Mutation Update for COL2A1 Gene Variants Associated with Type II Collagenopathies

Clinical utility of comprehensive gene panel testing for common and rare causes of skeletal dysplasia and other skeletal disorders: Results from the largest cohort to date

Molecular genetics enables more precise diagnoses of skeletal dysplasia and other skeletal disorders (SDs). We investigated the clinical utility of multigene panel testing for 5011 unrelated individuals with SD in the United States (December 2019-April 2022). Median (range) age was 8 (0-90) years, 70.5% had short stature and/or disproportionate growth, 27.4% had a positive molecular diagnosis (MDx), and 30 individuals received two MDx. Genes most commonly contributing to MDx were FGFR3 (16.9%), ALPL (13.0%), and COL1A1 (10.3%). Most of the 112 genes associated with ≥1 MDx were primarily involved in signal transduction (n = 35), metabolism (n = 23), or extracellular matrix organization (n = 17). There were implications associated with specific care/treatment options for 84.4% (1158/1372) of MDx-positive individuals; >50% were linked to conditions with targeted therapy approved or in clinical development, including osteogenesis imperfecta, achondroplasia, hypophosphatasia, and mucopolysaccharidosis. Forty individuals with initially inconclusive results became MDx-positive following family testing. Follow-up mucopolysaccharidosis enzyme activity testing was positive in 14 individuals (10 of these were not MDx-positive). Our findings showed that inclusion of metabolic genes associated with SD increased the clinical utility of a gene panel and confirmed that integrated use of comprehensive gene panel testing with orthogonal testing reduced the burden of inconclusive results.

The molecular complexity of COL2A1 splicing variants and their significance in phenotype severity

Pathogenic single nucleotide variants (SNVs) found in the COL2A1 gene are associated with a broad range of skeletal dysplasias due to their impact on the structure and function of the Col2a1 protein. However, the molecular mechanisms of some nucleotide variants detected during diagnostic testing remain unclear. The interpretation of missense and splicing variants caused by SNVs poses a significant challenge for clinicians. In this work, we analyzed 22 splicing variants in the COL2A1 gene which have been found in patients with COL2A1-associated skeletal dysplasias. Using a minigene system, we investigated the impact of these SNVs on splicing and gained insights into their molecular mechanisms and genotype-phenotype correlations for each patient. The results of our study are very useful for improving the accuracy of diagnosis and the management of patients with skeletal dysplasias caused by SNVs in the COL2A1 gene.

What do osteoporosis and osteoarthritis have in common? An integrated study of overlapping differentially expressed genes in bone mesenchymal stem cells of osteoporosis and osteoarthritis

OBJECTIVE

For identification of aberrantly expressed genes in mesenchymal stem cells of osteoporosis (OP) and osteoarthritis (OA), Gene Expression Omnibus (GEO) datasets were integrated to investigate the intersection point.

METHODS

GSE35958 (osteoporosis) and GSE19664 (osteoarthritis) datasets were obtained from GEO database. The abnormally expressed genes were analyzed by GEO2R. Functional enrichment was explored by Metascape database and R software. The String database and Cytoscape software were used to build the protein-protein interaction network and identify hub genes. GSE35957 and GSE116925 were used as verification datasets. Single-cell analysis and pseudotime analysis were undertaken. CTDbase, Network Analyst, HPA database, HERB database and MIRW database were used to research the information, tissue and cell distribution, regulation, interaction and ingredients targeting the hub genes. Additionally, in vitro experiments such as RT-PCR, ALP staining and immunofluorescence were undertaken as verification tests.

RESULTS

Ten hub genes were identified in this study. All these genes play an important role in bone or cartilage generation. They have diagnostic values and therapeutic potential for OA and OP. Single-cell analysis visualized the cell distribution and pseudotime distribution of these genes. Some potential therapeutic ingredients of these genes were identified, such as curcumin, wogonin and glycerin. In vitro experiments, RT-PCR results showed that COL9A3 and MMP3 were downregulated and PTH1R was upregulated during osteogenic induction of BMSC. Immunohistochemical results showed the expression trend of MMP3 and COL2A1.

CONCLUSION

Ten abnormal hub genes of osteoporosis and osteoarthritis were identified successfully by this study. They were important regulatory genes for healthy bone and cartilage. These genes could be the common connections between osteoporosis and osteoarthritis as well as treatment targets. Further study of the regulatory mechanism and treatment effects of these genes would be valuable. The results of this study could contribute to further research.

Exome sequencing-aided precise diagnosis of four families with type I Stickler syndrome

BACKGROUND

Stickler syndrome is a multisystemic disorder characterized by ophthalmological and non-ophthalmological abnormalities, frequently misdiagnosed due to high clinical heterogeneity. Stickler syndrome type I (STL1) is predominantly caused by mutations in the COL2A1 gene.

METHODS

Exome sequencing and co-segregation analysis were utilized to scrutinize 35 families with high myopia, and pathogenic mutations were identified. Mutant COL2A1 was overexpressed in cells for mechanistic study. A retrospective genotype-phenotype correlation analysis was further conducted.

RESULTS

Two novel pathogenic mutations (c.2895+1G>C and c.3505G>A (p.Val1169Ile)) and two reported mutations (c.1597C>T (p.Arg533*) and c.1693C>T (p.Arg565Cys)) in COL2A1 were identified causing STL1. These mutations are all in the G-X-Y triplet, and c.2895+1G>C contributed to aberrant RNA splicing. COL2A1 mutants tended to form large aggregates in the endoplasmic reticulum (ER) and elevated ER stress. Additionally, mutations c.550G>A (p.Ala184Thr) and c.2806G>A (p.Gly936Ser) in COL2A1 were found in high myopia families, but were likely benign, although c.2806G>A (p.Gly936Ser) is on G-X-Y triplet. Moreover, genotype-phenotype correlation analysis revealed that mutations in exon 2 mainly contribute to retinal detachment, whereas mutations in the collagen alpha-1 chain region of COL2A1 tend to cause non-ophthalmologic symptoms.

CONCLUSION

This study broadens the COL2A1 gene mutation spectrum, provides evidence for ER stress caused by pathogenic COL2A1 mutations and highlights the importance of non-ophthalmological examination in clinical diagnosis of high myopia.

A Severe Case of Spondylometaphyseal Dysplasia Algerian Type with Two Mutations in COL2A1

Spondylometaphyseal dysplasia Algerian type (MIM no.: 184253) is an uncommon autosomal dominant skeletal dysplasia caused by heterozygous mutations in the COL2A1 gene (MIM no.: 120140). In this case based review, we reported a 5-year-old boy with short stature, severe dorsolumbar scoliosis, lumbar hyperlordosis, short trunk, and severe genu valgum . Radiological examination showed platyspondyly, irregular metaphyseal radiolucencies intermingled with radiodensities, and corner fractures. The patient has a c.3275G > A; p.Gly1092Asp mutation in exon 47 of the COL2A1 gene and a variant of unknown significance in c.1366-13C > A in intron 21. This latter sequence variant could partially or completely disrupt the natural splice acceptor site of intron 21/exon 22 in the COL2A1 gene leading to a potential modification of the phenotypic severity.

Streamlining Genetic Diagnosis With Long-Range Polymerase Chain Reaction (PCR)-Based Next-Generation Sequencing for Type I and Type II Collagenopathies

In the practice of clinical genetics, gene testing is usually guided by clinical diagnosis. When dealing with rare diseases, it is often necessary to create new test systems. The handling of a gene with a substantial number of exons poses a challenge both in sequential Sanger sequencing for each exon, and in the setup of capture probes to each exon for next-generation sequencing (NGS). We present very long amplicon sequencing (vLAS), an optimized long-range polymerase chain reaction (PCR)-based NGS method that overcomes this challenge. By utilizing approximately 20 Kb long PCR products and short-read NGS, vLAS is emerging as a highly adaptable and effective solution, especially for genes with numerous exons concentrated in a limited genomic region. Here, we demonstrate vLAS in the analysis of five patients with type I and two with type II collagenopathies. The integration of user-friendly NGS methods into genetic diagnosis enhances the practicality of clinical genetics.

