A Twist-Box domain of the C. elegans Twist homolog, HLH-8, plays a complex role in transcriptional regulation.

TWIST1 is a basic helix-loop-helix (bHLH) transcription factor in humans that functions in mesoderm differentiation. TWIST1 primarily regulates genes as a transcriptional repressor often through TWIST-Box domain-mediated protein-protein interactions. The TWIST-Box also can function as an activation domain requiring 3 conserved, equidistant amino acids (LXXXFXXXR). Autosomal dominant mutations in TWIST1, including 2 reported in these conserved amino acids (F187L and R191M), lead to craniofacial defects in Saethre-Chotzen syndrome (SCS). Caenorhabditis elegans has a single TWIST1 homolog, HLH-8, that functions in the differentiation of the muscles responsible for egg laying and defecation. Null alleles in hlh-8 lead to severely egg-laying defective and constipated animals due to defects in the corresponding muscles. TWIST1 and HLH-8 share sequence identity in their bHLH regions; however, the domain responsible for the transcriptional activity of HLH-8 is unknown. Sequence alignment suggests that HLH-8 has a TWIST-Box LXXXFXXXR motif; however, its function also is unknown. CRISPR/Cas9 genome editing was utilized to generate a domain deletion and several missense mutations, including those analogous to SCS patients, in the 3 conserved HLH-8 amino acids to investigate their functional role. The TWIST-Box alleles did not phenocopy hlh-8 null mutants. The strongest phenotype detected was a retentive (Ret) phenotype with late-stage embryos in the hermaphrodite uterus. Further, GFP reporters of HLH-8 downstream target genes (arg-1::gfp and egl-15::gfp) revealed tissue-specific, target-specific, and allele-specific defects. Overall, the TWIST-Box in HLH-8 is partially required for the protein's transcriptional activity, and the conserved amino acids contribute unequally to the domain's function.

Synchondrosis fusion contributes to the progression of postnatal craniofacial dysmorphology in syndromic craniosynostosis.

Syndromic craniosynostosis (CS) patients exhibit early, bony fusion of calvarial sutures and cranial synchondroses, resulting in craniofacial dysmorphology. In this study, we chronologically evaluated skull morphology change after abnormal fusion of the sutures and synchondroses in mouse models of syndromic CS for further understanding of the disease. We found fusion of the inter-sphenoid synchondrosis (ISS) in Apert syndrome model mice (Fgfr2S252W/+ ) around 3 weeks old as seen in Crouzon syndrome model mice (Fgfr2cC342Y/+ ). We then examined ontogenic trajectories of CS mouse models after 3 weeks of age using geometric morphometrics analyses. Antero-ventral growth of the face was affected in Fgfr2S252W/+ and Fgfr2cC342Y/+ mice, while Saethre-Chotzen syndrome model mice (Twist1+/- ) did not show the ISS fusion and exhibited a similar growth pattern to that of control littermates. Further analysis revealed that the coronal suture synostosis in the CS mouse models induces only the brachycephalic phenotype as a shared morphological feature. Although previous studies suggest that the fusion of the facial sutures during neonatal period is associated with midface hypoplasia, the present study suggests that the progressive postnatal fusion of the cranial synchondrosis also contributes to craniofacial dysmorphology in mouse models of syndromic CS. These morphological trajectories increase our understanding of the progression of syndromic CS skull growth.

Syndromic Craniosynostosis: A Comprehensive Review.

