Insights into the ANKRD11 variants and short-stature phenotype through literature review and ClinVar database search.

Ankyrin repeat domain containing-protein 11 (ANKRD11), a transcriptional factor predominantly localized in the cell nucleus, plays a crucial role in the expression regulation of key genes by recruiting chromatin remodelers and interacting with specific transcriptional repressors or activators during numerous biological processes. Its pathogenic variants are strongly linked to the pathogenesis and progression of multisystem disorder known as KBG syndrome. With the widespread application of high-throughput DNA sequencing technologies in clinical medicine, numerous pathogenic variants in the ANKRD11 gene have been reported. Patients with KBG syndrome usually exhibit a broad phenotypic spectrum with a variable degree of severity, even if having identical variants. In addition to distinctive dental, craniofacial and neurodevelopmental abnormalities, patients often present with skeletal anomalies, particularly postnatal short stature. The relationship between ANKRD11 variants and short stature is not well-understood, with limited knowledge regarding its occurrence rate or underlying biological mechanism involved. This review aims to provide an updated analysis of the molecular spectrum associated with ANKRD11 variants, investigate the prevalence of the short stature among patients harboring these variants, evaluate the efficacy of recombinant human growth hormone in treating children with short stature and ANKRD11 variants, and explore the biological mechanisms underlying short stature from both scientific and clinical perspectives. Our investigation indicated that frameshift and nonsense were the most frequent types in 583 pathogenic or likely pathogenic variants identified in the ANKRD11 gene. Among the 245 KBGS patients with height data, approximately 50% displayed short stature. Most patients showed a positive response to rhGH therapy, although the number of patients receiving treatment was limited. ANKRD11 deficiency potentially disrupts longitudinal bone growth by affecting the orderly differentiation of growth plate chondrocytes. Our review offers crucial insights into the association between ANKRD11 variants and short stature and provides valuable guidance for precise clinical diagnosis and treatment of patients with KBG syndrome.

Loss-of-function variants in ERF are associated with a Noonan syndrome-like phenotype with or without craniosynostosis.

Pathogenic, largely truncating variants in the ETS2 repressor factor (ERF) gene, encoding a transcriptional regulator negatively controlling RAS-MAPK signaling, have been associated with syndromic craniosynostosis involving various cranial sutures and Chitayat syndrome, an ultrarare condition with respiratory distress, skeletal anomalies, and facial dysmorphism. Recently, a single patient with craniosynostosis and a phenotype resembling Noonan syndrome (NS), the most common disorder among the RASopathies, was reported to carry a de novo loss-of-function variant in ERF. Here, we clinically profile 26 individuals from 15 unrelated families carrying different germline heterozygous variants in ERF and showing a phenotype reminiscent of NS. The majority of subjects presented with a variable degree of global developmental and/or language delay. Their shared facial features included absolute/relative macrocephaly, high forehead, hypertelorism, palpebral ptosis, wide nasal bridge, and low-set/posteriorly angulated ears. Stature was below the 3rd centile in two-third of the individuals, while no subject showed typical NS cardiac involvement. Notably, craniosynostosis was documented only in three unrelated individuals, while a dolichocephalic aspect of the skull in absence of any other evidence supporting a premature closing of sutures was observed in other 10 subjects. Unilateral Wilms tumor was diagnosed in one individual. Most cases were familial, indicating an overall low impact on fitness. Variants were nonsense and frameshift changes, supporting ERF haploinsufficiency. These findings provide evidence that heterozygous loss-of-function variants in ERF cause a "RASopathy" resembling NS with or without craniosynostosis, and allow a first dissection of the molecular circuits contributing to MAPK signaling pleiotropy.

Noonan syndrome-like phenotype associated with an ERF frameshift variant.