Surgical treatment of atlantoaxial dysplasia and scoliosis in spondyloepiphyseal dysplasia congenita: A case report

BACKGROUND

Spondyloepiphyseal dysplasia congenita (SEDC) is a rare autosomal dominant hereditary disease caused by COL2A1 mutations. SEDC primarily involves the skeletal system, with typical clinical manifestations, including short stature, hip dysplasia, and spinal deformity. Due to the low incidence of SEDC, there are only a few case reports regarding the surgical treatment of SEDC complicated with spinal deformities.

CASE SUMMARY

We report a case of a 16-year-old male patient with SEDC. He presented with typical short stature, atlantoaxial dysplasia, scoliosis, and hip dysplasia. Cervical magnetic resonance imaging showed spinal canal stenosis at the atlas level and cervical spinal cord compression with myelopathy. The scoliosis was a right thoracic curve with a Cobb angle of 65°. He underwent atlantoaxial reduction, decompression, and internal fixation from C1–C2 to relieve cervical myelopathy. Three months after cervical surgery, posterior correction surgery for scoliosis was performed from T3 to L4. Scoliosis was corrected from 66° to 8° and remained stable at 2-year follow-up.

CONCLUSION

This is the first case report of a patient with SEDC who successfully underwent surgery for atlantoaxial dysplasia and scoliosis. The study provides an important reference for the surgical treatment of SEDC complicated with spinal deformities.

Case report: Whole exome sequencing and genome-wide methylation profiling of Czech dysplasia in a Chinese pedigree

Background

Czech dysplasia is a rare skeletal disorder with symptomatology including platyspondyly, brachydactyly of the third and fourth toes, and early-onset progressive pseudorheumatoid arthritis. The disorder segregates in an autosomal dominant fashion. A specific missense mutation (R275C, c.823C > T) in exon 13 of the COL2A1 gene has been identified in German and Japanese families.

Case summary

We present the case of a Chinese woman diagnosed with Czech dysplasia (proband) who carried a variant in the COL2A1 gene. Whole-exome sequencing (WES) identified the COL2A1 missense mutation (R275C, c.823C > T) in close relatives of the proband who also exhibited the same disorder.

Conclusion

This study is a thorough clinical and physiological description of Czech dysplasia in a Chinese patient.

Knee osteoarthritis: Current status and research progress in treatment (Review)

Knee osteoarthritis (KOA) is a common chronic articular disease worldwide. It is also the most common form of OA and is characterized by high morbidity and disability rates. With the gradual increase in life expectancy and ageing population, KOA not only affects the quality of life of patients, but also poses a burden on global public health. OA is a disease of unknown etiology and complex pathogenesis. It commonly affects joints subjected to greater loads and higher levels of activity. The knee joint, which is the most complex joint of the human body and bears the greatest load among all joints, is therefore most susceptible to development of OA. KOA lesions may involve articular cartilage, synovium, joint capsule and periarticular muscles, causing irreversible articular damage. Factors such as mechanical overload, inflammation, metabolism, hormonal changes and ageing serve key roles in the acceleration of KOA progression. The clinical diagnosis of KOA is primarily based on combined analysis of symptoms, signs, imaging and laboratory examination results. At present, there is no cure for KOA and the currently available therapies primarily focus on symptomatic treatment and delay of disease progression. Knee replacement surgery is typically performed in patients with advanced disease. The current study presents a review of epidemiological characteristics, risk factors, histopathological manifestations, pathogenesis, diagnosis, treatment modalities and progress in KOA research.

Exome sequencing improves genetic diagnosis of congenital orofacial clefts

Objective: This retrospective study aims to evaluate the utility of exome sequencing (ES) in identifying genetic causes of congenital orofacial clefts (OFCs) in fetuses with or without other structural abnormalities, and to further explore congenital OFCs genetic causes. Methods: The study enrolled 107 singleton pregnancies diagnosed with fetal OFCs between January 2016 and May 2022, and categorized them into two groups: isolated cleft lip and/or palate (CL/CP) and syndromic CL/CP. Cases with positive karyotyping and chromosomal microarray analysis results were excluded. Whole-exome sequencing was performed on eligible fetuses and their parents. Monogenic variants identified by ES and perinatal outcomes were recorded and evaluated during postnatal follow-up. Results: Clinically significant variants were identified in 11.2% (12/107) of fetuses, with no significant difference in detection rate between the isolated CL/CP group and the syndromic CL/CP group (8/83, 9.6% vs. 4/24, 16.7%, p = 0.553). Additionally, sixteen (16/107, 15.0%) fetuses had variants of uncertain significance. We identified 12 clinically significant variations that correlated with clinical phenotypes in 11 genes from 12 fetuses, with CHD7 being the most frequently implicated gene (n = 2). Furthermore, we observed a significant difference in termination rates and survival rates between the isolated CL/CP and syndromic CL/CP groups (41.0% vs. 70.8% and 56.6% vs. 20.8%, p < 0.05 for both). Conclusion: Based on our findings, it is clear that ES provides a significant increase in diagnostic yield for the molecular diagnosis of congenital OFCs, thereby substantially improving the existing prenatal diagnostic capabilities. This study also sheds light on seven novel pathogenic variants, broadening our understanding of the genetic underpinnings of OFCs and expanding the disease spectrums of relevant genes.

The Genetic Landscape of Children Born Small for Gestational Age with Persistent Short Stature

INTRODUCTION

Among children born small for gestational age, 10-15% fail to catch up and remain short (SGA-SS). The underlying mechanisms are mostly unknown. We aimed to decipher genetic aetiologies of SGA-SS within a large single-centre cohort.

METHODS

Out of 820 patients treated with growth hormone (GH), 256 were classified as SGA-SS (birth length and/or birth weight <-2 SD for gestational age and life-minimum height <-2.5 SD). Those with the DNA triplet available (child and both parents) were included in the study (176/256). Targeted testing (karyotype/FISH/MLPA/specific Sanger sequencing) was performed if a specific genetic disorder was clinically suggestive. All remaining patients underwent MS-MLPA to identify Silver-Russell syndrome, and those with unknown genetic aetiology were subsequently examined using whole-exome sequencing or targeted panel of 398 growth-related genes. Genetic variants were classified using ACMG guidelines.

RESULTS

The genetic aetiology was elucidated in 74/176 (42%) children. Of these, 12/74 (16%) had pathogenic or likely pathogenic (P/LP) gene variants affecting pituitary development (LHX4, OTX2, PROKR2, PTCH1, POU1F1), the GH-IGF-1 or IGF-2 axis (GHSR, IGFALS, IGF1R, STAT3, HMGA2), 2/74 (3%) the thyroid axis (TRHR, THRA), 17/74 (23%) the cartilaginous matrix (ACAN, various collagens, FLNB, MATN3), and 7/74 (9%) the paracrine chondrocyte regulation (FGFR3, FGFR2, NPR2). In 12/74 (16%), we revealed P/LP affecting fundamental intracellular/intranuclear processes (CDC42, KMT2D, LMNA, NSD1, PTPN11, SRCAP, SON, SOS1, SOX9, TLK2). SHOX deficiency was found in 7/74 (9%), Silver-Russell syndrome in 12/74 (16%) (11p15, UPD7), and miscellaneous chromosomal aberrations in 5/74 (7%) children.

CONCLUSIONS

The high diagnostic yield sheds a new light on the genetic landscape of SGA-SS, with a central role for the growth plate with substantial contributions from the GH-IGF-1 and thyroid axes and intracellular regulation and signalling.

