Craniofacial developmental abnormalities

METTL3-dependent m6A modification of PSEN1 mRNA regulates craniofacial development through the Wnt/β-catenin signaling pathway

Craniofacial malformations, often associated with syndromes, are prevalent birth defects. Emerging evidence underscores the importance of m6A modifications in various bioprocesses such as stem cell differentiation, tissue development, and tumorigenesis. Here, in vivo, experiments with zebrafish models revealed that mettl3-knockdown embryos at 144 h postfertilization exhibited aberrant craniofacial features, including altered mouth opening, jaw dimensions, ethmoid plate, tooth formation and hypoactive behavior. Similarly, low METTL3 expression inhibited the proliferation and migration of BMSCs, HEPM cells, and DPSCs. Loss of METTL3 led to reduced mRNA m6A methylation and PSEN1 expression, impacting craniofacial phenotypes. Co-injection of mettl3 or psen1 mRNA rescued the level of Sox10 fusion protein, promoted voluntary movement, and mitigated abnormal craniofacial phenotypes induced by mettl3 knockdown in zebrafish. Mechanistically, YTHDF1 enhanced the mRNA stability of m6A-modified PSEN1, while decreased METTL3-mediated m6A methylation hindered β-catenin binding to PSEN1, suppressing Wnt/β-catenin signaling. Pharmacological activation of the Wnt/β-catenin pathway partially alleviated the phenotypes of mettl3 morphant and reversed the decreases in cell proliferation and migration induced by METTL3 silencing. This study elucidates the pivotal role of METTL3 in craniofacial development via the METTL3/YTHDF1/PSEN1/β-catenin signaling axis.

Exploring the roles of noncoding RNAs in craniofacial abnormalities: A systematic review

Congenital craniofacial abnormalities are congenital anomalies of variable expressivity and severity with a recognizable set of abnormalities, which are derived from five identifiable primordial structures. They can occur unilaterally or bilaterally and include various malformations such as cleft lip with/without palate, craniosynostosis, and craniofacial microsomia. To date, the molecular etiology of craniofacial abnormalities is largely unknown. Noncoding RNAs (ncRNAs), including microRNAs, long ncRNAs, circular RNAs and PIWI-interacting RNAs, function as major regulators of cellular epigenetic hallmarks via regulation of various molecular and cellular processes. Recently, aberrant expression of ncRNAs has been implicated in many diseases, including craniofacial abnormalities. Consequently, this review focuses on the role and mechanism of ncRNAs in regulating craniofacial development in the hope of providing clues to identify potential therapeutic targets.

Long-term ophthalmic outcomes in 120 children with unilateral coronal synostosis: a 20-year retrospective analysis

BACKGROUND

Prior studies comparing ophthalmic outcomes after treating unicoronal synostosis (UCS) by early endoscopic strip craniectomy (ESC) versus later fronto-orbital advancement (FOA) are modest in sample size, or lack consistent age adjustment. We report long-term, age-adjusted ophthalmic outcomes for a large cohort after nonrandomized treatment by one of these two options.

METHODS

The following data was retrieved from a retrospective review of the medical records of patients with treated UCS born since 2000: cycloplegic refractions, sensorimotor examinations, and strabismus procedures before craniofacial repair and postoperatively at approximately 18 and 60 months of age. V-pattern strabismus was graded as mild (absent or + 1/-1 oblique dysfunction) versus moderate-to-severe (≥+2/-2 oblique dysfunction or left to right vertical alignment change of ≥20^Δ or ocular torticollis >15°).

RESULTS

A total of 120 infants were included: 60 treated by FOA and 60 by ESC. By the late examination, aniso-astigmatism was present in 72% of FOA-treated patients and 46% of ESC-treated patients (P < 0.0001). By late examination, the age-adjusted odds ratio of moderate-to-severe V-pattern strabismus after treatment by FOA versus ESC was 2.65 (95% CI, 1.37-6.28; P = 0.02); strabismus surgery was performed in 26 infants treated by FOA compared with 13 treated by ESC (OR = 2.8; P = 0.02). Amblyopia developed in 60% of FOA-treated patients compared with 35% of those treated by ESC (OR 3.0; 95% CI, 1.3-6.7; P = 0.02).

