of which should trigger investigation for ATP1A3 mutations. Our findings, and the presence of multiple distinct ATP1A3-related phenotypes, support the possibility that there are differences in the underlying mechanisms.

Modeling Normal and Pathological Ear Cartilage in vitro Using Somatic Stem Cells in Three-Dimensional Culture

Microtia (underdeveloped ear) is a rare congenital dysmorphology affecting the development of the outer ear. Although human microtic cartilage has not been fully characterized, chondrogenic cells derived from this tissue have been proposed as a suitable source for autologous auricular reconstruction. The aim of this study was to further characterize native microtic cartilage and investigate the properties of cartilage stem/progenitor cells (CSPCs) derived from it. Two-dimensional (2D) systems are most commonly used to assess the chondrogenic potential of somatic stem cells in vitro, but limit cell interactions and differentiation. Hence here we investigated the behavior of microtic CSPCs in three-dimensional spheroid cultures. Remarkable similarities between human microtic cartilages from five patients, as compared to normal cartilage, were observed notwithstanding possibly different etiologies of the disease. Native microtic cartilage displayed poorly defined perichondrium and hyper-cellularity, an immature phenotype that resembled that of the normal developing human auricular cartilage we studied in parallel. Crucially, our analysis of microtic ears revealed for the first time that, unlike normal cartilage, microtic cartilages are vascularized. Importantly, CSPCs isolated from human microtic and normal ear cartilages were found to recapitulate many characteristics of pathological and healthy tissues, respectively, when allowed to differentiate as spheroids, but not in monolayer cultures. Noteworthily, starting from initially homogeneous cell pellets, CSPC spheroids spontaneously underwent a maturation process in culture, and formed two regions (inner and outer region) separated by a boundary, with distinct cell types that differed in chondrogenic commitment as indicated by expression of chondrogenic markers. Compared to normal ear-derived spheroids, microtic spheroids were asymmetric, hyper-cellularized and the inner and outer regions did not develop properly. Hence, their organization resembled that of native microtic cartilage. Together, our results identify novel features of microtic ears and highlight the importance of 3D self-organizing in vitro systems for better understanding somatic stem cell behavior and disease modeling. Our observations of ear-derived chondrogenic stem cell behavior have implications for choice of cells for tissue engineered reconstructive purposes and for modeling the etiopathogenesis of microtia.

An analytical study of neocartilage from microtia and otoplasty surgical remnants: A possible application for BMP7 in microtia development and regeneration

To investigate auricular reconstruction by tissue engineering means, this study compared cartilage regenerated from human chondrocytes obtained from either microtia or normal (conchal) tissues discarded from otoplasties. Isolated cells were expanded in vitro, seeded onto nanopolyglycolic acid (nanoPGA) sheets with or without addition of bone morphogenetic protein-7 (BMP7), and implanted in nude mice for 10 weeks. On specimen harvest, cartilage development was assessed by gross morphology, histology, and RT-qPCR and microarray analyses. Neocartilages from normal and microtia surgical tissues were found equivalent in their dimensions, qualitative degree of proteoglycan and elastic fiber staining, and quantitative gene expression levels of types II and III collagen, elastin, and SOX5. Microarray analysis, applied for the first time for normal and microtia neocartilage comparison, yielded no genes that were statistically significantly different in expression between these two sample groups. These results support use of microtia tissue as a cell source for normal auricular reconstruction. Comparison of normal and microtia cells, each seeded on nanoPGA and supplemented with BMP7 in a slow-release hydrogel, showed statistically significant differences in certain genes identified by microarray analysis. Such differences were also noted in several analyses comparing counterpart seeded cells without BMP7. Summary data suggest a possible application for BMP7 in microtia cartilage regeneration and encourage further studies to elucidate whether such genotypic differences translate to phenotypic characteristics of the human microtic ear. The present work advances understanding relevant to the potential clinical use of microtia surgical remnants as a suitable cell source for tissue engineering of the pinna.

