Microcephalic Osteodysplastic Primordial Dwarfism Type Research Articles

Novel mutation in patients with microcephalic osteodysplastic primordial dwarfism type II (MOPD II).

A rare type of autosomal recessive skeletal disorder, known as microcephalic osteodysplastic primordial dwarfism (MOPD) type II, causes a wide range of clinical abnormalities, including skeletal dysplasia, microcephaly, abnormal skin pigmentation, insulin resistance, typical facial features, and severe tooth deformities. Given the diverse manifestations of MOPD disorders and the overlapping clinical characteristics among primordial dwarfism (PD) subtypes, mutation analysis is crucial for accurate diagnosis and confirmation of MOPD II. In this study, whole-exome sequencing (WES) and GAP-PCR were employed to identify relevant genetic variants in three patients suspected of having MOPD.The clinical characteristics of three Iranian patients exhibiting hallmark features of MOPD were assessed. All patients were the offspring of consanguineous marriages and were referred from various provinces of Iran. WES was performed, and the identified variants were prioritized according to the standard filtration criteria. In the next step, Sanger sequencing was conducted to validate the candidate variants identified through WES in patients and their parents. Finally, GAP-PCR was implemented to resolve conflicting results between WES and Sanger sequencing for one of the patients.Analysis of three distinct cases revealed a novel homozygous copy number variation (CNV) in Case 3, consisting of a 490bp deletion harboring exon 19 in the PCNT gene. Additionally, a nonsense homozygous variant in the PCNT gene (c.2812C > T, p.Gln 938*) was found in Cases 1 and 2. This pathogenic variant has been previously documented in the literature.Reporting a novel deletion in the PCNT gene improves genetic testing services, including PND and pre-implantation genetic diagnosis (PGD) for MOPD II.

Myocardial infarction in a 17-year-old patient diagnosed with MPOD II syndrome.

Microcephalic osteodysplastic primordial dwarfism (MOPD) syndrome type 2, caused by a mutation in the PCNT gene (21q22.3), is a rare autosomal recessive disorder. Patients present with bone dysplasia, insulin resistance, kidney diseases, and cardiac malformations, making them prone to vascular diseases. Cardiomyopathy, hypertension, and coronary diseases are documented. The prognosis is associated with cerebrovascular complications. We report a case of a patient with MOPD type II who suffered a myocardial infarction in our institution. Informed consent for publishing was obtained. A 17-year-old female with MPOD II syndrome (20 kg and 86 cm) was referred for chest pain. Thoracic pains had been occurring for over a month, increasing in intensity, with an episode prompting emergency consultation. Initial tests revealed elevated troponin and an inflammatory response. Electrocardiogram (ECG) showed ST-segment depression and elevation. Echocardiography revealed hypokinetic inferior walls with moderate concentric hypertrophy. A coronary CT scan showed subendocardial hypodensity. Diagnostic coronary angiography revealed tri-branch lesions and almost complete stenoses or occlusions on the circumflex artery (Image). No indication for interventional treatment due to diffuse atheromatous lesions. Exclusive medical treatment was initiated. MPOD II syndrome is associated with cardiac malformations and neurovascular complications, including myocardial infarction. Regular ECG monitoring is advisable. Active surveillance for coronary diseases is necessary from adolescence. Recognising this complication allows for prompt intervention. This case highlights the need for specific monitoring and prompt management of chest pain in patients with MPOD II syndrome. Primary prevention could mitigate the occurrence of coronary events in this high-risk population.

B-cell immune deficiency in twin sisters expands the phenotype of MOPDI.

Microcephalic osteodysplastic primordial dwarfism type I (MOPDI) is a very rare and severe autosomal recessive disorder characterized by marked intrauterine growth retardation, skeletal dysplasia, microcephaly and brain malformations. MOPDI is caused by biallelic mutations in RNU4ATAC, a non-coding gene involved in U12-type splicing of 1% of the introns in the genome, which are recognized by their specific splicing consensus sequences. Here, we describe a unique observation of immunodeficiency in twin sisters with mild MOPDI, who harbor a novel n.108_126del mutation, encompassing part of the U4atac snRNA 3' stem-loop and Sm protein binding site, and the previously reported n.111G>A mutation. Interestingly, both twin sisters show mild B-cell anomalies, including low naive B-cell counts and increased memory B-cell and plasmablasts counts, suggesting partial and transitory blockage of B-cell maturation and/or excessive activation of naive B-cells. Hence, the localization of a mutation in stem II of U4atac snRNA, as observed in another RNU4ATAC-opathy with immunodeficiency, that is, Roifman syndrome (RFMN), is not required for the occurrence of an immune deficiency. Finally, we emphasize the importance of considering immunodeficiency in MOPDI management to reduce the risk of serious infectious episodes.