Rgp1 contributes to craniofacial cartilage development and Rab8a-mediated collagen II secretion

Rgp1 was previously identified as a component of a guanine nucleotide exchange factor (GEF) complex to activate Rab6a-mediated trafficking events in and around the Golgi. While the role of Rgp1 in protein trafficking has been examined in vitro and in yeast, the role of Rgp1 during vertebrate embryogenesis and protein trafficking in vivo is unknown. Using genetic, CRISPR-induced zebrafish mutants for Rgp1 loss-of-function, we found that Rgp1 is required for craniofacial cartilage development. Within live rgp1-/- craniofacial chondrocytes, we observed altered movements of Rab6a+ vesicular compartments, consistent with a conserved mechanism described in vitro. Using transmission electron microscopy (TEM) and immunofluorescence analyses, we show that Rgp1 plays a role in the secretion of collagen II, the most abundant protein in cartilage. Our overexpression experiments revealed that Rab8a is a part of the post-Golgi collagen II trafficking pathway. Following loss of Rgp1, chondrocytes activate an Arf4b-mediated stress response and subsequently respond with nuclear DNA fragmentation and cell death. We propose that an Rgp1-regulated Rab6a-Rab8a pathway directs secretion of ECM cargoes such as collagen II, a pathway that may also be utilized in other tissues where coordinated trafficking and secretion of collagens and other large cargoes is required for normal development and tissue function.

Thiophanate-methyl induces notochord toxicity by activating the PI3K-mTOR pathway in zebrafish (Danio rerio) embryos

Thiophanate-methyl (TM), a typical pesticide widely used worldwide, was detected in rivers, soil, fruits, and vegetables. Thus, it is urgent to identify the potential harm of TM residual to non-target organisms and its molecular mechanisms. We used zebrafish (Danio rerio) in this study to evaluate TM toxicity. TM exposure induced developmental toxicity, including inhibited hatchability, reduced heart rates, restrained spontaneous locomotion, and decreased body length. Furthermore, we observed obvious toxicity in the notochord and detected increased expression levels of notochord-related genes (shha, col2a, and tbxta) by in situ hybridization in zebrafish larvae. In addition, calcein staining, alkaline phosphatase (ALP) activity analysis, and anatomic analysis indicated that TM induced notochord toxicity. We used rescue experiments to verify whether the PI3K-mTOR pathway involved in the notochord development was the cause of notochord abnormalities. Rapamycin and LY294002 (an inhibitor of PI3K) relieve notochord toxicity caused by TM, including morphological abnormalities. In summary, TM might induce notochord toxicity by activating the PI3K-mTOR pathway in zebrafish.

Molecular diagnosis and novel genes and phenotypes in a pediatric thoracic insufficiency cohort

Thoracic insufficiency syndromes are a genetically and phenotypically heterogeneous group of disorders characterized by congenital abnormalities or progressive deformation of the chest wall and/or vertebrae that result in restrictive lung disease and compromised respiratory capacity. We performed whole exome sequencing on a cohort of 42 children with thoracic insufficiency to elucidate the underlying molecular etiologies of syndromic and non-syndromic thoracic insufficiency and predict extra-skeletal manifestations and disease progression. Molecular diagnosis was established in 24/42 probands (57%), with 18/24 (75%) probands having definitive diagnoses as defined by laboratory and clinical criteria and 6/24 (25%) probands having strong candidate genes. Gene identified in cohort patients most commonly encoded components of the primary cilium, connective tissue, and extracellular matrix. A novel association between KIF7 and USP9X variants and thoracic insufficiency was identified. We report and expand the genetic and phenotypic spectrum of a cohort of children with thoracic insufficiency, reinforce the prevalence of extra-skeletal manifestations in thoracic insufficiency syndromes, and expand the phenotype of KIF7 and USP9X-related disease to include thoracic insufficiency.

Toxicity mechanisms regulating bone differentiation and development defects following abnormal expressions of miR-30c targeted by triclosan in zebrafish

As a ubiquitous environmental estrogen-disrupting chemical, triclosan (TCS) can induce severe osteotoxicity; however, the underlying molecular mechanisms remain uncertain. Herein, we evaluated the toxic effects of TCS on the development of cartilage and osteogenesis in 5-dpf zebrafish. Under TCS exposure from 62.5 to 250 μg/L, several osteodevelopmental malformations were observed, such as defect of craniofacial cartilage, pharyngeal arch cartilage dysplasia, and impairments on skeletal mineralization. Further, the morphology of mature chondrocytes became swollen and deformed, their number decreased, nucleus displacement occurred, and most immature chondrocytes were crowded at both ends of ceratobranchial. SEM observation of larval caudal fin revealed that, the layer of collagen fibers and the mineralized calcium nodules were significantly decreased, with the collagen fibers becoming shorter upon TCS exposure. The activity of bone-derived alkaline phosphatase significantly reduced, and marker functional genes related to cartilage and osteoblast development were abnormally expressed. RNA-seq and bioinformatics analysis indicated, that changes in marker genes intimately related to the negative regulation of miR-30c-5p overexpression targeted by TCS, and the up-regulation of miR-30c induced bone developmental defects by inhibiting the bone morphogenetic protein (BMP) signaling pathway. These findings were confirmed by artificially intervening the expression of miR-30c and using BMP pathway agonists in vivo. In sum, TCS induced osteototoxicity by targeting miR-30c up-regulation and interfering in the BMP signaling pathway. These findings enhance mechanistic understanding of TCS-induced spontaneous bone disorders and bone metastatic diseases. Further research is necessary to monitor chronic TCS-exposure levels in surrounding environments and develop relevant safety precautions based on TCS environmental risk.

RHOA inhibits chondrogenic differentiation of mesenchymal stem cells in adolescent idiopathic scoliosis

PURPOSE

The etiology of adolescent idiopathic scoliosis (AIS) remains unclear. The chondrogenic differentiation of mesenchymal stem cells (MSCs) is important in AIS, and the Ras homolog gene family member A (RHOA) is associated with chondrogenesis. The purpose of this study was to explore the effect of RHOA on the chondrogenic differentiation of MSCs in AIS.

METHODS

We isolated MSCs from patients with AIS (AIS MSCs) and individuals without AIS (control MSCs). The inhibitor Y27632 was used to inhibit the function of RHOA/ROCK signaling, and plasmid-based overexpression and siRNA-mediated knockdown were used to manipulate RHOA expression. CCK-8 was used to detect cell viability. The phosphorylation levels of LIMK1, MLC2 and cofilin were detected by Western blotting. The mRNA expression of aggrecan, SOX9, and COL2A1 were confirmed using RT-PCR. Immunofluorescence was used to analyze F-actin and collagen II. Alcian blue staining was performed to assess the secretion of glycosaminoglycans (GAGs).

RESULTS

We found that RHOA was significantly upregulated in AIS MSCs, and the phosphorylation levels of LIMK1, MLC2, and cofilin were increased. The mRNA expressions of aggrecan, SOX9, and COL2A1 were notably reduced in AIS MSCs. However, these effects were abolished by Y27632 treatment and RHOA knockdown in AIS MSCs. In addition, RHOA knockdown in AIS MSCs increased the content of collagen II and GAGs. RHOA overexpression in the control MSCs markedly activated the RHOA/ROCK signaling and decreased the expression of aggrecan, SOX9, and COL2A1, F-actin, and GAGs.

CONCLUSION

RHOA regulates the chondrogenic differentiation ability of MSCs in AIS via the RHOA/ROCK signaling pathway and this regulation may involve SOX9.

Exploring and expanding the phenotype and genotype diversity in seven Chinese families with spondylo-epi-metaphyseal dysplasia

Spondylo-epi-metaphyseal dysplasia (SEMD) is a heterogeneous group of disorders with different modes of inheritance and is characterized by disproportionate or proportionate short stature. To date, more than 30 disease-causing genes have been identified, and different types of SEMD exhibit greatly overlapping clinical features, which usually complicate the diagnosis. This study was performed to expand the clinical and molecular spectrum of SEMD among Chinese subjects and to explore their potential phenotype–genotype relations. We enrolled seven families including 11 affected patients with SEMD, and their clinical, radiographic, and genetic data were carefully analyzed. All the seven probands showed different degrees of short stature, and each of them exhibited additional specific skeletal manifestations; four probands had extraosseous manifestations. X-rays of the seven probands showed common features of SEMD, including vertebral deformities, irregular shape of the epiphysis, and disorganization of the metaphysis. Seven variants were identified in TRPV4 (c.694C&gt; T, p.Arg232Cys), COL2A1 (c.654 + 1G &gt; C; c.3266_3268del, p.Gly1089del), CCN6 (c.396 T&gt; G, p.Cys132Trp; c.721 T&gt;C, p.Cys241Arg), SBDS (c.258 + 2T&gt; C), and ACAN (c.1508C&gt; A, p.Thr503Lys) genes, and two of them were novel. Two families with TRPV4 variants showed considerable intrafamily and interfamily heterogeneities. In addition, we reported one case of SEMD with a severe phenotype caused by ACAN gene mutation. Our study expands the phenotype and genetic spectrum of SEMD and provides evidence for the phenotype–genotype relations, aiding future molecular and clinical diagnosis as well as procreative management of SEMD.

