IFITM5 mutations and osteogenesis imperfecta

"Unveiling the genetic symphony: Diversity and expression of chicken IFITM genes in Aseel and Kadaknath breeds"

In this investigation, single nucleotide variants (SNVs) within the chicken interferon-inducible transmembrane protein (chIFITM) genes were explored in Aseel and Kadaknath breeds. Comparative analysis with the GRCg6a reference genome revealed 9 and 16 SNVs in the chIFITM locus for Aseel and Kadaknath breeds, respectively. When referencing the Genome Reference Consortium GRCg7b, Kadaknath exhibited 10 variants, contrasting with none in Aseel. Notably, 17, 8, 2, and 5 SNVs were identified in chIFITM1, chIFITM2, chIFITM3, and chIFITM5 genes, with chIFITM1 showing the highest polymorphism in Kadaknath, featuring 10 intronic variants, including three SNVs (rs16457112, rs16457111, and rs313341707) common to both breeds. Two synonymous exonic variants (g.1817767C > A and g.1819102C > T) were also noted in chIFITM1. Although chIFITM protein sequences were generally conserved, genetic variations clustered predominantly in UTR and intronic regions. Examination of immune response dynamics in live embryos uncovered notable variations in chIFITM gene expression across diverse organs and chicken breeds. Specifically, chIFITM1 mRNA was abundant in cecal tonsils for both breeds and bursa of Aseel (7.61 folds), but it was absent in the heart and lung tissues of both breeds. Conversely, chIFITM3 consistently exhibited heightened expression, particularly in bursa of Aseel (10.23 folds). Whereas mRNA of the chIFITM2 gene was found to be abundant in the heart of Kadaknath (11.03 folds) and lung of both breeds. Furthermore, the expression pattern of chIFITM5 diverged between the two breeds, the heart of Kadaknath chickens showed highest (10.45 folds). The study discovered that breed-specific genetic variants within these genes present a potential pathway for selection and breeding to improve disease resistance in chicken. The observed genetic variation among chicken populations highlights the critical importance of these variants in reinforcing virus resistance, exhibiting applicability across a wide range of breeds.

The 'dispanins' and related proteins in physiology and neurological disease

The dispanins are a family of 15 transmembrane proteins that have diverse and often unclear physiological functions. Many dispanins, including synapse differentiation induced gene 1 (SynDIG1), proline-rich transmembrane protein 1 (PRRT1)/SynDIG4, and PRRT2, are expressed in the central nervous system (CNS), where they are involved in the development of synapses, regulation of neurotransmitter release, and interactions with ion channels, including AMPA receptors (AMPARs). Others, including transmembrane protein 233 (TMEM233) and trafficking regulator of GLUT4-1 (TRARG1), are expressed in the peripheral nervous system (PNS); however, the function of these dispanins is less clear. Recently, a family of neurotoxins isolated from the giant Australian stinging tree was shown to target TMEM233 to modulate the function of voltage-gated sodium (NaV) channels, suggesting that the dispanins are inherently druggable. Here, we review current knowledge about the structure and function of the dispanins, in particular TMEM233 and its two most closely related homologs PRRT2 and TRARG1, which may be drug targets involved in neurological disease.

The IFITM5 mutation in osteogenesis imperfecta type V is associated with an ERK/SOX9-dependent osteoprogenitor differentiation defect

Osteogenesis imperfecta (OI) type V is the second most common form of OI, distinguished by hyperplastic callus formation and calcification of the interosseous membranes, in addition to the bone fragility. It is caused by a recurrent, dominant pathogenic variant (c.-14C>T) in interferon-induced transmembrane protein 5 (IFITM5). Here, we generated a conditional Rosa26-knockin mouse model to study the mechanistic consequences of the recurrent mutation. Expression of the mutant Ifitm5 in osteo-chondroprogenitor or chondrogenic cells resulted in low bone mass and growth retardation. Mutant limbs showed impaired endochondral ossification, cartilage overgrowth, and abnormal growth plate architecture. The cartilage phenotype correlates with the pathology reported in patients with OI type V. Surprisingly, expression of mutant Ifitm5 in mature osteoblasts caused no obvious skeletal abnormalities. In contrast, earlier expression in osteo-chondroprogenitors was associated with an increase in the skeletal progenitor cell population within the periosteum. Lineage tracing showed that chondrogenic cells expressing the mutant Ifitm5 had decreased differentiation into osteoblastic cells in diaphyseal bone. Moreover, mutant IFITM5 disrupted early skeletal homeostasis in part by activating ERK signaling and downstream SOX9 protein, and inhibition of these pathways partially rescued the phenotype in mutant animals. These data identify the contribution of a signaling defect altering osteo-chondroprogenitor differentiation as a driver in the pathogenesis of OI type V.