Trends in Serum Cytokine Expression in Pediatric Skeletal Dysplasia.

The skeletal dysplasias are a heterogeneous group of genetic conditions caused by abnormalities of growth, development, and maintenance of bone and cartilage. Little is known about the roles that cytokines play in the inflammatory and non-inflammatory pathophysiology of skeletal dysplasia. We sought to test our hypothesis that cytokines would be differentially expressed in children with skeletal dysplasia as compared to typically growing controls. Cytokine levels were analyzed using the Cytokine Human Magnetic 25-Plex Panel (Invitrogen, Waltham, MA, USA); 136 growing individuals with skeletal dysplasia and compared to a cohort of 275 healthy pediatric control subjects. We focused on the expression of 12 cytokines across nine dysplasia cohorts. The most common skeletal dysplasia diagnoses were: achondroplasia (58), osteogenesis imperfecta (19), type II collagenopathies (11), multiple epiphyseal dysplasia (MED: 9), diastrophic dysplasia (8), metatropic dysplasia (8), and microcephalic osteodysplastic primordial dwarfism type II (MOPDII: 8). Of the 108 specific observations made, 45 (41.7%) demonstrated statistically significant differences of expression between controls and individuals with skeletal dysplasia. Four of the 12 analyzed cytokines demonstrated elevated expression above control levels in all of the dysplasia cohorts (interleukin 12 [IL-12], IL-13, interferon γ-induced protein 10 kDa [IP-10], regulated on activation, normal T cell expressed and secreted [RANTES]) and two demonstrated expression below control levels across all dysplasia cohorts (monocyte chemoattractant protein 1 [MCP-1], macrophage inflammatory protein-1β [MIP-1β]). The highest levels of overexpression were seen in MOPDII, with expression levels of IP-10 being increased 3.8-fold (p < 0.0001). The lowest statistically significant levels of expressions were in type II collagenopathies, with expression levels of MCP-1 being expressed 0.43-fold lower (p < 0.005). With this data, we hope to lay the groundwork for future directions in dysplasia research that will enhance our understanding of these complex signaling pathways. Looking forward, validating these early trends in cytokine expression, and associating the observed variations with trends in the progression of dysplasia may offer new candidates for clinical biomarkers or even new therapeutics. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Whole-Exome and Transcriptome Sequencing Expands the Genotype of Majewski Osteodysplastic Primordial Dwarfism Type II.

Microcephalic Osteodysplastic Primordial Dwarfism type II (MOPDII) represents the most common form of primordial dwarfism. MOPD clinical features include severe prenatal and postnatal growth retardation, postnatal severe microcephaly, hypotonia, and an increased risk for cerebrovascular disease and insulin resistance. Autosomal recessive biallelic loss-of-function genomic variants in the centrosomal pericentrin (PCNT) gene on chromosome 21q22 cause MOPDII. Over the past decade, exome sequencing (ES) and massive RNA sequencing have been effectively employed for both the discovery of novel disease genes and to expand the genotypes of well-known diseases. In this paper we report the results both the RNA sequencing and ES of three patients affected by MOPDII with the aim of exploring whether differentially expressed genes and previously uncharacterized gene variants, in addition to PCNT pathogenic variants, could be associated with the complex phenotype of this disease. We discovered a downregulation of key factors involved in growth, such as IGF1R, IGF2R, and RAF1, in all three investigated patients. Moreover, ES identified a shortlist of genes associated with deleterious, rare variants in MOPDII patients. Our results suggest that Next Generation Sequencing (NGS) technologies can be successfully applied for the molecular characterization of the complex genotypic background of MOPDII.

Hereditary dentin defects with systemic diseases.