Accessory tragus: Report of a case in a rare location on the nasal vestibule

A case of an accessory tragus located on the nasal vestibule is reported. This represents the third case of this entity located outside of a derivative of a branchial arch. All three of these cases were located in the nose/glabella region.

Review of Preferential Suspicious Genes in Microtia Patients Through Various Approaches

Recently, an increasing trend of the birth prevalence of anotia/microtia is observed in China, contributed by changes of social environment and lifestyle. There seems to be no major breakthroughs in exact pathogenesis of microtia, though the research results related to molecular genetics unceasingly appear. In this review, the authors focus on the results of various research methods which the authors regard as the preferential suspicious gene pool to facilitate the exploration of the pathogenic genes of microtia, knowing that the mechanism of microtia is very complicated. The advantages and limitations of these various approaches will also be systematically delineated. The authors believe that this review will give a deep insight in the genetic research of microtia and help plastic surgeons manage congenital microtia more effectively.

The Developmental Origin of the Auricula Revisited

OBJECTIVES/HYPOTHESIS

Congenital auricular anomalies are common. Additionally, the auricle plays an important role in the staging of human embryos. However, little is known about the embryological development of the auricle. The most commonly reproduced developmental theory by His (1885) describes six hillocks; three on the first and three on the second pharyngeal arch. The aim of this study was to assess the validity of this theory by modern techniques and to expand the knowledge of the embryological development and morphology of the auricle.

STUDY DESIGN

22 human embryos from the Carnegie collection between Carnegie stage 13 and 23 (28-60 days) were selected based on their histological quality.

METHODS

Histological sections of the selected embryos were examined. Three-dimensional (3D) reconstructions were prepared. Additionally, literature research was performed.

RESULTS

The hillocks were absent in most stages. Contrary to common knowledge, the auricle is almost entirely innervated by branches of the facial nerve. The branches of the trigeminal nerve only innervate the tragus and the anterior external auditory meatus (EAM). Consequently, this indicates that almost the entire auricle is derived from the second pharyngeal arch, with the exception of the tragus and the anterior EAM.

CONCLUSIONS

The 3D reconstructions show the anatomy and development of the auricle to be different from concepts presented in current textbooks. As a consequence, we propose that preauricular sinuses should be classified as first pharyngeal arch anomalies.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:2467-2474, 2020.

The Phenolyzer Suite: Prioritizing the Candidate Genes Involved in Microtia

OBJECTIVE

Microtia is a congenital malformation of the external ear. Great progress about the genetic of microtia has been made in recent years. This article was to prioritize the potential candidate pathogenic genes of microtia based on existing studies and reports, with the purpose of narrowing the range of following study scientifically and quickly.

METHOD

A computational tool called Phenolyzer (phenotype-based gene analyzer) was used to prioritize microtia genes. Microtia, as a query term, was input in the interface of Phenolyzer. After several steps, including disease match, gene query, gene score system, seed gene growth, and gene ranking, the final results about genetic information of microtia were provided. Then we tracked details of the top 10 genes ranked by Phenolyzer on the basis of previous reports.

RESULTS

We detected 10 348 genes associated with microtia or related syndromes, and 78 genes of those genes belonged to seed genes. Every gene was given a score, and the gene with higher scores was more likely influence microtia. The top 10 ranked genes included HOXA2, CHD7, CDT1, ORC1, ORC4, ORC6, CDC6, MED12, TWIST1, and GLI3. Otherwise, four gene-gene interactions were displayed.

CONCLUSION

This article prioritized candidate genes of microtia for the first time. High-throughput methods provide tens of thousands of single-nucleotide variants, indels, and structural variants, and only a handful are relevant to microtia or associated syndromes. Combine the ranked potential pathogenic genes list from Phenolyzer with the results of samples provided by high-throughput methods, and more precise research directions are presented.

Identification of sequence variants associated with severe microtia-astresia by targeted sequencing

Background

Microtia-atresia is characterized by abnormalities of the auricle (microtia) and aplasia or hypoplasia of the external auditory canal, often associated with middle ear abnormalities. To date, no causal genetic mutations or genes have been identified in microtia-atresia patients.