IFITM5-related (type V) osteogenesis imperfecta with evidence of perinatal involvement: A case report

Osteogenesis imperfecta (OI) is a rare hereditary disorder characterized by bone fragility and frequent fractures. While most cases are attributed to variations in collagen-coding genes COL1A1 and COL1A2, other genes such as IFITM5 have also been associated with the disease, accounting for up to 5 % of cases. Here, we report a case of a 3-month-old female with a femur fracture and limb deformity. X-rays revealed evidence of osteopenia and previous fractures in the arms, clavicle, ribs, and left limb, alongside prenatal bone deformities detected by ultrasound. Initial clinical evaluation suggested progressively deforming (Sillence's type III) osteogenesis imperfecta (OI). Molecular testing led to the diagnosis of IFITM5-related OI, identifying the c.-14C>T (rs587776916) variant. Although this variant has been previously reported in patients with IFITM5-related OI, prenatal involvement had not been associated with this variant.

Engineered interleukin-6-derived cytokines recruit artificial receptor complexes and disclose CNTF signaling via the OSMR

Ciliary neurotrophic factor (CNTF) activates cells via the non-signaling α-receptor CNTF receptor (CNTFR) and the two signaling β-receptors glycoprotein 130 (gp130) and leukemia inhibitory factor receptor (LIFR). The CNTF derivate, Axokine, was protective against obesity and insulin resistance, but clinical development was halted by the emergence of CNTF antibodies. The chimeric cytokine IC7 used the framework of interleukin (IL-)6 with the LIFR-binding site from CNTF to activate cells via IL-6R:gp130:LIFR complexes. Similar to CNTF/Axokine, IC7 protected mice from obesity and insulin resistance. Here, we developed CNTF-independent chimeras that specifically target the IL-6R:gp130:LIFR complex. In GIL-6 and GIO-6, we transferred the LIFR binding site from LIF or OSM to IL-6, respectively. While GIO-6 signals via gp130:IL-6R:LIFR and gp130:IL-6R:OSMR complexes, GIL-6 selectively activates the IL-6R:gp130:LIFR receptor complex. By re-evaluation of IC7 and CNTF, we discovered the Oncostatin M receptor (OSMR) as an alternative non-canonical high-affinity receptor leading to IL-6R:OSMR:gp130 and CNTFR:OSMR:gp130 receptor complexes, respectively. The discovery of OSMR as an alternative high-affinity receptor for IC7 and CNTF designates GIL-6 as the first truly selective IL-6R:gp130:LIFR cytokine, whereas GIO-6 is a CNTF-free alternative for IC7.

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.

Osteogenesis imperfecta: a cross-sectional study of skeletal and extraskeletal features in a large cohort of Italian patients

Introduction

The present study aims to describe a large cohort of Italian patients affected by osteogenesis imperfecta, providing a picture of the clinical bony and non-bony features and the molecular background to improve knowledge of the disease to inform appropriate management in clinical practice.

Methods

A total of 568 subjects (from 446 unrelated Italian families) affected by osteogenesis imperfecta who received outpatient care at Istituto Ortopedico Rizzoli from 2006 to 2021 were considered in the present study.

Results

Skeletal and extraskeletal features were analyzed showing a lower height (mean z-scores equal to -1.54 for male patients and -1.47 for female patients) compared with the general Italian population. Half of the patient population showed one or more deformities, and most of the patients had suffered a relatively low number of fractures (<10). An alteration in the sclera color was identified in 447 patients. Similarly, several extraskeletal features, like deafness, dental abnormalities, and cardiac problems, were investigated. Additionally, inheritance and genetic background were evaluated, showing that most of the patients have a positive family history and the majority of pathogenic variants detected were on collagen genes, as per literature.

Conclusion

This study supports the definition of a clear picture of the heterogeneous clinical manifestations leading to variable severity in terms of skeletal and extra-skeletal traits and of the genetic background of an Italian population of osteogenesis imperfecta patients. In this perspective, this clearly highlights the crucial role of standardized and structured collection of high-quality data in disease registries particularly in rare disease scenarios, helping clinicians in disease monitoring and follow-up to improve clinical practice.