This review aimed to summarize recent progress on syndromic dentin defects, promoting a better understanding of systemic diseases with dentin malformations, the molecules involved, and related mechanisms. References on genetic diseases with dentin malformations were obtained from various sources, including PubMed, OMIM, NCBI, and other websites. The clinical phenotypes and genetic backgrounds of these diseases were then summarized, analyzed, and compared. Over 10 systemic diseases, including osteogenesis imperfecta, hypophosphatemic rickets, vitamin D-dependent rickets, familial tumoral calcinosis, Ehlers-Danlos syndrome, Schimke immuno-osseous dysplasia, hypophosphatasia, Elsahy-Waters syndrome, Singleton-Merten syndrome, odontochondrodysplasia, and microcephalic osteodysplastic primordial dwarfism type II were examined. Most of these are bone disorders, and their pathogenic genes may regulate both dentin and bone development, involving extracellular matrix, cell differentiation, and metabolism of calcium, phosphorus, and vitamin D. The phenotypes of these syndromic dentin defects various with the involved genes, part of them are similar to dentinogenesis imperfecta or dentin dysplasia, while others only present one or two types of dentin abnormalities such as discoloration, irregular enlarged or obliterated pulp and canal, or root malformation. Some specific dentin defects associated with systemic diseases may serve as important phenotypes for dentists to diagnose. Furthermore, mechanistic studies on syndromic dentin defects may provide valuable insights into isolated dentin defects and general dentin development or mineralization.

Clinical Findings and Dental Manifestations Associated With Microcephalic Osteodysplastic Primordial Dwarfism Type II: A Case Report

Background: Microcephalic Osteodysplastic Primordial Dwarfism type 2 (MOPD II) is a rare untreatable genetic disorder characterized by severe prenatal and postnatal growth retardation, microcephaly, bird-headed face (receding forehead and chin, a beaklike nose, and prominent eyes), skeletal abnormalities, abnormal dentition, abnormal hair and skin changes, high-pitched nasal voice, and an increased risk for insulin resistance and cerebrovascular disease. MOPDII is caused by mutations in the pericentrin gene and is inherited in an autosomal recessive manner. This study aims to report a MOPD II child patient. Case Presentation: A seven-year-old girl genetically diagnosed with MOPD II has been presented in this case report. Clinical, radiological, and laboratory findings with emphasis on oral features have been reported, and her dental problems management has also been described. Conclusions: MOPD II patients have a shorter life expectancy. The main health complications which need regular care include vascular changes of the central nervous system, diabetes mellitus, renal problems, blood pressure, cardiac pathologies, and hematologic profile. MOPD II patients have a high risk of caries because they consume soft and cariogenic foods due to microdontia, oligodontia, and an incompetent masticatory system. On the other hand, dental treatment for such patients can be very challenging. MOPD II cases and their families should be aware of the importance of oral hygiene and routine dental follow-ups.

Abstract #1151796: Hypophosphatasia and Microcephalic Osteodysplastic Primordial Dwarfism type II: Diagnosing patients with minor symptoms

Hypophosphatasia (HPP) and Microcephalic Osteodysplastic Primordial Dwarfism type II (MOPD II) are rare inherited diseases which arise from the ALPL gene and PCNT gene respectively. HPP has nonspecific alkaline phosphatase (TNSALP) deficiency which causes the manifestations of skeletal deformities, fractures, nephrocalcinosis, seizures, respiratory failure and poor dentition. While in MOPD typically presents with bone, vascular and hematological abnormalities. Both of these diseases have a variety of symptoms which can vary in severity which can make the diagnosis difficult but important to avoid future complications.

Novel frameshift variant in the PCNT gene associated with Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II and small kidneys

BackgroundMicrocephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II is an autosomal recessive condition encompassing a heterogeneous group of disorders characterized by symmetrical growth retardation leading to dwarfism, microcephaly, and a range of multiple medical complications including neurovascular diseases. Biallelic pathogenic variants in the pericentrin gene (PCNT) have been implicated in its pathogenesis.Case presentationWe performed whole-exome sequencing to ascertain the diagnosis of a 2 year and 6 months old boy who presented with severe failure to thrive, microcephaly, and facial gestalt suggestive of MOPD Type II which included features such as retrognathia, small ears, prominent nasal root with a large nose, microdontia, sparse scalp hair, bilateral fifth finger clinodactyly. He had a small ostium secundum atrial septal defect and bilaterally small kidneys. Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II was confirmed based on a pathogenic compound heterozygous frameshift variant in the PCNT gene c.5059_5060delAA | p. Asn1687fs (novel variant) and c.9535dup (p. Val3179fs). His parents were found to be heterozygous carriers for the variants.ConclusionWe report a novel frameshift variant in the PCNT gene and a previously unreported phenotype for Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II.