Craniosynostosis is a fetal skull condition that occurs when one or multiple sutures merge prematurely. This leads to limited growth perpendicular to the fused suture, which results in compensatory growth of cranial bones parallel to it. Syndromic craniosynostosis ensues when the cranial deformity is accompanied by respiratory, neurological, cardiac, musculoskeletal, and audio-visual abnormalities. The most common syndromes are Apert, Crouzon, Pfeiffer, Muenke, and Saethre-Chotzen syndromes and craniofrontonasal syndrome. Each of these syndromes has distinct genetic mutations that contribute to their development. Mutations in genes such as FGFR, TWIST, and EFNB1 have been identified as playing a role in the development of these syndromes. Familiarity with the genetic basis of each syndrome is not only essential for identifying them but also advantageous for current pharmacological investigations. Surgical treatment is often necessary for syndromic craniosynostosis to correct the cranial deformities. Advances have been made in surgical techniques for each specific syndrome, but further research is needed to develop personalized approaches that address the unique symptoms and complications of individual patients, particularly those related to neurological and respiratory issues. This group of syndromes included in cranial synostosis presents significant educational and clinical interest due to the wide range of symptoms and the variable course of the disease, especially in the last decades when crucial advances in diagnosis and treatment have been achieved, altering the prognosis as well as the quality of life of these patients. In summary, this article provides a comprehensive overview of syndromic craniosynostosis, including the genetic mutations associated with each syndrome and the surgical treatment options available.

Case Report: Posterolateral Epidural Supra-C2-Root Approach (PESCA) for Biopsy of a Retro-Odontoid Lesions in Same Sitting After Occipitocervical Fixation and Decompression in a Case of Crowned Dens Syndrome With Brainstem Compression and Displacement.

Background: 'Crowned dens syndrome' (CDS) is a special form of calcium pyrophosphate dihydrate deposition disease which is characterized radiologically by a halo-like or crown-like distribution in the periodontoid region and clinically by cervical pain. Herein, we will describe our experience of posterolateral epidural supra-C2-root approach (PESCA) for biopsy of retro-odontoid lesions in one surgical session after occipitocervical fixation and decompression in a patient with CDS and massive brainstem compression. Case Presentation: A 70-year-old woman presented to our department with a 4-week history of progressive walking impairment, neck pain, neck rigidity, fever, dizziness, slight palsy of the left hand, and multiple fall episodes. Magnetic resonance imaging (MRI) of the craniovertebral junction (CVJ) and cervical spine revealed a lesion of the odontoid process and the retro-odontoid region with mainly solid components, as well as small cystic components, and brainstem compression and displacement. In first step, fusion surgery of the CVJ C0-C4 was performed with occiptocervical decompression. After fusion and decompression the lower lateral part of the C1 arc and the lateral superior part of the left side of the C2 arc were removed. The entry point was located directly above the superior part of the C2 root. A biopsy of the lateral portions of the lesions was obtained by bioptic forceps under microscope guidance. Pathologic examination of the mass revealed deposition of birefringent crystals compatible with calcium pyrophosphate. In addition to the clinical symptoms (especially neck pain), the diagnosis of CDS was made. Non-steroidal inflammatory drugs (NSAIDs) and colchicine (and later magnesium) were started. At follow-up examination 6 months after surgery, an MRI scan of the cervical spine revealed regression of the pannus and the cyst with replacement of the brainstem, clinical improvement of walking, and increased strength of the left hand. Conclusions: This study demonstrates that PESCA can be used to obtain tissue for pathological analysis in one surgical sitting after fusion and decompression and that fusion, decompression, and PESCA (in the same session) together with subsequent conservative management could be a good alternative for the treatment of CDS.

Differential diagnosis of syndromic craniosynostosis: a case series.

PURPOSE: Syndromic craniosynostosis is a rare genetic disease caused by premature fusion of one or multiple cranial sutures combined with malformations of other organs. The aim of this publication is to investigate sonographic signs of different syndromic craniosynostoses and associated malformations to facilitate a precise and early diagnosis. METHODS: We identified in the period of 2000-2019 thirteen cases with a prenatal suspected diagnosis of syndromic craniosynostosis at our department. We analyzed the ultrasound findings, MRI scans, genetic results as well as the mode of delivery, and postnatal procedures. RESULTS: Eight children were diagnosed with Apert Syndrome, two with Saethre Chotzen syndrome, one with Crouzon syndrome, and one with Greig cephalopolysyndactyly syndrome. One child had a mutation p.(Pro253Leu) in the FGFR2 gene. We identified characteristic changes of the head shape as well as typical associated malformations. CONCLUSION: Second trimester diagnosis of syndromic craniosynostosis is feasible based on the identified sonographic signs. In case of a suspected diagnosis a genetic, neonatal as well as surgical counseling is recommended. We also recommend to offer a fetal MRI. The delivery should be planned in a perinatal center.

