Novel Mutations in SERPINF1 Result in Rare Osteogenesis Imperfecta Type VI

SERPINF1 knockdown attenuates chondrocyte senescence, hypertrophy, and inflammation in osteoarthritis to offer a potential therapeutic strategy

Osteoarthritis (OA) is characterized by cartilage degradation, synovial inflammation, subchondral bone remodeling, and osteophyte formation, leading to chronic pain and impaired mobility. Chondrocyte senescence, inflammation, and hypertrophic differentiation critically contribute to OA progression. Integrated analysis of four GEO datasets identified SERPINF1 as a consistently upregulated gene in both human and animal OA samples. Histopathological and immunohistochemical analyses confirmed increased SERPINF1 in OA cartilage, where chondrocytes showed elevated SERPINF1 protein alongside reduced aggrecan expression. Functional studies revealed that SERPINF1 knockdown in OA chondrocytes diminished senescence markers (p21, p16, p53) while increasing Lamin B1, and reduced levels of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6). Conversely, overexpression of SERPINF1 in normal chondrocytes induced senescence and increased inflammatory mediator expression, accompanied by altered extracellular matrix metabolism and hypertrophy marker expression. Mechanistic analysis further implicated the TNF-α/NF-κB signaling pathway in mediating these effects. In a destabilization of the medial meniscus (DMM) mouse model, intra-articular SERPINF1 knockdown attenuated cartilage destruction, reduced senescence and inflammatory markers, and restored ECM integrity. Collectively, these findings demonstrate that SERPINF1 promotes OA progression by exacerbating chondrocyte senescence, inflammation, and hypertrophy, suggesting that targeting SERPINF1 may offer a novel therapeutic strategy for OA.

Investigation of oral health findings and genotype correlations in osteogenesis imperfecta

Osteogenesis imperfecta, a common genetic connective tissue disorder affecting bone with multisystemic implications, is caused by genomic alterations at various levels that disrupt the biosynthesis stages of collagen Type I. This study evaluated the intraoral and clinical findings of 43 OI cases in relation to genetic variants, aiming to contribute new insights into the roles of collagen and non-collagen genes in the oral-dental pathology of OI. Significant associations were found between OI variants and dental anomalies such as dentinogenesis imperfecta, enamel hypoplasia, taurodontism, and hypodontia. COL1A1/2-truncated variants were linked to atypical intercanine width, and midface hypoplasia correlated with reduced overjet and overbite. Bisphosphonate treatment, especially when initiated before age two, was associated with enamel hypoplasia. Oral hygiene habits, including brushing frequency and use of additional products, were linked to lower DMFT. In the OI group, significant associations were noted between Angle Class III malocclusion and reduced brushing frequency, as well as between deep palatal vault and increased DMFT. A correlation was also observed between maximum mouth opening and joint hypermobility. These findings, along with new dental observations related to non-collagen variants, shed light on the oral health challenges in OI patients. Our study underscores the importance of multidisciplinary collaboration between dentistry and medical genetics in understanding complex conditions like OI. The comprehensive analysis of oral and dental findings in OI cases is expected to inform future research and enhance clinical approaches to managing the dental challenges associated with this disorder.

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

Osteogenesis imperfecta (OI) is an uncommon genetic disorder characterized by shortness of stature, hearing loss, poor bone mass, recurrent fractures, and skeletal abnormalities. Pathogenic variations have been found in over 20 distinct genes that are involved in the pathophysiology of OI, contributing to the disorder's clinical and genetic variability. Although medications, surgical procedures, and other interventions can partially alleviate certain symptoms, there is still no known cure for OI. In this Review, we provide a comprehensive overview of genetic pathogenesis, existing treatment modalities, and new developments in biotechnologies such as gene editing, stem cell reprogramming, functional differentiation, and transplantation for potential future OI therapy.

Genetic variants and altered expression of SERPINF1 confer disease susceptibility in patients with otosclerosis