Noonan syndrome is a so-called "RASopathy," that is characterized by short stature, distinctive facial features, congenital heart defects, and developmental delay. Of individuals with a clinical diagnosis of Noonan syndrome, 80%-90% have pathogenic variants in the known genes implicated in the disorder, but the molecular mechanism is unknown in the remaining cases. Heterozygous pathogenic variants of ETS2 repressor factor (ERF), which functions as a repressor in the RAS/MAPK signaling pathway, cause syndromic craniosynostosis. Here, we report an ERF frameshift variant cosegregating with a Noonan syndrome-like phenotype in a family. The proband was a 3-year-old female who presented with dysmorphic facial features, including proptosis, hypertelorism, slightly down slanted palpebral fissures, low-set posteriorly rotated ears, depressed nasal bridge, short stature, and developmental delay. Exome sequencing of the proband identified a heterozygous ERF variant [NM_006494.4: c.185del p.(Glu62Glyfs*15)]. Her mother and sister showed a similar phenotype and had the same heterozygous ERF variant. A large proportion of the previously reported patients with syndromic craniosynostosis and pathogenic ERF variants also showed characteristic features that overlap with those of Noonan syndrome. The present finding supports an association between heterozygous ERF variants and a Noonan syndrome-like phenotype.

New diagnostic criteria for metopic ridges and trigonocephaly: a 3D geometric approach.

BACKGROUND: Trigonocephaly occurs due to the premature fusion of the metopic suture, leading to a triangular forehead and hypotelorism. This condition often requires surgical correction for morphological and functional indications. Metopic ridges also originate from premature metopic closure but are only associated with mid-frontal bulging; their surgical correction is rarely required. Differential diagnosis between these two conditions can be challenging, especially in minor trigonocephaly. METHODS: Two hundred seven scans of patients with trigonocephaly (90), metopic rigdes (27), and controls (90) were collected. Geometric morphometrics were used to quantify skull and orbital morphology as well as the interfrontal angle and the cephalic index. An innovative method was developed to automatically compute the frontal curvature along the metopic suture. Different machine-learning algorithms were tested to assess the predictive power of morphological data in terms of classification. RESULTS: We showed that control patients, trigonocephaly and metopic rigdes have distinctive skull and orbital shapes. The 3D frontal curvature enabled a clear discrimination between groups (sensitivity and specificity > 92%). Furthermore, we reached an accuracy of 100% in group discrimination when combining 6 univariate measures. CONCLUSION: Two diagnostic tools were proposed and demonstrated to be successful in assisting differential diagnosis for patients with trigonocephaly or metopic ridges. Further clinical assessments are required to validate the practical clinical relevance of these tools.

Comparative analysis of ocular biometry, ocular protrusion, and palpebral fissure dimensions in brachycephalic and nonbrachycephalic dog breeds.

This study compared skull morphology and ocular parameters in brachycephalic (BC, n = 16) and nonbrachycephalic (NB, n = 16) dogs using head CT scans. The results of a Schirmer tear test I (STT I), intraocular pressure (IOP), ocular biometry, external structure, ocular protrusion, and palpebral fissure dimensions were evaluated and compared between BC and NB dogs. There were no statistically significant differences in the STT I results, IOP, globe dimensions, globe volume, internal structure, and external structure between BC and NB dogs (P > .05). Brachycephalic dogs exhibited significantly greater ocular protrusion and significantly larger palpebral fissure dimensions compared with NB dogs. For all dogs, we found a strong positive correlation between globe volume and body weight (r = 0.836, P = .0000). The globe volumes, external structure parameters, and ocular protrusion were normalized by body weight and were also significantly larger in BC dogs compared with NB dogs (P < .001). The ocular protrusion (r = 0.521, P < .0000) and horizontal palpebral fissure (r = 0.372, P = .0024) showed a moderate positive correlation with the cephalic index (CI). Additionally, normalized globe volume (r = 0.435, P = .0003), normalized orbital depth (r = 0.419, P = .0005), and normalized retrobulbar depth (r = 0.444, P = .0002) had a moderate positive correlation with the CI. The study emphasizes how the distinctive skull structure of BC dogs, with shortened facial bones and thickened retrobulbar soft tissue, influences their ocular appearance and raises the risk of eye problems.

Syndromic craniosynostosis caused by a novel missense variant in MAP4K4: Expanding the genotype-phenotype relationship in RASopathies.