Familial Aggregation of a Novel Missense Variant of COL2A1 Gene Associated with Short Extremities: Case Report and Review of the Literature

We present two cases of family members (first cousins) with short extremities caused by a novel variant of COL2A1 gene (NM_001844.5). Case 1 description: A 29-year-old woman presented in her first pregnancy for a second trimester anomaly scan at 23 weeks of gestation. Fetal long bones were measured below the third centile for gestational age. Follow-up scans revealed fetal long bone growth deceleration. Initial genetic work-up was negative and the rest of the maternal follow-up was unremarkable. A male baby weighing 3180 g was delivered at 39 weeks and 4 days of gestation. Case 2 description: A 33-year-old pregnant woman presented for a routine second trimester anomaly scan at 20 weeks and 4 days of gestation. All fetal measurements were appropriate for the gestational age. The routine growth scan performed at 32 weeks showed fetal long bone measurements below the third centile for gestational age, while the follow-up growth scan at 36 weeks and 4 days of gestation revealed consistent, below the third centile, fetal long bone growth. Given that the fetuses of these two cases were related (first cousins), whole exome sequencing (WES) was performed on Case 2. WES revealed a novel heterozygous missense variant c.1132G>A (p. Gly378Ser) of COL2A1 gene (NM_001844.5). Subsequently, targeted genetic sequencing for the variant was performed on Case 1 and the same novel variant was found. Targeted sequencing revealed the same variant in the mother of Case 1 and the father of Case 2 (siblings). A female baby weighing 3200 g was delivered at 40 weeks and 4 days of gestation.

Pathogenic Copy Number and Sequence Variants in Children Born SGA With Short Stature Without Imprinting Disorders

CONTEXT

Children born small-for-gestational-age with short stature (SGA-SS) is associated with (epi)genetic defects, including imprinting disorders (IDs), pathogenic copy number variants (PCNVs), and pathogenic variants of genes involved in growth. However, comprehensive studies evaluating these 3 factors are very limited.

OBJECTIVE

To clarify the contribution of PCNVs and candidate pathogenic variants to SGA-SS.

DESIGN

Comprehensive molecular analyses consisting of methylation analysis, copy number analysis, and multigene sequencing.

METHODS

We enrolled 140 patients referred to us for genetic testing for SGA-SS. Among them, we excluded 42 patients meeting Netchine-Harbison clinical scoring system criteria for Silver-Russell syndrome and 4 patients with abnormal methylation levels of the IDs-related differentially methylated regions. Consequently, we conducted copy number analysis and multigene sequencing for 86 SGA-SS patients with sufficient sample volume. We also evaluated clinical phenotypes of patients with PCNVs or candidate pathogenic variants.

RESULTS

We identified 8 (9.3%) and 11 (12.8%) patients with PCNVs and candidate pathogenic variants, respectively. According to the American College of Medical Genetics standards and guidelines, 5 variants were classified as pathogenic and the remaining 6 variants were classified as variants of unknown significance. Genetic diagnosis was made in 12 patients. All patients with PCNVs or candidate pathogenic variants did not correspond perfectly to characteristic clinical features of each specific genetic cause.

CONCLUSION

We clarified the contribution of PCNVs and pathogenic variants to SGA-SS without IDs. Comprehensive molecular analyses, including copy number analysis and multigene sequencing, should be considered for patients with unknown SGA-SS etiology.

Genetic testing in four Indian families with suspected Stickler syndrome

Purpose:

Stickler syndrome is associated with the development of rhegmatogenous retinal detachment (RRD), and often presents with ocular, auditory, skeletal, and orofacial abnormalities. Molecular analysis has proven effective in diagnosis, confirmation and classification of the disease. We aimed to describe the utility of next-generation sequencing (NGS) in genetic analysis of four Indian families with suspected Stickler syndrome.

Methods:

The index cases presented with retinal detachment with family history. Genetic analysis in the index case was performed by next-generation sequencing of inherited retinal degeneration genes, and validated by Sanger sequencing followed by co-segregation analysis in the other family members.

Results:

Twenty patients were included for the genetic analysis (15 males and 5 females from four families). Clinical details were available for 15 patients (30 eyes). Fourteen eyes (11 patients) developed RRD. In the 16 eyes without RRD, 8 underwent barrage laser to lattice degeneration and 8 were under observation. Disease segregating heterozygous mutations with pathogenic/likely pathogenic effect was identified in COL2A1 (c.4318-1G>A, c.141G>A, c.1221+1G>A for 3 families) and COL11A1 (c.1737+1 G>A for 1 family) gene. In addition to the mutation in the COL2A1 gene, a pathogenic heterozygous variant associated with risk for arrhythmogenic right ventricular cardiomyopathy (ARVC) was identified in one member.

Conclusion:

NGS testing confirmed the presence of the causative gene for Stickler syndrome in the index case followed by evaluation of family members and confirmation of genetic and ocular findings. We believe that this may be the first such report of families with RRD from India.

Curative Cell and Gene Therapy for Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) describes a series of genetic bone fragility disorders that can have a substantive impact on patient quality of life. The multidisciplinary approach to management of children and adults with OI primarily involves the administration of antiresorptive medication, allied health (physiotherapy and occupational therapy), and orthopedic surgery. However, advances in gene editing technology and gene therapy vectors bring with them the promise of gene-targeted interventions to provide an enduring or perhaps permanent cure for OI. This review describes emergent technologies for cell- and gene-targeted therapies, major hurdles to their implementation, and the prospects of their future success with a focus on bone disorders. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Expanding the clinical spectrum of COL2A1 related disorders by a mass like phenotype

MASS phenotype is a connective tissue disorder clinically overlapping with Marfan syndrome and caused by pathogenic variants in FBN1. We report four patients from three families presenting with a MASS-like phenotype consisting of tall stature, arachnodactyly, spinal deformations, dural ectasia, pectus and/or feet deformations, osteoarthritis, and/or high arched palate. Gene panel sequencing was negative for FBN1 variants. However, it revealed likely pathogenic missense variants in three individuals [c.3936G > T p.(Lys1312Asn), c.193G > A p.(Asp65Asn)] and a missense variant of unknown significance in the fourth patient [c.4013G > A p.(Ser1338Asn)] in propeptide coding regions of COL2A1. Pathogenic COL2A1 variants are associated with type II collagenopathies comprising a remarkable clinical variablility. Main features include skeletal dysplasia, ocular anomalies, and auditory defects. A MASS-like phenotype has not been associated with COL2A1 variants before. Thus, the identification of likely pathogenic COL2A1 variants in our patients expands the phenotypic spectrum of type II collagenopathies and suggests that a MASS-like phenotype can be assigned to various hereditary disorders of connective tissue. We compare the phenotypes of our patients with related disorders of connective tissue and discuss possible pathomechanisms and genotype–phenotype correlations for the identified COL2A1 variants. Our data recommend COL2A1 sequencing in FBN1-negative patients suggestive for MASS/Marfan-like phenotype (without aortopathy).