Otosclerosis (OTSC) is a focal and diffuse bone disorder of the human middle ear characterized by abnormal bone growth and deposition at the stapes' footplate. This hinders the transmission of acoustic waves to the inner ear leading to subsequent conductive hearing loss. The plausible convections for the disease are genetic and environmental factors with yet an unraveled root cause. Recently, exome sequencing of European individuals with OTSC revealed rare pathogenic variants in the Serpin Peptidase Inhibitor, Clade F (SERPINF1) gene. Here, we sought to investigate the causal variants of SERPINF1 in the Indian population. The gene and protein expression was also evaluated in otosclerotic stapes to ameliorate our understanding of the potential effect of this gene in OTSC. A total of 230 OTSC patients and 230 healthy controls were genotyped by single-strand conformational polymorphism and Sanger sequencing methods. By comparing the case controls, we identified five rare variants (c.72 C > T, c.151 G > A, c.242 C > G, c.823 A > T, and c.826 T > A) only in patients. Four variants c.390 T > C (p = 0.048), c.440-39 C > T (p = 0.007), c.643 + 9 G > A (p = 0.035), and c.643 + 82 T > C (p = 0.005) were found to be significantly associated with the disease. Down-regulation of SERPINF1 transcript level in otosclerotic stapes was quantified by qRT-PCR, ddPCR and further validated by in situ hybridization. Similarly, reduced protein expression was observed by immunohistochemistry and immunofluorescence in otosclerotic stapes that corroborate with immunoblotting of patients' plasma samples. Our findings identified that SERPINF1 variants are associated with the disease. Furthermore, reduced expression of SERPINF1 in otosclerotic stapes might contribute to OTSC pathophysiology.

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).

Osteogenesis imperfecta in 140 Turkish families: Molecular spectrum and, comparison of long-term clinical outcome of those with COL1A1/A2 and biallelic variants

BACKGROUND

Osteogenesis imperfecta (OI) is a clinically and genetically heterogeneous group of diseases characterized by increased bone fragility and deformities. Although most patients with OI have heterozygous mutations in COL1A1 or COL1A2, 17 genes have been reported to cause OI, most of which are autosomal recessive (AR) inherited, during the last years. The aim of this study is to determine the mutation spectrum in Turkish OI cohort and to investigate the genotype-phenotype correlation.

METHODS

150 patients from 140 Turkish families with OI phenotype were included in this study. Mutations in OI-related genes were identified using targeted gene panel, MLPA analysis for COL1A1 and whole exome sequencing. 113 patients who had OI disease-causing variants were followed for 1-20 years.

RESULTS

OI disease-causing variants were detected in 117 families, of which 62.4% in COL1A1/A2, 35.9% in AR-related genes. A heterozygous variant in IFITM5 and a hemizygous in MBTPS2 were also described, one in each patient. Eighteen biallelic variants (13 novel) were identified in nine genes (FKBP10, P3H1, SERPINF1, TMEM38B, WNT1, BMP1, CRTAP, FAM46A, MESD) among which FKBP10, P3H1 and SERPINF1 were most common. The most severe phenotypes were in patients with FKBP10, SERPINF1, CRTAP, FAM46A and MESD variants. P3H1 patients had moderate, while BMP1 had the mild phenotype. Clinical phenotypes were variable in patients with WNT1 and TMEM38B mutations. We also found mutations in ten genes (PLS3, LRP5, ANO5, SLC34A1, EFEMP2, PRDM5, GORAB, OCRL1, TNFRSF11B, DPH1) associated with diseases presenting clinical features which overlap OI, in eleven families.

CONCLUSION

We identified disease-causing mutations in 83.6% in a large Turkish pediatric OI cohort. 40 novel variants were described. Clinical features and long-term follow-up findings of AR inherited OI types and especially very rare biallelic variants were presented for the first time. Unlike previously reported studies, the mutations that we found in P3H1 were all missense, causing a moderate phenotype.

Pan-cancer analysis of osteogenesis imperfecta causing gene SERPINF1

Osteogenesis imperfecta (OI) type VI causative gene SERPINF1, encodes a member of the serpin family that does not display the serine protease inhibitory activity shown by many of the other serpin proteins. The encoded protein (pigment epithelium-derived factor, PEDF) has anti-tumor, anti-angiogenesis, anti-inflammation, nutrition and nerve protection functions, and participates in fat metabolism. In this paper, a series of bioinformatics analyses were conducted based on the regulation of SERPINF1 in the human. Pan-cancer analysis of SERPINF1 revealed it to play a role in the prognosis of tumors, especially in KIRC, and that high expression of SERPINF1 leads to a poor prognosis of the disease, the occurrence of which is largely related to the high expression of SERPINF1 leading to immune infiltration of cancer associated fibroblasts. Mutation analysis found that SERPINF1 had eight identical amino acids alterations sites with different in both cancer and OI patients. which hints the possible relationship between genotype and phenotype.