Whole genome sequencing identifies pathogenic RNU4ATAC variants in a child with recurrent encephalitis, microcephaly, and normal stature

Biallelic pathogenic variants in RNU4ATAC have been linked to microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1). Although children with MOPD1 have been reported to show profound, life-limiting clinical decompensation at the time of a febrile illness, these episodes including magnetic resonance imaging (MRI) findings have not been well characterized. We present acute MRI brain findings for a 10-year-old girl with homozygous variants in RNU4ATAC (NR_023343.1) n.55G>A, who presented with two episodes of clinical decompensation associated with a febrile illness in early childhood. The pathogenic variants were identified by whole genome sequencing as RNU4ATAC is not captured in most exome products. Her MRI of the brain revealed symmetric, diffusion restriction of the deep gray nuclei that initially pointed to a mitochondrial disease or acute necrotizing encephalopathy. Her phenotype included microcephaly and profound cognitive impairment that can be seen with MOPD1. However, she did not demonstrate clinical or radiographic evidence of a spondyloepimetaphyseal dysplasia or "primordial dwarfism" that is characteristic of this disease. As such, the predominant neurological presentation of this child represents an atypical variant of RNU4ATAC-associated disease and should be a diagnostic consideration for geneticists and neurologists caring for children, particularly in the event of an acute clinical decline.

Clinical relevance of targeted exome sequencing in patients with rare syndromic short stature

BackgroundLarge-scale genomic analyses have provided insight into the genetic complexity of short stature (SS); however, only a portion of genetic causes have been identified. In this study, we identified disease-causing mutations in a cohort of Korean patients with suspected syndromic SS by targeted exome sequencing (TES).MethodsThirty-four patients in South Korea with suspected syndromic disorders based on abnormal growth and dysmorphic facial features, developmental delay, or accompanying anomalies were enrolled in 2018–2020 and evaluated by TES.ResultsFor 17 of 34 patients with suspected syndromic SS, a genetic diagnosis was obtained by TES. The mean SDS values for height, IGF-1, and IGFBP-3 for these 17 patients were − 3.27 ± 1.25, − 0.42 ± 1.15, and 0.36 ± 1.31, respectively. Most patients displayed distinct facial features (16/17) and developmental delay or intellectual disability (12/17). In 17 patients, 19 genetic variants were identified, including 13 novel heterozygous variants, associated with 15 different genetic diseases, including many inherited rare skeletal disorders and connective tissue diseases (e.g., cleidocranial dysplasia, Hajdu–Cheney syndrome, Sheldon–Hall, acromesomelic dysplasia Maroteaux type, and microcephalic osteodysplastic primordial dwarfism type II). After re-classification by clinical reassessment, including family member testing and segregation studies, 42.1% of variants were pathogenic, 42.1% were likely pathogenic variant, and 15.7% were variants of uncertain significance. Ultra-rare diseases accounted for 12 out of 15 genetic diseases (80%).ConclusionsA high positive result from genetic testing suggests that TES may be an effective diagnostic approach for patients with syndromic SS, with implications for genetic counseling. These results expand the mutation spectrum for rare genetic diseases related to SS in Korea.

Microcephalic osteodysplastic primordial dwarfism type II is associated with global vascular disease

BackgroundMicrocephalic osteodysplastic primordial dwarfism type II (MOPDII) is the most common form of primordial dwarfism, caused by bialleic mutations in the pericentrin gene (PCNT). Aside from its classic features, there are multiple associated medical complications, including a well-documented risk of neurovascular disease. Over the past several years, it has become apparent that additional vascular issues, as well as systemic hypertension and kidney disease may also be related to MOPDII. However, the frequency and extent of the vasculopathy was unclear. To help address this question, a vascular substudy was initiated within our Primordial Dwarfism Registry.ResultsMedical records from 47 individuals, living and deceased, ranging in age from 3 to 41 years of age were interrogated for this purpose. Of the total group, 64% were diagnosed with moyamoya, intracranial aneurysms, or both. In general, the age at diagnosis for moyamoya was younger than aneurysms, but the risk for neurovascular disease was throughout the shortened lifespan. In addition to neurovascular disease, renal, coronary and external carotid artery involvement are documented. 43% of the total group was diagnosed with hypertension, and 17% had myocardial infarctions. A total of 32% of the entire cohort had some form of chronic kidney disease, with 4% of the total group necessitating a kidney transplant. In addition, 38% had diabetes/insulin resistance. Ages of diagnoses, treatment modalities employed, and location of vasculopathies were notated as available and applicable, as well as frequencies of other comorbidities.ConclusionsIt is now clear that vascular disease in MOPDII is global and screening of the cardiac and renal vessels is warranted along with close monitoring of blood pressure. We recommend a blood pressure of 110/70 mmHg as a starting point for an upper limit, especially if the individual has a history of neurovascular disease, chronic kidney disease and/or diabetes. Additionally, providers need to be at high alert for the possibility of myocardial infarctions in young adults with MOPDII, so that appropriate treatment can be initiated promptly in an acute situation.