Comparative Transcriptome Analysis of Spleen Reveals Potential Regulation of Genes and Immune Pathways Following Administration of Aeromonas salmonicida subsp. masoucida Vaccine in Atlantic Salmon (Salmo salar)

Aeromonas salmonicida is a global fish pathogen. Aeromonas salmonicida subsp. masoucida (ASM) is classified as atypical A. salmonicida and caused huge losses to salmonid industry in China. Hence, it is of great significance to develop ASM vaccine and explore its protection mechanism in salmonids. In this regard, we conducted RNA-seq analysis with spleen tissue of Atlantic salmon after ASM vaccination to reveal genes, their expression patterns, and pathways involved in immune protections. In our results, a total of 441.63 million clean reads were obtained, and 389.37 million reads were mapped onto the Atlantic salmon reference genome. In addition, 1125, 2126, 1098, 820, and 1351 genes were significantly up-regulated, and 747, 2626, 818, 254, and 908 genes were significantly down-regulated post-ASM vaccination at 12 h, 24 h, 1 month, 2 months, and 3 months, respectively. Subsequent pathway analysis revealed that many differentially expressed genes (DEGs) following ASM vaccination were involved in cytokine-cytokine receptor interaction (TNFRSF11b, IL-17RA, CCR9, and CXCL11), HTLV-I infection (MR1 and HTLV-1), MAPK signaling pathway (MAPK, IL8, and TNF-α-1), PI3K-Akt signaling pathway (PIK3R3, THBS4, and COL2A1), and TNF signaling pathway (PTGS2, TNFRSF21-l, and CXCL10). Finally, the results of qRT-PCR showed a significant correlation with RNA-seq results, suggesting the reliability of RNA-seq for gene expression analysis. This study provided insights into regulation of gene expression and their involved pathways in Atlantic salmon spleen in responses to vaccine, and set the foundation for further study on the vaccine protective mechanism in Atlantic salmon as well as other teleost species.

The Year in Growth and Short Stature

The papers and communications selected here, published in 2020-2021, report major advances in pathophysiology, diagnostics, treatment and patient care in the fields of growth hormones and disorders. © 2022 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Clinical and Genetic Characteristics of COL2A1-Associated Skeletal Dysplasias in 60 Russian Patients: Part I

The significant variability in the clinical manifestations of COL2A1-associated skeletal dysplasias makes it necessary to conduct a clinical and genetic analysis of individual nosological variants, which will contribute to improving our understanding of the pathogenetic mechanisms and prognosis. We presented the clinical and genetic characteristics of 60 Russian pediatric patients with type II collagenopathies caused by previously described and newly identified variants in the COL2A1 gene. Diagnosis confirmation was carried out by new generation sequencing of the target panel with subsequent validation of the identified variants using automated Sanger sequencing. It has been shown that clinical forms of spondyloepiphyseal dysplasias predominate in childhood, both with more severe clinical manifestations (58%) and with unusual phenotypes of mild forms with normal growth (25%). However, Stickler syndrome, type I was less common (17%). In the COL2A1 gene, 28 novel variants were identified, and a total of 63% of the variants were found in the triple helix region resulted in glycine substitution in Gly-XY repeats, which were identified in patients with clinical manifestations of congenital spondyloepiphyseal dysplasia with varying severity, and were not found in Stickler syndrome, type I and Kniest dysplasia. In the C-propeptide region, five novel variants leading to the development of unusual phenotypes of spondyloepiphyseal dysplasia have been identified.

De novo mutation in COL2A1 leads to lethal foetal skeletal dysplasia

OBJECTIVE

Skeletal dysplasia caused by genetic mutations places a heavy burden on families and society. This study was performed to precise diagnosis of variants of unknown significance and to expand the genotypic spectrum of lethal skeletal dysplasia.

METHODS

According to the ultrasonic phenotype of the proband and whole-exome sequencing results, variation sites or genes that may be related to the disease were screened out. We verified the accuracy of the variation site through Sanger sequencing. Using bioinformatics, zebrafish models, and assisted reproduction technology (ART) combined with preimplantation genetic testing for monogenic diseases, the disease-causing mutation was verified.

RESULTS

A missense mutation (c.3944G>A, p.Cys1315Tyr) was found in the coding region of COL2A1. Although the mutation is a variant of unknown significance, it is highly conserved and was predicted to be harmful by the SIFT and PolyPhen-2 software. In contrast to the control group, col2a1a mutation-expressing zebrafish larvae showed significant spinal curvature. Through preimplantation genetic testing for monogenic diseases excluding the missense mutation, a child conceived by ART was birthed with normal bone development.

CONCLUSION

We identified a de novo mutation in human COL2A1 related to lethal skeletal dysplasia and expanded the mutation spectrum of type II collagenopathies. In addition, we provided a new strategy based on a zebrafish model and ART for patients who harbour variants of unknown significance to have a healthy baby without genetic disease similar to the proband.

Genetic Characteristics and Phenotype of Korean Patients with Stickler Syndrome: A Korean Multicenter Analysis Report No. 1

Stickler syndrome is an inherited connective tissue disorder of collagen. There are relatively few reports of East Asian patients, and no large-scale studies have been conducted in Korean patients yet. In this study, we retrospectively analyzed the genetic characteristics and clinical features of Korean Stickler syndrome patients. Among 37 genetically confirmed Stickler syndrome patients, 21 types of gene variants were identified, of which 12 were novel variants. A total of 30 people had variants in the COL2A1 gene and 7 had variants in the COL11A1 gene. Among the types of pathogenic variants, missense variants were found in 11, nonsense variants in 8, and splice site variants in 7. Splicing variants were frequently associated with retinal detachment (71%) followed by missense variants. This is the first large-scale study of Koreans with Stickler syndrome, which will expand the spectrum of genetic variations of Stickler syndrome.

A Novel Splicing Variant of COL2A1 in a Fetus with Achondrogenesis Type II: Interpretation of Pathogenicity of In-Frame Deletions

Achondrogenesis type II (ACG2) is a lethal skeletal dysplasia caused by dominant pathogenic variants in COL2A1. Most of the variants found in patients with ACG2 affect the glycine residue included in the Gly-X-Y tripeptide repeat that characterizes the type II collagen helix. In this study, we reported a case of a novel splicing variant of COL2A1 in a fetus with ACG2. An NGS analysis of fetal DNA revealed a heterozygous variant c.1267-2_1269del located in intron 20/exon 21. The variant occurred de novo since it was not detected in DNA from the blood samples of parents. We generated an appropriate minigene construct to study the effect of the variant detected. The minigene expression resulted in the synthesis of a COL2A1 messenger RNA lacking exon 21, which generated a predicted in-frame deleted protein. Usually, in-frame deletion variants of COL2A1 cause a phenotype such as Kniest dysplasia, which is milder than ACG2. Therefore, we propose that the size and position of an in-frame deletion in COL2A1 may be relevant in determining the phenotype of skeletal dysplasia.

Case report of the first molecular diagnosis of Stickler syndrome with a pathogenic COL2A1 variant in a Mongolia family

Background

Stickler syndrome is a group of connective tissue disorders that can affect eye (myopia, cataract, and retinal detachment), skeleton (spondyloepiphyseal dysplasia and precocious arthritis), craniofacies (midfacial under development and cleft palate), and inner ear (conductive and sensorineural); with the degree of symptoms varying among patients. Mutations in the COL2A1, COL11A1, COL11A2, COL9A1, COL9A2, and COL9A3 procollagen genes cause Stickler syndrome.

Case presentation

A 16‐year‐old Mongolian girl approached our clinics with retinal detachment. The proband had vitreous degeneration in both eyes, rhegmatogenous retinal detachment in her right eye, a large area of retina degeneration in her left eye, and coupled with severe myopia. No obvious hearing disorder was found, no abnormalities in bones and joints, and her communication and learning capability were also normal. Further clinical examination showed that the patient's other five family members across three generations had vitreous and retina degenerations. Exome sequencing showed a heterozygous splicing variant in COL2A1 in all patients.

Conclusions

In this case report, a pathogenic splicing variant in the COL2A1 gene was identified in a Mongolian family affected with Stickler syndrome type I by exome sequencing. This heterozygous splicing variant in COL2A1 (NM_001844.4:C.2518‐1G>A) that may impair splicing, which was suggested by in silico prediction. Next‐generation sequencing is helpful for the differential diagnosis of this clinically variable and genetically heterogeneous disorder.