Coding and noncoding RNA profile of human heterotopic ossifications - Risk factors and biomarkers

Heterotopic ossification (HO) means the formation of bone in muscles and soft tissues, such as ligaments or tendons. HO could have a genetic history or develop after a traumatic event, as a result of muscle injury, fractures, burns, surgery, or neurological disorders. Many lines of evidence suggest that the formation of HO is related to the pathological differentiation of stem or progenitor cells present within soft tissues or mobilized from the bone marrow. The cells responsible for the initiation and progression of HO are generally called HO precursor cells. The exact mechanisms behind the development of HO are not fully understood. However, several factors have been identified as potential contributors. For example, local tissue injury and inflammation disturb soft tissue homeostasis. Inflammatory cells release growth factors and cytokines that promote osteogenic or chondrogenic differentiation of HO precursor cells. The bone morphogenetic protein (BMP) is one of the main factors involved in the development of HO. In this study, next-generation sequencing (NGS) and RT-qPCR were performed to analyze the differences in mRNA, miRNA, and lncRNA expression profiles between muscles, control bone samples, and HO samples coming from patients who underwent total hip replacement (THR). As a result, crucial changes in the level of gene expression between HO and healthy tissues were identified. The bioinformatic analysis allowed to describe the processes most severely impacted, as well as genes which level differed the most significantly between HO and control samples. Our analysis showed that the level of transcripts involved in leukocyte migration, differentiation, and activation, as well as markers of chronic inflammatory diseases, that is, miR-148, increased in HO, as compared to muscle. Furthermore, the levels of miR-195 and miR-143, which are involved in angiogenesis, were up-regulated in HO, as compared to bone. Thus, we suggested that inflammation and angiogenesis play an important role in HO formation. Importantly, we noticed that HO is characterized by a higher level of TLR3 expression, compared to muscle and bone. Thus, we suggest that infection may also be a risk factor in HO development. Furthermore, an increased level of transcripts coding proteins involved in osteogenesis and signaling pathways, such as ALPL, SP7, BGLAP, BMP8A, BMP8B, SMPD3 was noticed in HO, as compared to muscles. Interestingly, miR-99b, miR-146, miR-204, and LINC00320 were up-regulated in HO, comparing to muscles and bone. Therefore, we suggested that these molecules could be important biomarkers of HO formation and a potential target for therapies.

The novel role of IFITM1-3 in myogenic differentiation of C2C12 cells

Interferon-induced transmembrane proteins (IFITMs 1, 2, and 3) play a critical role in preventing pathogen infection in vertebrates. They are also involved in the occurrence and prognosis of cancer. Myogenesis is a complex process regulated by several factors. This study disclosed that Ifitm1-3 were upregulated in the process of myogenic differentiation of C2C12 myoblasts on days 3, 5, and 7. This positively correlated with the expression of differentiation factors MyoD, myogenin, Mrf5, and desmin. Furthermore, knockdown of Ifitm1-3 by their individual siRNAs inhibited myogenesis of C2C12 myoblasts, with relative downregulation of MyoD, myogenin, Mrf5, and desmin. Subsequently, myotube formation and fusion percentage decreased. Co-immunoprecipitation combined with LC-MS/MS analysis uncovered the interaction proteins of IFITM1 and IFITM3 in C2C12 myoblasts. A total of 84 overlapped interaction proteins of IFITM1 and IFITM3 were identified, and one of the clusters was engaged in cytoskeletal and sarcomere proteins, including desmin, myosin, actin, vimentin, nestin, ankycorbin, and nucleolin. Hence, we hypothesize that these interacting proteins may function as scaffolds for IFITM1-3, possibly through the interaction protein desmin to initiate further interaction with other proteins to participate in myogenesis; however, the molecular mechanisms remain unclear. Our study may contribute to the development of novel therapeutics for myopathic diseases.