Biallelic variants in four genes underlying recessive osteogenesis imperfecta

Osteogenesis imperfecta (OI) is an inherited heterogeneous rare skeletal disorder characterized by increased bone fragility and low bone mass. The disorder mostly segregates in an autosomal dominant manner. However, several rare autosomal recessive and X-linked forms, caused by mutations in 18 different genes, have also been described in the literature. Here, we present five consanguineous families segregating OI in an autosomal recessive pattern. Affected individuals in the five families presented severe forms of skeletal deformities. It included frequent bone fractures with abnormal healing, short stature, facial dysmorphism, osteopenia, joint laxity, and severe scoliosis. In order to search for the causative variants, DNA of at least one affected individual in three families (A-C) were subjected to whole exome sequencing (WES). In two other families (D-E), linkage analysis using highly polymorphic microsatellite markers was followed by Sanger sequencing. Sequence analysis revealed two novels and three previously reported disease-causing variants. The two novel homozygous variants including [c.824G > A; p.(Cys275Tyr)] in the SP7 gene and [c.397C > T, p.(Gln133*)] in the SERPINF1 gene were identified in families A and B, respectively. The three previously reported homozygous variants including [c.497G > A; p.(Arg166His)] in the SPARC gene, (c.359-3C > G; intron 2) and [c.677C > T; p.(Ser226Leu)] in the WNT1 gene were identified in family C, D, and E. In conclusion, our findings provided additional evidence of involvement of homozygous sequence variants in the SP7, SERPINF1, SPARC and WNT1 genes causing severe OI. It also highlights the importance of extensive genetic investigations to search for the culprit gene in each case of skeletal deformity.

A novel missense mutation in P4HB causes mild osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a rare heritable bone disorder characterized by low bone mineral density (BMD), recurrent bone fractures, and progressive bone deformities. P4HB encodes protein disulfide isomerase (PDI) and is identified as a novel candidate gene of OI. The purposes of the present study are to detect pathogenic mutation, to evaluate the phenotypes of a Chinese family with mild OI, and to investigate the effects of bisphosphonates on bone of the proband. We detected the pathogenic mutation by next generation sequencing and Sanger sequencing. Laboratory and radiological investigations were conducted to evaluate the phenotypes. The proband was a 12-year-old girl with low BMD, history of recurrent non-traumatic fractures, slight scoliosis, with bluish grey sclera and ligamentous laxity. Her father suffered from one fragility fracture and slight wedge changes of vertebras, with bluish grey sclera. We identified a novel heterozygous missense mutation (c.692A>C, p.His231Pro) in P4HB in the proband and her father. This mutation was predicted to affect the combination of PDI with type I procollagen and lead to the disorder of its triple helix formation. Bisphosphonates were effective in reducing bone resorption and increasing BMD of the proband with well tolerance. In conclusion, we identified a novel mutation in P4HB in a Chinese family with mild OI, which expanded the genotypic and phenotypic spectrum of OI. Bisphosphonates were effective to this extremely rare OI induced by P4HB mutation.

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.

Health-related quality of life in children with osteogenesis imperfecta: a large-sample study

In this large-sample study, we demonstrated that osteogenesis imperfecta (OI) significantly impaired the quality of life (QoL) in children. Moderate/severe OI patients had worse QoL scores than patients with mild OI. Furthermore, the QoL for OI patients was correlated with the presence of pathogenic gene mutations.

INTRODUCTION

Osteogenesis imperfecta (OI) is a hereditary disease characterized by multiple fragility fractures and progressive skeletal deformities. No detailed investigations about the quality of life (QoL) have been carried out in a large sample of patients with OI. We evaluated the QoL and its influencing factors in a large and well-characterized OI cohort.

METHODS

We used a validated questionnaire of PedsQL 4.0 to evaluate the health-related quality of life (HRQoL) of children and adolescents with OI. We compared HRQoL among patients with OI types I, III, and IV. The relationship between HRQoL and pathogenic mutations in candidate OI genes was investigated. We also evaluated the influencing factors of HRQoL in OI patients.

RESULTS

A total of 138 children with OI and 138 healthy controls were enrolled in this study. The HRQoL scores of OI patients were 64.4 ± 30.0, 71.9 ± 22.2, 75.7 ± 24.8, 63.7 ± 24.5, and 68.9 ± 22.0 in physical, emotional, social, school functioning, and total score, respectively, which were significantly lower than those of healthy children (86.5 ± 12.7, 83.3 ± 16.0, 92.1 ± 11.8, 87.5 ± 11.8, and 87.3 ± 10.7, all p < 0.01). Moderate and severe OI (type III/IV) patients had poorer HRQoL scores than patients with mild OI (type I). Gene mutations inducing qualitative defects in type I collagen led to worse HRQoL scores than those with quantitative defects in type I collagen, except in emotional functioning. The total HRQoL score was positively correlated with family income, lumbar, and femoral bone mineral density (BMD) Z-scores and negatively correlated with disease severity and fracture frequency.

CONCLUSION

HRQoL was significantly impaired in OI patients, and patients with more severe OI had poorer HRQoL scores. For the first time, we found that children with qualitative defects in type I collagen had poorer HRQoL scores than those with quantitative defects in type I collagen.

