Mutation analysis of the COL1A1 and COL1A2 genes in Vietnamese patients with osteogenesis imperfecta

Diagnostic Challenges in Bone Fragility: Osteogenesis Imperfecta Case Series

Osteogenesis imperfecta (OI) is a rare hereditary connective tissue disorder. Diagnosis is typically clinical; genetic testing can contribute. Objectives: We are presenting a case series of type I OI in Romanian patients, showcasing the difficulties in diagnostic and case management in pediatric and adult cases. Methods: Nine patients were referred to the Regional Centre for Medical Genetics (CRGM), Dolj, Craiova, between 2021 and 2024. Genetic testing was conducted using the commercially available kit Illumina® TruSight™ One. Results: Most of the patients showed blue sclerae, significant fracture history, and reduced stature. In our case series, the genetic variants for seven of the cases identified are primarily in the COL1A1 and COL1A2 genes. Our study reveals significant clinical variability among patients, even among those with identical genetic variants. This emphasizes the importance of tailored surgical and rehabilitation programs to improve the quality of life for these patients. Conclusions: Our study contributes to the genetic landscape of OI. Future research should aim to include larger, more diverse cohorts and incorporate advanced genetic analysis techniques to identify additional genetic variants and mechanisms involved in OI.

GraphLOGIC: Lethality prediction of osteogenesis imperfecta on type I collagen by a mechanics-informed graph neural network

Collagen plays a crucial role in human bodies and has a significant presence in connective tissues. As such, the impact of collagen mutations can be devastating. Osteogenesis imperfecta (OI), a rare genetic disease affecting 1 in every 15,000 to 20,000 people, is one such example characterized by brittle bones. Severe cases of OI could lead to prenatal death. Previous studies have provided insights into the impact of mutations on collagen molecules and predictions of lethality. However, these discussions have focused mainly on mutations in the α1 chain, and some mutation types exhibit poor predictive performance. Coverage of α2 mutations is also limited. We propose a method to predict the risk of lethality for OI-inducing mutations, where a novel mechanics-informed graph representation of the collagen fibril is proposed based on full atomistic simulations to encode sequential and structural information. The method demonstrated improved accuracy in predicting the risk of lethality associated with mutations occurring on both α1 and α2chains. We also found a correlation between the sequences and the predicted OI lethality with the use of a variant of the Grad-CAM technique, where the results agree well with previous studies. Our findings provide insights into the molecular mechanism of collagen on OI lethality.

A novel chemical chaperone ameliorates osteoblast homeostasis and extracellular matrix in osteogenesis imperfecta

AIMS

Osteogenesis imperfecta (OI) is a collagen I-related heritable family of skeletal diseases associated to extreme bone fragility and deformity. Its classical forms are caused by dominant mutations in COL1A1 and COL1A2, which encode for the protein α chains, and are characterized by impairment in collagen I structure, folding, and secretion. Mutant collagen I assembles in an altered extracellular matrix affecting mineralization and bone properties and partially accumulating inside the cells, leading to impaired trafficking and cellular stress. Recently, the chemical chaperone 4-phenylbutyrate (4-PBA) has been proposed as an innovative drug for OI based on its ability to restore intracellular homeostasis, stimulate secretion, and ameliorate collagen-producing cell functions, positively affecting bone properties. However, the limited half-life of the molecule represents a serious hurdle for its use.

MATERIALS AND METHODS

To efficiently target cellular stress as OI treatment, two new compounds were designed by molecular modelling based on the 4-PBA structure to increase its stability and its ability to implement protein secretion. The short butyryl fatty acid chain of 4-PBA was substituted with a nitro functional group or with a glycine, respectively. The latter, N-benzyl glycine (N-BG), showed the best docking score, less toxicity, and higher stability than 4-PBA.

KEY FINDINGS

N-BG improved extracellular matrix quality and mineral content together with ameliorating OI cells' homeostasis by increasing ER-associated degradation pathway, reducing apoptosis, and stimulating protein secretion, thus facilitating intracellular clearance from accumulated misfolded proteins.

SIGNIFICANCE

In conclusion, N-BG represents a novel potential available compound to target altered homeostasis in OI with the aim to ameliorate the disease phenotype.

Molecular Genetic Diagnosis with Targeted Next Generation Sequencing in a Cohort of Turkish Osteogenesis Imperfecta Patients and their Genotype-phenotype Correlation

Objective

Osteogenesis imperfecta (OI) consists of a group of phenotypically and genetically heterogeneous connective tissue disorders that share similar skeletal anomalies causing bone fragility and deformation. The aim was to investigate the molecular genetic etiology and determine the relationship between genotype and phenotype in OI patients using targeted next-generation sequencing (NGS).

Methods

A targeted NGS analysis panel (Illumina TruSight One) containing genes involved in collagen/bone synthesis was performed on the Illumina Nextseq550 platform in patients with a confirmed diagnosis of OI.

Results

Fifty-six patients (female/male: 25/31) from 46 different families were included. Consanguinity was noted in 15 (32.6%) families. Based on Sillence classification 18 (33.1%) were type 1 OI, 1 (1.7%) type 2, 26 (46.4%) type 3 and 11 (19.6%) type 4. Median body weight was -1.1 (-6.8, - 2.5) standard deviation scores (SDS), and height was -2.3 (-7.6, - 1.2) SDS. Bone deformity affected 30 (53.5%), while 31 (55.4%) were evaluated as mobile. Thirty-six (60.7%) had blue sclera, 13 (23.2%) had scoliosis, 12 (21.4%) had dentinogenesis imperfecta (DI), and 2 (3.6%) had hearing loss. Disease-causing variants in COL1A1 and COL1A2 were found in 24 (52.1%) and 6 (13%) families, respectively. In 8 (17.3%) of the remaining 16 (34.7%) families, the NGS panel revealed disease-causing variants in three different genes (FKBP10, SERPINF1, and P3H1). Nine (23.6%) of the variants detected by NGS panel had not previously been reported and were also classified as pathogenic based on American College of Medical Genetics guidelines pathogenity scores. In ten (21.7%) families, a disease-related variant was not found in any of the 13 OI genes on the panel.

Conclusion

Genetic etiology was found in 38 (82.6%) of 46 families by targeted NGS analysis. Furthermore, nine new variants were identified in known OI genes which were classified as pathogenic by standard guidelines.