Dental Characteristics of Microcephalic Osteodysplastic Primordial Dwarfism Type II

Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is an autosomal recessive inherited disorder form of primordial dwarfism, caused by mutations in the pericentrin gene. The purpose of the study was to examine the clinical and radiological features, physicochemical properties and microstructures of the tooth affected with MOPD II. The mandibular 2nd molar was collected from the MOPD II patient. Micro-computerized tomography, scanning electron microscopy, energy dispersive spectrometry and Vickers microhardness analysis were performed on the MOPD II and the normal control. The morphology of the MOPD II tooth appeared to have malformed pulp and root and showed a small size. The mineral density measurement showed that the MOPD II tooth had similar scores in the enamel, but lower scores in the root 1/2 and apical dentin compared to the normal control. The microhardness values were smaller in the cusp enamel, root 1/2 dentin and apical dentin of the MOPD II compared to the normal control. In this study, the dental characteristics and the physicochemical properties of a tooth affected with MOPD II were analyzed to improve understanding of the oral manifestations of the disease and to assist in proper dental treatment by identifying precautions.

Novel PCNT variants in MOPDII with attenuated growth restriction and pachygyria.

Biallelic loss‐of‐function mutations in the centrosomal pericentrin gene (PCNT) cause microcephalic osteodysplastic primordial dwarfism type II (MOPDII), which is characterized by extreme growth retardation, microcephaly, skeletal dysplasia, and dental anomalies. Life expectancy is reduced due to a high risk of cerebral vascular anomalies. Here, we report two siblings with MOPDII and attenuated growth restriction, and pachygyria. Compound heterozygosity for two novel truncated PCNT variants was identified. Both truncated PCNT proteins were expressed in patient's fibroblasts, with a reduced total protein amount compared to control. Patient's fibroblasts showed impaired cell cycle progression. As a novel finding, 20% of patient's fibroblasts were shown to express PCNT comparable to control. This was associated with normal mitotic morphology and normal co‐localization of mutated PCNT with centrosome‐associated proteins γ‐tubulin and centrin 3, suggesting some residual function of truncated PCNT proteins. These data expand the clinical and molecular spectrum of MOPDII and indicate that residual PCNT function might be associated with attenuated growth restriction in MOPDII.

A Novel PCNT Frame Shift Variant (c.7511delA) Causing Osteodysplastic Primordial Dwarfism of Majewski Type 2 (MOPD II)

Background: Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is an autosomal recessive and skeletal disorder included wide spectrum of clinical abnormalities such as fetal growth restriction, disproportionate face, microcephaly, post-natal growth retardation, adult height under 100 cm, abnormal skin pigmentation, insulin resistance, and susceptibility to cerebrovascular and hematologic abnormalities. Due to heterogeneous feature of MOPDs diseases and common clinical features among the different subtypes, mutation analysis can be considered as fundamental in the accurate diagnosis and confirmation of the MOPD II disease. Some studies revealed that, variants of gene encoding Pericentrin protein, PCNT, were associated with MOPD II.Methods: We performed whole exome sequencing based on the next generation sequencing (Illumina platform), to perform correct diagnosis in a 17-year-old girl with an unknown disease who was referred to the Diabetes Research Center in Yazd, Iran. The clinical features of the patient were short stature, generalized brachydactyly, gradual deterioration of brain functioning, menstrual irregularity, clitoromegaly, acanthosis nigricans, diabetes mellitus, hyperinsulinemia, insulin resistance, and dyslipidemia. Accordingly, her parents were also first cousin with no background disease. After identifying the novel variant, it was confirmed in the proband and her family using bi-directional Sanger sequencing, and its pathogenicity was also checked by different online tools.Results: Our study revealed a novel frame-shift variant in PCNT gene (c.7511delA, p.K2504Sfs*27), which causes premature termination of Pericentrin protein. The result disclosed that, the proband was affected by MOPD II disease. In addition, the Sanger sequencing confirmed the novel homozygote variant in the proband and heterozygote one in her parents, and the extended family perfectly segregated among them. Online tools such as Varsome and MutationTaster also showed a high level of pathogenicity for the variant identified.Conclusion: A novel variant was identified in the proband and her extended family, which emphasized the importance of PCNT gene mutations analysis in the screening and accurate identification of MOPD II disease, especially in prenatal diagnosis.

