Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature

BACKGROUND

Auriculocondylar syndrome (ARCND) is a rare congenital craniofacial developmental malformation syndrome of the first and second pharyngeal arches with external ear malformation at the junction between the lobe and helix, micromaxillary malformation, and mandibular condylar hypoplasia. Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).

METHODS

This study reports a case of ARCND2 resulting from a novel pathogenic variant in the PLCB4 gene, and summarizes PLCB4 gene mutation sites and phenotypes of ARCND2.

RESULTS

The proband, a 5-day-old male neonate, was referred to our hospital for respiratory distress. Micrognathia, microstomia, distinctive question mark ears, as well as mandibular condyle hypoplasia were identified. Trio-based whole-exome sequencing identified a novel missense variant of NM_001377142.1:c.1928C>T (NP_001364071.1:p.Ser643Phe) in the PLCB4 gene, which was predicted to impair the local structural stability with a result that the protein function might be affected. From a review of the literature, only 36 patients with PLCB4 gene mutations were retrieved.

CONCLUSION

As with other studies examining familial cases of ARCND2, incomplete penetrance and variable expressivity were observed within different families' heterozygous mutations in PLCB4 gene. Although, motor and intellectual development are in the normal range in the vast majority of patients with ARCND2, long-term follow-up and assessment are still required.

A Case of Trigeminal Neuralgia in an Adult Patient With Lambdoid Synostosis

Trigeminal neuralgia (TN) is characterized by sudden, brief intense pain in the distribution of the unilateral trigeminal nerve (TGN). Neurovascular compression (NVC) of the TGN is the most common cause of TN. Recent studies have suggested that a structural anomaly of the posterior cranial fossa might be involved in the development of TN, and several studies have documented the association between NVC-related TN and congenital posterior cranial deformities in adults. We present the case of a 56-year-old woman with NVC-related TN and unilateral lambdoid synostosis (ULS), along with a literature review, to investigate the relationship between TN and structural anomalies of the posterior fossa. This is the first report of TN in an adult with ULS. Mild and asymptomatic cases of lambdoid synostosis might have a higher incidence of NVC-related TN in association with posterior cranial fossa deformities.

Trio cooperates with Myh9 to regulate neural crest-derived craniofacial development

Trio is a unique member of the Rho-GEF family that has three catalytic domains and is vital for various cellular processes in both physiological and developmental settings. TRIO mutations in humans are involved in craniofacial abnormalities, in which patients present with mandibular retrusion. However, little is known about the molecular mechanisms of Trio in neural crest cell (NCC)-derived craniofacial development, and there is still a lack of direct evidence to assign a functional role to Trio in NCC-induced craniofacial abnormalities. Methods: In vivo, we used zebrafish and NCC-specific knockout mouse models to investigate the phenotype and dynamics of NCC development in Trio morphants. In vitro, iTRAQ, GST pull-down assays, and proximity ligation assay (PLA) were used to explore the role of Trio and its potential downstream mediators in NCC migration and differentiation. Results: In zebrafish and mouse models, disruption of Trio elicited a migration deficit and impaired the differentiation of NCC derivatives, leading to craniofacial growth deficiency and mandibular retrusion. Moreover, Trio positively regulated Myh9 expression and directly interacted with Myh9 to coregulate downstream cellular signaling in NCCs. We further demonstrated that disruption of Trio or Myh9 inhibited Rac1 and Cdc42 activity, specifically affecting the nuclear export of β-catenin and NCC polarization. Remarkably, craniofacial abnormalities caused by trio deficiency in zebrafish could be partially rescued by the injection of mRNA encoding myh9, ca-Rac1, or ca-Cdc42. Conclusions: Here, we identified that Trio, interacting mostly with Myh9, acts as a key regulator of NCC migration and differentiation during craniofacial development. Our results indicate that trio morphant zebrafish and Wnt1-cre;Trio^fl/fl mice offer potential model systems to facilitate the study of the pathogenic mechanisms of Trio mutations causing craniofacial abnormalities.

Association of Dysplastic Coronoid Process with Long-Face Morphology

Vertical malocclusion is a developmental condition, resulting from complex interactions among multiple etiological factors during the growth period. As a tricky dentofacial deformity clinically, long-face (LF) morphology is characterized by excessive vertical facial growth with severe disarrangement of jaws and teeth. Since the improvement of LF patients on facial profile and occlusion is often difficult and lacks long-term stability, it becomes important to unravel the etiology of LF pattern formation for early prevention and treatment. In the current studies, we identified a transgenic mouse model that exhibited a dysplastic coronoid process and LF morphology. Although the mutant mice exhibited jaw structures and occlusion comparable to controls at birth, they all acquired typical LF morphology with anterior open bite during postnatal growth, resembling clinical features of the selected skeletal class III patients. Since the coronoid process provides an insertion site for the temporalis attachment, we examined the initial development and differentiation of the temporalis and found identical results in both control and mutant mice before E17.5 when the temporal muscle makes attachment to the coronoid process. However, thereafter, we observed altered orientation and reduced size of the cross-sectional area of the temporalis in mutant mice, which persisted to the weaning stage. Biomechanical analysis and simulation modeling further support the idea that altered morphology of the coronoid process may impair the efficiency of the vertical temporalis contraction and appears to correlate with LF formation. Consistently, we present evidence that a dysplastic mandibular coronoid process was also seen in some human patients with skeletal III LF morphology. Taken together, the results presented in this study establish an association of the craniofacial bony structures with vertical patterning, which will have implications in earlier prediction for clinical precaution and intervention.

Evaluating aesthetics of the nasolabial region in children with cleft lip and palate: professional analysis and patient satisfaction

Cleft lip and palate is one of the most common deformities of the craniofacial region, and treatment of this deformity is essential for social reintegration. One of the major goals of surgery and treatment of craniofacial deformities is to improve the aesthetic appearance of the face, and thereby improve the patient's social acceptability. Here, we present a critical review of the criteria for aesthetic evaluation of the nasolabial region in cleft patients by assessing publications with the highest level of evidence, including professional evaluation, and patient satisfaction. The findings indicate treatment of this condition represents a major challenge for multidisciplinary team care.