Bmp5 Mutation Alters miRNA Expression During Embryonic External Ear Development.

ABSTRACT: To understand the changes in gene regulation and expression of MicroRNA (miRNA) involved in external mouseear embryonic development after point mutation of the Bmp5 gene, the outer ear tissues of developed E15.5 and E17.5 mouse embryos were obtained using a Bmp5 short ear mouse model, and the changes in miRNA expression profiles were detected. Changes in miRNA expression in the experimental and control groups were identified during Bmp5 short ear mouse embryo development at E15.5 and E17.5. GO and Kyoto Encyclopedia of Genes and Genomes functional annotations were performed on differentially expressed miRNAs. Multiple signal pathways related to miRNA expression were enhanced during the development of E15.5 and E17.5 embryos of Bmp5 short-ear mice. Based on the basic characteristics of miRNAs, this study aimed to determine the differential expression of miRNAs in Bmp5 short-ear mice during the development of external ear embryos using advanced sequencing techniques. The results showed differences in some key regulatory miRNA changes after point mutations in the Bmp5 gene. This study provides new insights into the mechanism by which miRNAs regulate the development of the external mouse ear. Changes in miRNA expression profiles can also provide clues for studying the biological regulatory mechanism of external ear embryonic development.

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.

Treating Scars in the Auricle Region.

This article provides a review of the surgical and nonsurgical options available to manage a variety of auricular scars. The basics of wound healing are discussed in addition to the etiology of keloids and the cauliflower ear. Many auricular scars can be revised with scar excision techniques, but separate discussions for the treatment of keloids and the cauliflower ear are provided. The management plan for auricular scarring requires appropriate patient counseling regarding the risk of recurrence in keloids, regrowth of scar tissue in cauliflower ears, scar hypertrophy at the line of closure, widening of the scar, and persisting ear contour deformities.

Morphogenesis of the middle ear ossicles and spatial relationships with the external and inner ears during the embryonic period.

We describe the three-dimensional morphogenesis of the middle ear ossicles (MEOs) according to Carnegie stage (CS) in human embryos. Seventeen samples including 33 MEOs from CS18 to 23 were selected from the Kyoto Collection. The primordia of the MEOs and related structures were histologically observed and three-dimensionally reconstructed from digital images. The timing of chondrogenesis was variable among structures. The stapes was recognizable as a vague condensation of the mesenchymal cells in all samples from CS18, whereas the malleus and incus were recognizable at CS19. Chondrogenesis of all MEOs was evident in all samples after CS21. The chondrocranium was recognizable in all samples by CS18, and the perichondrium border of the auricular cartilage and otic capsule was distinct in all samples at CS23. At CS19, the MEOs were positioned in the anterior to posterior direction, following the order malleus, incus, stapes, which adjusted gradually during development. The MEOs connected in all samples after CS22. The stapes was located close to the vestibular part of the inner ear, although the basal part was not differentiated into the "footplate" form, even at CS23. The handles of the malleus were close to the tubotympanic recess at CS23, but were distant from the external auditory meatus. Determining the timeline of the formation of MEOs and connection of the external and inner ears can be informative for understanding hearing loss caused by failure of this connection. These data may provide a useful standard for morphogenesis, and will contribute to distinguishing between normal and abnormal MEO development. Anat Rec, 299:1325-1337, 2016. © 2016 Wiley Periodicals, Inc.

The development of the mammalian outer and middle ear.

The mammalian ear is a complex structure divided into three main parts: the outer; middle; and inner ear. These parts are formed from all three germ layers and neural crest cells, which have to integrate successfully in order to form a fully functioning organ of hearing. Any defect in development of the outer and middle ear leads to conductive hearing loss, while defects in the inner ear can lead to sensorineural hearing loss. This review focuses on the development of the parts of the ear involved with sound transduction into the inner ear, and the parts largely ignored in the world of hearing research: the outer and middle ear. The published data on the embryonic origin, signalling, genetic control, development and timing of the mammalian middle and outer ear are reviewed here along with new data showing the Eustachian tube cartilage is of dual embryonic origin. The embryonic origin of some of these structures has only recently been uncovered (Science, 339, 2013, 1453; Development, 140, 2013, 4386), while the molecular mechanisms controlling the growth, structure and integration of many outer and middle ear components are hardly known. The genetic analysis of outer and middle ear development is rather limited, with a small number of genes often affecting either more than one part of the ear or having only very small effects on development. This review therefore highlights the necessity for further research into the development of outer and middle ear structures, which will be important for the understanding and treatment of conductive hearing loss.