The Role of Mitochondrial Homeostasis in Mesenchymal Stem Cell Therapy-Potential Implications in the Treatment of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a hereditary disorder characterized by bones that are fragile and prone to breaking. The efficacy of existing therapies for OI is limited, and they are associated with potentially harmful side effects. OI is primarily due to a mutation of collagen type I and hence impairs bone regeneration. Mesenchymal stem cell (MSC) therapy is an attractive strategy to take advantage of the potential benefits of these multipotent stem cells to address the underlying molecular defects of OI by differentiating osteoblasts, paracrine effects, or immunomodulation. The maintenance of mitochondrial homeostasis is an essential component for improving the curative efficacy of MSCs in OI by affecting the differentiation, signaling, and immunomodulatory functions of MSCs. In this review, we highlight the MSC-based therapy pathway in OI and introduce the MSC regulation mechanism by mitochondrial homeostasis. Strategies aiming to modulate the metabolism and reduce the oxidative stress, as well as innovative strategies based on the use of compounds (resveratrol, NAD+, α-KG), antioxidants, and nanomaterials, are analyzed. These findings may enable the development of new strategies for the treatment of OI, ultimately resulting in improved patient outcomes.

The double whammy of ER-retention and dominant-negative effects in numerous autosomal dominant diseases: significance in disease mechanisms and therapy

The endoplasmic reticulum (ER) employs stringent quality control mechanisms to ensure the integrity of protein folding, allowing only properly folded, processed and assembled proteins to exit the ER and reach their functional destinations. Mutant proteins unable to attain their correct tertiary conformation or form complexes with their partners are retained in the ER and subsequently degraded through ER-associated protein degradation (ERAD) and associated mechanisms. ER retention contributes to a spectrum of monogenic diseases with diverse modes of inheritance and molecular mechanisms. In autosomal dominant diseases, when mutant proteins get retained in the ER, they can interact with their wild-type counterparts. This interaction may lead to the formation of mixed dimers or aberrant complexes, disrupting their normal trafficking and function in a dominant-negative manner. The combination of ER retention and dominant-negative effects has been frequently documented to cause a significant loss of functional proteins, thereby exacerbating disease severity. This review aims to examine existing literature and provide insights into the impact of dominant-negative effects exerted by mutant proteins retained in the ER in a range of autosomal dominant diseases including skeletal and connective tissue disorders, vascular disorders, neurological disorders, eye disorders and serpinopathies. Most crucially, we aim to emphasize the importance of this area of research, offering substantial potential for understanding the factors influencing phenotypic variability associated with genetic variants. Furthermore, we highlight current and prospective therapeutic approaches targeted at ameliorating the effects of mutations exhibiting dominant-negative effects. These approaches encompass experimental studies exploring treatments and their translation into clinical practice.

Collagen mutation and age contribute to differential craniofacial phenotypes in mouse models of osteogenesis imperfecta

Craniofacial and dentoalveolar abnormalities are present in all types of osteogenesis imperfecta (OI). Mouse models of the disorder are critical to understand these abnormalities and underlying OI pathogenesis. Previous studies on severely affected OI mice report a broad spectrum of craniofacial phenotypes, exhibiting some similarities to the human disorder. The Brtl/+ and G610c/+ are moderately severe and mild-type IV OI, respectively. Little is known about the aging effects on the craniofacial bones of these models and their homology to human OI. This study aimed to analyze the Brtl/+ and G610c/+ craniofacial morphometries during aging to establish suitability for further OI craniofacial bone intervention studies. We performed morphological measurements on the micro-CT-scanned heads of 3-wk-old, 3-mo-old, and 6-mo-old female Brtl/+ and G610c/+ mice. We observed that Brtl/+ skulls are shorter in length than WT (P < .05), whereas G610c/+ skulls are similar in length to their WT counterparts. The Brtl/+ mice exhibit alveolar bone with a porotic-like appearance that is not observed in G610c/+. As they age, Brtl/+ mice show severe bone resorption in both the maxilla and mandible (P < .05). By contrast, G610c/+ mice experience mandibular resorption consistently across all ages, but maxillary resorption is only evident at 6 mo (P < .05). Western blot shows high osteoclastic activities in the Brtl/+ maxilla. Both models exhibit delayed pre-functional eruptions of the third molars (P < .05), which are similar to those observed in some bisphosphonate-treated OI subjects. Our study shows that the Brtl/+ and G610c/+ mice display clear features found in type IV OI patients; both show age-related changes in the craniofacial growth phenotype. Therefore, understanding the craniofacial features of these models and how they age will allow us to select the most accurate mouse model, mouse age, and bone structure for the specific craniofacial bone treatment of differing OI groups.

Collagen XII-Related Myopathy: An Emerging Spectrum of Extracellular Matrix-Related Myopathy

Collagen XII, a member of a protein family called fibril associated collagen with interrupted triple helices (FACIT), is an important component of extracellular matrix and is essential for bridging the neighbouring fibrils. Mutations in collagen XII have been recently described to cause a rare extracellular matrix-related myopathy in those whose phenotype resembles collagen VI-related dystrophies and were negative for pathogenic variants in COL6A genes. The authors report a 4-year old girl presented with a phenotype mimicking Ullrich congenital muscular dystrophy and genetically confirmed to have pathogenic variants in COL12A1 gene thus, expanding the phenotypic spectrum of COL12A1-related myopathy.

Expanding the genetic and clinical spectrum of osteogenesis imperfecta: identification of novel rare pathogenic variants in type I collagen-encoding genes

Introduction

Osteogenesis imperfecta (OI) is a clinically and genetically heterogeneous skeletal disorder. The majority of affected cases are attributed to autosomal dominant pathogenic variants (PVs) found in the COL1A1 and COL1A2 genes, which encode type I collagen. However, PVs in other genes involved in collagen posttranslational modification, processing, crosslinking, osteoblast differentiation, and bone mineralization have also been associated with OI.

Methods

In this study, we present the results of next-generation sequencing (NGS) analysis using a custom panel of 11 genes known to be associated with OI. This clinical study enrolled a total of 10 patients, comprising 7 male and 3 female patients from 7 families, all from the Puglia Region in South Italy, providing a detailed overview of their age, gender, family history, OI type, and non-skeletal features.

Results

The genetic analysis revealed 5 PVs in the COL1A1 gene and 2 PVs in the COL1A2 gene. Importantly, three of these PVs have not been previously reported in the literature. These include two novel heterozygous frameshift PVs in COL1A1 (c.2890_2893del and c.3887del) and one novel heterozygous missense PV in COL1A2 (c.596G>T).

Discussion

The identification of these previously unreported PVs expands the variant spectrum of the COL1A1 and COL1A2 genes and may have implications for accurate diagnosis, genetic counselling, and potential therapeutic interventions in affected individuals and their families.