Methods

We designed a panel of 131 genes associated with external/middle or inner ear deformity. Targeted genomic capturing combined with next-generation sequencing (NGS) was utilized to screen for mutations in 40 severe microtia-atresia patients. Mutations detected by NGS were filtered and validated. And then mutations were divided into three categories—rare or novel variants, low-frequency variants and common variants—based on their frequency in the public database. The rare or novel mutations were prioritized by pathogenicity analysis. For the low-frequency variants and common variants, we used association studies to explore risk factors of severe microtia-atresia.

Results

Sixty-five rare heterozygous mutations of 42 genes were identified in 27 (67.5%) severe microtia-atresia patients. Association studies to determine genes that were potentially pathogenic found that PLEC, USH2A, FREM2, DCHS1, GLI3, POMT1 and GBA genes were significantly associated with severe microtia-atresia. Of these, DCHS1 was strongly suggested to cause severe microtia-atresia as it was identified by both low-frequency and common variants association studies. A rare mutation (c.481C > T, p.R161C) in DCHS1 identified in one individual may be deleterious and may cause severe microtia-atresia.

Conclusion

We identified several genes that were significantly associated with severe microtia-atresia. The findings provide new insights into genetic background of external ear deformities.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0475-x) contains supplementary material, which is available to authorized users.

Correlation Between the Sites of Onset of Basal Cell Carcinoma and the Embryonic Fusion Planes in the Auricle

Objectives:

This study aims at the identification of the distribution of basal cell carcinomas (BCCs) in the auricle in correlation with the currently most credited sites of the embryonic fusion planes of the auricle.

Methods:

An overall number of 69 patients with 72 BCCs of the auricle were enrolled in the study over a period of 14 years, from June 2003 to October 2017. All the cases underwent medical preoperative digital photography and the specific location of each BCC was coded on an original full-size anatomical diagram of the auricle derived from the reports by Streeter, Wood-Jones, Park, Porter, and Minoux showing the currently most credited sites of the embryonic fusion planes arbitrarily featured as two 5-mm-wide ribbon-like areas: (1) the hyoid-mandibular fusion plane (HM-FP) running from the upper margin of the tragus toward the concha and then deflecting toward the lower margin of the tragus and (2) the free ear fold-hyoid fusion plane (FEFH-FP) running from the cranial-most portion of the helix to the mid-portion of the ascending helix. The latter fusion planes were comprehensively termed embryological fusion planes (EFP) while all of the remaining surface of the auricle was comprehensively termed non-fusion area (NFA). The surfaces of all of the latter areas were calculated using the ImageJ software.

Results:

According to our data, the greatest number of BCCs was observed within the currently most credited sites of the embryonic fusion planes of the auricle. The latter sites displayed a 12-fold increased tumor incidence in comparison with the remaining surface of the ear.

Conclusions:

A correspondence between the sites of onset of BCCs and the sites of merging and/or fusion of embryonal processes was demonstrated in the auricle. Therefore, the latter sites might be considered as high-risk areas for the development of a BCC. Such an evidence provides further support to the hypothesis of an embryological pathogenesis of BCC.

Neural crest contributions to the ear: Implications for congenital hearing disorders

Congenital hearing disorders affect millions of children worldwide and can significantly impact acquisition of speech and language. Efforts to identify the developmental genetic etiologies of conductive and sensorineural hearing losses have revealed critical roles for cranial neural crest cells (NCCs) in ear development. Cranial NCCs contribute to all portions of the ear, and defects in neural crest development can lead to neurocristopathies associated with profound hearing loss. The molecular mechanisms governing the development of neural crest derivatives within the ear are partially understood, but many questions remain. In this review, we describe recent advancements in determining neural crest contributions to the ear, how they inform our understanding of neurocristopathies, and highlight new avenues for further research using bioinformatic approaches.