Undenatured Type II Collagen Relieves Bone Impairment through Improving Inflammation and Oxidative Stress in Ageing db/db Mice

Ageing-related bone impairment due to exposure to hyperglycemic environment is scarcely researched. The aim was to confirm the improvement effects of undenatured type II collagen (UC II) on bone impairment in ageing db/db mice, and the ageing model was established by normal feeding for 48-week-old. Then, the ageing db/db mice were randomly assigned to UC II intervention, the ageing model, and the chondroitin sulfate + glucosamine hydrochloride control groups. After 12 weeks of treatment, femoral microarchitecture and biomechanical parameters were observed, biomarkers including bone metabolism, inflammatory cytokines, and oxidative stress were measured, and the gastrocnemius function and expressions of interleukin (IL) 1β, receptor activator of nuclear factor (NF)-κB ligand (RANKL), and tartrate-resistant acid phosphatase (TRAP) were analyzed. The results showed that the mice in the UC II intervention group showed significantly superior bone and gastrocnemius properties than those in the ageing model group, including bone mineral density (287.65 ± 72.77 vs. 186.97 ± 32.2 mg/cm³), gastrocnemius index (0.46 ± 0.07 vs. 0.18 ± 0.01%), muscle fiber diameter (0.0415 ± 0.005 vs. 0.0330 ± 0.002 mm), and cross-sectional area (0.0011 ± 0.00007 vs. 0.00038 ± 0.00004 mm²). The UC II intervention elevated bone mineralization and formation and decreased bone resorption, inflammatory cytokines, and the oxidative stress. In addition, lower protein expression of IL-1β, RANKL, and TRAP in the UC II intervention group was observed. These findings suggested that UC II improved bones impaired by T2DM during ageing, and the likely mechanism was partly due to inhibition of inflammation and oxidative stress.

A novel homozygous variant of COL2A1 in a Chinese male with type II collagenopathy: a case report

Background

Type II collagenopathies are a spectrum of diseases and skeletal dysplasia is one of the prominent features of collagenopathies. Molecular defects of the COL2A1 gene cause type II collagenopathies that is mainly an autosomal dominant disease, whereas some rare cases with autosomal recessive inheritance of mode have also been identified.

Case presentation

The patient was a 5-year-old male with a short neck, flat face, epiphyseal dysplasia, irregular vertebral endplates, and osteochondritis. Sequencing result indicated NM_001844.4: c.3662C > T; p. (Ser1221Phe) a novel missense variant, leading to a serine-to-phenylalanine substitution. Sanger sequencing confirmed the variant compared to his parents and brother.

Conclusions

We identified a novel homozygous variant of the COL2A1 gene as the cause of type II collagenopathies in a Chinese male, enriching the spectrum of genotypes. This is the first case of type II collagenopathies inherited in an autosomal recessive manner in China and East Asia, and it is the first case that resulted from serine substitution in the world.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01048-0.

Pleiotropy of a Stickler syndrome genotype

PURPOSE

To report a case of pleiotropy in the COL2A1 gene typically associated with Stickler Syndrome Type 1.

OBSERVATIONS

A patient with a confirmed mutation of the COL2A1 gene presented with an isolated retinitis pigmentosa phenotype.

CONCLUSIONS

The mutated COL2A1 gene in Stickler Syndrome Type 1 represents a site of pleiotropy, highlighting a change in phenotype across the same genotype potentially due to tissue alternative splicing.

COL2A1 Mutation (c.611G>C) Leads to Early-Onset Osteoarthritis in a Chinese Family

Mutations in the gene coding collagen type II α1 chain (COL2A1) are associated with a series of human disorders mainly involving the skeletal system. Here, we describe the second family with COL2A1 mutation, c.611G>C, Gly204Ala, leading to a replacement of glycine in the core triple helical (Gly-X-Y) domain of COL2A1 gene. The replacements of glycine in every third position of the triple with other amino acids will cause failure in the structure of type II collagen. The affected family members manifested early-onset osteoarthritis involving multiple joints. We propose that the COL2A1 gene should be taken into consideration for genetic counseling for patients with hereditary premature osteoarthritis and individuals carrying this mutation should receive early interventions for osteoarthritis.

Combined exome sequencing and deep phenotyping in highly selected fetuses with skeletal dysplasia during the first and second trimesters improves diagnostic yield

OBJECTIVE

To investigate the genetic etiology of skeletal dysplasia in highly selected fetuses during the first and second trimesters using deep phenotyping and exome sequencing (ES).

METHOD

Fetuses with short femurs were identified using the established prenatal diagnostic approach. A multidisciplinary team reviewed fetal phenotypic information (prenatal ultrasound findings, fetal postmortem, and radiographs) in a cohort of highly selected fetuses with skeletal dysplasia during the first and second trimesters. The affected families underwent multiplatform genetic tests.

RESULTS

Of the 27 affected fetuses, 21 (77.8%) had pathogenic or potential pathogenic variations in the following genes: COL1A1, FGFR3, COL2A1, COL1A2, FLNB, DYNC2LI1, and TRIP11. Two fetuses had compound heterozygous mutations in DYNC2LI1 and TRIP11, respectively, and the other 19 carried de novo autosomal dominant variants. Novel variants were identified in COL1A1, COL2A1, COL1A2, DYNC2LI1, and TRIP11 in 11 fetuses. We also included the first description of the phenotype of odontochondrodysplasia in a prenatal setting.

CONCLUSIONS

ES or panel sequencing offers a high diagnostic yield for fetal skeletal dysplasia during the first and second trimesters. Comprehensive and complete phenotypic information is indispensable for genetic analysis and the expansion of genotype-phenotype correlations in fetal skeletal abnormalities.

A novel mutation of COL2A1 in a large Chinese family with avascular necrosis of the femoral head

Avascular necrosis of the femoral head (ANFH) is a debilitating bone disease, characterized by collapse of the femoral head and subsequent loss of hip joint function. Heterozygous mutations in COL2A1 have been identified to cause familial ANFH. Here we report on a large Chinese family with ANFH and a novel heterozygous mutation (c.3517 G > A, p.Gly1173Ser) in exon 50 of COL2A1 in the Gly-X–Y domain. Previously, only five different COL2A1 mutations have been described in patients with familial ANFH. Therefore, our findings provide significant clues to the phenotype–genotype relationships in familial ANFH and may be helpful in clinical diagnosis. Furthermore, these results should assist further studies of the mechanisms underlying collagen diseases.

Familial Short Stature-A Novel Phenotype of Growth Plate Collagenopathies

CONTEXT

Collagens are the most abundant proteins in the human body. In a growth plate, collagen types II, IX, X, and XI are present. Defects in collagen genes cause heterogeneous syndromic disorders frequently associated with short stature. Less is known about oligosymptomatic collagenopathies.

OBJECTIVE

This work aims to evaluate the frequency of collagenopathies in familial short stature (FSS) children and to describe their phenotype, including growth hormone (GH) treatment response.

METHODS

Eighty-seven FSS children (pretreatment height ≤ -2 SD both in the patient and his or her shorter parent) treated with GH were included in the study. Next-generation sequencing was performed to search for variants in the COL2A1, COL9A1, COL9A2, COL9A3, COL10A1, COL11A1, and COL11A2 genes. The results were evaluated using American College of Medical Genetics and Genomics guidelines. The GH treatment response of affected children was retrospectively evaluated.

RESULTS

A likely pathogenic variant in the collagen gene was found in 10 of 87 (11.5%) children. Detailed examination described mild asymmetry with shorter limbs and mild bone dysplasia signs in 2 of 10 and 4 of 10 affected children, respectively. Their growth velocity improved from a median of 5.3 cm/year to 8.7 cm/year after 1 year of treatment. Their height improved from a median of -3.1 SD to -2.6 SD and to -2.2 SD after 1 and 3 years of therapy, respectively. The final height reached by 4 of 10 children differed by -0.67 to +1.0 SD and -0.45 to +0.5 SD compared to their pretreatment height and their affected untreated parent's height, respectively.