COL1A2 (p.Gly322Ser) Mutation Causes Late-Onset Osteogenesis Imperfecta: A Case Report

Osteogenesis imperfecta (OI) is a genetically inherited disorder that mainly affects the bones and causes a generalized decrease in bone mass. OI has a broad clinical spectrum ranging from the most severe form of OI which may cause in-utero death or stillbirth to the milder form. Clinical manifestations normally mitigate with an increase in age. We report a case of a healthy 12-year-old male who presented with a spontaneous fracture of the femur without trauma. The patient has no previous history of fractures, bone deformities or systemic conditions. The initial physical examination was unremarkable except for a bilateral subtle grayish sclera. Calcium, phosphorus, vitamin D, blood urea nitrogen (BUN), creatinine, and parathyroid hormone (PTH) values were within normal range. After genetic testing, the patient was diagnosed with OI due to a pathogenic COL1A2 (c.964G>A [p.Gly322Ser]) mutation. The first manifestation was at 12 years of age with a femur spontaneous fracture, which brings to the fact that the patient has a late onset of OI.

Accelerated aging in cyclophilin B deficient mice downstream of p21‐Cip1 /Waf1

Loss of bone mass and strength is a common problem of advanced age in humans. Defective bone is also a primary finding in osteogenesis imperfecta (OI), a genetic condition most commonly caused by autosomal dominant mutations in the type I collagen genes. Although altered collagen has been proposed to correlate with cellular processes that underlie aging, the causal relationships between them in vivo have not yet been completely explored. Whether aging plays a promoting role in OI development or whether OI contributes to aging, also remains unknown. The PpiB gene encodes cyclophilin B (CypB), a prolyl isomerase residing in the endoplasmic reticulum required for normal assembly of collagen. Germline deletion or mutations of CypB in mice or humans cause autosomal recessive OI (type IX). Here, we show that mice lacking CypB develop early onset of aging‐associated phenotypes, including kyphosis, fat reduction and weight loss, as well as abnormal teeth, skin, and muscle. Elevated senescence‐associated beta‐galactosidase (SA‐β‐Gal) activity was observed in fat tissues and in bone marrow–derived multipotent stromal cells. Protein levels of the cyclin‐dependent kinase (cdk)‐inhibitor p21‐Cip1/Waf1, a well known senescence marker, were significantly elevated in CypB‐deficient primary cells and mouse tissues. Importantly, loss of p21 in CypB knockout mice attenuated SA‐β‐Gal activity and delayed the development of kyphosis. In addition, less adipose tissue depot and higher SA‐β‐Gal activity were observed in a second OI model, Cola2^oim mutant mice. A potential upregulation of p21 was also revealed in a limited number of these mice. These findings suggest that some of the features in OI patients may be mediated in part through activation of the p21‐dependent pathway, one of which is closely associated with senescence and aging. This study provides new mechanistic insight into relationships between OI and aging and raises the possibility of using senolytics drugs to treat OI in the future. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Application of whole exome sequencing in fetal cases with skeletal abnormalities

Objectives

To investigate the role of whole exome sequencing (WES) technology in fetuses with skeletal abnormalities (SKA) for establishing an appropriate clinical diagnosis and treatment path.

Methods

From April 2019 to August 2020, eight special families were enrolled into the study. Their fetuses showed abnormal SKA by ultrasonic testing during pregnancy, but it is inconsistent with the normal results identified by chromosomal microarray analysis (CMA) of amniotic fluid or abortion. For further diagnosis, WES was performed to detect the causative genes mutations followed by Sanger sequencing.

Results

Among of these eight fetuses with SKA, we found more than half of pathogenic mutations were in COL1A1/2 gene, except for a known hotspot mutation in FGFR3 gene (c.1138G>A). Three heterozygous mutations of COL1A1 gene, c.2885G>A p (Gly962Asp), c.994G>A p (Gly332Arg) and c.1002 + 5G>T, were de novo mutations. The c.1002 + 5G>T mutation in COL1A1 was firstly reported. In addition, one fetus carried a novel heterozygous mutation of COL1A1 c.644G>A p (Gly215Asp), which was inherited from the mother. Another novel heterozygous mutation c.2482G>T p (Val828Phe) in the COL1A2 gene was identified in another fetus and was inherited from the father. Among of these COL1A1 mutations, these results might involve in two novel splicing mutations.

Conclusion

Our study reported several novel heterozygous mutations which expands the COL1A1/2 mutation spectrum for prenatal diagnosis of SKA. Most importantly, WES technology is necessary as a routine step of the SKA diagnosis before or during pregnancy, combining with the detection of chromosome level.

Transcriptome Analysis Reveals the Differentially Expressed Genes Associated with Growth in Guangxi Partridge Chickens

The Guangxi Partridge chicken is a well-known chicken breed in southern China with good meat quality, which has been bred as a meat breed to satisfy the increased demand of consumers. Compared with line D whose body weight is maintained at the average of the unselected group, the growth rate and weight of the selected chicken group (line S) increased significantly after breeding for four generations. Herein, transcriptome analysis was performed to identify pivotal genes and signal pathways of selective breeding that contributed to potential mechanisms of growth and development under artificial selection pressure. The average body weight of line S chickens was 1.724 kg at 90 d of age, which showed a significant increase at 90 d of age than line D chickens (1.509 kg), although only the internal organ ratios of lung and kidney changed after standardizing by body weight. The myofiber area and myofiber density of thigh muscles were affected by selection to a greater extent than that of breast muscle. We identified 51, 210, 31, 388, and 100 differentially expressed genes (DEGs) in the hypothalamus, pituitary, breast muscle, thigh muscle, and liver between the two lines, respectively. Several key genes were identified in the hypothalamus-pituitary-muscle axis, such as FST, THSB, PTPRJ, CD36, PITX1, PITX2, AMPD1, PRKAB1, PRKAB2, and related genes for muscle development, which were attached to the cytokine–cytokine receptor interaction signaling pathway, the PPAR signaling pathway, and lipid metabolism. However, signaling molecular pathways and the cell community showed that elevated activity in the liver of line S fowl was mainly involved in focal adhesion, ECM-receptor interaction, cell adhesion molecules, and signal transduction. Collectively, muscle development, lipid metabolism, and several signaling pathways played crucial roles in the improving growth performance of Guangxi Partridge chickens under artificial selection for growth rate. These results support further study of the adaptation of birds under selective pressure.

