Embryonic requirements for Tcf12 in the development of the mouse coronal suture

A major feature of Saethre-Chotzen syndrome is coronal craniosynostosis, the fusion of the frontal and parietal bones at the coronal suture. It is caused by heterozygous loss-of-function mutations in either of the basic HLH transcription factors TWIST1 and TCF12. While compound heterozygous Tcf12; Twist1 mice display severe coronal synostosis, the individual role of Tcf12 had remained unexplored. Here we show that Tcf12 controls several key processes in calvarial development, including the rate of frontal and parietal bone growth, and the boundary between sutural and osteogenic cells. Genetic analysis supports an embryonic requirement for Tcf12 in suture formation, as combined deletion of Tcf12 in embryonic neural crest and mesoderm, but not in postnatal suture mesenchyme, disrupts the coronal suture. We also detect asymmetric distribution of mesenchymal cells on opposing sides of the wild-type frontal and parietal bones, which prefigures later bone overlap at the sutures. In Tcf12 mutants, reduced asymmetry is associated with bones meeting end-on-end, possibly contributing to synostosis. Our results support embryonic requirements of Tcf12 in proper formation of the overlapping coronal suture.

Study on Morphometric Features of Coronal Suture Along with it Absence and Craniosynostosis

Background: Cranial sutures are syndesmosis between the cranial bones. The coronal suture is oblique in direction and extends between the frontal and the parietal bones. Craniosynostosis is a rare birth defect that occurs when the coronal suture in the skull fuses prematurely, but the brain continues to grow and develop. This leads to a misshapen head. There are a number of forms of this defect, such as coronal, sagittal, lambdoid, and metopic. Materials and Methods: Total 500 skulls were used for study, coronal suture length measured by thread method, distance between Nasion to bregma and midsupraorbital rim to coronal suture were measured. For finding skull with absence of coronal, sagittal, lambdoid, and metopic suture, we examined many skulls during routine osteology classes of Medical, Dental and other medical sciences students. Around 500 skull observed and we find only one skull with absence of left coronal suture completely. Results: The length of coronal suture was 24.8+1.4cm length, the distance between nasion to bregma was 126.7 +10.25 mm and Midsupraorbital rim to cranial suture was 102.76+8.64mm We have found only one skull with absence of coronal suture. Some of the skulls shows partly fusion of sagittal, coronal sutures. The skull with complete absence of coronal suture showing the features of other sutures clearly and right side of coronal suture is showing the complete suture. The skull was not damaged and it is in perfect condition which was using by students for their osteology study. Conclusion: We found the skull with absence of left coronal suture, which may resulted due to craniosynostosis. It may be due to hot climate in India also might be resulted for absence of suture. KEY WORDS: Birth defect, Skull, Coronal suture, Craniosynostosis.

Single-cell analysis identifies a key role for Hhip in murine coronal suture development

Craniofacial development depends on formation and maintenance of sutures between bones of the skull. In sutures, growth occurs at osteogenic fronts along the edge of each bone, and suture mesenchyme separates adjacent bones. Here, we perform single-cell RNA-seq analysis of the embryonic, wild type murine coronal suture to define its population structure. Seven populations at E16.5 and nine at E18.5 comprise the suture mesenchyme, osteogenic cells, and associated populations. Expression of Hhip, an inhibitor of hedgehog signaling, marks a mesenchymal population distinct from those of other neurocranial sutures. Tracing of the neonatal Hhip-expressing population shows that descendant cells persist in the coronal suture and contribute to calvarial bone growth. In Hhip−/− coronal sutures at E18.5, the osteogenic fronts are closely apposed and the suture mesenchyme is depleted with increased hedgehog signaling compared to those of the wild type. Collectively, these data demonstrate that Hhip is required for normal coronal suture development.

Description of three new species of frog–biting midges (Diptera: Corethrellidae) from the Central Brazilian Amazon

Three species of Corethrella Coquillett, 1902 from the state of Amazonas, Brazil are described as new to science based on female adult specimens. Corethrella cabocla Feijó, Belchior, Marialva & Pessoa sp. nov. possesses four large setae on the frons between the ventromedial area of ommatidia, a wide clypeus with 1–4 setae, a wing with the apex of R2 basal to the apex of M2 and with a midlength band, and with the abdomen entirely dark brown. Corethrella ielemdei Feijó, Ramires, Lima & Pessoa sp. nov. possesses an elongated coronal suture, four large setae on the frons between the ventromedial area of ommatidia, a clypeus squarish with 42–43 setae, a wing with the apex of R2 basal to the apex of M1 and with a midlength band and dark scales on the basal and subbasal areas of the anterior margin, legs with dark scales, and with the abdomen entirely dark brown. Corethrella menini Feijó, Picelli, Ríos-Velásquez & Pessoa sp. nov. possesses wings with the apex of R2 basal to the apex of M2 and a midlength band, with darker basal scales along all veins, basal band dark scales on C, Sc, R, M, and Cu and the abdomen entirely dark brown. With the addition of the new species, the numbers of frog-biting midges described in the Amazon basin, Brazil and in Neotropical region are now 31, 49 and 80 species, respectively.