Discovering candidate imprinted genes and imprinting control regions in the human genome

BackgroundGenomic imprinting is a process thereby a subset of genes is expressed in a parent-of-origin specific manner. This evolutionary novelty is restricted to mammals and controlled by genomic DNA segments known as Imprinting Control Regions (ICRs) and germline Differentially Methylated Regions (gDMRs). Previously, I showed that in the mouse genome, the fully characterized ICRs/gDMRs often includes clusters of 2 or more of a set of composite-DNA-elements known as ZFBS-morph overlaps.ResultsBecause of the importance of the ICRs to regulating parent-of-origin specific gene expression, I developed a genome-wide strategy for predicting their positions in the human genome. My strategy consists of creating plots to display the density of ZFBS-morph overlaps along the entire chromosomal DNA sequences. In initial evaluations, I found that peaks in these plots pinpointed several of the known ICRs/gDMRs along the DNA in chromosomal bands. I deduced that in density-plots, robust peaks corresponded to actual or candidate ICRs in the DNA. By locating the genes in the vicinity of candidate ICRs, I could discover potential imprinting genes. Additionally, my assessments revealed a connection between several of the potential imprinted genes and human developmental anomalies. Examples include Leber congenital amaurosis 11, Coffin-Siris syndrome, progressive myoclonic epilepsy-10, microcephalic osteodysplastic primordial dwarfism type II, and microphthalmia, cleft lip and palate, and agenesis of the corpus callosum.ConclusionWith plots displaying the density of ZFBS-morph overlaps, researchers could locate candidate ICRs and imprinted genes. Since the datafiles are available for download and display at the UCSC genome browser, it is possible to examine the plots in the context of Single nucleotide polymorphisms (SNPs) to design experiments to discover novel ICRs and imprinted genes in the human genome.

Microcephalic osteodysplastic primordial dwarfism type II: Additional nine patients with implications on phenotype and genotype correlation.

PCNT encodes a large coiled- protein localizing to pericentriolar material and is associated with microcephalic osteodysplastic primordial dwarfism type II syndrome (MOPD II). We report our experience of nine new patients from seven unrelated consanguineous Egyptian families with the distinctive clinical features of MOPD II in whom a customized NGS panel showed homozygous truncating variants of PCNT. The NGS panel results were validated thereafter using Sanger sequencing revealing three previously reported and three novel PCNT pathogenic variants. The core phenotype appeared homogeneous to what had been reported before although patients differed in the severity showing inter and intra familial variability. The orodental pattern showed atrophic alveolar ridge (five patients), rootless tooth (four patients), tooth agenesis (three patients), and malformed tooth (three patients). In addition, mesiodens was a novel finding found in one patient. The novel c.9394-1G>T variant was found in two sibs who had tooth agenesis. CNS anomalies with possible vascular sequelae were documented in two male patients (22.2%). Simplified gyral pattern with poor development of the frontal horns of lateral ventricles was seen in four patients and mild thinning of the corpus callosum in two patients. Unilateral coronal craniosynstosis was noted in one patient and thick but short corpus callosum was an unusual finding noted in another. The later has not been reported before. Our results refine the clinical, neuroradiological, and orodental features and expand the molecular spectrum of MOPD II.

Loss of U11 small nuclear RNA in the developing mouse limb results in micromelia.

Disruption of the minor spliceosome due to mutations in RNU4ATAC is linked to primordial dwarfism in microcephalic osteodysplastic primordial dwarfism type 1, Roifman syndrome, and Lowry-Wood syndrome. Similarly, primordial dwarfism in domesticated animals is linked to positive selection in minor spliceosome components. Despite being vital for limb development and size regulation, its role remains unexplored. Here, we disrupt minor spliceosome function in the developing mouse limb by ablating one of its essential components, U11 small nuclear RNA, which resulted in micromelia. Notably, earlier loss of U11 corresponded to increased severity. We find that limb size is reduced owing to elevated minor intron retention in minor intron-containing genes that regulate cell cycle. As a result, limb progenitor cells experience delayed prometaphase-to-metaphase transition and prolonged S-phase. Moreover, we observed death of rapidly dividing, distally located progenitors. Despite cell cycle defects and cell death, the spatial expression of key limb patterning genes was maintained. Overall, we show that the minor spliceosome is required for limb development via size control potentially shared in disease and domestication.

