Disruption of ALX1 causes frontonasal dysplasia syndrome-3, characterized by extreme microphthalmia, severe midfacial hypoplasia, and orofacial clefting. Recent studies have revealed critical tissue-specific roles of ALX1 in patterning both cranial mesoderm and cranial neural crest-derived facial mesenchyme. However, the molecular mechanisms regulating Alx1 gene expression during craniofacial development are largely unknown. In this study, we have identified a distal enhancer (Alx1-DE1) residing in a large intron of the neighboring Lrriq1 gene and demonstrate that deletion of this enhancer specifically affects Alx1 gene expression in the cranial neural crest-derived frontonasal mesenchyme and causes frontonasal and ocular defects partly phenocopying Alx1-deficient mice. We further functionally analyzed four evolutionary conserved regions, ECR1 - ECR4, in the Alx1-DE1 enhancer. Remarkably, ECR1, whose homologous region in the human genome harbors a lead single nucleotide variation significantly associated with facial and cranial vault shape differences, exhibits high enrichment of Twist1 transcription factor occupancy in mouse embryonic frontonasal tissues and drove Twist1-dependent reporter transgene expression specifically in the developing periocular and frontonasal mesenchyme in transgenic mice. These results reveal Alx1-DE1 as a crucial tissue-specific enhancer through which Twist1 and other major craniofacial developmental regulators control craniofacial patterning and morphogenesis.

Holoprosencephaly results from incomplete separation of the cerebral hemispheres. Cyclopia is a facial manifestation of Holoprosencephaly, characterized by a midline single orbit and proboscis. Prenatal diagnosis is done by ultrasonography and can be supplemented by MRI. This case uniquely presents ultrasound and gross morphology correlation of cyclopia in a resource limited setting, and a correlation between facial features, intra-cranial anatomy, and lifespan. We report a 39-year-old gravida 3 para 2 woman with a history of alcohol consumption who presented for her first antenatal checkup at 19 weeks of gestation. Ultrasound revealed a single lateral ventricle with fused thalami, absent orbital structures, and a midline cystic protrusion (proboscis). After thorough counseling, pregnancy was terminated, and cyclopia was confirmed on gross inspection. Karyotyping and fetal echocardiography were not done due to parental preference. Alobar holoprosencephaly, the most severe subtype, is diagnosed by identification of single ventricle and associated facial anomalies. Lobar holoprosencephaly, however, requires coronal imaging to demonstrate absence of cavum septum pellucidum and fusion of frontal horns. The severity of facial anomalies correlates with underlying brain malformations. Chromosomal anomalies, maternal diabetes, infections, and teratogenic exposures like alcohol are known risk factors. Differential diagnoses include proboscis lateralis, midline encephaloceles and frontonasal dysplasia. This case highlights the prognostic significance of facial and brain anomalies and diagnostic utility of prenatal ultrasound in diagnosing holoprosencephaly underscoring the necessity of timely prenatal visits. Definitive genomic studies were not feasible, but maternal alcohol consumption can be considered as a possible risk factor.

Loss of ALX1 gene function causes severe facial clefting and extreme microphthalmia. Previous studies suggest that ALX1 protein function is crucial for patterning the cranial neural crest cell (CNCC)-derived frontonasal mesenchyme, but how ALX1 regulates eye development is not well understood. Here, we show that Alx1 is transiently expressed in the embryonic cranial mesoderm and that Alx1-/- mice exhibit agenesis of extraocular muscles (EOMs) without affecting other muscles. We show that cranial mesoderm-specific Alx1 inactivation resulted in complete EOM agenesis accompanied by failure of activation of the core myogenic regulatory network specifically in, and increased apoptosis of, the EOM progenitor cells. Analysis of mice with temporally induced Alx1 inactivation demonstrated that EOM myogenesis requires Alx1 function before, but not after, formation of the EOM primordium. These data identify ALX1 as a unique and specific upstream regulator of EOM myogenesis, and provide new insights into pathogenic mechanisms underlying ALX1-type frontonasal dysplasia, as well as molecular mechanisms controlling cell fate specification in the early cranial mesoderm.

SPECC1L encodes a cytoskeletal scaffolding protein that interacts with filamentous actin, microtubules, and cell junctional components. In humans, autosomal dominant mutations in SPECC1L cause a syndrome characterized by craniofrontonasal anomalies including broad nasal bridge, ocular hypertelorism, prominent forehead, and cleft lip/palate. Complete loss of SPECC1L in mice on a homogeneous genetic background results in perinatal lethality, accompanied by subtle cranial differences and incompletely penetrant cleft palate. This lethality limits postnatal analysis of craniofacial development. Because cranial neural crest cells (CNCCs) contribute extensively to the formation of anterior craniofacial structures, we investigated whether disruption of SPECC1L in CNCCs contributes to the craniofrontonasal phenotypes observed in SPECC1L-related syndrome. We generated a Specc1l-floxed allele and crossed it with the Wnt1-Cre2 deleter strain, which drives Cre recombinase expression in the dorsal neuroectoderm and NCCs. Most homozygous Specc1l ΔCNCC mutants survived postnatally and exhibited hallmark features of the human SPECC1L-related syndrome, including shortened skulls, reduced frontal bone area, nasal defects, and midface hypoplasia. The cranial mesenchyme of Specc1l ΔCNCC mice displayed shortened primary cilia and increased Hedgehog (Hh) signaling activity at E13.5, as evidenced by enhanced GLI1 immunostaining. These defects were also observed early in E9.5 facial prominences, indicating that they may drive the adult phenotype. Collectively, Specc1l ΔCNCC mice provide a novel model for investigating the roles of CNCCs, primary cilia, and Hh signaling in frontonasal prominence and midfacial development.

Frontonasal dysplasia (FND) is a rare craniofacial anomaly characterized by hypertelorism and nasal deformities. Traditional intracranial approaches for correction, such as box osteotomy or facial bipartition, are effective but associated with high morbidity. This study presents an extracranial umbrella graft technique for nasal reconstruction in patients with FND. Between 2014 and 2024, 55 patients with FND were retrospectively evaluated, and 14 met the criteria for extracranial nasal reconstruction. Inclusion criteria were interorbital distance (IOD) <40 mm and the presence of inwardly projecting concave nasal cartilage. Through a midline incision, inverted U-shaped osteotomies were performed to medialize nasal bones. Concave cartilage was harvested, inverted, and used as an umbrella graft to restore nasal projection. Septal cartilage grafts supported the lower nasal framework. Outcomes were assessed by complications and Whitaker classification. This study included 9 females and 5 males (mean age 8.3 years). Mean follow-up was 2.3 years. No major complications, such as cerebrospinal fluid leakage, visual impairment, or infection, were observed. One patient developed pressure sores from splints, and two underwent minor scar revisions. Mean anterior IOD decreased from 34 to 26.9 mm. Three patients reported insufficient projection, whereas all others achieved significant improvement. According to Whitaker classification, 10 patients were category I and 4 were category II. This technique offers a safe, less invasive alternative for nasal reconstruction in selected patients with FND, providing satisfactory esthetic results with minimal morbidity. Although long-term outcomes remain to be clarified, this approach may serve as a valuable option.