Skeletal dysplasia-causing TRPV4 mutations suppress the hypertrophic differentiation of human iPSC-derived chondrocytes

Mutations in the TRPV4 ion channel can lead to a range of skeletal dysplasias. However, the mechanisms by which TRPV4 mutations lead to distinct disease severity remain unknown. Here, we use CRISPR-Cas9-edited human-induced pluripotent stem cells (hiPSCs) harboring either the mild V620I or lethal T89I mutations to elucidate the differential effects on channel function and chondrogenic differentiation. We found that hiPSC-derived chondrocytes with the V620I mutation exhibited increased basal currents through TRPV4. However, both mutations showed more rapid calcium signaling with a reduced overall magnitude in response to TRPV4 agonist GSK1016790A compared to wildtype (WT). There were no differences in overall cartilaginous matrix production, but the V620I mutation resulted in reduced mechanical properties of cartilage matrix later in chondrogenesis. mRNA sequencing revealed that both mutations up-regulated several anterior HOX genes and down-regulated antioxidant genes CAT and GSTA1 throughout chondrogenesis. BMP4 treatment up-regulated several essential hypertrophic genes in WT chondrocytes; however, this hypertrophic maturation response was inhibited in mutant chondrocytes. These results indicate that the TRPV4 mutations alter BMP signaling in chondrocytes and prevent proper chondrocyte hypertrophy, as a potential mechanism for dysfunctional skeletal development. Our findings provide potential therapeutic targets for developing treatments for TRPV4-mediated skeletal dysplasias.

A Patient with Bone Fragility, Multiple Fractures, Osteosarcoma, and the Variant c.143A>G in the IFITM5 Gene: A Case Report

Osteogenesis imperfecta (OI) is a group of genetic skeletal disorders, with a prevalence of 1 in 15,000-20,000 births. OI type V has been described in approximately 150 cases and all patients carry the variant (c.-14C> T) in the IFITM5 gene. However, two other variants, p.S40L and p.N48S have been reported in this gene, leading to clinical phenotypes different from OI type V. Here we described a patient with multiple bone fractures, scoliosis, skull alteration (plagiocephaly), bone deformation, bone rickets, and intramedullary epithelioid osteosarcoma that bears the recently reported heterozygous variant c.143A>G (p.N48S) in the IFITM5 gene. This case supports the pathogenicity of this new variant in the IFITM5 gene and adds information regarding its clinical phenotype.

Does the c.-14C>T Mutation in the IFITM5 Gene Provide Identical Phenotypes for Osteogenesis Imperfecta Type V? Data from Russia and a Literature Review

Osteogenesis imperfecta (OI) is a large group of genetically heterogeneous diseases resulting from decreased bone density and an abnormal microarchitecture, which are clinically manifested by abnormal bone fractures. A distinctive clinical feature of this group of diseases is the presence of spontaneous fractures and skeletal deformities. However, the clinical manifestations of different types of OI are characterized by marked polymorphism with variable severity of skeletal and extra-skeletal features. Previous studies have shown that a mutation (c.-14C>T) in the IFITM5 gene is responsible for autosomal dominant OI type V. However, the mutation has a variable expression pattern and marked clinical heterogeneity. In this study, a clinical and genetic analysis of 12 cases with molecularly confirmed OI type V from 12 unrelated families was performed. Significant clinical heterogeneity of the disease with the same molecular defect was detected. In six subjects (50%), there were no classic signs of OI type V (formation of a hyperplastic bone callus, calcification of the interosseous membrane and dislocation of the radial head). In all cases, the mutation occurred de novo.

Specific Characteristic of Hyperplastic Callus in a Larger Cohort of Osteogenesis Imperfecta Type V

Hyperplastic callus (HPC) is the most conspicuous features of osteogenesis imperfecta (OI) type V, of which accurate diagnosis and treatment are facing challenges. We investigate the clinical features, and impact factors of HPC in OI type V patients. In this retrospective single-center study, a total of 21 patients with type V OI confirmed by IFITM5 mutation were included. Radiological characteristics of bone were evaluated by X-rays, dual-energy X-ray absorptiometry, and computed tomography scan. Bone biopsy specimens were performed and stained by routine hematoxylin-eosin. The effects of bisphosphonates on HPC were investigated. Eleven patients (52.3%) had HPCs at 19 skeletal sites, 11 of which affected the femur. Three patients developed four (21.1%) HPCs after fractures, and 15 (78.9%) HPCs occurred in absence of bone fracture. The progress of HPCs was variable, of which most HPCs enlarged in the initial phase and remained stable, and only one HPC dwindled in size. One patient had a rapidly growing mass on the right humerus, and biopsy showed irregular trabeculae of woven bone and immature bone and cartilage in the loose and edematous collagenous network without signs of tumor. Bisphosphonates treatment had no significant effects on HPC of OI patients. HPC is the specific characteristic of OI type V patients, and its location, shape, size, and progression are variable, and the femur is the most frequently involved site. It is very important to make a diagnosis of HPC through detecting IFITM5 mutation and completing pathological diagnosis if necessary. The treatment of HPC is worth further exploration.