Phenotypic Variation in Vietnamese Osteogenesis Imperfecta Patients Sharing a Recessive P3H1 Pathogenic Variant

Osteogenesis imperfecta (OI) is a syndromic disorder of bone fragility with high variation in its clinical presentation. Equally variable is molecular aetiology; recessive forms are caused by approximately 20 different genes, many of which are directly implicated in collagen type I biosynthesis. Biallelic variants in prolyl 3-hydroxylase 1 (P3H1) are known to cause severe OI by affecting the competence of the prolyl 3-hydroxylation—cartilage associated protein—peptidyl-prolyl cis-trans isomerase B (P3H1-CRTAP-CyPB) complex, which acts on the Pro986 residue of collagen type I α 1 (COL1A1) and Pro707 collagen type I α 2 (COL1A2) chains. The investigation of an OI cohort of 146 patients in Vietnam identified 14 families with P3H1 variants. The c.1170+5G>C variant was found to be very prevalent (12/14) and accounted for 10.3% of the Vietnamese OI cohort. New P3H1 variants were also identified in this population. Interestingly, the c.1170+5G>C variants were found in families with the severe clinical Sillence types 2 and 3 but also the milder types 1 and 4. This is the first time that OI type 1 is reported in patients with P3H1 variants expanding the clinical spectrum. Patients with a homozygous c.1170+5G>C variant shared severe progressively deforming OI type 3: bowed long bones, deformities of ribcage, long phalanges and hands, bluish sclera, brachycephaly, and early intrauterine fractures. Although it remains unclear if the c.1170+5G>C variant constitutes a founder mutation in the Vietnamese population, its prevalence makes it valuable for the molecular diagnosis of OI in patients of the Kinh ethnicity. Our study provides insight into the clinical and genetic variation of P3H1-related OI in the Vietnamese population.

Phenotypic Spectrum and Molecular Basis in a Chinese Cohort of Osteogenesis Imperfecta With Mutations in Type I Collagen

Osteogenesis imperfecta (OI) is a rare inherited connective tissue dysplasia characterized with skeletal fragility, recurrent fractures and bone deformity, predominantly caused by mutations in the genes COL1A1 or COL1A2 that encode the chains of type I collagen. In the present study, clinical manifestations and genetic variants were analysed from 187 Chinese OI patients, majority of whom are of southern Chinese origin. By targeted sequencing, 63 and 58 OI patients were found carrying mutations in COL1A1 and COL1A2 respectively, including 8 novel COL1A1 and 7 novel COL1A2 variants. We validated a novel splicing mutation in COL1A1. A diverse mutational and phenotypic spectrum was observed, coupling with the heterogeneity observed in the transcriptomic data derived from osteoblasts of six patients from our cohort. Missense mutations were significantly associated (χ²p = 0.0096) with a cluster of patients with more severe clinical phenotypes. Additionally, the severity of OI was more correlated with the quality of bones, rather than the bone mineral density. Bone density is most responsive to bisphosphonate treatment during the juvenile stage (10–15 years old). In contrast, height is not responsive to bisphosphonate treatment. Our findings expand the mutational spectrum of type I collagen genes and the genotype-phenotype correlation in Chinese OI patients. The observation of effective bisphosphonate treatment in an age-specific manner may help to improve OI patient management.

Osteogenesis Imperfecta: Search for Mutations in Patients from the Republic of Bashkortostan (Russia)

Osteogenesis imperfecta (OI) is an inherited disease of bone characterized by increased bone fragility. Here, we report the results of the molecular architecture of osteogenesis imperfecta research in patients from Bashkortostan Republic, Russia. In total, 16 mutations in COL1A1, 11 mutations in COL1A2, and 1 mutation in P3H1 and IFIMT5 genes were found in isolated states; 11 of them were not previously reported in literature. We found mutations in CLCN7, ALOX12B, PLEKHM1, ERCC4, ARSB, PTH1R, and TGFB1 that were not associated with OI pathogenesis in patients with increased bone fragility. Additionally, we found combined mutations (c.2869C>T, p. Gln957* in COL1A1 and c.1197+5G>A in COL1A2; c.579delT, p. Gly194fs in COL1A1 and c.1197+5G>A in COL1A2; c.2971G>C, p. Gly991Arg in COL1A2 and c.212G>C, p.Ser71Thr in FGF23; c.-14C>T in IFITM5 and c.1903C>T, p. Arg635* in LAMB3) in 4 patients with typical OI clinic phenotypes.

Collagen type 1 alpha 1 chain is a novel predictive biomarker of poor progression-free survival and chemoresistance in metastatic lung cancer

Background: Collagen type 1 alpha 1 chain (COL1A1) is an extracellular matrix protein comprising two alpha 1 chains and one alpha 2 chain. Our previous study identified that COL1A1 is the key gene during the development and progression of lung adenocarcinoma by multi-omics analysis. However, the clinical significance of COL1A1 expression in lung cancer samples remains largely unknown. Here, we aimed to evaluate the level of COL1A1 in lung cancer samples and correlate its level with the clinical outcome.

Methods:COL1A1 gene expression in lung cancer samples was analyzed using the Oncomine database (www.oncomine.org). A total of 308 lung cancer samples (208 formalin-fixed paraffin-embedded tissues and 100 blood samples) were assessed for protein expression of COL1A1. Immunohistochemistry staining and enzyme-linked immunosorbent assay were used to detect COL1A1 expression in tissues and serum, respectively.

Results: We identified an elevation of COL1A1 in mRNA level and gene amplification in lung cancer tissues compared with normal lung tissues. High COL1A1 expression was observed in lung cancer tissues and serum (P < 0.05), it was significantly correlated with the peripheral type tumor, the larger diameter of the tumor, the occurrence of lymph node metastases and distant metastases, a higher TNM stage, and smoking (P < 0.05). High COL1A1 expression was associated with poor progression-free survival (PFS) and chemoresistance in lung cancer patients (P < 0.05). Multivariable Cox-regression analysis showed that COL1A1 expression was an independent prognostic factor (P < 0.05). Furthermore, the area under the receiver operating characteristic (AUC) curve was 0.909 for the combined COL1A1 and carcinoembryonic antigen (CEA) measurement.

Conclusion: Our findings revealed that COL1A1 could be used as a novel diagnostic, prognostic, and chemoresistance biomarker of human lung cancer, and these results provide a potential therapeutic strategy for lung cancer patients.

Genetic analysis in Japanese patients with osteogenesis imperfecta: Genotype and phenotype spectra in 96 probands

BACKGROUND

Osteogenesis imperfecta (OI) is a rare connective-tissue disorder characterized by bone fragility. Approximately 90% of all OI cases are caused by variants in COL1A1 or COL1A2. Additionally, IFITM5 variants are responsible for the unique OI type 5. We previously analyzed COL1A1/2 variants in 22 Japanese families with OI through denaturing high-performance liquid chromatography screening, but our detection rate was low (41%).

METHODS

To expand the genotype-phenotype correlations, we performed a genetic analysis of COL1A1/2 and IFITM5 in 96 non-consanguineous Japanese OI probands by Sanger sequencing.

RESULTS

Of these individuals, 54, 41, and 1 had type 1 (mild), type 2-4 (moderate-to-severe), and type 5 phenotypes, respectively. In the mild group, COL1A1 nonsense and splice-site variants were prevalent (n = 30 and 20, respectively), but there were also COL1A1 and COL1A2 triple-helical glycine substitutions (n = 2 and 1, respectively). In the moderate-to-severe group, although COL1A1 and COL1A2 glycine substitutions were common (n = 14 and 18, respectively), other variants were also detected. The single case of type 5 had the characteristic c.-14C>T variant in IFITM5.

