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Nucleic Acids Research Oct 2023Faithful cell division is the basis for the propagation of life and DNA replication must be precisely regulated. DNA replication stress is a prominent endogenous source...
Faithful cell division is the basis for the propagation of life and DNA replication must be precisely regulated. DNA replication stress is a prominent endogenous source of genome instability that not only leads to ageing, but also neuropathology and cancer development in humans. Specifically, the issues of how vertebrate cells select and activate origins of replication are of importance as, for example, insufficient origin firing leads to genomic instability and mutations in replication initiation factors lead to the rare human disease Meier-Gorlin syndrome. The mechanism of origin activation has been well characterised and reconstituted in yeast, however, an equal understanding of this process in higher eukaryotes is lacking. The firing of replication origins is driven by S-phase kinases (CDKs and DDK) and results in the activation of the replicative helicase and generation of two bi-directional replication forks. Our data, generated from cell-free Xenopus laevis egg extracts, show that DONSON is required for assembly of the active replicative helicase (CMG complex) at origins during replication initiation. DONSON has previously been shown to be essential during DNA replication, both in human cells and in Drosophila, but the mechanism of DONSON's action was unknown. Here we show that DONSON's presence is essential for replication initiation as it is required for Cdc45 and GINS association with Mcm2-7 complexes and helicase activation. To fulfil this role, DONSON interacts with the initiation factor, TopBP1, in a CDK-dependent manner. Following its initiation role, DONSON also forms a part of the replisome during the elongation stage of DNA replication. Mutations in DONSON have recently been shown to lead to the Meier-Gorlin syndrome; this novel replication initiation role of DONSON therefore provides the explanation for the phenotypes caused by DONSON mutations in patients.
Topics: Humans; Cell Cycle Proteins; Chromatin; Congenital Microtia; Cyclin-Dependent Kinases; DNA Replication; Growth Disorders; Micrognathism; Minichromosome Maintenance Proteins; Patella; Replication Origin; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 37638758
DOI: 10.1093/nar/gkad694 -
Genetics in Medicine : Official Journal... Nov 2023Coffin-Siris and Nicolaides-Baraitser syndromes are recognizable neurodevelopmental disorders caused by germline variants in BAF complex subunits. The SMARCC2 BAFopathy...
PURPOSE
Coffin-Siris and Nicolaides-Baraitser syndromes are recognizable neurodevelopmental disorders caused by germline variants in BAF complex subunits. The SMARCC2 BAFopathy was recently reported. Herein, we present clinical and molecular data on a large cohort.
METHODS
Clinical symptoms for 41 novel and 24 previously published affected individuals were analyzed using the Human Phenotype Ontology. For genotype-phenotype correlations, molecular data were standardized and grouped into non-truncating and likely gene-disrupting (LGD) variants. Missense variant protein expression and BAF-subunit interactions were examined using 3D protein modeling, co-immunoprecipitation, and proximity-ligation assays.
RESULTS
Neurodevelopmental delay with intellectual disability, muscular hypotonia, and behavioral disorders were the major manifestations. Clinical hallmarks of BAFopathies were rare. Clinical presentation differed significantly, with LGD variants being predominantly inherited and associated with mildly reduced or normal cognitive development, whereas non-truncating variants were mostly de novo and presented with severe developmental delay. These distinct manifestations and non-truncating variant clustering in functional domains suggest different pathomechanisms. In vitro testing showed decreased protein expression for N-terminal missense variants similar to LGD.
CONCLUSION
This study improved SMARCC2 variant classification and identified discernible SMARCC2-associated phenotypes for LGD and non-truncating variants, which were distinct from other BAFopathies. The pathomechanism of most non-truncating variants has yet to be investigated.
Topics: Humans; Abnormalities, Multiple; Face; Micrognathism; Intellectual Disability; Facies; Neurodevelopmental Disorders; Phenotype; DNA-Binding Proteins; Transcription Factors
PubMed: 37551667
DOI: 10.1016/j.gim.2023.100950 -
Lin Chuang Er Bi Yan Hou Tou Jing Wai... Aug 2023To explore the perioperative airway management and treatment of newborns with micrognathia and laryngomalacia. From January to December 2022, a total of 6 newborns with...