Case report: A third variant in the 5' UTR of TWIST1 creates a novel upstream translation initiation site in a child with Saethre-Chotzen syndrome.

Introduction: Saethre-Chotzen syndrome, a craniosynostosis syndrome characterized by the premature closure of the coronal sutures, dysmorphic facial features and limb anomalies, is caused by haploinsufficiency of TWIST1. Although the majority of variants localize in the coding region of the gene, two variants in the 5' UTR have been recently reported to generate novel upstream initiation codons. Methods: Skeletal dysplasia Next-generation sequencing (NGS) panel was used for genetic analysis in a patient with bicoronal synostosis, facial dysmorphisms and limb anomalies. The variant pathogenicity was assessed by a luciferase reporter promoter assay. Results: Here, we describe the identification of a third ATG-creating de novo variant, c.-18C>T, in the 5' UTR of TWIST1 in the patient with a clinical diagnosis of Saethre-Chotzen syndrome. It was predicted to create an out-of-frame new upstream translation initiation codon resulting in a 40 amino acid larger functionally inactive protein. We performed luciferase reporter promoter assays to demonstrate that the variant does indeed reduce translation from the main open reading frame. Conclusion: This is the third variant identified in this region and confirms the introduction of upstream ATGs in the 5' UTR of TWIST1 as a pathogenic mechanism in Saethre-Chotzen syndrome. This case report shows the necessity for performing functional characterization of variants of unknown significance within national health services.

Syndrome-related outcomes following posterior vault distraction osteogenesis.

PURPOSE: The most commonly occurring syndromic craniosynostoses are Apert syndrome, Crouzon syndrome, Pfeiffer syndrome, and Saethre-Chotzen syndrome. There is insufficient data regarding postoperative syndrome-related outcomes following the posterior vault distraction osteogenesis (PVDO) procedure, as well as data addressing whether or not additional procedures will be subsequently necessary to comprehensively treat children who undergo PVDO. Thus, the objective of this study is to describe and compare syndrome-related potential complications and outcomes associated with the PVDO procedure. METHODS: An observational retrospective study was performed on consecutive patients (n=24) with Apert syndrome, Crouzon syndrome, Pfeiffer syndrome, or Saethre-Chotzen syndrome, respectively, who underwent PVDO between 2012 and 2019. Demographic data (patient gender and age when the PVDO procedure was performed), diagnosis, surgery-related data, and outcome data (perioperative and midterm complications and need for additional surgery) were verified. RESULTS: Total relative blood transfusion volumes per kilogram for the patients were as follows: 22.75 ± 9.30 ml for Apert syndrome, 10.73 ± 2.28 ml for Crouzon syndrome (Apert versus Crouzon, p<0.05), 18.53 ± 8.08 ml for Pfeiffer syndrome, and 19.74 ± 9.12 ml for Saethre-Chotzen syndrome. None of the patients required a secondary procedure to alleviate intracranial pressure except for a Saethre-Chotzen patient. CONCLUSION: PVDO is an effective technique to address elevated intracranial pressure in SC patients that alleviates the need for secondary procedures at midterm follow-up. Apert syndrome patients presented relatively higher total blood transfusion rates than Crouzon syndrome patients who were operated on at a later age and weighed more.