RASopathies represent a distinct class of neurodevelopmental syndromes caused by germline variants in the Ras/MAPK pathways. Recently, a novel disease-gene association was implicated in MAPK kinase kinase kinase 4 (MAP4K4), which regulates the upstream signals of the MAPK pathways. However, to our knowledge, only two studies have reported the genotype-phenotype relationships in the MAP4K4-related disorder. This study reports on a Korean boy harboring a novel de novo missense variant in MAP4K4 (NM_001242559:c.569G>T, p.Gly190Val), revealed by trio exome sequencing, and located in the hotspot of the protein kinase domain. The patient exhibited various clinical features, including craniofacial dysmorphism, language delay, congenital heart defects, genitourinary anomalies, and sagittal craniosynostosis. Our study expands the phenotypic association of the MAP4K4-related disorder to include syndromic craniosynostosis, thereby providing further insights into the role of the RAS/MAPK pathways in the development of premature fusion of calvarial sutures.

An Ultra-Rare Mixed Phenotype with Combined AP-4 and ERF Mutations: The First Report in a Pediatric Patient and a Literature Review.

The adaptor protein 4 (AP-4) constitutes a conserved hetero-tetrameric complex within the family of adaptor protein (AP) complex, crucial for the signal-mediated trafficking of integral membrane proteins. Mutations affecting all subunits of the AP-4 complex have been linked to autosomal-recessive cerebral palsy and a complex hereditary spastic paraparesis (HSP) phenotype. Our report details the case of a 14-year-old boy born to consanguineous parents, presenting psychomotor delay, severe intellectual disability, microcephaly, and trigonocephaly. Despite a history of febrile seizures, subsequent years were devoid of seizures, with normal EEG. Exome sequencing revealed pathogenic variants in both the AP4B1 and ERF genes. Significantly, the patient exhibited features associated with AP4B1 mutations, including distinctive traits such as cranial malformations. The ERF gene variant, linked to craniosynostosis, likely contributes to the observed trigonocephaly. This case represents the initial documentation of a concurrent mutation in the AP4B1 and ERF genes, underscoring the critical role of exome analysis in unraveling complex phenotypes. Understanding these complex genotypes offers valuable insights into broader syndromic conditions, facilitating comprehensive patient management.

A second hotspot for pathogenic exon-skipping variants in CDC45.

Biallelic pathogenic variants in CDC45 are associated with Meier-Gorlin syndrome with craniosynostosis (MGORS type 7), which also includes short stature and absent/hypoplastic patellae. Identified variants act through a hypomorphic loss of function mechanism, to reduce CDC45 activity and impact DNA replication initiation. In addition to missense and premature termination variants, several pathogenic synonymous variants have been identified, most of which cause increased exon skipping of exon 4, which encodes an essential part of the RecJ-orthologue's DHH domain. Here we have identified a second cohort of families segregating CDC45 variants, where patients have craniosynostosis and a reduction in height, alongside common facial dysmorphisms, including thin eyebrows, consistent with MGORS7. Skipping of exon 15 is a consequence of two different variants, including a shared synonymous variant that is enriched in individuals of East Asian ancestry, while other variants in trans are predicted to alter key intramolecular interactions in α/ß domain II, or cause retention of an intron within the 3'UTR. Our cohort and functional data confirm exon skipping is a relatively common pathogenic mechanism in CDC45, and highlights the need for alternative splicing events, such as exon skipping, to be especially considered for variants initially predicted to be less likely to cause the phenotype, particularly synonymous variants.

Yoda1 opens the lymphatic path for craniosynostosis therapy.

The rediscovery of meningeal lymphatic vessels (MLVs) has sparked research interest in their function in numerous neurological pathologies. Craniosynostosis (CS) is caused by a premature fusion of cranial sutures during development. In this issue of the JCI, Matrongolo and colleagues show that Twist1-haploinsufficient mice that develop CS exhibit raised intracranial pressure, diminished cerebrospinal fluid (CSF) outflow, and impaired paravascular CSF-brain flow; all features that were associated with MLV defects and exacerbated pathology in mouse models of Alzheimer's disease. Activation of the mechanosensor Piezo1 with Yoda1 restored MLV function and CSF perfusion in CS models and in aged mice, opening an avenue for further development of therapeutics.

Atypical sagittal suture craniosynostosis: pathological considerations for early closure of the anterior part of the sagittal suture.