CONCLUSION

Oligosymptomatic collagenopathies are a frequent cause of FSS. The short-term response to GH treatment is promising.

Heterozygous COL9A3 variants cause severe peripheral vitreoretinal degeneration and retinal detachment

The COL9A3 gene encodes one of the three alpha chains of Type IX collagen, with heterozygous variants reported to cause multiple epiphyseal dysplasia, and suggested as contributory in some cases of sensorineural hearing loss. Patients with homozygous variants have midface hypoplasia, myopia, sensorineural hearing loss, epiphyseal changes and carry a diagnosis of Stickler syndrome. Variants in COL9A3 have not previously been reported to cause vitreoretinal degeneration and/or retinal detachments. This report describes two families with autosomal dominant inheritance and predominant features of peripheral vitreoretinal lattice degeneration and retinal detachment. Genomic sequencing revealed a heterozygous splice variant in COL9A3 [NG_016353.1(NM_001853.4):c.1107 + 1G>C, NC_000020.10(NM_001853.4):c.1107 + 1G>C, LRG1253t1] in Family 1, and a heterozygous missense variant [NG_016353.1(NM_001853.4):c.388G>A p.(Gly130Ser)] in Family 2, each segregating with disease. cDNA studies of the splice variant demonstrated an in-frame deletion in the COL2 domain, and the missense variant occurred in the COL3 domain, both indicating the critical role of Type IX collagen in the vitreous base of the eye.

Identification of Novel Candidate Genes and Variants for Hearing Loss and Temporal Bone Anomalies

Background: Hearing loss remains an important global health problem that is potentially addressed through early identification of a genetic etiology, which helps to predict outcomes of hearing rehabilitation such as cochlear implantation and also to mitigate the long-term effects of comorbidities. The identification of variants for hearing loss and detailed descriptions of clinical phenotypes in patients from various populations are needed to improve the utility of clinical genetic screening for hearing loss. Methods: Clinical and exome data from 15 children with hearing loss were reviewed. Standard tools for annotating variants were used and rare, putatively deleterious variants were selected from the exome data. Results: In 15 children, 21 rare damaging variants in 17 genes were identified, including: 14 known hearing loss or neurodevelopmental genes, 11 of which had novel variants; and three candidate genes IST1, CBLN3 and GDPD5, two of which were identified in children with both hearing loss and enlarged vestibular aqueducts. Patients with variants within IST1 and MYO18B had poorer outcomes after cochlear implantation. Conclusion: Our findings highlight the importance of identifying novel variants and genes in ethnic groups that are understudied for hearing loss.

A novel de novo mutation in COL2A1 gene associated with fetal skeletal dysplasia

OBJECTIVE

Skeletal dysplasias, caused by genetic mutations, are a heterogenous group of heritable disorders affecting bone development during fetal life. Stickler syndrome, one of the skeletal dysplasias, is an autosomal dominant connective tissue disorder caused by abnormal collagen synthesis owing to a genetic mutation in COL2A1.

CASE REPORT

We present the case of a 38-year-old multipara woman whose first trimester screening showed a normal karyotype. However, the bilateral femur and humerus length symmetrically shortened after 20 weeks. Next-generation sequencing for mutations in potential genes leading to skeletal dysplasia detected a novel de novo mutation (c.1438G > A, p.Gly480Arg) in COL2A1, causing Stickler syndrome type 1. This pathogenic mutation might impair or destabilize the collagen structure, leading to collagen type II, IX, and XI dysfunction.

CONCLUSION

We identified a novel de novo mutation in COL2A1 related to the STL1 syndrome and delineated the extent of the skeletal dysplasia disease spectrum.

Generation and characterization of human induced pluripotent stem cells line JLUEYEi001-A from a 45 year old female with Stickler syndrome

Peripheral blood was extracted from a 45-year old female patient clinically diagnosed with Stickler syndrome harboring a heterozygous splicing mutation in COL2A1 (NM_033150, IVS22-1C>T). Induced pluripotent stem cells (iPSC) were reprogrammed by sendai virus encoding Klf-4, c-Myc, Oct-4, and Sox-2. The iPSC line showed pluripotency, which was verified by immunofluorescence staining. The iPSC line showed normal karyotype, and could form embryoid bodies in vitro and differentiate into the 3 germ layers in vivo. This in vitro cellular model can be used to study the pathogenesis underlying Stickler syndrome.

A novel COL2A1 mutation causing spondyloepiphyseal dysplasia congenita in a Chinese family

Background

Spondyloepiphyseal dysplasia congenita is an autosomal dominant cartilaginous dysplasia characterized by short trunk, abnormal epiphysis, and flattened vertebral body. Skeletal features of SEDC are present at birth and evolve over time. Other features of SEDC include myopia and/or retinal degeneration with retinal detachment and cleft palate. A mutation in the COL2A1 gene located in 12q13.11 is considered as one of the important causes of SEDC. In 2016, Barat‐Houari et al. reported a large number of COL2A1 mutations. Among them, a non‐synonymous mutation in COL2A1 exon 37, c.2437G>A (p. Gly813Arg), has been reported to cause SEDC in only one patient from France so far.

Methods

We followed up a patient with SEDC phenotype and his family members. The clinical manifestations, physical examination and imaging examination, including X‐ray, CT and MRI, were recorded. The whole‐exome sequencing was used to detect the patients' genes, and the pathogenic genes were screened out by comparing with many databases.

Results

We report a Chinese patient with SEDC phenotype characterized by short trunk, abnormal epiphysis, flattened vertebral body, narrow intervertebral space, dysplasia of the odontoid process, chicken chest, scoliosis, hip and knee dysplasia, and joint hypertrophy. Gene sequencing analysis showed that the patient had a heterozygous mutation (c.2437G>A; p. Gly813Arg) in the COL2A1 gene. No COL2A1 mutation or SEDC phenotype was observed in his family members. This is the first report of SEDC caused by this mutation in an East Asian family.

Conclusion

This report provides typical clinical, imaging, and genetic evidence for SEDC, confirming that a de novo mutation in the COL2A1 gene, c.2437G>A (p. Gly813Arg), causes SEDC in Chinese population.

Radiologic Features of Type II and Type XI Collagenopathies

Type II collagen is a major component of the cartilage matrix. Pathogenic variants (ie, disease-causing aberrations) in the type II collagen gene (COL2A1) lead to an abnormal structure of type II collagen, causing a large group of skeletal dysplasias termed type II collagenopathies. Because type II collagen is also located in the vitreous body of the eyes and inner ears, type II collagenopathies are commonly associated with vitreoretinal degeneration and hearing impairment. Type II collagenopathies can be radiologically divided into two major groups: the spondyloepiphyseal dysplasia congenita (SEDC) group and the Kniest-Stickler group. The SEDC group is characterized by delayed ossification of the juxtatruncal bones, including pear-shaped vertebrae. These collagenopathies comprise achondrogenesis type 2, hypochondrogenesis, SEDC, and other uncommon subtypes. The Kniest-Stickler group is characterized by disordered tubular bone growth that leads to "dumbbell" deformities. It comprises Kniest dysplasia and Stickler dysplasia type 1, whose radiographic manifestations overlap with those of type XI collagenopathies (a group of disorders due to abnormal type XI collagen) such as Stickler dysplasia types 2 and 3. This phenotypic overlap is caused by type II and type XI collagen molecules sharing part of the same connective tissues. The authors describe the diagnostic pathways to type II and type XI collagenopathies and the associated differential diagnoses. In addition, they review the clinical features and genetic bases of these conditions, which radiologists should know to participate in multidisciplinary care and translational research. Online supplemental material is available for this article. ^©RSNA, 2020.

Hypochondrogenesis: A pictorial assay combining ultrasound, MRI and low-dose computerized tomography

We present a case of hypochondrogenesis, a rare autosomal dominant skeletal dysplasia that often results in infant death shortly after birth. Hypochondrogenesis can present similarly to other skeletal dysplasia diseases, notably achondrogenesis type II. The diagnosis of hypochondrogenesis was given during the prenatal stage after fetal imaging was performed using ultrasound, magnetic resonance imaging (MRI), and low-dose computerized tomography (CT). To the best of our knowledge, this is the first known case that reported the use of low-dose CT to assist in the prenatal diagnosis of hypochondrogenesis.