Síndrome de Saethre-Chotzen: a propósito de un caso / Saethre-Chotzen syndrome: a case report

El síndrome de Saethre-Chotzen es un síndrome malformativo craneofacial caracterizado por una sinostosis de las suturas coronales y alteraciones de extremidades. Tiene una prevalencia de 1 de cada 25 000-50 000 recién nacidos vivos. Se presenta el caso de un neonato sin antecedentes de interés con alteraciones craneofaciales al nacer. Ante los rasgos fenotípicos del paciente, se realizó una tomografía axial computada craneal, que mostró la fusión parcial de la sutura coronal y evidenció la presencia de huesos wormianos en localización metópica y lambdoidea derecha. Con la sospecha clínica de síndrome malformativo craneofacial, se solicitó análisis del exoma dirigido, que confirmó que el paciente era portador heterocigoto de la variante patogénica c.415C>A, que inducía un cambio de prolina a treonina en la posición 139 del gen TWIST1, responsable del síndrome. La presencia de huesos wormianos, hallazgo no descrito hasta ahora en la literatura, amplía la variabilidad fenotípica conocida de este síndrome.

The Saethre-Chotzen syndrome is a craniofacial malformation syndrome characterized by synostosis of coronal sutures and limb anomalies. The estimated prevalence of this syndrome is 1 in 25 000-50 000 live births. We present a case report of a neonate, without relevant family history, who presented craniofacial alterations at birth. Given the phenotypic features, a cranial computed tomography scan was performed, showing partial fusion of the coronal suture, evidencing the presence of wormian bones in the metopic and right lambdoid location. With the clinical suspicion of craniofacial malformation syndrome, an analysis of the directed exome was requested confirming that the patient is a heterozygous carrier of the pathogenic variant c.415C>A, which induces a change of proline to threonine at position 139 of the TWIST1 gene, responsible for Saethre-Chotzen syndrome.The presence of wormian bones, a finding not described so far in the literature, extends the well-known phenotypic variability of this syndrome.

[Saethre-Chotzen syndrome: a case report]. / Síndrome de Saethre-Chotzen: a propósito de un caso.

The Saethre-Chotzen syndrome is a craniofacial malformation syndrome characterized by synostosis of coronal sutures and limb anomalies. The estimated prevalence of this syndrome is 1 in 25 000-50 000 live births. We present a case report of a neonate, without relevant family history, who presented craniofacial alterations at birth. Given the phenotypic features, a cranial computed tomography scan was performed, showing partial fusion of the coronal suture, evidencing the presence Síndrome de Saethre-Chotzen: a propósito de un caso Saethre-Chotzen syndrome: a case report of wormian bones in the metopic and right lambdoid location. With the clinical suspicion of craniofacial malformation syndrome, an analysis of the directed exome was requested confirming that the patient is a heterozygous carrier of the pathogenic variant c.415C>A, which induces a change of proline to threonine at position 139 of the TWIST1 gene, responsible for Saethre-Chotzen syndrome. The presence of wormian bones, a finding not described so far in the literature, extends the well-known phenotypic variability of this syndrome.

El síndrome de Saethre-Chotzen es un síndrome malformativo craneofacial caracterizado por una sinostosis de las suturas coronales y alteraciones de extremidades. Tiene una prevalencia de 1 de cada 25 000-50 000 recién nacidos vivos. Se presenta el caso de un neonato sin antecedentes de interés con alteraciones craneofaciales al nacer. Ante los rasgos fenotípicos del paciente, se realizó una tomografía axial computada craneal, que mostró la fusión parcial de la sutura coronal y evidenció la presencia de huesos wormianos en localización metópica y lambdoidea derecha. Con la sospecha clínica de síndrome malformativo craneofacial, se solicitó análisis del exoma dirigido, que confirmó que el paciente era portador heterocigoto de la variante patogénica c.415C>A, que inducía un cambio de prolina a treonina en la posición 139 del gen TWIST1, responsable del síndrome. La presencia de huesos wormianos, hallazgo no descrito hasta ahora en la literatura, amplía la variabilidad fenotípica conocida de este síndrome.

Vertical transmission of a large calvarial ossification defect due to heterozygous variants of ALX4 and TWIST1.