Sagittal suture synostosis is one of the most common craniosynostoses and is often diagnosed by characteristic narrow and long skull shape, scaphocephaly. However, some patients with sagittal suture synostosis do not present with typical scaphocephaly, making early diagnosis difficult. In this study, five cases of characteristic skull deformity showing a narrowing of the cranium posterior to the coronal suture on computed tomography (CT) are presented. The three older children presented with papilledema and intellectual disability and a closed sagittal suture on CT. The two infant cases were diagnosed with the characteristic cranial deformities with aggravation of the deformity over time, but sagittal suture closure was not evident on CT. All patients underwent cranial remodeling surgery. In the two infant cases, the histopathological findings showed that the anterior part of the sagittal suture was firmly fused with fibrous tissue without bony fusion. These findings suggested that narrowing of the cranium posterior to the coronal suture might be due to functional fusion of the anterior portion of the sagittal suture prior to bony fusion. In an infant presenting with such a deformity that shows aggravation of the deformity over time, surgical treatment should be considered.

Data-driven cranial suture growth model enables predicting phenotypes of craniosynostosis.

We present the first data-driven pediatric model that explains cranial sutural growth in the pediatric population. We segmented the cranial bones in the neurocranium from the cross-sectional CT images of 2068 normative subjects (age 0-10 years), and we used a 2D manifold-based cranial representation to establish local anatomical correspondences between subjects guided by the location of the cranial sutures. We designed a diffeomorphic spatiotemporal model of cranial bone development as a function of local sutural growth rates, and we inferred its parameters statistically from our cross-sectional dataset. We used the constructed model to predict growth for 51 independent normative patients who had longitudinal images. Moreover, we used our model to simulate the phenotypes of single suture craniosynostosis, which we compared to the observations from 212 patients. We also evaluated the accuracy predicting personalized cranial growth for 10 patients with craniosynostosis who had pre-surgical longitudinal images. Unlike existing statistical and simulation methods, our model was inferred from real image observations, explains cranial bone expansion and displacement as a consequence of sutural growth and it can simulate craniosynostosis. This pediatric cranial suture growth model constitutes a necessary tool to study abnormal development in the presence of cranial suture pathology.

Technical evolution of pediatric neurosurgery: craniosynostosis from 1972 to 2023 and beyond.

Very few clinical entities have undergone so many different treatment approaches over such a short period of time as craniosynostosis. Surgical treatments for this condition have ranged from simple linear craniectomies, accounting for the specific role of cranial sutures in assuring the normal growth of the skull, to more complex cranial vault reconstructions, based on the perceived role of the skull base in affecting the growth of the skull. While a great deal of evolution has occurred, there remains controversy regarding the ideal treatment including the best surgical technique, the optimal age for surgery, and the long-term morphological and neurodevelopmental outcomes. The evolution of the surgical management of craniosynostosis in the last 50 years has been affected by several factors. This includes the awareness of needing to operate on affected children during infancy to achieve the best results, the use of multistage operations, the availability of more sophisticated surgical tools, and improved perioperative care. In some forms of craniosynostosis, the operations can be carried out at a very young age with low morbidity, and with the postoperative use of a molding helmet, springs, or distractors, these operations prove to be as effective as traditional larger cranial reconstructions performed in older children. As a consequence, complex surgical operations have become progressively less utilized. A second relevant advance was the more recent advent of a molecular diagnosis, which allowed us to understand the pathogenesis of some associated malformations and neurodevelopmental issues that were observed in some children despite appropriate surgical treatment. Future research should focus on improving the analysis of longer-term outcomes and understanding the natural history of craniofacial conditions, including what issues persist despite optimal surgical correction. Progress in molecular investigations concerning the normal and pathological development of cranial sutures could be a further significant step in the management of craniosynostosis, possibly favoring a "medical" treatment in the near future. Artificial intelligence will likely have a role in establishing the diagnosis with less reliance on radiographic studies and in assisting with surgical planning. Overall, much progress has been made, but there remains much to do.

Familial monoallelic CYP26B1 truncating variant causes a syndromic craniosynostosis due to haploinsufficiency ?

Autosomal recessive CYP26B1 disorder is characterised by syndromic craniosynostosis of variable severity, and survival ranging from prenatal lethality to survival into adulthood. Here we report on two related individuals of Asian-Indian origin with syndromic craniosynostosis characterised by craniosynostosis, and dysplastic radial heads, caused by monoallelic CYP26B1 likely pathogenic variant NM_019885.4:c.86C > A:p. (Ser29Ter). We propose the possibility of autosomal dominant phenotype of CYP26B1 variant.