Development and Integration of the Ear.

The perception of our environment via sensory organs plays a crucial role in survival and evolution. Hearing, one of our most developed senses, depends on the proper function of the auditory system and plays a key role in social communication, integration, and learning ability. The ear is a composite structure, comprised of the external, middle, and inner ear. During development, the ear is formed from the integration of a number of tissues of different embryonic origin, which initiate in distinct areas of the embryo at different time points. Functional connections between the components of the hearing apparatus have to be established and maintained during development and adulthood to allow proper sound submission from the outer to the middle and inner ear. This highly organized and intimate connectivity depends on intricate spatiotemporal signaling between the various tissues that give rise to the structures of the ear. Any alterations in this chain of events can lead to the loss of integration, which can subsequently lead to conductive hearing loss, in case of outer and middle ear defects or sensorineural hearing loss, if inner ear structures are defective. This chapter aims to review the current knowledge concerning the development of the three ear compartments as well as mechanisms and signaling pathways that have been implicated in the coordination and integration process of the ear.

Movement of the external ear in human embryo.

INTRODUCTION: External ears, one of the major face components, show an interesting movement during craniofacial morphogenesis in human embryo. The present study was performed to see if movement of the external ears in a human embryo could be explained by differential growth. METHODS: In all, 171 samples between Carnegie stage (CS) 17 and CS 23 were selected from MR image datasets of human embryos obtained from the Kyoto Collection of Human Embryos. The three-dimensional absolute position of 13 representative anatomical landmarks, including external and internal ears, from MRI data was traced to evaluate the movement between the different stages with identical magnification. Two different sets of reference axes were selected for evaluation and comparison of the movements. RESULTS: When the pituitary gland and the first cervical vertebra were selected as a reference axis, the 13 anatomical landmarks of the face spread out within the same region as the embryo enlarged and changed shape. The external ear did move mainly laterally, but not cranially. The distance between the external and internal ear stayed approximately constant. Three-dimensionally, the external ear located in the caudal ventral parts of the internal ear in CS 17, moved mainly laterally until CS 23. When surface landmarks eyes and mouth were selected as a reference axis, external ears moved from the caudal lateral ventral region to the position between eyes and mouth during development. CONCLUSION: The results indicate that movement of all anatomical landmarks, including external and internal ears, can be explained by differential growth. Also, when the external ear is recognized as one of the facial landmarks and having a relative position to other landmarks such as the eyes and mouth, the external ears seem to move cranially.

Reference intervals for fetal ear length between 19 and 24 weeks of pregnancy on 3-dimensional sonography.

OBJECTIVES: The purpose of this study was to establish reference intervals for fetal ear length using 3-dimensional sonography in the rendering mode. METHODS: A cross-sectional study was conducted on 114 women from 19 weeks to 23 weeks 6 days of normal pregnancy. Fetal ear length measurement was performed in the rendering mode, obtained from 2-dimensional mode reconstruction. To determine the correlation between ear length and gestational age, scatterplots were constructed, and the Pearson correlation coefficient was calculated. Mean, median, SD, maximum, and minimum values and percentiles for each gestational age were calculated. To calculate the intraobserver reproducibility, we used the intraclass correlation coefficient. RESULTS: The mean ear length ± SD increased from 14.43 ± 1.28 mm (range, 12.80-16.50 mm) in the 19th week of pregnancy to 19.72 ± 1.87 mm (range, 17.20-22.40 mm) in the 23rd week. Three-dimensional sonographic ear length measurements were correlated with gestational age, with the best adjustment represented by the following exponential equation: ear length = exp(1.215 × gestational age - 8.692) (R(2) = 0.423). The intraobserver reproducibility was excellent, resulting in an intraclass correlation coefficient of 0.967 (95% confidence interval, 0.939-0.982). CONCLUSIONS: Reference intervals for fetal ear length using 3-dimensional sonography in the rendering mode from 19 weeks to 23 weeks 6 days of pregnancy were determined and proved reproducible.