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.

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: Mechanisms and Signaling Pathways Connecting Classical and Rare OI Types

Osteogenesis imperfecta (OI) is a phenotypically and genetically heterogeneous skeletal dysplasia characterized by bone fragility, growth deficiency, and skeletal deformity. Previously known to be caused by defects in type I collagen, the major protein of extracellular matrix, it is now also understood to be a collagen-related disorder caused by defects in collagen folding, posttranslational modification and processing, bone mineralization, and osteoblast differentiation, with inheritance of OI types spanning autosomal dominant and recessive as well as X-linked recessive. This review provides the latest updates on OI, encompassing both classical OI and rare forms, their mechanism, and the signaling pathways involved in their pathophysiology. There is a special emphasis on mutations in type I procollagen C-propeptide structure and processing, the later causing OI with strikingly high bone mass. Types V and VI OI, while notably different, are shown to be interrelated by the interferon-induced transmembrane protein 5 p.S40L mutation that reveals the connection between the bone-restricted interferon-induced transmembrane protein-like protein and pigment epithelium-derived factor pathways. The function of regulated intramembrane proteolysis has been extended beyond cholesterol metabolism to bone formation by defects in regulated membrane proteolysis components site-2 protease and old astrocyte specifically induced-substance. Several recently proposed candidate genes for new types of OI are also presented. Discoveries of new OI genes add complexity to already-challenging OI management; current and potential approaches are summarized.

X-Linked Osteogenesis Imperfecta Possibly Caused by a Novel Variant in PLS3

Osteogenesis imperfecta (OI) represents a complex spectrum of genetic bone diseases that occur primarily due to mutations and deletions of the COL1A1 and COL1A2 genes. Recent molecular studies of the network of signaling pathways have contributed to a better understanding of bone remodeling and the pathogenesis of OI caused by mutations in many other genes associated with normal bone mineralization. In this paper, a case of a rare X-linked variant of OI with a change in the gene encoding plastin 3—a protein important for the regulation of the actin cytoskeleton, is presented. A 16-year-old patient developed ten bone fractures caused by minor trauma or injury, including a compression fracture of the second lumbar vertebra during his lifetime. Next-generation sequencing analysis did not show pathologically relevant deviations in the COL1A1 and COL1A2 genes. Targeted gene analyses (Skeletal disorder panel) of the patient, his father, mother and sister were then performed, detecting variants of uncertain significance (VUS) for genes PLS3, FN1 and COL11A2. A variant in the PLS3 gene were identified in the patient, his mother and sister. Since the PLS3 gene is located on the X chromosome, the mother and sister showed no signs of the disease. Although the variant in the PLS3 gene (c.685G>A (p.Gly229Arg)) has not yet been described in the literature, nor is its pathogenicity known, clinical findings combined with genetic testing showed that this variant may explain the cause of X-linked OI in our patient. This rare case of the PLS3 variant of X-linked OI might point to a novel target for personalized therapy in patients with this severe disease.

Integrative overview of IFITMs family based on Bioinformatics analysis

Human interferon-induced transmembrane proteins (IFITMs) family is a multi-functional biomacromolecule family playing a critical role in various physiological processes, such as, antiviral immunity, tumor suppression, and bone formation. Although there are many studies proving that a subset of tumors strongly links to the changes of IFITMs, the link between different IFITMs mutant types and diverse tumors has not been studied thoroughly. To investigate the law of expression among IFITMs internal members and the linking of IFITMs mutant types and cancers, online databases were used to pool together relevant data for bioinformatics analysis. Here, we summarize mutations, expression, and functions of human IFITMs, analyze diverse expression levels of IFITMs in physiological and pathological tissues, predict protein-protein interaction (PPI) networks, and target miRNAs and relevant signaling pathways of IFITMs. The results show that IFITM1, IFITM2, and IFITM3 have similar motif pattern constructions and physiological functions, while IFITM5 and IFITM10 show far diversity from them. Particularly, IFITM1-3, in conjunction with interacting proteins, is strongly related to development and overall survival rates of a portion of cancers, including renal cancer and uveal melanoma (UVM). This trait may make IFITM1-3 become a prognostic marker of cancers. Meanwhile, hsa_circ_0116375 has been found as the common circRNA for IFITM2, IFITM3, IFITM5, and IFITM10.