The developing mouse coronal suture at single-cell resolution

Sutures separate the flat bones of the skull and enable coordinated growth of the brain and overlying cranium. The coronal suture is most commonly fused in monogenic craniosynostosis, yet the unique aspects of its development remain incompletely understood. To uncover the cellular diversity within the murine embryonic coronal suture, we generated single-cell transcriptomes and performed extensive expression validation. We find distinct pre-osteoblast signatures between the bone fronts and periosteum, a ligament-like population above the suture that persists into adulthood, and a chondrogenic-like population in the dura mater underlying the suture. Lineage tracing reveals an embryonic Six2+ osteoprogenitor population that contributes to the postnatal suture mesenchyme, with these progenitors being preferentially affected in a Twist1+/−; Tcf12+/− mouse model of Saethre-Chotzen Syndrome. This single-cell atlas provides a resource for understanding the development of the coronal suture and the mechanisms for its loss in craniosynostosis.

Anterior endoscopic transcortical approach to a pineal region cavernous hemangioma

A 57-year-old female presented with headache and dizziness for 3 months. Preoperative MRI revealed a lesion located at the pineal region and back side of the third ventricle, accompanied by hydrocephalus. The infratentorial supracerebellar approach may cause visuomotor, acousticomotor, and hearing disturbances. With the patient in a supine position, the authors used a frontal linear incision that was 3 cm anterior to the coronal suture and 2 cm away from the midline and an anterior endoscopic transcortical approach, which could achieve endoscopic third ventriculostomy, alleviating and preventing hydrocephalus due to postoperative adhesion and resection of the lesion at the same time. The pathological diagnosis was cavernous hemangioma. The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID215.

Magnetic resonance imaging analysis of human skull diploic venous anatomy

Background: The skull diploic venous space (DVS) represents a potential route for cerebrospinal fluid (CSF) diversion and absorption in the treatment of hydrocephalus. The goal of this study was to carry out a detailed characterization of the drainage pattern of the DVS of the skull using high-resolution MRI, especially the diploic veins draining to the lacunae laterales (LLs) since the LLs constitute an important channel for the CSF to access the superior sagittal sinus and subsequently the systemic circulation. The objective was to identify those skull regions optimally suited for an intraosseous CSF diversion system. Methods: High-resolution, T1-weighted MRI scans from 20 adult and 16 pediatric subjects were selected for analysis. Skulls were divided into four regions, that is, frontal, parietal, temporal, and occipital. On each scan, a trained observer counted all diploic veins in every skull region. Each diploic vein was also followed to determine its final drainage pathway (i.e., dural venous sinus, dural vein, LL, or indeterminate). Results: In the adult age group, the frontal and occipital skull regions showed the highest number of diploic veins. However, the highest number of draining diploic veins connecting to the lacunae lateralis was found in the frontal and parietal skull region, just anterior and just posterior to the coronal suture. In the pediatric age group, the parietal skull region, just posterior to the coronal suture, showed the highest overall number of diploic veins and also the highest number of draining diploic veins connecting to the LL. Conclusion: This study suggested that diploic venous density across the skull varies with age, with more parietal diploic veins in the pediatric age range, and more occipital and frontal diploic veins in adults. If the DVS is ultimately used for CSF diversion, our anatomical data point to optimal sites for the insertion of specially designed intraosseous infusion devices for the treatment of hydrocephalus. Likely the optimal sites for CSF diversion would be the parietal region just posterior to the coronal suture in children, and in adults, frontal and/or parietal just anterior or just posterior to the coronal suture.

The developing mouse coronal suture at single-cell resolution

Sutures separate the flat bones of the skull and enable coordinated growth of the brain and overlying cranium. To uncover the cellular diversity within sutures, we generated single-cell transcriptomes and performed extensive expression validation of the embryonic murine coronal suture. We identify Erg and Pthlh as markers of osteogenic progenitors in sutures, and distinct pre-osteoblast signatures between the bone fronts and periosteum. In the ectocranial layers above the suture, we observe a ligament-like population spanning the frontal and parietal bones. In the dura mater underlying the suture, we detect a chondrocyte-like signature potentially linked to cartilage formation under pathological conditions. Genes mutated in coronal synostosis are preferentially expressed in proliferative osteogenic cells, as well as meningeal layers, suggesting discrete cell types that may be altered in different syndromes. This single-cell atlas provides a resource for understanding development of the coronal suture, the suture most commonly fused in monogenic craniosynostosis.