CONCLUSION

These results increase our previous detection rate for COL1A1/2 variants to 99% and provide insight into the genotype-phenotype correlations in OI.

Clinical and genetic analysis in 185 Chinese probands of osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a well-known heritable disorder of connective tissue characterized by skeletal fragility and low bone mass. Nearly 90% of patients with OI have disease variants in COL1A1 and COL1A2 that encode for the α1 and α2 chains of type I collagen.

MATERIALS AND METHODS

A retrospective analysis of 185 probands who were diagnosed with OI in Shanghai Jiao Tong University Affiliated Sixth People's Hospital from March 2005 to December 2019 was performed.

RESULTS

A total of 140 mutations in COL1A1 and 45 mutations in COL1A2 were identified, of which 18 variations were novel. In the phenotype analysis, there were more sporadic cases than familial OI cases in China (54.6% vs. 45.4%, P < 0.001). A total of 98.9% of patients presented with a fracture history. The most common fracture sites were extremity long bones (femur, tibia-fibula and radius-ulna accounted for 36.6%, 17.1% and 11.7%, respectively). Patients with OI types III and IV, especially type III, had a higher proportion of dentinogenesis imperfecta (DI) than patients with OI type I (55% vs. 28%, P < 0.001). Interestingly, G767S and D1219N in COL1A1 and G337S in COL1A2 were the most frequent (3.52%, 2.11% and 8.89%, respectively), which seem to be hotspot mutations in the COL1A1 and COL1A2 genes in Chinese patients.

CONCLUSIONS

This study describes the mutations in the main pathogenic genes, COL1A1 and COL1A2, and the clinical characteristics of osteogenesis imperfecta in China. Furthermore, these findings help reveal the genetic basis of Asian OI patients and contribute to genetic counselling.

A novel de novo mutation in COL1A1 leading to osteogenesis imperfecta confirmed by zebrafish model

Our study reports a novel dominant COL1A1 mutation in OI. Using a zebrafish model, we confirmed that the glycine to serine substitution at position 608 of the COL1A1 protein has deleterious effects on bone development.

PURPOSE

Osteogenesis imperfecta (OI), also known as brittle bone disease, is a group of genetic disorders. Mutations in two genes, collagen type I alpha 1 chain (COL1A1) and collagen type I alpha 1 chain (COL1A2), which encode the pro-a1 (I) and pro-a2 (I) chains of type I collagen, respectively, the most abundant form of collagen in the human body, cause most cases of OI.

METHODS

In this study, we used panel-based next-generation sequencing for prenatal diagnosis of a fetus whose ultrasound images suggested OI. A de novo mutation in COL1A1 gene was suspected to cause the phenotype. To validate the effect of this mutation in a zebrafish model, we constructed a plasmid containing the corresponding mutation in the zebrafish gene col1a1a (c.1744 G > A), and overexpressed the mutant protein in zebrafish larvae.

RESULTS

We identified a novel COL1A1 mutation (c.1822 G > A; p.Gly608Ser) in the fetus but not in her parents by an skeletal dysplasias panel. Bioinformatic analysis showed that the affected residue (p.Gly608) is highly conserved from zebrafish to humans. In contrast to larvae expressing wild-type (WT) col1a1a and enhanced green fluorescent protein (EGFP), col1a1a mutation-expressing larvae showed significant spinal curvature and embryonic lethality, mimicking the phenotype of human OI.

CONCLUSIONS

Our study revealed the pathogenicity of a de novo mutation, c.1822 G > A, in human COL1A1, which expands the mutation spectrum of OI.

Over-Representation of Recessive Osteogenesis Imperfecta in Asian Indian Children

Several genes are implicated in the etiology of early onset osteogenesis imperfecta (OI). The various genes causing severe OI include WNT1 , SERPINF1 , P3H1 , CREB3L1 , and CRTAP , although glycine substitutions in COL1A1chains have also been predicted to cause perinatal lethal OI . Patients with early onset OI present decreased mobility, recurrent rib fractures, bony deformities, and chest infections that lead to an early death. We reported our experience in children with OI in Asian Indian families, which includes two patients with SERPINF1 pathogenic variants; and another two patients with severe OI and antenatal fractures caused by pathogenic variants in the CRTAP gene, identified by next generation sequencing (NGS). For one affected fetus, medical termination of pregnancy was done. The other baby was started on zoledronate therapy just after birth and is now 3 years old. Prenatal diagnosis was subsequently done on chorionic villus sample in the latter family.

Osteogenesis imperfecta: Novel genetic variants and clinical observations from a clinical exome study of 54 Indian patients

Osteogenesis imperfecta (OI) is a group of inherited disorders with increased bone fragility and wide genetic heterogeneity. We report the outcome of clinical exome sequencing validated by Sanger sequencing in clinically diagnosed 54 OI patients in Indian population. In 52 patients, we report 20 new variants involving both dominant and recessive OI-specific genes and correlate these with phenotypes. COL1A1 and COL1A2 gene variants were identified in 44.23%, of which 28.84% were glycine substitution abnormalities. Two novel compound heterozygous variants in the FKBP10 gene were seen in two unrelated probands. A novel heterogeneous duplication of chromosomal region chr17: 48268168-48278884 from exons 1-33 of the COL1A1 gene was found in one proband. In five probands, there were additional variants in association with OI. These were ANO5 in association with CRTAP in two probands of the same family causing gnathodiaphyseal dysplasia, COL5A2 with LEPRE1 causing Ehlers Danlos syndrome, COL11A1 in addition to COL1A1 causing Stickler syndrome, and a previously unreported combination of SLC34A1 gene variant with FKBP10 leading to Fanconi renal tubular syndrome type II. Our findings demonstrate the efficacy of clinical exome sequencing in screening OI patients, classifying its subtypes, and identifying associated disorders in consanguineous populations.