Spondylo-epiphyseal dysplasia in two sibs due to a homozygous splicing variant in COL2A1

Type 2 collagenopathies encompass a large group of chondrodysplasias ranging from the perinatally lethal achondrogenesis type 2 and hypochondrogenesis at the severe end of the spectrum to early-onset osteoarthritis with normal stature at the milder end of the spectrum. With the exception of a few reported cases, these dysplasias are predominantly caused by heterozygous variants in the COL2A1 gene and hence show an autosomal dominant inheritance pattern. Here we report on two siblings, originating from a consanguineous family, who presented with disproportionate short stature, ocular abnormalities, cleft palate and hearing impairment. The radiographic study showed signs of a spondyloepiphyseal dysplasia, compatible with a type 2 collagen disorder. Indeed, both siblings were homozygous for a c.3111+2T > Cp.(Glu1033Lysfs*5) splice site variant in the COL2A1 gene. cDNA analysis performed on skin fibroblasts from the affected sibs revealed the co-occurrence of the wild-type transcript and an aberrant splice product, the latter believed to be degraded by nonsense-mediated mRNA decay. The parents who were heterozygous for this variant were phenotypically normal. This paper confirms that type 2 collagenopathies can show an autosomal recessive inheritance.

A CRISPR-engineered swine model of COL2A1 deficiency recapitulates altered early skeletal developmental defects in humans

Loss-of-function mutations in the COL2A1 gene were previously described as a cause of type II collagenopathy (e.g., spondyloepiphyseal dysplasia, Stickler syndrome type I), a major subgroup of genetic skeletal diseases. However, the pathogenic mechanisms associated with COL2A1 mutations remain unclear, and there are few large-mammal models of these diseases. In this study, we established a swine model carrying COL2A1 mutations using CRISPR/Cas9 and somatic cell nuclear transfer technologies. Animals mutant for COL2A1 exhibited severe skeletal dysplasia characterized by shortened long bones, abnormal vertebrae, depressed nasal bridge, and cleft palate. Importantly, COL2A1 mutant piglets suffered tracheal collapse, which was almost certainly the cause of their death shortly after birth. In conclusion, we have demonstrated for the first time that overt and striking skeletal dysplasia occurring in human patients can be recapitulated in large transgenic mammals. This model underscores the importance of employing large animals as models to investigate the pathogenesis and potential therapeutics of skeletal diseases.

Inherited and de novo biallelic pathogenic variants in COL11A1 result in type 2 Stickler syndrome with severe hearing loss

Background

Type 2 Stickler syndrome is usually a dominant disorder resulting from pathogenic variants in COL11A1 encoding the alpha 1 chain of type XI collagen. Typical molecular changes result in either substitution of an obligate glycine within the Gly‐Xaa‐Yaa amino acid sequence repeat region of the molecule, mRNA missplicing or deletions/duplications that typically leaves the message in‐frame. Clinical features include myopia, retinal detachment, craniofacial, joint, and hearing problems. Fibrochondrogenesis is also a COL11A1 related disorder, but here disease‐associated variants are recessive and may be either null alleles or substitutions of glycine, and the condition is usually lethal in infancy.

Methods

The patient was assessed in the NHS England Stickler syndrome diagnostic service. DNA from the patient and family were analyzed with Next Generation Sequencing on a panel of genes known to cause Stickler Syndrome. The effect of sequence variants was assessed using minigene analysis. Allele‐specific RT‐PCR was performed.

Results

This patient had clinical type 2 Stickler syndrome but with severe hearing loss and severe ocular features including retinal atrophy and retinal tears in childhood. We identified a de novo in frame deletion of COL11A1 (c.4109_4126del) consistent with dominantly inherited Stickler syndrome but also a second inherited variant (c.1245+2T>C), on the other allele, affecting normal splicing of COL11A1 exon 9.

Conclusion

Exon 9 of COL11A1 is alternatively expressed and disease causing changes affecting only this exon modify the phenotype resulting from biallelic COL11A1 disease‐associated variants and, instead of fibrochondrogenesis, produce a form of Stickler syndrome with severe hearing loss. Disease phenotypes from de novo pathogenic variants can be modified by inherited recessive variants on the other allele. This highlights the need for functional and family analysis to confirm the mode of inheritance in COL11A1‐related disorders, particularly for those variants that may alter normal pre‐mRNA splicing.

Surgical management in a severe OSA patient diagnosed with Stickler syndrome

Stickler syndrome is a genetic disorder of connective tissue. One of the major symptoms associated with this disorder is an oro-facial malformation, which may cause a submucous cleft or a complete cleft of the hard palate. A 32-year-old man diagnosed with Stickler syndrome and a submucosal cleft palate (SMCP) visited our hospital with a chief complaint of excessive daytime sleepiness. The patient was diagnosed with severe obstructive sleep apnea (OSA), and administration of a polysomnography test revealed an apnea-hypopnea index (AHI) of 30.9 events/hour (h). Auto-titrating continuous positive airway pressure was initiated to control the OSA symptoms and subsequently the patient showed some improvement. However, due to continuous velopharyngeal insufficiency symptoms, intravelar veloplasty was performed. Three months after surgery, the AHI had decreased to 12.4 events/h. Recent studies have described a greater risk for OSA in individuals with cleft palate, than in the general population. The present case demonstrates surgical success in a patient with OSA and SMCP, suggesting that palatal surgery may be considered an optional surgical treatment for OSA patients with SMCP.

Next-generation sequencing-aided precise diagnosis of Stickler syndrome type I

PURPOSE

To explore an early, rapid and precise diagnosis of Stickler syndrome type I (STL1) and to enrich the spectrum of COL2A1 mutations in the Chinese population, which is poorly studied at present.

METHODS

In the current study, we analysed 115 patients with high myopia by next-generation sequencing and identified five STL1 patients from four unrelated Chinese families. The clinical features of all patients were reviewed in detail.

RESULTS

Four variants of COL2A1 were identified, including two novel variants (c.1435delG and c.184delG) and two previously reported variants (c.1221+1G>A and c.1030C>T). Three variants caused premature termination codons which were common in STL1. In addition, we proposed a new diagnostic tactic to improve early diagnostics of STL1 in patients.

CONCLUSION

In this study, our findings expanded the spectrum of COL2A1 mutations with two novel variants and provided a new diagnostic tactic for reference, which was of great significance. Precise diagnosis on the basis of clinical manifestations and genetic testing will become the gold standard to diagnose inherited ocular disorders or syndromes in the future.

Expanding the phenotype spectrum associated with pathogenic variants in the COL2A1 and COL11A1 genes

We report the clinical findings of 26 individuals from 16 unrelated families carrying variants in the COL2A1 or COL11A1 genes. Using Sanger and next-generation sequencing, 11 different COL2A1 variants (seven novel), were identified in 13 families (19 affected individuals), all diagnosed with Stickler syndrome (STL) type 1. In nine families, the COL2A1 disease-causing variant arose de novo. Phenotypically, we observed myopia (95%) and retinal detachment (47%), joint hyperflexibility (92%), midface retrusion (84%), cleft palate (53%), and various degrees of hearing impairment (50%). One patient had a splenic artery aneurysm. One affected individual carrying pathogenic variant in COL2A1 showed no ocular signs including no evidence of membranous vitreous anomaly. In three families (seven affected individuals), three novel COL11A1 variants were found. The propositus with a de novo variant showed an ultrarare Marshall/STL overlap. In the second family, the only common clinical sign was postlingual progressive sensorineural hearing impairment (DFNA37). Affected individuals from the third family had typical STL2 signs. The spectrum of disease phenotypes associated with COL2A1 or COL11A1 variants continues to expand and includes typical STL and various bone dysplasias, but also nonsyndromic hearing impairment, isolated myopia with or without retinal detachment, and STL phenotype without clinically detectable ocular pathology.