To explore the perioperative airway management and treatment of newborns with micrognathia and laryngomalacia. From January to December 2022, a total of 6 newborns with micrognathia and laryngomalacia were included. Preoperative laryngoscopy revealed concomitant laryngomalacia. These micrognathia were diagnosed as Pierre Robin sequences. All patients had grade Ⅱ or higher symptoms of laryngeal obstruction and required oxygen therapy or non-invasive ventilatory support. All patients underwent simultaneous laryngomalacia surgery and mandibular distraction osteogenesis. The shortened aryepiglottic folds were ablated using a low-temperature plasma radiofrequency during the operation. Tracheal intubation was maintained for 3-5 days postoperatively. Polysomnography(PSG) and airway CT examination were performed before and 3 months after the surgery. Among the 6 patients, 4 required oxygen therapy preoperatively and 2 required non-invasiveventilatory support. The mean age of patients was 40 days at surgery. The inferior alveolar nerve bundle was not damaged during the operation, and there were no signs of mandibular branch injury such as facial asymmetry after the surgery. Laryngomalacia presented as mixed type: type Ⅱ+ type Ⅲ. The maximum mandibular distraction distance was 20 mm, the minimum was 12 mm, and the mean was 16 mm. The posterior airway space increased from a preoperative average of 3.5 mm to a postoperative average of 9.5 mm. The AHI decreased from a mean of 5.65 to 0.85, and the lowest oxygen saturation increased from a mean of 78% to 95%. All patients were successfully extubated after the surgery, and symptoms of laryngeal obstruction such as hypoxia and feeding difficulties disappeared. Newborns with micrognathia and laryngomalacia have multi-planar airway obstruction. Simultaneous laryngomalacia surgery and mandibular distraction osteogenesis are safe and feasible, and can effectively alleviate symptoms of laryngeal obstruction such as hypoxia and feeding difficulties, while significantly improving the appearance of micrognathia.
Topics: Humans; Infant, Newborn; Infant; Micrognathism; Laryngomalacia; Treatment Outcome; Mandible; Airway Obstruction; Intubation, Intratracheal; Laryngeal Diseases; Osteogenesis, Distraction; Oxygen; Retrospective Studies
PubMed: 37551568
DOI: 10.13201/j.issn.2096-7993.2023.08.004 -
Molecular Genetics & Genomic Medicine Nov 2023BICRA, a transcript regulator, was identified as the genetic factor of Coffin-Siris syndrome 12 (CSS12) recently, which was characterized by diverse neurodevelopmental...
BACKGROUND
BICRA, a transcript regulator, was identified as the genetic factor of Coffin-Siris syndrome 12 (CSS12) recently, which was characterized by diverse neurodevelopmental delays. Up to now, limited studies of BICRA in neurodevelopmental delay have been reported.
METHODS
Clinical data such as EEGs, MRIs, routine blood, and physical examination were collected. Trio whole exome sequencing (WES) of the family was performed, and all variants with a minor allele frequency (<0.01) in exon and canonical splicing sites were selected for further pathogenic evaluation. Candidate variants were validated by Sanger sequencing. The BICRA-related literature was reviewed and the clinical characteristics were summarized.
RESULTS
We reported a CSS12 proband with a narrow and slightly clinical phenotype who only exhibited language developmental delay, hypotonia, and slight gastrointestinal features. WES revealed a de novo variant in exon 6 of BICRA [NM_015711.3: c.1666C>T, p.Gln556*]. This variant resulted in an early translation termination at 556th of BICRA, not collected in the public population database (gnomAD), and classified as pathogenic according to the ACMG guideline.
CONCLUSION
Our results expanded the pathogenic genetic and clinical spectrum of BICRA-related diseases.
Topics: Humans; Transcription Factors; Intellectual Disability; Abnormalities, Multiple; Micrognathism
PubMed: 37485815
DOI: 10.1002/mgg3.2250 -
International Journal of Molecular... Jun 2023Cleft palate is one of the most common birth defects. Previous studies revealed that multiple factors, including impaired intracellular or intercellular signals, and...