MALDI-TOF-MS-based high throughput genotyping of mutations associated with body measurement traits in cattle

Exploration of genes in relation to body measurement traits through large-scaled mutation identification is highly conductive for the genomics-assisted breeding of superior productivity cattle. In this investigation, 31 objective mutations were genotyped synchronously in 384 yellow cattle of 8 breeds through the application of optimized MALDI-TOF-MS and multiplex PCR techniques. High genotyping rate was obtained as well as greatly decreased cost which was below one thirtieth of the routine analysis. Results from genotyping revealed 23 mutations as valid mutations in the studied cattle population with gene heterozygosity and effective allele number varying from 0.0052 to 0.4998 and 1.0052 to 1.9991, respectively. Among the 23 effective mutations, 12 was classified as moderate polymorphism (0.25 < PIC < 0.5) while the other 11 belonged to low polymorphism (PIC < 0.25), 7 mutations did not obey the HW equilibrium (p < 0.05) and linkage mainly appeared between mutations of UCP2 and PTHR1 genes. Furthermore, 8 body measurement traits in the 384 cattle were recorded to validate their association with tag mutations, and significant correlations were found in 12 mutations of 9 genes including PTHR1, CDK6, IHH, HHIP, GHRL, COL1A1, INS, GDF5 and UCP2, of which, PTHR1 was proved to be the most potential contributor to bone modeling in cattle. Results highlight the potential application value of 12 novel mutations in enhancing cattle production traits as well as the high genotyping rate achieved by MALDI-TOF-MS coupled with multiplex PCR technique.

The pathogenicity of novel GUCY2D mutations in Leber congenital amaurosis 1 assessed by HPLC-MS/MS

Leber congenital amaurosis (LCA) is a group of severe congenital retinal diseases. Variants in the guanylate cyclase 2D gene (GUCY2D), which encodes guanylate cyclase 1 (ROS-GC1), are associated with LCA1 and account for 6%–21% of all LCA cases. In this study, one family with LCA1 was recruited from China. A combination of next generation sequencing and Sanger sequencing was used to screen for disease-causing mutations. We found three novel mutations (c.139delC, p.Ala49Profs*36; c.835G>A, p.Asp279Asn and c.2783G>A, p.Gly928Glu) in the GUCY2D gene. Proband III-2 carries mutations c.139delC and c.2783G>A, which are inherited from the heterozygous mutation carriers, II-2 (c.139delC) and II-3 (c.2783G>A) that possess c.139delC and c.2783G>A. Additionally, II-8 carries heterozygous mutation c.835G>A. Sanger sequencing was used to confirm the presence of the three novel mutations in other family members. Mutation c.139delC results in a truncated protein. Mutations c.835G>A and c.2783G>A significantly reduce the catalytic activity of ROS-GC1. Our findings highlight the gene variants range of LCA. Moreover, HPLC-coupled tandem mass spectrometry (HPLC-MS/MS) was used to analyze the concentration of 3',5'-cyclic guanosine monophosphate (cGMP), suggesting that HPLC-MS/MS is an effective alternative method to evaluate the catalytic activity of wild-type and mutant ROS-GC1.

Inter- and Intrafamilial Phenotypic Variability in Individuals with Collagen-Related Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a rare genetic disorder also known as a “brittle bone disease.” Around 90% of patients with OI harbor loss‐of‐function or dominant negative pathogenic variants in the COL1A1 and COL1A2 genes, which code for collagen type I α1 and α2 chains. Collagen‐related forms of the disorder are classified as Sillence OI types I–IV. OI phenotype expression ranges from mild to lethal. The current study aims to evaluate associations between interfamilial and intrafamilial phenotypic variability and genotype characteristics of patients with collagen‐related OI. The study was based on a systematic review of collagen‐related OI cases from the University of Tartu OI database (n = 137 individuals from 81 families) and the Dalgleish database (n = 479 individuals). Interfamilial variability analysis has shown that 17.74% of all studied OI‐related variants were associated with the same phenotype. The remaining 82.26% of pathogenic variants were associated with variable phenotypes. Additionally, higher interfamilial variability correlated with the COL1A1 gene (P value = 0.001) and dominant‐negative variants (P value = 0.0007). Within intrafamilial variability, 32.81% families had increasing or decreasing OI phenotype severity across generations. Higher intrafamilial variability of phenotypes correlated with the collagen I dominant negative variants (P value = 0.0246). The current study shows that, in line with other phenotype modification factors, OI interfamilial and intrafamilial diversity potential is associated with the genotype characteristics of the OI‐causing pathogenic variants. The results of the current study may advance knowledge of OI phenotype modification as well as assist family planning and the evaluation of disease progression in subsequent generations.

A family with homozygous and heterozygous p.Gly337Ser mutations in COL1A2

Osteogenesis imperfecta (OI) is commonly caused by monoallelic mutations in COL1A1 or COL1A2. Biallelic mutations are extremely rare. Only five previous reports have identified seven OI patients with homozygous mutations in COL1A2. OI is a genetically and phenotypically heterogeneous disorder which challenges an establishment of genotype-phenotype correlation. Notably, more than thirty patients with OI possess the heterozygous mutation, p.Gly337Ser, in COL1A2. Their clinical severity ranges from mild OI type I to severe types III and IV. Here, we report a 17-year-old Thai female with recurrent bone fractures, short stature, blue sclerae, triangular face, missing teeth, dentinogenesis imperfecta (DI), skeletal deformities, and scoliosis. She was diagnosed with OI type III. Her parents were second-cousin-once-removed. The father was a professional Thai boxer. Both had normal bone mineral density, no history of bone fractures, and only teeth problems. They were diagnosed with DI without OI. Whole exome sequencing identified that the proband harbored the homozygous mutation, c.1009G > A (p.Gly337Ser), in exon 19 of COL1A2 while her parents were heterozygous for this mutation. This study reports the eighth child with OI and the homozygous mutation in COL1A2; and the first two individuals with the heterozygous p.Gly337Ser mutation in COL1A2 causing an isolated DI without OI.

Osteogenesis imperfecta in Brazilian patients

Osteogenesis Imperfecta (OI) is a heterogeneous genetic disorder characterized by bone fragility and fracture. Mutations in 20 distinct genes can cause OI, and therefore, the genetic diagnosis of OI is frequently difficult to obtain because of the great number of genes that can be related with this disease. Studies that report the most frequently mutated genes in OI patients can help to improve molecular strategies for diagnosis of the disease. In order to characterize the mutation profile of OI in Brazilian patients, we analyzed 30 unrelated patients through SSCP screening, NGS gene panel, and/or Sanger sequencing for the 11 most frequently mutated genes in the database of mutations, including COL1A1, COL1A2, P3H1, CRTAP, PPIB, SERPINH1, SERPINF1, FKBP10, SP7, WNT1 and IFITM5. Disease-causing variants were identified in COL1A1, COL1A2, FKBP10, P3H1, and IFITM5. A total of 28 distinct mutations were identified, including seven novel changes. Our data show that the analysis of these five genes is able to detect at least 95% of causative mutations in OI disorder from Brazilian population. However, it has to be taken into considerations that distinct populations can have different frequencies of disease-causing variants. Hence, it is important to replicate this study in other groups.