Molecular Scalpels: The Future of Pediatric Craniofacial Surgery?

SUMMARY: CRISPR-Cas genome editing tools are among the most substantial advances in the life sciences in modern history. Single-dose gene therapies to correct pathogenic mutations have moved quickly from bench to bedside, with several therapeutics designed by CRISPR pioneers entering various stages of clinical investigation. Applications of these genetic technologies are poised to reshape the practice of both medicine and surgery. Many of the most morbid conditions treated by craniofacial surgeons are syndromic craniosynostoses caused by mutations in fibroblast growth factor receptor genes, including Apert, Pfeiffer, Crouzon, and Muenke syndromes. The fact that pathogenic mutations in these genes are recurrent in the majority of affected families presents a unique opportunity to develop "off-the-shelf" gene editing therapies to correct these mutations in affected children. The therapeutic potential of these interventions could reshape pediatric craniofacial surgery, potentially first eliminating the need for midface advancement procedures in affected children.

Review of Recurrently Mutated Genes in Craniosynostosis Supports Expansion of Diagnostic Gene Panels.

Craniosynostosis, the premature fusion of the cranial sutures, affects ~1 in 2000 children. Although many patients with a genetically determined cause harbor a variant in one of just seven genes or have a chromosomal abnormality, over 60 genes are known to be recurrently mutated, thus comprising a long tail of rarer diagnoses. Genome sequencing for the diagnosis of rare diseases is increasingly used in clinical settings, but analysis of the data is labor intensive and involves a trade-off between achieving high sensitivity or high precision. PanelApp, a crowd-sourced disease-focused set of gene panels, was designed to enable prioritization of variants in known disease genes for a given pathology, allowing enhanced identification of true-positives. For heterogeneous disorders like craniosynostosis, these panels must be regularly updated to ensure that diagnoses are not being missed. We provide a systematic review of genetic literature on craniosynostosis over the last 5 years, including additional results from resequencing a 42-gene panel in 617 affected individuals. We identify 16 genes (representing a 25% uplift) that should be added to the list of bona fide craniosynostosis disease genes and discuss the insights that these new genes provide into pathophysiological mechanisms of craniosynostosis.

Histopathologic and Spectrometric Evaluation of Bony Components of Synostotic Suture and Parietal Bone in Children with Sagittal Synostosis.

AIM: To understand the characterization of the ossification process both in the synostotic suture, and the adjacent parietal bone. MATERIAL AND METHODS: The surgical procedure for the 28 patients diagnosed with sagittal synostosis consisted of removing the synostotic bone as a whole, if possible, "Barrel-Stave" relaxation osteotomies, and strip osteotomies to the parietal and temporal bones perpendicular to the synostotic suture. The synostotic (group I) and parietal (group II) bone segments are obtained during osteotomies. Atomic absorption spectrometry was used to determine the amount of calcium in both groups, which is an indicator of ossification. Scanning electron microscopy and immunohistochemistry were employed to assess trabecular bone formation, osteoblastic density, and osteopontin, which is one of the in vivo indicators of new bone formation. RESULTS: Histopathologically, trabecular bone formation scores did not indicate any significant difference between the groups. However, the osteoblastic density and calcium accumulation in group I were higher than those in group II, and the difference was significant. Osteopontin staining scores in cells showing membranous and cytoplasmic staining with osteopontin antibodies significantly increased in group II. CONCLUSION: In this study, we found reduced differentiation of osteoblasts despite their increase in number. Moreover, the osteoblastic maturation rate was low in synostotic sutures, bone resorption becomes slower than new bone formation, and the remodeling rate is low in sagittal synostosis.

An algorithmic clinicoradiological approach to paediatric cranial vault lesions: distinguishing normal variants from pathologies.

Lesions of the paediatric cranial vault are diverse both in their presentation and aetiology. As such, they pose a diagnostic challenge to the paediatric neurosurgeon and neuroradiologist. In this article, we delineate the spectrum of paediatric calvarial pathology into four distinct groups: (1) lytic lesion(s); (2) focal sclerotic lesion(s); (3) diffuse cranial vault sclerosis; and (4) abnormal shape of the cranial vault. It is our aim that this more pragmatic, algorithmic approach may mitigate diagnostic uncertainty and aid the more accurate diagnosis of paediatric calvarial lesions.