Cleft palate is one of the most common birth defects. Previous studies revealed that multiple factors, including impaired intracellular or intercellular signals, and incoordination of oral organs led to cleft palate, but were little concerned about the contribution of the extracellular matrix (ECM) during palatogenesis. Proteoglycans (PGs) are one of the important macromolecules in the ECM. They exert biological functions through one or more glycosaminoglycan (GAG) chains attached to core proteins. The family with sequence similarity 20 member b (Fam20b) are newly identified kinase-phosphorylating xylose residues that promote the correct assembly of the tetrasaccharide linkage region by creating a premise for GAG chain elongation. In this study, we explored the function of GAG chains in palate development through mice, which exhibited complete cleft palate, malformed tongue, and micrognathia. In contrast, mice, in which was deleted only in palatal mesenchyme, showed no abnormality, suggesting that failed palatal elevation in mice was secondary to micrognathia. In addition, the reduced GAG chains promoted the apoptosis of palatal cells, primarily resulting in reduced cell density and decreased palatal volume. The suppressed BMP signaling and reduced mineralization indicated an impaired osteogenesis of palatine, which could be rescued partially by constitutively active . Together, our study highlighted the key role of GAG chains in palate morphogenesis.
Topics: Animals; Mice; Catalysis; Cleft Palate; Gene Expression Regulation, Developmental; Glycosaminoglycans; Mesoderm; Micrognathism; Neural Crest; Palate; Proteoglycans
PubMed: 37298583
DOI: 10.3390/ijms24119634 -
Facial fillers: a new challenge for airway assessment in patients with retrognathia or micrognathia.British Journal of Anaesthesia Jul 2023
Topics: Humans; Micrognathism; Retrognathia; Intubation, Intratracheal; Respiratory System
PubMed: 37198031
DOI: 10.1016/j.bja.2023.03.028 -
Molecular Genetics & Genomic Medicine Jul 2023Miller syndrome is a rare type of postaxial acrofacial dysostosis caused by biallelic mutations in the DHODH gene, which is characterized mainly by craniofacial...
BACKGROUND
Miller syndrome is a rare type of postaxial acrofacial dysostosis caused by biallelic mutations in the DHODH gene, which is characterized mainly by craniofacial malformations of micrognathia, orofacial clefts, cup-shaped ears, and malar hypoplasia, combined with postaxial limb deformities like the absence of fifth digits.
METHODS
In this study, a prenatal case with multiple orofacial-limb abnormities was enrolled, and a thorough clinical and imaging examination was performed. Subsequently, genetic detection with karyotyping, chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) was carried out. In vitro splicing analysis was also conducted to clarify the impact of one novel variant.
RESULTS
The affected fetus displayed typical manifestations of Miller syndrome, and WES identified a diagnostic compound heterozygous variation in DHODH, consisting of two variants: exon(1-3)del and c.819 + 5G > A. We conducted a further in vitro validation with minigene system, and the result indicated that the c.819 + 5G > A variant would lead to an exon skipping in mRNA splicing.
CONCLUSIONS
These findings provided with the first exonic deletion and first splice site variant in DHODH, which expanded the mutation spectrum of Miller syndrome and offered reliable evidence for genetic counseling to the affected family.
Topics: Female; Humans; Pregnancy; Cleft Lip; Cleft Palate; Dihydroorotate Dehydrogenase; East Asian People; Micrognathism; Prenatal Diagnosis
PubMed: 37120754
DOI: 10.1002/mgg3.2186 -
Disease Models & Mechanisms Jun 2023Facial development requires a complex and coordinated series of cellular events that, when perturbed, can lead to structural birth defects. A quantitative approach to...