Collagen transport and related pathways in Osteogenesis Imperfecta

Osteogenesis Imperfecta (OI) comprises a heterogeneous group of patients who share bone fragility and deformities as the main characteristics, albeit with different degrees of severity. Phenotypic variation also exists in other connective tissue aspects of the disease, complicating disease classification and disease course prediction. Although collagen type I defects are long established as the primary cause of the bone pathology, we are still far from comprehending the complete mechanism. In the last years, the advent of next generation sequencing has triggered the discovery of many new genetic causes for OI, helping to draw its molecular landscape. It has become clear that, in addition to collagen type I genes, OI can be caused by multiple proteins connected to different parts of collagen biosynthesis. The production of collagen entails a complex process, starting from the production of the collagen Iα1 and collagen Iα2 chains in the endoplasmic reticulum, during and after which procollagen is subjected to a plethora of posttranslational modifications by chaperones. After reaching the Golgi organelle, procollagen is destined to the extracellular matrix where it forms collagen fibrils. Recently discovered mutations in components of the retrograde transport of chaperones highlight its emerging role as critical contributor of OI development. This review offers an overview of collagen regulation in the context of recent gene discoveries, emphasizing the significance of transport disruptions in the OI mechanism. We aim to motivate exploration of skeletal fragility in OI from the perspective of these pathways to identify regulatory points which can hint to therapeutic targets.

The evolution of the nosology of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a relatively common genetic skeletal disorder with an estimated frequency of 1 in 20 000 worldwide. The manifestations are diverse and although individually rare, the several different forms contribute to the production of a significant number of affected individuals with considerable morbidity and mortality. During the last decade, there have been extensive molecular investigations into the etiology of OI and these advances have direct relevance to the medical management of the disorder, and the purpose of this review is to document the history and evolution of the nosology of OI. The current nosology, based on molecular concepts, which are crucial in the identification of genotype-phenotype correlations in persons with OI, is also outlined. The successive revisions of the nosology and classification of OI have highlighted the importance of the nomenclature of the condition in order for it to be recognized by clinicians, scientists and patient advocacy groups. In this way, improved counseling of patients and individualized, tailored therapeutic approaches based on the underlying pathophysiology of the individual's type of OI have been facilitated.

A novel variant of the IFITM5 gene within the 5'-UTR causes neonatal transverse clavicular fracture: Expanding the genetic spectrum

Background

Osteogenesis imperfecta (OI) type V is a rare heritable bone disorder caused by pathogenic variants of IFITM5. Only two mutated alleles in IFITM5 have been identified worldwide, the role of which in OI pathology is not fully understood.

Methods

A neonatal case of suspected OI, clinically manifested as a rare clavicle transection fracture with delayed early fracture healing, was studied. Subtle variants of OI‐associated genes were analyzed by whole exome sequencing and confirmed by Sanger sequencing.

Results

A de novo heterozygous pathogenic variant of IFITM5 within the 5′‐UTR (c.‐9C > A) was discovered in the proband. Bioinformatics analysis using a combination of various algorithms predicted that the variant would generate a new in‐frame start codon 9 bp upstream of the original and express a mutant IFITM5 protein with three additional amino acids (Met‐Glu‐Pro). After transfection into a eukaryocyte in vitro, the mutant IFITM5 construct produced a longer transcription product than that of wild‐type IFITM5.

Conclusion

This study identified a novel pathogenic variant of IFITM5, which not only manifested the molecular characteristics of IFITM5, but also provided new evidence for the study of the molecular mechanisms of IFITM5 association with OI.

