Illustrated review of the embryology and development of the facial region, part 3: an overview of the molecular interactions responsible for facial development

Intelligence among ear deformities and cleft lip and/or alveolus and/or cleft palate patients during 50 years in Israel

PURPOSE

We evaluated hearing loss and general intelligence among persons with auricle anomalies and cleft lip and/or alveolus and/or cleft palate (CLAP).

METHODS

A nationwide cross-sectional study of data recorded during 1966-2019, as mandatory pre-military recruitment of individuals.

RESULTS

Of 3 182 892 adolescents, 548 were diagnosed with auricle anomalies and 2072 with CLAP. For the latter, the adjusted odds ratios for the low, low to medium and medium general intelligence categories compared to the highest category were 1.4 [95% CI 1.5-1.2], 1.2 [95% CI 1.4-1.1] and 1.1 [95% CI 1.2-0.9] respectively. The corresponding values for the auricle anomalies were not significant.

CONCLUSIONS

General intelligence was impaired among individuals with CLAP, but no significant correlation was found among individuals suffering from auricle anomalies.

Congenital Midline Upper Lip Sinus: Case Report and Review of the Literature

Congenital midline sinus of the upper lip are rare congenital malformations. We recently identified a case featuring a congenital midline sinus of the upper lip. The punctate opening was positioned at the midline of the philtrum, immediately below the base of the columella. Surgical removal of the sinus tract was conducted through an intraoral approach. Up to now, fewer than 70 cases have been reported. Several postulates, including the fusion theory, merging theory, and invagination theory, have been proposed to explain the formation of the congenital midline sinus of the upper lip. Nevertheless, the etiology of this uncommon abnormality remains unclear. This report details a case of a congenital upper lip sinus presenting as a congenital midline sinus of the upper lip and reviews the current literature on this condition.

The Differential Diagnosis of Congenital Developmental Midline Nasal Masses: Histopathological, Clinical, and Radiological Aspects

Developmental midline nasal masses including nasal dermoids (NDs), encephaloceles (EPHCs), and nasal glial heterotopias (NGHs) are a consequence of disrupted embryonal developmental processes in the frontonasal region. Surgery is the only method of treatment in order to prevent local and intracranial inflammatory complications as well as distant deformities of the facial skeleton. Due to their rarity, similar location, and clinical and radiological symptoms, meticulous preoperative differential diagnostics is mandatory. The aim of this thorough literature review was to present and discuss all clinical, histopathological, and radiological aspects of NDs, NGHs, and EPHCs that are crucial for their differential diagnosis.

Nasal Bifidity: An Unusual Pediatric Congenital Anomaly and Review of the Literature

Congenital nasal anomalies are rare, with an estimated incidence of 1/20,000 to 40,000 live births. Hyperplasia and duplication anomalies are the most uncommon, comprising about 1% of reported cases. The authors present the case of a 6-year-old girl who presented to our institution with an isolated congenital bifid nasal septum. Parents reported a visibly abnormal nose since birth, and it had been continuously monitored by the parents and pediatrician. She demonstrated no history of difficulty breathing or other nasal concerns and was otherwise growing and developing normally. On physical examination, she was breathing comfortably through her bilateral nasal airways. Her nasal examination revealed a widened mid-vault with deep dorsal grooving and a bifid tip. Magnetic resonance imaging demonstrated an isolated bifid nasal septum without other facial malformation or intracranial extension. She underwent an open septorhinoplasty. Intraoperatively, the authors identified an anomalous dorsal nasal bone extension with a resultant bifidity in the body and caudal portions of the septum. Ostectomy and cartilaginous repositioning allowed for an autogenous reconstruction without the need for grafting. She subsequently recovered well without postoperative complications and continues to have improved nasal appearance with maintenance of function. A review of recent literatures revealed 2 other cases that are similar in presentation. The authors proposed that embryologically there might have been a change in expression of bone morphogenetic protein in the frontonasal area leading to caudal extension of the nasal bone. This in turn interferes with the fusion of nasal septum resulting in the bifid septum and dual dome morphology.

Understanding the distinction between cleft lip and cleft palate: a critical step for successful prenatal detection

PURPOSE OF REVIEW

Orofacial clefts (OCs) are among the most common congenital anomalies, however, prenatal detection of cleft palate without cleft lip (CP) remains low. CP is associated with a higher risk of associated structural anomalies, recurrence risk and genetic aberrations. There is opportunity to optimize prenatal diagnosis, counseling and diagnostic genetic testing for OCs.

RECENT FINDINGS

Improving prenatal diagnosis of CP requires understanding that embryologically, the secondary palate develops from the 6th to the 10th week and fuses with the primary palate by the 12th week. Multiple first, second and third trimester 2D ultrasonographic markers for OCs have been described including the maxillary gap, frontal space, maxilla-nasion-mandible angle, retronasal triangle, palatino-maxillary diameter, equal sign, nonvisualization or gap in the soft to hard palate interface and loss of the superimposed line. We discuss the technique, evidence and limitations of each.