ALX4 is a homeobox gene expressed in the mesenchyme of developing bone and is known to play an important role in the regulation of osteogenesis. Enlarged parietal foramina (EPF) is a phenotype of delayed intramembranous ossification of calvarial bones due to variants of ALX4. The contrasting phenotype of premature ossification of sutures is observed with heterozygous loss-of-function variants of TWIST1, which is an important regulator of osteoblast differentiation. Here, we describe an individual with a large cranium defect, with dominant transmission from the mother, both carrying disease causing heterozygous variants in ALX4 and TWIST1. The distinct phenotype of absent superior and posterior calvarium in the child and his mother was in sharp contrast to the other affected maternal relatives with a recognizable ALX4-related EPF phenotype. This report demonstrates comorbid disorders of Saethre-Chotzen syndrome and EPF in a mother and her child, resulting in severe skull defects reminiscent of calvarial abnormalities observed with bilallelic ALX4 variants. To our knowledge this is the first instance of ALX4 and TWIST1 variants acting synergistically to cause a unique phenotype influencing skull ossification.

Lateral and Frontal Cephalometric Measurements in a Cohort With Saethre-Chotzen Syndrome.

OBJECTIVE: Descriptions of the craniofacial morphology in Saethre-Chotzen syndrome (SCS) are primarily based on case reports or visual assessments of affected families. The aim of this study was to compare cephalometric measurements of the craniofacial skeleton in a cohort of individuals with SCS and age- and sex-matched individuals without craniofacial anomalies. DESIGN: Retrospective case series. PATIENTS: Eight girls and 4 boys with SCS (age range, 7.0-19.2 years). METHODS: Cephalometric measurements were performed using lateral and frontal cephalograms. RESULTS: Most of the individuals with Saethre-Chotzen syndrome exhibited lower values for SNA, SNB, s-n and s-ar, while their NSL/NL, NSL/ML, NL/ML, and n-s-ba values were higher than the respective mean reference values for healthy individuals. In comparison with age- and sex-matched individuals without craniofacial anomalies, the individuals with SCS showed higher values for the maxillary and mandibular angular measurements, as well as for the menton midline angle. CONCLUSIONS: This sample of 12 unrelated individuals with SCS is the largest collected to date for cephalometric measurements. We found that the syndrome is associated with bimaxillary retrognathism, posterior maxillary and mandibular inclination, neutral sagittal relation as well as a tendency toward an open vertical skeletal relation, a short and flattened skull base, and facial asymmetry, as compared to individuals without the syndrome.

Pharmacological targeting of KDM6A and KDM6B, as a novel therapeutic strategy for treating craniosynostosis in Saethre-Chotzen syndrome.

BACKGROUND: During development, excessive osteogenic differentiation of mesenchymal progenitor cells (MPC) within the cranial sutures can lead to premature suture fusion or craniosynostosis, leading to craniofacial and cognitive issues. Saethre-Chotzen syndrome (SCS) is a common form of craniosynostosis, caused by TWIST-1 gene mutations. Currently, the only treatment option for craniosynostosis involves multiple invasive cranial surgeries, which can lead to serious complications. METHODS: The present study utilized Twist-1 haploinsufficient (Twist-1del/+) mice as SCS mouse model to investigate the inhibition of Kdm6a and Kdm6b activity using the pharmacological inhibitor, GSK-J4, on calvarial cell osteogenic potential. RESULTS: This study showed that the histone methyltransferase EZH2, an osteogenesis inhibitor, is downregulated in calvarial cells derived from Twist-1del/+ mice, whereas the counter histone demethylases, Kdm6a and Kdm6b, known promoters of osteogenesis, were upregulated. In vitro studies confirmed that siRNA-mediated inhibition of Kdm6a and Kdm6b expression suppressed osteogenic differentiation of Twist-1del/+ calvarial cells. Moreover, pharmacological targeting of Kdm6a and Kdm6b activity, with the inhibitor, GSK-J4, caused a dose-dependent suppression of osteogenic differentiation by Twist-1del/+ calvarial cells in vitro and reduced mineralized bone formation in Twist-1del/+ calvarial explant cultures. Chromatin immunoprecipitation and Western blot analyses found that GSK-J4 treatment elevated the levels of the Kdm6a and Kdm6b epigenetic target, the repressive mark of tri-methylated lysine 27 on histone 3, on osteogenic genes leading to repression of Runx2 and Alkaline Phosphatase expression. Pre-clinical in vivo studies showed that local administration of GSK-J4 to the calvaria of Twist-1del/+ mice prevented premature suture fusion and kept the sutures open up to postnatal day 20. CONCLUSION: The inhibition of Kdm6a and Kdm6b activity by GSK-J4 could be used as a potential non-invasive therapeutic strategy for preventing craniosynostosis in children with SCS. Pharmacological targeting of Kdm6a/b activity can alleviate craniosynostosis in Saethre-Chotzen syndrome. Aberrant osteogenesis by Twist-1 mutant cranial suture mesenchymal progenitor cells occurs via deregulation of epigenetic modifiers Ezh2 and Kdm6a/Kdm6b. Suppression of Kdm6a- and Kdm6b-mediated osteogenesis with GSK-J4 inhibitor can prevent prefusion of cranial sutures.