Expression of protocadherin-19 in the nervous system of the embryonic zebrafish.

We have analyzed the expression pattern of protocadherin-19, a member of the delta2-protocadherins, in the nervous system of developing zebrafish using in situ hybridization methods. mRNA encoding protocadherin-19 (Pcdh19) began to be expressed at about 12 hours post fertilization (hpf) showing a segmental expression pattern in the anterior 1/3 of the neural keel, with strong expression in the presumptive forebrain, cerebellum/rhombomere 1 and rhombomere 4. Pcdh19 expression in the posterior neural keel was continuous and confined to the midline region. By 24 hpf, Pcdh19 was expressed widely in the brain and spinal cord, with higher expression levels in the ventral telencephalon, dorsal and central thalamus, optic tectum, central tegmentum, cerebellum and dorsolateral regions of the hindbrain. As development proceeded, Pcdh19 expression domains became restricted to the dorsal and/or lateral regions of the central nervous system, and Pcdh19 expression was not detected in the spinal cord of two- and three-day old embryos. Pcdh19 was also expressed by the eye primordium, developing retina, lens and otic vesicle. Similar to its expression in the brain, Pcdh19 expression in the eye and ear was also spatially and temporally regulated.

The histologic relationship of preauricular sinuses to auricular cartilage.

OBJECTIVE: To determine the histologic relationship and distance between excised preauricular epithelial sinus tract and the adjacent auricular cartilage (sinocartilaginous distance) in a series of patients. The excision of preauricular sinuses is a common surgical procedure. Recurrences are frequent and can be technically challenging. While advocated by several authors, the surgical removal of adjacent auricular cartilage is not universally performed. DESIGN: Retrospective case series. SETTING: Children's Hospital of Philadelphia. PATIENTS: Fifty-two pediatric patients who underwent surgical excision of preauricular sinus tracts and adjacent auricular cartilage. INTERVENTIONS: Between September 1, 2005, and July 31, 2007, the preauricular sinus tracts and adjacent auricular cartilage were excised from 52 pediatric patients. A pathologist reviewed a total of 58 specimens to determine the relationship between epithelial tract and cartilage. MAIN OUTCOME MEASURE: The sinocartilaginous distance in microns. RESULTS: Patient ages ranged from 8 months to 17 years (mean age, 4 years). In all but 1 case, the tracts were in close proximity to the cartilage. The average sinocartilaginous distance was 472 mum (median distance, 400 mum); the 25th percentile was 250 mum. In over 50% of the specimens, the sinocartilaginous distance was less than 0.5 mm, and in nearly all of the these, the epithelial tract was in continuity with stromal tissue histologically indistinguishable from perichondrium. CONCLUSIONS: The observed sinocartilaginous distances suggest that it may be difficult to dissect most sinus tracts from the cartilage. The routine removal of a small portion of auricular cartilage along with the sinus tract may yield a more thorough excision and help to prevent recurrence.

Embryology and epidemiology of microtia.

The auricle derives from six hillocks arising from the first and second branchial arches. Different hillocks give rise to different parts of the pinna. In the course of embryonic development, the auricle migrates postero-cranially as the mandible enlarges. Auricular malformations, such as microtia, are thought to be related to cell death of the first and second arch derivatives. The prevalence and characteristics of microtia vary in different populations. The prevalence ranges from 0.83 to 17.4 per 10,000. Microtia is more common in males, and right-sided dominance varies from 57 to 67%. The prevalence of aural atresia or stenosis varies from 55 to 93%. Microtia has been associated with numerous risk factors including race and gender. Genetic factors are likely to have an effect at least in some patients with microtia.

Genetics of microtia and associated syndromes.