SUMMARY

Prenatal detection of OC can be optimized by employing 2D sonographic markers. Prenatal detection of CP may be improved by recognizing its high association with retrognathia/micrognathia.

Congenital midline upper lip sinuses with intracranial extension - A variant of nasal dermoid? An embryology-based concept

OBJECTIVE

The study aimed to present the comparative analysis of midline congenital upper lip sinuses (MCULS) and nasal dermoids (NDs). The clinical similarity of congenital midline pathologies of the midface was interesting subject for further studies. Therefore, histopathological, and embryological background were also analyzed to verify a hypothesis that NDs and MCULSs are the different variants of the same entity.

MATERIAL AND METHODS

The study group included 27 surgically treated pediatric cases with the congenital midline sinus of the nose (n = 25) or upper lip (n = 2). Seven children presented intraoperatively confirmed intracranial extension of the abnormality, 6 in NDs group and 1 in MCULS group. Apart from clinical characteristics also histopathological results were compared in both groups. An analysis of the literature concerning the proposed theories of origin of NDs as well as the current classification systems of MCULSs and NDs were conducted.

RESULTS

The analysis revealed that MCULSs present the same clinical characteristics as NDs. No differences were noticed in the histopathological results. The embryological theories presented so far are insufficient to convincingly explain the precise process of origin of abnormalities such as ND and MCULS. Nevertheless, the developmental embryological processes of the midface shed a new light on the common origin of NDs and MCULSs. The proposal of an update of the existing classification of midline congenital midface sinuses was presented.

CONCLUSIONS

The comparative analysis of clinical, histopathological, and embryological characteristics confirms that NDs and MCULSs are different forms of the same entity. Embryological implications result in the possibility of intracranial extension in each case of MCULS. Therefore, CT and MR imaging which provide irreplaceable information are recommended for all patients with MCULS. The updated classification of midline congenital midface sinuses should be taken into consideration.

Decoding the Human Face: Progress and Challenges in Understanding the Genetics of Craniofacial Morphology

Variations in the form of the human face, which plays a role in our individual identities and societal interactions, have fascinated scientists and artists alike. Here, we review our current understanding of the genetics underlying variation in craniofacial morphology and disease-associated dysmorphology, synthesizing decades of progress on Mendelian syndromes in addition to more recent results from genome-wide association studies of human facial shape and disease risk. We also discuss the various approaches used to phenotype and quantify facial shape, which are of particular importance due to the complex, multipartite nature of the craniofacial form. We close by discussing how experimental studies have contributed and will further contribute to our understanding of human genetic variation and then proposing future directions and applications for the field.

Ciliary Hedgehog signaling regulates cell survival to build the facial midline

Craniofacial defects are among the most common phenotypes caused by ciliopathies, yet the developmental and molecular etiology of these defects is poorly understood. We investigated multiple mouse models of human ciliopathies (including Tctn2, Cc2d2a, and Tmem231 mutants) and discovered that each displays hypotelorism, a narrowing of the midface. As early in development as the end of gastrulation, Tctn2 mutants displayed reduced activation of the Hedgehog (HH) pathway in the prechordal plate, the head organizer. This prechordal plate defect preceded a reduction of HH pathway activation and Shh expression in the adjacent neurectoderm. Concomitant with the reduction of HH pathway activity, Tctn2 mutants exhibited increased cell death in the neurectoderm and facial ectoderm, culminating in a collapse of the facial midline. Enhancing HH signaling by decreasing the gene dosage of a negative regulator of the pathway, Ptch1, decreased cell death and rescued the midface defect in both Tctn2 and Cc2d2a mutants. These results reveal that ciliary HH signaling mediates communication between the prechordal plate and the neurectoderm to provide cellular survival cues essential for development of the facial midline.

Insights into the genetic architecture of the human face

The human face is complex and multipartite, and characterization of its genetic architecture remains challenging. Using a multivariate genome-wide association study meta-analysis of 8,246 European individuals, we identified 203 genome-wide-significant signals (120 also study-wide significant) associated with normal-range facial variation. Follow-up analyses indicate that the regions surrounding these signals are enriched for enhancer activity in cranial neural crest cells and craniofacial tissues, several regions harbor multiple signals with associations to different facial phenotypes, and there is evidence for potential coordinated actions of variants. In summary, our analyses provide insights into the understanding of how complex morphological traits are shaped by both individual and coordinated genetic actions.