Systematic Review of the Clinical and Experimental Research Assessing the Effects of Craniosynostosis on the Brain.

Although neurocognitive impairment has been considered as the main argument for the surgical treatment of craniosynostosis (CS), recent studies reported subtle deficits in neurological function even in operated patients. However, the cause of these deficits remains poorly understood. This systematic review sought to examine the impact of CS on the brain microstructure, mainly on functional connectivity, and comprehensively summarize the clinical and experimental research available on this topic. A systematic review was performed considering the publications of the last 20 years in PubMed and Web of Science, including relevant human and animal studies of the types of brain-microstructure disturbances in CS. Among the 560 papers identified, 11 were selected for analysis. Seven of those were conducted in humans and 4 in animal models. Resting-state functional magnetic resonance imaging, task-based magnetic resonance imaging, and diffusion tensor imaging were the main instruments used to investigate brain connectivity in humans. The main findings were increased connectivity of the posterior segment of cingulum gyri, reduced interconnectivity of the frontal lobes, and reduced diffusivity on diffusion tensor imaging, which were associated with hyperactivity behaviors and poorer performance on neurocognitive tests. Conversely, despite the lack of evidence of brain dysfunction in animal studies, they reported a tendency toward the development of hyperactive behaviors and impairment of neurocognitive function. Skull restriction caused by CS apparently chronically increases the intracranial pressure and produces white matter injuries. The current evidence supports the contention that an early surgical approach could minimize brain-connectivity impairment in this context.

Brachycephalic obstructive airway syndrome: much more than a surgical problem.

Brachycephalic obstructive airway syndrome (BOAS) is a chronic, lifelong, debilitating, primarily obstructive airway disease which adversely affects the quality of life of many popular dog breeds. Respiratory restriction in bulldog breeds, pugs and Boston terriers frequently co-exist with pathologies of the gastrointestinal tract. In addition, many brachycephalic dogs that appear clinically normal are, in fact suffering from chronic hypoxia and its systemic consequences. Concurrent gastroesophageal reflux-associated conditions, sleep disorders and systemic hypertension further impact the welfare of affected dogs. Acceptance of BOAS and associated clinical signs as being 'normal for the breed' is common amongst owners. While surgical correction of the upper airway is the mainstay of treatment, the provision of subsequent, frequently lifelong medical management is equally important for the maintenance of an acceptable quality of life, at least for some affected patients. Here we review the current knowledge concerning brachycephaly, combine it with shared clinical experience in the management of this debilitating condition, and discuss ethical considerations and the responsibility of veterinarians to contribute public education and to support appropriate breed standards for animals under our care.

Diploic vein morphology in normal and craniosynostotic adult human skulls.

Diploic veins (DV) run within the cranial diploe, where they leave channels that can be studied in osteological samples. This study investigates overall DV variability in human adults and the effects of sex, age, cranial dimensions, and dysmorphogenesis associated with craniosynostosis (CS). The morphology of macroscopic diploic channels was analyzed in a set of the qualitative and quantitative variables in computed tomography-images of crania of anatomically normal and craniosynostotic adult individuals. Macroscopic diploic channels occur most frequently in the frontal and parietal bones, often with a bilaterally symmetrical pattern. DV-features (especially DV-pattern) are characterized by high individual diversity. On average, there are 5.4 ± 3.5 large macroscopic channels (with diameters >1 mm) per individual, with a mean diameter of 1.7 ± 0.4 mm. Age and sex have minor effects on DV, and cranial proportions significantly influence DV only in CS skulls. CS is associated with changes in the DV numbers, distributions, and diameters. Craniosynostotic skulls, especially brachycephalic skulls, generally present smaller DV diameters, and dolichocephalic skulls display increased number of frontal DV. CS, associated with altered cranial dimensions, suture imbalance, increased intracranial pressure, and with changes of the endocranial craniovascular system, significantly also affects the macroscopic morphology of DV in adults, in terms of both structural (topological redistribution) and functional factors. The research on craniovascular morphology and CS may be of interest in biological anthropology, paleopathology, medicine (e.g., surgical planning), but also in zoology and paleontology.