Microtia is a congenital anomaly, characterised by a small, abnormally shaped auricle (pinna). It is usually accompanied by a narrow, blocked or absent ear canal. Microtia can occur as the only clinical abnormality or as part of a syndrome. The estimated prevalence of microtia is 0.8-4.2 per 10 000 births, and it is more common in men. Microtia can have a genetic or environmental predisposition. Mendelian hereditary forms of microtia with an autosomal dominant or recessive mode of inheritance, and some forms due to chromosomal aberrations have been reported. Several responsible genes have been identified, most of them being homeobox genes. Mouse models have been very useful to study these genes, providing valuable information on the development of the auditory system. In this article, we review the epidemiological characteristics of microtia and the environmental causes involved. In addition, we discuss the development of the auditory system, specifically the relevant aspects of external and middle ear development. The focus of this review is to discuss the genetic aspects of microtia and associated syndromes. The clinical aspects of various disorders involving microtia are also discussed in relation to the genes that are causing them.

Expression of ERK signaling inhibitors Dusp6, Dusp7, and Dusp9 during mouse ear development.

The levels of fibroblast growth factor (FGF) signaling play important roles in coordinating development of the mouse inner, middle, and outer ears. Extracellular signal-regulated kinases (ERKs) are among the effectors that transduce the FGF signal to the nucleus and other cellular compartments. Attenuation of ERK activity by dephosphorylation is necessary to modulate the magnitude and duration of the FGF signal. Recently, we showed that inactivation of the ERK phosphatase, dual specificity phosphatase 6 (DUSP6), causes partially penetrant postnatal lethality, hearing loss and skeletal malformations. To determine whether other Dusps may function redundantly with Dusp6 during otic development, we surveyed the expression domains of the three ERK-specific DUSP transcripts, Dusp6, Dusp7, and Dusp9, in the embryonic mouse ear. We show that each is expressed in partially overlapping patterns that correspond to regions of active FGF signaling, suggesting combinatorial roles in negative regulation of this pathway during ear development.

A new phenotypical variant of intrauterine growth restriction?

OBJECTIVES: A link between intrauterine growth restriction and major adult-onset diseases has been reported. In this study we observed a series of hitherto-unrecognized clinical features in a population of children with intrauterine growth restriction. PATIENTS AND METHODS: A total of 77 Italian children (aged 9.45 +/- 2.08 years) with antenatally diagnosed intrauterine growth restriction and small-for-gestational-age birth, along with their parents, were examined. The children with intrauterine growth restriction and were small for gestational age were subdivided into 2 groups ("variant" versus control subjects) according to evidence of auricle morphology deviation from normal. The following variables were determined: (1) external ear auricle geometry; (2) function of the posterior communicating arteries of the circle of Willis, as assessed by transcranial Doppler ultrasonography; (3) articular mobility, as assessed by Beighton's 9-point scale; (4) skin softness; and (5) distortion product-evoked otoacoustic emissions. RESULTS: Intrauterine growth restriction-variant children (n = 27) showed a significant female predominance, a lower proportion of maternal pregnancy-induced hypertension/preeclampsia, and a higher head circumference as compared with intrauterine growth restriction control subjects. Mothers of small-for-gestational-age-variant children showed significantly different auricular geometry parameters as compared with the intrauterine growth restriction controls mothers. An excess of bilaterally nonfunctioning posterior communicating arteries was observed both in the children with the intrauterine growth restriction-variant phenotype and their mothers as compared with the control groups. Significantly increased proportions of joint hypermobility and skin softness were observed in the intrauterine growth restriction-variant children as compared with controls subjects. Children with the intrauterine growth restriction-variant phenotype and their mothers showed bilateral distortion product-evoked otoacoustic emissions notches versus none in the control subjects, with an associated reduction of the area under the curve in both the intrauterine growth restriction-variant children and their mothers. No significant differences between the variant and control groups regarding the fathers were observed. CONCLUSIONS: We propose that the observed phenotypical constellation may represent an unrecognized variant of intrauterine growth restriction.

Characterizing regeneration in the vertebrate ear.