Normal embryonic development of the greater horseshoe bat Rhinolophus ferrumequinum, with special reference to nose leaf formation

The order Chiroptera (bats) is the second largest group of mammals, composed of more than 1,300 species. Although powered flight and echolocation in bats have attracted many biologists, diversity in bat facial morphology has been almost neglected. Some bat species have a "nose leaf," a leaf-like epithelial appendage around their nostrils. The nose leaf appears to have been acquired at least three times independently in bat evolution, and its morphology is highly diverse among bats species. Internal tissue morphology of nose-leaves has been investigated through histological analyses of late-stage fetuses of some bat species possessing the nose leaf. However, the proximate factors that bring about chiropteran nose-leaves have not been identified. As an initial step to address the question above, we describe the normal embryonic development of the greater horseshoe bat Rhinolophus ferrumequinum, and examine development of the tissues associated with their nose leaf during embryogenesis through histological analyses. We found that the nose leaf of R. ferrumequinum is formed through two phases. First, the primordium of the nose leaf appears as two tissue bulges aligned top and bottom on the face at embryonic stages 15-16. Second, the sub-regions of the nose leaf are differentiated through ingrowth as well as outgrowth of the epithelium at stage 17. In embryogenesis of Carollia perspicillata, a phyllostomid species with a nose leaf, the nose leaf primordium is formed as a small tissue bulge on the nostril at stage 17. This tissue bulge grows into a dorsally projected thin epithelial structure. Such differences in the nose leaf developmental process between chiropteran lineages may suggest that distinct developmental mechanisms have been employed in each lineage's nose leaf evolution.

Mandible exosomal ssc-mir-133b regulates tooth development in miniature swine via endogenous apoptosis

Signal transduction between different organs is crucial in the normal development of the human body. As an important medium for signal communication, exosomes can transfer important information, such as microRNAs (miRNAs), from donors to receptors. MiRNAs are known to fine-tune a variety of biological processes, including maxillofacial development; however, the underlying mechanism remains largely unknown. In the present study, transient apoptosis was found to be due to the expression of a miniature swine maxillofacial-specific miRNA, ssc-mir-133b. Upregulation of ssc-mir-133b resulted in robust apoptosis in primary dental mesenchymal cells in the maxillofacial region. Cell leukemia myeloid 1 (Mcl-1) was verified as the functional target, which triggered further downstream activation of endogenous mitochondria-related apoptotic processes during tooth development. More importantly, mandible exosomes were responsible for the initial apoptosis signal. An animal study demonstrated that ectopic expression of ssc-mir-133b resulted in failed tooth formation after 12 weeks of subcutaneous transplantation in nude mice. The tooth germ developed abnormally without the indispensable exosomal signals from the mandible.

The delivery of the small regulatory molecule microRNA-133b via extracellular vesicles released from the lower jaw is required for tooth formation in pigs and mice. Several microRNAs have been implicated in tooth development, but their precise roles are poorly understood. Songlin Wang at Capital Medical University, China, and colleagues found that microRNA-133b causes temporary cell death at sites of molar development by reducing the levels of the pro-survival protein myeloid cell leukemia-1. Moreover, they showed that microRNA-133b is delivered from the lower jaw in exosomes and that interrupting this signal prevents tooth development. These findings highlight the importance of cross-talk between jaw and tooth tissue for normal development and reveal a possible mechanism for the prevention and treatment of abnormal tooth formation.

CT and MRI of congenital nasal lesions in syndromic conditions

Congenital malformations of the nose can be associated with a variety of syndromes, including solitary median maxillary central incisor syndrome, CHARGE syndrome, Bosma syndrome, median cleft face syndrome, PHACES association, Bartsocas-Papas syndrome, Binder syndrome, duplication of the pituitary gland-plus syndrome and syndromic craniosynsotosis (e.g., Apert and Crouzon syndromes) among other craniofacial syndromes. Imaging with CT and MRI plays an important role in characterizing the nasal anomalies as well as the associated brain and cerebrovascular lesions, which can be explained by the intimate developmental relationship between the face and intracranial structures, as well as certain gene mutations. These conditions have characteristic imaging findings, which are reviewed in this article.

Comparative effects of neonatal diethylstilbestrol on external genitalia development in adult males of two mouse strains with differential estrogen sensitivity

The effect of neonatal exposure to diethylstilbestrol (DES), a potent synthetic estrogen, was examined to evaluate whether the CD-1 (estrogen insensitive, outbred) and C57 (estrogen sensitive, inbred) mouse strains differ in their response to estrogen disruption of male ExG differentiation. CD-1 and C57BL/6 litters were injected with sesame oil or DES (200 ng/g/5 μl in sesame oil vehicle) every other day from birth to day 10. Animals were sacrificed at the following time points: birth, 5, 10 and 60 days postnatal. Neonatally DES-treated mice from both strains had many ExG abnormalities that included the following: (a) severe truncation of the prepuce and glans penis, (b) an abnormal urethral meatus, (c) ventral tethering of the penis, (d) reduced os penis length and glans width, (e) impaired differentiation of cartilage, (f) absence of urethral flaps, and (g) impaired differentiation of erectile bodies. Adverse effects of DES correlated with the expression of estrogen receptors within the affected tissues. While the effects of DES were similar in the more estrogen-sensitive C57BL/6 mice versus the less estrogen-sensitive CD-1 mice, the severity of DES effects was consistently greater in C57BL/6 mice. We suggest that many of the effects of DES, including the induction of hypospadias, are due to impaired growth and tissue fusion events during development.