Ablepharon and craniosynostosis in a patient with a localized TWIST1 basic domain substitution.

The TWIST family is a group of highly conserved basic helix-loop-helix transcription factors. In humans, TWIST1 haploinsufficiency causes Saethre-Chotzen syndrome, which is characterized by craniosynostosis. Heterozygous localized TWIST1 and TWIST2 basic domain substitutions exert antimorphic effects to cause Sweeney-Cox syndrome, Barber-Say syndrome, and ablepharon-macrostomia syndrome, respectively. Sweeney-Cox syndrome, Barber-Say syndrome, and ablepharon-macrostomia syndrome share the facial features of ablepharon, hypertelorism, underdevelopment of the eyelids, and cheek pads adjacent to the corners of the mouth. Existence of phenotypic overlap between Saethre-Chotzen syndrome and Sweeney-Cox syndrome remains unknown. Herein, we document a male infant with the distinctive facial features of ablepharon, hypertelorism, cheek pads adjacent to the corners of the mouth, and bilateral coronal suture craniosynostosis who had a de novo heterozygous mutation in the basic domain of TWIST1, that is, c.351C>G p.Glu117Asp. The pathogenicity of this variant was supported by in silico and in vivo evidence. Our review showed that Sweeney-Cox syndrome appears to share many characteristics with Barber-Say syndrome and ablepharon-macrostomia syndrome except for craniosynostosis, which is a cardinal feature of Saethre-Chotzen syndrome. An amino acid substitution from Glu117 to Asp, both of which are the sole members of negatively charged amino acids, resulted in a prototypic Sweeney-Cox syndrome phenotype. This suggests that any amino acid substitutions at Glu117 would likely lead to the Sweeney-Cox syndrome phenotype or lethality. The present observation suggests that a localized TWIST1 basic domain substitution, that is, p.Glu117Asp, in TWIST1 may exert a mild antimorphic effect similar to that of haploinsufficiency, leading to craniosynostosis and ablepharon.

Altered bone growth dynamics prefigure craniosynostosis in a zebrafish model of Saethre-Chotzen syndrome.

Cranial sutures separate the skull bones and house stem cells for bone growth and repair. In Saethre-Chotzen syndrome, mutations in TCF12 or TWIST1 ablate a specific suture, the coronal. This suture forms at a neural-crest/mesoderm interface in mammals and a mesoderm/mesoderm interface in zebrafish. Despite this difference, we show that combinatorial loss of TCF12 and TWIST1 homologs in zebrafish also results in specific loss of the coronal suture. Sequential bone staining reveals an initial, directional acceleration of bone production in the mutant skull, with subsequent localized stalling of bone growth prefiguring coronal suture loss. Mouse genetics further reveal requirements for Twist1 and Tcf12 in both the frontal and parietal bones for suture patency, and to maintain putative progenitors in the coronal region. These findings reveal conservation of coronal suture formation despite evolutionary shifts in embryonic origins, and suggest that the coronal suture might be especially susceptible to imbalances in progenitor maintenance and osteoblast differentiation.