Genetic Regulation of Pigment Epithelium-Derived Factor (PEDF): An Exome-Chip Association Analysis in Chinese Subjects With Type 2 Diabetes

Elevated circulating levels of pigment epithelium-derived factor (PEDF) have been reported in patients with type 2 diabetes (T2D) and its associated microvascular complications. This study aimed to 1) identify the genetic determinants influencing circulating PEDF levels in a clinical setting of T2D, 2) examine the relationship between circulating PEDF and diabetes complications, and 3) explore the causal relationship between PEDF and diabetes complications. An exome-chip association study on circulating PEDF levels was conducted in 5,385 Chinese subjects with T2D. A meta-analysis of the association results of the discovery stage (n = 2,936) and replication stage (n = 2,449) was performed. The strongest association was detected at SERPINF1 (p.Met72Thr; P_combined = 2.06 × 10^-57; β [SE] -0.33 [0.02]). Two missense variants of SMYD4 (p.Arg131Ile; P_combined = 7.56 × 10^-25; β [SE] 0.21 [0.02]) and SERPINF2 (p.Arg33Trp; P_combined = 8.22 × 10^-10; β [SE] -0.15 [0.02]) showed novel associations at genome-wide significance. Elevated circulating PEDF levels were associated with increased risks of diabetic nephropathy and sight-threatening diabetic retinopathy. Mendelian randomization analysis showed suggestive evidence of a protective role of PEDF on sight-threatening diabetic retinopathy (P = 0.085). Our study provided new insights into the genetic regulation of PEDF and further support for its potential application as a biomarker for diabetic nephropathy and sight-threatening diabetic retinopathy. Further studies to explore the causal relationship of PEDF with diabetes complications are warranted.

Novel mutations of the SERPINF1 and FKBP10 genes in Chinese families with autosomal recessive osteogenesis imperfecta

The aim of the present study was to characterize the clinical manifestations and identify the mutations of Serpin family F member 1 (SERPINF1) and FK506 binding protein 10 (FKBP10) genes in Chinese patients with osteogenesis imperfecta (OI). Using whole‑exome sequencing in the first and third probands, a novel mutation was identified in SERPINF1 and a novel compound heterozygous mutation was revealed in FKBP10. Using Sanger sequencing, an additional novel mutation in SERPINF1 was identified in a proband of family 2. In family 1, the proband presented with a novel homozygous missense mutation of the SERPINF1 gene, c.1067T>A (V356E). In family 2, the proband had a novel homozygous deletion mutation of the SERPINF1 gene, c.283+473_643+104del (p.Ala96_Gly215del). Serum pigment‑epithelium‑derived factor concentration was not detected in probands with OI type VI. For both families, the proband's father was demonstrated to have a heterozygous mutation of SERPINF1, whereas no mutations was detected in the probands' mothers. An assessment of allelic copy numbers revealed a deletion of SERPINF1 in the mother of family 1. The results of the present study demonstrate that patients may have mild symptoms of OI with a large fragment deletion in the SERPINF1 gene. Thus, the phenotype of Chinese patients with type VI OI is milder than that of Caucasian and Korean patients. In family 3, the proband displayed a novel compound heterozygous mutation in FKBP10, c.813_814delGA (p.Glu271AspfsX101) and c.831delC (p.Gly278AlafsX20), and did not have Bruck syndrome. Codon 831 of the FKBP10 gene may represent a mutation hotspot for human OI. These results extend both the phenotypic and the genotypic contents of OI patients with SERPINF1 or FKBP10 mutations.

Pigment epithelium derived factor play a positive role in bone mineralization of osteoblasts derived from diabetic patients

Pigment epithelium-derived factor (PEDF) is a multifunctional secreted protein which plays important role in anti-angiogenic, anti-tumorigenic, as well as involves in the metabolism and regeneration of bone. In this study, our aim is to investigate the role of PEDF in regulating mineralization of osteoblasts from diabetic patients (DP). We isolated and cultured osteoblasts derived from DP and non-diabetic patients (NDP), in order to analyze the variable differences via gene expression and calcification assay in vitro. Gene expression analysis and alizarin red S staining revealed that osteoblasts from DP exhibited defective mineralization. PEDF and vascular endothelial growth factor (VEGF) levels were lower in osteoblasts from DP than those from NDP. Interestingly, exogenous PEDF could upregulate the gene expression levels of VEGF and osteoblast-related genes, further to restore mineralization ability in osteoblasts from DP. Our results demonstrated that PEDF played a positive role in maintaining bone development in diabetic osteoblasts, therefore, we confidently believe that PEDF may be a promising cytokine to consider in development of treatments for diabetic bone diseases.