We have previously shown that MRL/MpJ mice have a capacity for regeneration instead of scar formation following an ear punch wound. Understanding the differences that occur between scar-free regeneration or repair with scarring will have great impact upon advances in skin tissue engineering. A key question that remains unanswered in the MRL/MpJ mouse model is whether regeneration was restricted to the ear or whether it extended to the skin. A histological analysis was conducted up to 4 months post-wounding, not only with 2-mm punch wounds to the ear but also to the skin on the backs of the same animals. MRL/MpJ mouse ear wounds regenerate faster than control strains, with enhanced blastema formation, a markedly thickened tip epithelium and reduced scarring. Interestingly, in the excisional back wounds, none of these regenerative features was observed and both the C57BL/6 control and MRL/MpJ mice healed with scarring. This review gives an insight into how this regenerative capacity may be due to evolutionary processes as well as ear anatomy. The ear is thin and surrounded on both sides by epithelia, and the dorsal skin is devoid of cartilage and under greater tensile strain. Analysis of apoptosis during ear regeneration is also discussed, assessing the role and expression of various members of the Bcl-2 family of proteins. Ongoing studies are focusing on de novo cartilage development in the regenerating ear, as well as understanding the role of downstream signalling cascades in the process. Identification of such signals could lead to their manipulation and use in a novel tissue-engineered skin substitute with scar-free integration.

Accessory tragus: A report of 2 cases.

The purpose of this article was to review the embryology of the external ear, as related to the clinical finding of accessory tragus (ear tags). Medical management of the accessory tragus is discussed, as well as differential diagnoses and associated syndromes. A general clinical description of accessory tragus is described, and 2 specific cases in pediatric patients are presented.

Tissue-specific roles of Tbx1 in the development of the outer, middle and inner ear, defective in 22q11DS patients.

Most 22q11.2 deletion syndrome (22q11DS) patients have middle and outer ear anomalies, whereas some have inner ear malformations. Tbx1, a gene hemizygously deleted in 22q11DS patients and required for ear development, is expressed in multiple tissues during embryogenesis. To determine the role of Tbx1 in the first pharyngeal pouch (PPI) in forming outer and middle ears, we tissue-specifically inactivated the gene using Foxg1-Cre. In the conditional mutants, PPI failed to outgrow, preventing the middle ear bone condensations from forming. Tbx1 was also inactivated in the otic vesicle (OV), resulting in the failure of inner ear sensory organ formation, and in duplication of the cochleovestibular ganglion (CVG). Consistent with the anatomical defects, the sensory genes, Otx1 and Bmp4 were downregulated, whereas the CVG genes, Fgf3 and NeuroD, were upregulated. To delineate Tbx1 cell-autonomous roles, a more selective ablation, exclusively in the OV, was performed using Pax2-Cre. In contrast to the Foxg1-Cre mutants, Pax2-Cre conditional mutant mice survived to adulthood and had normal outer and middle ears but had the same inner ear defects as the Tbx1 null mice, with the same gene expression changes. These results demonstrate that Tbx1 has non-cell autonomous roles in PPI in the formation of outer and middle ears and cell-autonomous roles in the OV. Periotic mesenchymal markers, Prx2 and Brn4 were normal in both conditional mutants, whereas they were diminished in Tbx1-/- embryos. Thus, Tbx1 in the surrounding mesenchyme in both sets of conditional mutants cannot suppress the defects in the OV that occur in the null mutants.

[Doubling of the pinna, a rare branchial arch developmental disorder]. / Doppelanlage der Ohrmuschel, eine seltene Kiemenbogen-Fehlbildung.

BACKGROUND: Auricular appendices are not unusual, but doubling of the pinna is rare. There is still a controversy if these are derivates from the first or the second branchial arch. PATIENT: The case of a 3 year old girl is described with doubling of the pinna and hemi facial atrophia. The second pinna was on third of the orthotop regular auricle. It seemed to come from the tragus anlage i. e. originating from the first otic hillock. RESULTS: The accessory pinna was resected, an aesthetic result could be achieved. CONCLUSION: Morphology and position of accessory pinnas arise again the question of the origin of the auricular hillocks. This case supports the opinion of Otto that the first hillock only belongs to the first branchial arch and the major part of the auricle is originating from the hillock 2-6 i. e. to the second branchial arch.