Saethre-Chotzen syndrome: Case report and literature review.

Saethre-Chotzen syndrome (SCS) belongs to a group of rare congenital disorders connected with craniosynostosis and syndactyly. The purpose of this paper is to provide a review of the literature, to collect all reported symptoms and to describe the case of an 11-year-old female with SCS. The electronic databases PubMed and Scopus were searched to gain all symptoms of SCS described in the literature. The most common features of SCS described in the literature are synostosis of the coronal suture, syndactyly, facial asymmetry, low hairline, prominent ear crus, prominent nasal bridge, eyelid ptosis, and ocular hypertelorism. Less common symptoms include hearing loss, renal abnormalities and cardiac defects. Intraoral manifestations of SCS include maxillary hypoplasia, mandibular prognathism and high arched palate. Moreover, in some patients mental disability is observed, which may be connected with the size of the deletion in the Twist gene. There are no pathognomonic symptoms of SCS, which would indicate a diagnostic problem. Our patient displayed small dysmorphic changes within the skull and limbs and proper intellectual development. On the basis of an intraoral, extraoral examination and X-rays, she was diagnosed with relative mandibular prognathism. Currently, she is treated with a removable appliance. This report emphasizes a considerable variability of symptoms in SCS and highlights the most common features.

Disruption of TWIST1 translation by 5' UTR variants in Saethre-Chotzen syndrome.

Saethre-Chotzen syndrome (SCS), one of the most common forms of syndromic craniosynostosis (premature fusion of the cranial sutures), results from haploinsufficiency of TWIST1, caused by deletions of the entire gene or loss-of-function variants within the coding region. To determine whether non-coding variants also contribute to SCS, we screened 14 genetically undiagnosed SCS patients using targeted capture sequencing, and identified novel single nucleotide variants (SNVs) in the 5' untranslated region (UTR) of TWIST1 in two unrelated SCS cases. We show experimentally that these variants, which create translation start sites in the TWIST1 leader sequence, reduce translation from the main open reading frame (mORF). This is the first demonstration that non-coding SNVs of TWIST1 can cause SCS, and highlights the importance of screening the 5' UTR in clinically diagnosed SCS patients without a coding mutation. Similar 5' UTR variants, particularly of haploinsufficient genes, may represent an under-ascertained cause of monogenic disease.

Recombinant mouse periostin ameliorates coronal sutures fusion in Twist1+/- mice.

BACKGROUND: Saethre-Chotzen syndrome is an autosomal dominantly inherited disorder caused by mutations in the twist family basic helix-loop-helix transcription factor 1 (TWIST1) gene. Surgical procedures are frequently required to reduce morphological and functional defects in patients with Saethre-Chotzen syndrome. Therefore, the development of noninvasive procedures to treat Saethre-Chotzen syndrome is critical. We identified that periostin, which is an extracellular matrix protein that plays an important role in both bone and connective tissues, is downregulated in craniosynostosis patients. METHODS: We aimed to verify the effects of different concentrations (0, 50, 100, and 200 µg/l) of recombinant mouse periostin in Twist1+/- mice (a mouse model of Saethre-Chotzen syndrome) coronal suture cells in vitro and in vivo. Cell proliferation, migration, and osteogenic differentiation were observed and detected. Twist1+/- mice were also injected with recombinant mouse periostin to verify the treatment effects. RESULTS: Cell Counting Kit-8 results showed that recombinant mouse periostin inhibited the proliferation of suture-derived cells in a time- and concentration-dependent manner. Cell migration was also suppressed when treated with recombinant mouse periostin. Real-time quantitative PCR and Western blotting results suggested that messenger ribonucleic acid and protein expression of alkaline phosphatase, bone sialoprotein, collagen type I, and osteocalcin were all downregulated after treatment with recombinant mouse periostin. However, the expression of Wnt-3a, Wnt-1, and ß-catenin were upregulated. The in vivo results demonstrated that periostin-treated Twist1+/- mice showed patent coronal sutures in comparison with non-treated Twist1+/- mice which have coronal craniosynostosis. CONCLUSION: Our results suggest that recombinant mouse periostin can inhibit coronal suture cell proliferation and migration and suppress osteogenic differentiation of suture-derived cells via Wnt canonical signaling, as well as ameliorate coronal suture fusion in Twist1+/- mice.