CONCLUSIONS

Our age-adjusted ophthalmic results confirm better long-term outcomes after treatment of USC by endoscopic strip craniectomy. Recognition and referral of affected infants by the earliest months of life facilitates the opportunity for endoscopic repair.

Evaluation and Management of V pattern Strabismus in Craniosynostosis

V pattern strabismus is the most common ocular motor disorder reported in patients with craniosynostosis. Strabismus management may prove challenging, and few studies provide perspective on surgical approach. The purpose of this review is to discuss evaluation and surgical options for treating V pattern strabismus in patients with craniosynostosis. We provide a step-by-step approach to facilitate surgical planning.

Strabismus in craniosynostosis

Strabismus is common in craniosynostosis, with rates from 39% to 90.9% in Crouzon, Apert, Pfeiffer, and Saethre-Chotzen syndromes. This article reviews the epidemiology of strabismus in these disorders and discusses competing theories of the mechanism, including absent muscles, excyclorotation of muscles, and instability of muscle pulleys. The authors then review options for surgical treatment of the often complex ocular misalignment in these disorders.

Cranial sutures as intramembranous bone growth sites

Intramembranous bone growth is achieved through bone formation within a periosteum or by bone formation at sutures. Sutures are formed during embryonic development at the sites of approximation of the membranous bones of the craniofacial skeleton. They serve as the major sites of bone expansion during postnatal craniofacial growth. For sutures to function as intramembranous bone growth sites, they need to remain in an unossified state, yet allow new bone to be formed at the edges of the overlapping bone fronts. This process relies on the production of sufficient new bone cells to be recruited into the bone fronts, while ensuring that the cells within the suture remain undifferentiated. Unlike endochondral growth plates, which expand through chondrocyte hypertrophy, sutures do not have intrinsic growth potential. Rather, they produce new bone at the sutural edges of the bone fronts in response to external stimuli, such as signals arising from the expanding neurocranium. This process allows growth of the cranial vault to be coordinated with growth of the neurocranium. Too little or delayed bone growth will result in wide-open fontanels and suture agenesis, whereas too much or accelerated bone growth will result in osseous obliteration of the sutures or craniosynostosis. Craniosynostosis in humans, suture fusion in animals, and induced suture obliteration in vitro has been associated with mutations or alterations in expression of several transcription factors, growth factors, and their receptors. Much of the data concerning signaling within sutures has been garnered from research on cranial sutures; hence, only the cranial sutures will be discussed in detail in this review. This review synthesizes classic descriptions of suture growth and pathology with modern molecular analysis of genetics and cell function in normal and abnormal suture morphogenesis and growth in a unifying hypothesis. At the same time, the reader is reminded of the importance of the suture as an intramembranous bone growth site.

Progress toward understanding craniofacial malformations

Significant advances in the study of the human face have revealed the genetic and gene-environment bases of numerous common and rare craniofacial disorders. Classification of craniofacial malformations based on clinical phenotypes is sometimes quite different from the genetic findings of patients. Different mutations in a single gene can cause distinct syndromes, and mutations in different genes can cause the same syndrome. The extracellular signaling molecule SHH, fibroblast growth factor receptors, and transcription factors GLI3, MSX2, and TWIST are discussed as examples of molecules involved in interrelated signal transduction networks regulating craniofacial development. Progress in the understanding of normal and abnormal craniofacial development, through the study of morphoregulatory signaling pathways, has benefited from multifactorial approaches recommended 40 years ago at the National Institute of Dental Research-sponsored landmark Gatlinburg Conference. The utilization of biochemistry, protein structure analyses, tissue culture, and animal model systems for developmental genetics has resulted in remarkable scientific advances. The evolutionary conservation of morphoregulatory pathways has revealed the homology of genes associated with human craniofacial malformations and their counterparts that regulate the morphogenesis of fruit flies. The continued investments in basic, translational, and patient-oriented research regarding normal and abnormal craniofacial development will translate into substantial improvements in the prevention, diagnosis, and treatment of craniofacial diseases and disorders.