COL1A1/2 Pathogenic Variants and Phenotype Characteristics in Ukrainian Osteogenesis Imperfecta Patients

Osteogenesis imperfecta (OI) is a hereditary bone disorder caused by defects of type I collagen. Although up to 90% of patients harbor pathogenic variants in the COL1A1/2 gene, which codes for collagen α1/2 chains, the spectrum of OI genotypes may differ between populations, and there is academic controversy around OI genotype-phenotype correlations. In the current study, 94 Ukrainian OI families were interviewed. Clinical and genealogical information was collected from patients in spoken form, and their phenotypes were described. To identify the spectrum of collagen I pathogenic variants, COL1A1/2 mutational analysis with Sanger sequencing was performed on the youngest affected individual of every family. Of the 143 patients investigated, 67 (46.85%) had type I OI, 24 (16.78%) had type III, 49 (34.27%) had type IV, and III (2.10%) had type V. The mean number of fractures suffered per patient per year was 1.32 ± 2.88 (type I 0.50 ± 0.43; type III 3.51 ± 6.18; type IV 1.44 ± 1.77; and type 5 0.77 ± 0.23). 87.23% of patients had skeletal deformations of different severity. Blue sclera, dentinogenesis imperfecta, and hearing loss were present in 87%, 55%, and 22% of patients, respectively. COL1A1/2 pathogenic variants were harbored by 60 patients (63.83%). 27 pathogenic variants are described herein for the first time. The majority of the pathogenic variants were located in the COL1A1 gene (76.19%). Half (49.21%) of the pathogenic variants were represented by structural variants. OI phenotype severity was highly correlated with type of collagen I defect. The current article presents an analysis of the clinical manifestations and COL1A1/2 mutational spectrum of 94 Ukrainian OI families with 27 novel COL1A1/2 pathogenic variants. It is hoped that this data and its analysis will contribute toward the increased understanding of the phenotype development and genetics of the disorder.

IFITM5 pathogenic variant causes osteogenesis imperfecta V with various phenotype severity in Ukrainian and Vietnamese patients

BACKGROUND

Osteogenesis imperfecta (OI) covers a spectrum of bone fragility disorders. OI is classified into five types; however, the genetic causes of OI might hide in pathogenic variants of 20 different genes. Often clinical OI types mimic each other. This sometimes makes it impossible to identify the OI type clinically, which can be a risk for patients. Up to 90% of OI types I-IV are caused by pathogenic variants in the COL1A1/2 genes. OI type V is caused by the c.-14C > T pathogenic variant in the 5'UTR of the IFITM5 gene and is characterized by hyperplastic callus formation and the ossification of interosseous membranes.

RESULTS

In the current study, we performed IFITM5 5'UTR region mutational analysis using Sanger sequencing on 90 patients who were negative for COL1A1/2 pathogenic variants. We also investigated the phenotypes of five patients with genetically confirmed OI type V. The proportion of OI type V patients in our cohort of all OI patients was 1.48%. In one family, there was a history of OI in at least three generations. Phenotype severity differed from mild to extremely severe among patients, but all patients harbored the same typical pathogenic variant. One patient had no visible symptoms of OI type V and was suspected to have had OI type IV previously. We also identified a case of extremely severe hyperplastic callus in a 15-year-old male, who has hearing loss and brittleness of teeth.

CONCLUSIONS

OI type V is underlined with some unique clinical features; however, not all patients develop them. The phenotype spectrum might be even broader than previously suspected, including typical OI features: teeth brittleness, bluish sclera, hearing loss, long bones deformities, and joint laxity. We suggest that all patients negative for COL1A1/2 pathogenic variants be tested for the presence of an IFITM5 pathogenic variant, even if they are not expressing typical OI type V symptoms. Further studies on the pathological nature and hyperplastic callus formation mechanisms of OI type V are necessary.

Genotype-phenotype relationship in a large cohort of osteogenesis imperfecta patients with COL1A1 mutations revealed by a new scoring system

BACKGROUND

Osteogenesis imperfecta (OI), a heritable bone fragility disorder, is mainly caused by mutations in COL1A1 gene encoding α1 chain of type I collagen. This study aimed to investigate the COL1A1 mutation spectrum and quantitatively assess the genotype-phenotype relationship in a large cohort of Chinese patients with OI.

METHODS

A total of 161 patients who were diagnosed as OI in Department of Endocrinology of Peking Union Medical College Hospital from January 2010 to December 2017 were included in the study. The COL1A1 mutation spectrum was identified by next generation sequencing and confirmed by Sanger sequencing. A new clinical scoring system was developed to quantitatively assess the clinical severity of OI and the genotype-phenotype relationship was analyzed. The independent sample t-test, analysis of variance, Mann-Whitney U-test, Chi-squared test, Pearson correlation, and multiple linear regression were applied for statistical analyses.

RESULTS

Among 161 patients with OI, 32.9% missense mutations, 16.8% non-sense mutations, 24.2% splice-site mutations, 24.8% frameshift mutations, and 1.2% whole-gene deletions were identified, of which 38 variations were novel. These mutations led to 53 patients carrying qualitative defects and 67 patients carrying quantitative defects in type I collagen. Compared to patients with quantitative mutations, patients with qualitative mutations had lower alkaline phosphatase level (296 [132, 346] U/L vs. 218 [136, 284] U/L, P = 0.009) and higher clinical score (12.2 ± 5.3 vs. 7.4 ± 2.4, P < 0.001), denoting more severe phenotypes including shorter stature, lower bone mineral density, higher fracture frequency, more bone deformity, vertebral compressive fractures, limited movement, and dentinogenesis imperfecta (DI). Patients would not present with DI if the glycine substitutions happened before the 79th amino acid in triple helix of α1 chains.

CONCLUSIONS

This presented distinctive COL1A1 mutation spectrum in a large cohort of Chinese patients with OI. This new quantitative analysis of genotype-phenotype correlation would be helpful to predict the prognosis of OI and genetic counseling.

De novo and inherited pathogenic variants in collagen-related osteogenesis imperfecta

Background

Osteogenesis imperfecta (OI) is a rare genetic bone fragility disorder. In the current study, differences between the genotypes and phenotypes of de novo and inherited collagen‐related OI were investigated.

Methods

A comparative analysis was performed of the genotypes and phenotypes of 146 unrelated inherited and de novo collagen I OI cases from Estonia, Ukraine, and Vietnam. Mutational analysis of the subjects and all available parents were performed with Sanger sequencing.

Results

Results showed that 56.16% of the OI cases were caused by de novo pathogenic variants. The proportion of OI types OI1, OI4, and OI3 among subjects with inherited OI was 45.31%, 46.88%, and 7.81%, respectively. Among subjects with de novo OI, the proportions of OI types (OI1, OI4, and OI3) were almost equal. Both inherited and de novo OI pathogenic variants occurred more often in the COL1A1 gene than in the COL1A2. The majority of de novo cases were missense pathogenic variants, whereas inherited OI was mostly caused by loss of function pathogenic variants.