Craniosynostosis as a clinical and diagnostic problem: molecular pathology and genetic counseling.

Craniosynostosis (occurrence: 1/2500 live births) is a result of premature fusion of cranial sutures, leading to alterations of the pattern of cranial growth, resulting in abnormal shape of the head and dysmorphic facial features. In approximately 85% of cases, the disease is isolated and nonsyndromic and mainly involves only one suture. Syndromic craniosynostoses such as Crouzon, Apert, Pfeiffer, Muenke, and Saethre-Chotzen syndromes not only affect multiple sutures, but are also associated with the presence of additional clinical symptoms, including hand and feet malformations, skeletal and cardiac defects, developmental delay, and others. The etiology of craniosynostoses may involve genetic (also somatic mosaicism and regulatory mutations) and epigenetic factors, as well as environmental factors. According to the published data, chromosomal aberrations, mostly submicroscopic ones, account for about 6.7-40% of cases of syndromic craniosynostoses presenting with premature fusion of metopic or sagittal sutures. The best characterized is the deletion or translocation of the 7p21 region containing the TWIST1 gene. The deletions of 9p22 or 11q23-qter (Jacobsen syndrome) are both associated with trigonocephaly. The genes related to the pathogenesis of the craniosynostoses itself are those encoding transcription factors, e.g., TWIST1, MSX2, EN1, and ZIC1, and proteins involved in osteogenic proliferation, differentiation, and homeostasis, such as FGFR1, FGFR2, RUNX2, POR, and many others. In this review, we present the clinical and molecular features of selected craniosynostosis syndromes, genotype-phenotype correlation, family genetic counseling, and propose the most appropriate diagnostic algorithm.

Contiguous gene deletion neighboring TWIST1 identified in a patient with Saethre-Chotzen syndrome associated with neurodevelopmental delay: Possible contribution of HDAC9.

Saethre-Chotzen syndrome (SCS) is an autosomal dominant craniosynostotic disorder characterized by coronal synostosis, facial asymmetry, ptosis, and limb abnormalities. Haploinsufficiency of TWIST1, a basic helix-loop-helix transcription factor is responsible for SCS. Here, we report a 15-month-old male patient with typical clinical features of SCS in addition to developmental delay, which is a rare complication in SCS. He showed a de novo 0.9-Mb microdeletion in 7p21, in which TWIST1, NPMIP13, FERD3L, TWISTNB, and HDAC9 were included. In comparison with previously reported patients, HDAC9 was suggested to contribute to developmental delay in SCS patients with 7p21 mirodeletions.

Syndromic Craniosynostosis.

Syndromic craniosynostosis affects up to 1:30,000 live births with characteristic craniofacial growth restrictions, deformities, and other associated abnormalities, such as carpal-pedal anomalies and cognitive function impairment. More than 150 syndromes are associated with craniosynostosis. This article describes some commonalities and distinguishing features and management of syndromic synostosis. Also addressed is secondary synostosis, which is often found in syndromic children with problems related to microcephaly, hydrocephalus, or shunt-induced craniosynostosis, although pathophysiologically and genetically different. The importance of obtaining a thorough history and a complete physical and examination is highlighted. Adjuvant testing and multidisciplinary management are discussed.