Facial development requires a complex and coordinated series of cellular events that, when perturbed, can lead to structural birth defects. A quantitative approach to quickly assess morphological changes could address how genetic or environmental inputs lead to differences in facial shape and promote malformations. Here, we report on a method to rapidly analyze craniofacial development in zebrafish embryos using facial analytics based on a coordinate extrapolation system, termed zFACE. Confocal images capture facial structures and morphometric data are quantified based on anatomical landmarks present during development. The quantitative morphometric data can detect phenotypic variation and inform on changes in facial morphology. We applied this approach to show that loss of smarca4a in developing zebrafish leads to craniofacial anomalies, microcephaly and alterations in brain morphology. These changes are characteristic of Coffin-Siris syndrome, a rare human genetic disorder associated with mutations in SMARCA4. Multivariate analysis of zFACE data facilitated the classification of smarca4a mutants based on changes in specific phenotypic characteristics. Together, zFACE provides a way to rapidly and quantitatively assess the impact of genetic alterations on craniofacial development in zebrafish.
Topics: Animals; Humans; Zebrafish; Face; Micrognathism; Abnormalities, Multiple; Intellectual Disability; DNA Helicases; Nuclear Proteins; Transcription Factors
PubMed: 37102214
DOI: 10.1242/dmm.049868 -
Fetal Diagnosis and Therapy 2023Gómez-López-Hernández syndrome (GLHS), also known as cerebello-trigeminal-dermal dysplasia, is an extremely rare neurocutaneous disease, classically described by the...
INTRODUCTION
Gómez-López-Hernández syndrome (GLHS), also known as cerebello-trigeminal-dermal dysplasia, is an extremely rare neurocutaneous disease, classically described by the triad of rhombencephalosynapsis (RES), bilateral focal alopecia, and trigeminal anesthesia. The clinical and radiographic spectrum of GLHS is now known to be broader, including craniofacial and supratentorial anomalies, as well as neurodevelopmental issues.
CASE PRESENTATION
Here, we present a case of antenatally diagnosed GLHS with RES, hydrocephaly, and craniofacial anomalies identified on ultrasound (low-set ears with posterior rotation, hypertelorism, midface hypoplasia, micrognathia, and anteverted nares) which were confirmed by autopsy after termination of pregnancy at 23 weeks of gestation.
DISCUSSION
As no known genetic causes have been identified and the classical triad is not applicable to prenatal imaging, prenatal diagnosis of GLHS is based on neuroimaging and the identification of supporting features. In presence of an RES associated with craniofacial abnormalities in prenatal (brachycephaly, turricephaly, low-set ears, midface retrusion, micrognathia), GLHS should be considered as "possible" according to postnatal criteria.
Topics: Female; Pregnancy; Humans; Micrognathism; Cerebellum; Craniofacial Abnormalities; Alopecia; Prenatal Diagnosis
PubMed: 37062278
DOI: 10.1159/000530643 -
European Journal of Human Genetics :... Aug 2023High-throughput sequencing has become a standard first-tier approach for both diagnostics and research-based genetic testing. Consequently, this hypothesis-free... (Review)
Review
High-throughput sequencing has become a standard first-tier approach for both diagnostics and research-based genetic testing. Consequently, this hypothesis-free testing manner has revealed the true breadth of clinical features for many established genetic disorders, including Meier-Gorlin syndrome (MGORS). Previously known as ear-patella short stature syndrome, MGORS is characterized by growth delay, microtia, and patella hypo/aplasia, as well as genital abnormalities, and breast agenesis in females. Following the initial identification of genetic causes in 2011, a total of 13 genes have been identified to date associated with MGORS. In this review, we summarise the genetic and clinical findings of each gene associated with MGORS and highlight molecular insights that have been made through studying patient variants. We note interesting observations arising across this group of genes as the number of patients has increased, such as the unusually high number of synonymous variants affecting splicing in CDC45 and a subgroup of genes that also cause craniosynostosis. We focus on the complicated molecular genetics for DONSON, where we examine potential genotype-phenotype patterns using the first 3D structural model of DONSON. The canonical role of all proteins associated with MGORS are involved in different stages of DNA replication and in addition to summarising how patient variants impact on this process, we discuss the potential contribution of non-canonical roles of these proteins to the pathophysiology of MGORS.
Topics: Female; Humans; Congenital Microtia; Patella; Growth Disorders; Micrognathism
PubMed: 37059840
DOI: 10.1038/s41431-023-01359-z