Minor intron splicing revisited: identification of new minor intron-containing genes and tissue-dependent retention and alternative splicing of minor introns

BackgroundMutations in minor spliceosome components such as U12 snRNA (cerebellar ataxia) and U4atac snRNA (microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1)) result in tissue-specific symptoms. Given that the minor spliceosome is ubiquitously expressed, we hypothesized that these restricted phenotypes might be caused by the tissue-specific regulation of the minor spliceosome targets, i.e. minor intron-containing genes (MIGs). The current model of inefficient splicing is thought to apply to the regulation of the ~ 500 MIGs identified in the U12DB. However this database was created more than 10 years ago. Therefore, we first wanted to revisit the classification of minor introns in light of the most recent reference genome. We then sought to address specificity of MIG expression, minor intron retention, and alternative splicing (AS) across mouse and human tissues.ResultsWe employed position-weight matrices to obtain a comprehensive updated list of minor introns, consisting of 722 mouse and 770 human minor introns. These can be found in the Minor Intron DataBase (MIDB). Besides identification of 99% of the minor introns found in the U12DB, we also discovered ~ 150 new MIGs. We then analyzed the RNAseq data from eleven different mouse tissues, which revealed tissue-specific MIG expression and minor intron retention. Additionally, many minor introns were efficiently spliced compared to their flanking major introns. Finally, we identified several novel AS events across minor introns in both mouse and human, which were also tissue-dependent. Bioinformatics analysis revealed that several of the AS events could result in the production of novel tissue-specific proteins. Moreover, like the major introns, we found that these AS events were more prevalent in long minor introns, while retention was favoured in shorter introns.ConclusionHere we show that minor intron splicing and AS across minor introns is a highly organised process that might be regulated in coordination with the major spliceosome in a tissue-specific manner. We have provided a framework to further study the impact of the minor spliceosome and the regulation of MIG expression. These findings may shed light on the mechanism underlying tissue-specific phenotypes in diseases associated with minor spliceosome inactivation. MIDB can be accessed at https://midb.pnb.uconn.edu.

New PCNT candidate missense variant in a patient with oral and maxillofacial osteodysplasia: a case report

BackgroundOsteodysplasia of the oral and maxillofacial bone is generally accompanied by systemic bone abnormalities (such as short stature, joint contracture) or other systemic abnormalities (such as renal, dermatological, cardiovascular, optic, or hearing disorders). However, it does not always present this way. Recent reports have suggested that genome-wide sequencing is an effective method for identifying rare or new disorders. Here, we performed whole-exome sequencing (WES) in a patient with a unique form of acquired, local osteodysplasia of the oral and maxillofacial region.Case presentationA 46-year-old woman presented to our hospital with the complaint of gradually moving mandibular teeth (for 6 months), changing facial appearance, and acquired osteolysis of the oral and maxillofacial bones, showing mandibular hypoplasia without family history. Upon skeletal examination, there were no abnormal findings outside of the oral and maxillofacial area; the patient had a height of 157 cm and bone mineral density (according to dual energy x-ray absorptiometry) of 90%. Results of blood and urine tests, including evaluation of bone metabolism markers and neurological and cardiovascular examinations, were normal. We performed WES of genomic DNA extracted from the blood of this patient and her mother, who did not have the disease, as a negative control. We identified 83 new missense variants in the patient, not detected in her mother, including a candidate single nucleotide variant in exon 14 of PCNT (pericentrin). Critical homozygous or compound heterozygous variants in PCNT are a known cause of microcephalic osteodysplastic primordial dwarfism type II accompanied by mandibular hypoplasia, which is similar to the maxillofacial phenotype in this patient.ConclusionsProtein simulations performed using Polymorphism Phenotyping v2 and Combined Annotation Dependent Depletion software indicated that this missense variant is likely to disrupt the PCNT protein structure. These results suggest that this is a new form of osteolysis related to this PCNT variant.