Conclusion

In summary, there were significant differences between the phenotypes and genotypes of subjects with de novo and inherited OI. These findings may promote the further understanding of OI etiology, and assist with diagnostics procedures, as well as with family planning.

Osteogenesis Imperfecta Due to Combined Heterozygous Mutations in Both COL1A1 and COL1A2, Coexisting With Pituitary Stalk Interruption Syndrome

Osteogenesis imperfecta (OI) is a hereditary connective tissue disorder, characterized by reduced bone content, fractures and skeletal malformation due to abnormal synthesis or dysfunction of type I collagen protein. Pituitary stalk interruption syndrome (PSIS) is usually associated with environmental and hereditary factors. Here, we report a rare case of OI and PSIS co-occurrence. A 19-year-old male patient sought treatment for growth delay and absent secondary sexual characteristics. Hormone measurements indicated the presence of hypopituitarism (secondary hypothyroidism, growth hormone deficiency, ACTH-cortisol hormone deficiency, hypogonadotropic hypogonadism). Pituitary magnetic resonance imaging indicated reduced morphology of the anterior lobe, absence of the pituitary stalk, and ectopic displacement of the posterior lobe to the infundibulum, supporting a diagnosis of PSIS. In addition, the patient, his monozygotic twin brother (no evidence of PSIS), and their mother all presented blue sclera and susceptibility to bone fractures before adulthood. Next-generation sequencing demonstrated that the family had compound heterozygous mutations in COL1A1 and COL1A2, with no known mutations related to PSIS, pituitary hormone deficiency (PHD), or holoprosencephaly (HPE). The mother experienced breech and natural delivery of the patient and his brother, respectively. Thus, we deduced that the patient's PSIS might have resulted from breech delivery. Although we cannot exclude the possibility that the proband might have an undetected genetic abnormality causing PSIS or increasing his susceptibility to damage to the hypothalamic-pituitary region due to the limitation of exome sequencing, this rare case suggests that breech delivery in the newborn with OI might be related to PSIS.

Pregnancies complicated by maternal osteogenesis imperfecta type III: a case report and review of literature

The restrictive lung disease can be exacerbated by growing fundus in women with osteogenesis imperfecta type III. Regional anesthesia can be performed in these women. Mode of delivery for women with osteogenesis imperfecta type III is generally cesarean delivery. Neonatal outcomes are complicated due to indicated preterm deliveries.

Diagnostic strategies and genotype-phenotype correlation in a large Indian cohort of osteogenesis imperfecta

Osteogenesis Imperfecta (OI) is a clinically and genetically heterogeneous disorder. Although differential diagnosis is greatly facilitated by next generation sequencing, its availability can vary considerably. In this study, we compared targeted gene panel or exome sequencing with clinical scoring and grouping in a cohort of 50 OI index patients recruited by a single Indian clinical center in an unselected fashion. In 48 patients we observed a total of 24 novel mutations and 24 known OI mutations, of which several were recurrent. In one patient neither gene panel nor exome sequencing revealed any significant mutation and another patient harbored a class III COL1A1 intronic variant. The percentage of autosomal recessive forms due to mutations in BMP1, FKBP10, LEPRE1, SERPINF1, and WNT1 was unusually high (48%). Grouping according to phenotypic and radiographic features revealed four individuals with Bruck syndrome due to FKBP10 mutations, three patients with hypertrophic callus caused by IFITM5 mutations, and twenty with pronounced bone bowing, of which eight carried WNT1 mutations. There was a clear correlation between genotype and phenotype severity: IFITM5=LEPRE1>WNT1>SERPINF1>COL1A1 (qualitative)>BMP1>FKBP10>COL1A2 (qualitative)>COL1A1 (quantitative)>COL1A2 (quantitative). In one patient we found heterozygous variants in COL1A1 and COL1A2 inherited from parents without an obvious bone phenotype indicating that both variants might contribute to the phenotype. Our findings demonstrate the clinical utility of gene panel testing for OI, but in cases with contractures, hypertrophic callus formation, or - to some extent - extensive bowing single gene analysis might still be more cost-effective.

A novel de novo COL1A1 mutation in a Thai boy with osteogenesis imperfecta born to consanguineous parents

Osteogenesis imperfecta (OI) is genetically heterogeneous. Mutations in COL1A1 and COL1A2 are responsible for at least 90% of the cases, which are transmitted in an autosomal dominant manner or are de novo events. We identified a Thai boy with OI whose parents were first cousins. Because the proband was the product of a consanguineous marriage, we hypothesized that he might be homozygous for a mutation in a known gene causing a recessive form of OI. Using whole exome sequencing (WES), we did not find any pathogenic mutations in any known gene responsible for an autosomal recessive form of OI. Instead, we identified a COL1A1 frameshift mutation, c.1290delG (p.Gly431Valfs*110) in heterozygosis. By Sanger sequencing, the mutation was confirmed in the proband, and not detected in his parents, indicating that it was a de novo mutation. These findings had implication for genetic counseling. In conclusion, we expanded the mutational spectrum of COL1A1 and provided another example of a de novo pathogenic mutation in heterozygosis in a patient born to consanguineous parents.

Mutational analysis of COL1A1 and COL1A2 genes among Estonian osteogenesis imperfecta patients

Background

Osteogenesis imperfecta (OI) is a rare bone disorder. In 90% of cases, OI is caused by mutations in the COL1A1/2 genes, which code procollagen α1 and α2 chains. The main aim of the current research was to identify the mutational spectrum of COL1A1/2 genes in Estonian patients. The small population size of Estonia provides a unique chance to explore the collagen I mutational profile of 100% of OI families in the country.

Methods

We performed mutational analysis of peripheral blood gDNA of 30 unrelated Estonian OI patients using Sanger sequencing of COL1A1 and COL1A2 genes, including all intron-exon junctions and 5′UTR and 3′UTR regions, to identify causative OI mutations.

Results

We identified COL1A1/2 mutations in 86.67% of patients (26/30). 76.92% of discovered mutations were located in the COL1A1 (n = 20) and 23.08% in the COL1A2 (n = 6) gene. Half of the COL1A1/2 mutations appeared to be novel. The percentage of quantitative COL1A1/2 mutations was 69.23%. Glycine substitution with serine was the most prevalent among missense mutations. All qualitative mutations were situated in the chain domain of pro-α1/2 chains.

Conclusion

Our study shows that among the Estonian OI population, the range of collagen I mutations is quite high, which agrees with other described OI cohorts of Northern Europe. The Estonian OI cohort differs due to the high number of quantitative variants and simple missense variants, which are mostly Gly to Ser substitutions and do not extend the chain domain of COL1A1/2 products.