A novel Ser40Trp variant in IFITM5 in a family with osteogenesis imperfecta and review of the literature

Osteogenesis imperfecta, is a genetically and clinically heterogeneous connective tissue disorder that disrupts bone architecture, making it fragile and more prone to fractures. While more than 85% of cases are due to variants in COL1A1 and COL1A2, variants in noncollagen genes have been identified in the remaining cases. The recurring heterozygous variant in IFITM5 (c.-14C>T) leads to osteogenesis imperfecta type V, a second missense variant in IFITM5 (c.119C>T, p.Ser40Leu) leads to phenotype resembling osteogenesis imperfecta type VI. In this report, we describe the first patient with Ser40Trp variant in IFITM5, who presented with multiple fractures in the prenatal period. She remained fracture free after birth (except for trauma-related fractures during puberty) with normal bone mineral densitometry. Her mother, who did not have a history of fracture, was noted to have somatogonadal mosaicism for this variant and became pregnant with a second child with multiple prenatal fractures, found to have the same variant. To our knowledge, this is the first case of somatogonadal mosaicism in IFITM5. In addition, we have summarized the literature on patients presenting with variant in codon 40 (serine) of IFTIM5 protein.

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.

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.

Expanding the Clinical Spectrum of Osteogenesis Imperfecta Type V: 13 Additional Patients and Review

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder characterized by bone fragility and is characterized by clinical and genetic heterogeneity. Previous studies showed that the same mutation (c.-14C> T) of the IFITM5 gene is responsible for autosomal dominant OI type V. However, the mutation has a variable expressivity. Clinical heterogeneity has been recognized in OI type V. In this study, we investigated 13 individuals with molecularly confirmed OI type V from seven Chinese families and explored the genotype-phenotype relationship. Increased callus formation is not observed in all individuals, and several novel clinical features were described: joint contractures (three individuals) and unexplained hip arthritis (six individuals). Significant clinical variability was observed even within families. Specific facial features were observed in six individuals from two families consistent with the facial features associated with OI type V reported so far in the literature. Interestingly, we report the process of hypertrophic callus formation in detail for the first time, and in five individuals with hyperplastic callus, increased erythrocyte sedimentation rate (ESR) and levels of C-reactive protein (C-RP) were measured, suggestive of inflammatory activation.

MECHANISMS IN ENDOCRINOLOGY: Genetics of human bone formation

Throughout life, bone is continuously remodelled to be able to fulfil its multiple functions. The importance of strictly regulating the bone remodelling process, which is defined by the sequential actions of osteoclasts and osteoblasts, is shown by a variety of disorders with abnormalities in bone mass and strength. The best known and most common example of such a disorder is osteoporosis, which is marked by a decreased bone mass and strength that consequently results in an increased fracture risk. As osteoporosis is a serious health problem, a large number of studies focus on elucidating the aetiology of the disease as well as on the identification of novel therapeutic targets for the treatment of osteoporotic patients. These studies have demonstrated that a large amount of variation in bone mass and strength is often influenced by genetic variation in genes encoding important regulators of bone homeostasis. Throughout the years, studies into the genetic causes of osteoporosis as well as several rare monogenic disorders with abnormal high or low bone mass and strength have largely increased the knowledge on regulatory pathways important for bone resorption and formation. This review gives an overview of genes and pathways that are important for the regulation of bone formation and that are identified through their involvement in monogenic and complex disorders with abnormal bone mass. Furthermore, novel bone-forming strategies for the treatment of osteoporosis that resulted from these discoveries, such as antibodies against sclerostin, are discussed as well.

Pharmacological and biological therapeutic strategies for osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized by bone fragility, low bone mass, and bone deformities. The majority of cases are caused by autosomal dominant pathogenic variants in the COL1A1 and COL1A2 genes that encode type I collagen, the major component of the bone matrix. The remaining cases are caused by autosomal recessively or dominantly inherited mutations in genes that are involved in the post-translational modification of type I collagen, act as type I collagen chaperones, or are members of the signaling pathways that regulate bone homeostasis. The main goals of treatment in OI are to decrease fracture incidence, relieve bone pain, and promote mobility and growth. This requires a multi-disciplinary approach, utilizing pharmacological interventions, physical therapy, orthopedic surgery, and monitoring nutrition with appropriate calcium and vitamin D supplementation. Bisphosphonate therapy, which has become the mainstay of treatment in OI, has proven beneficial in increasing bone mass, and to some extent reducing fracture risk. However, the response to treatment is not as robust as is seen in osteoporosis, and it seems less effective in certain types of OI, and in adult OI patients as compared to most pediatric cases. New pharmacological treatments are currently being developed, including anti-resorptive agents, anabolic treatment, and gene- and cell-therapy approaches. These therapies are under different stages of investigation from the bench-side, to pre-clinical and clinical trials. In this review, we will summarize the recent findings regarding the pharmacological and biological strategies for the treatment of patients with OI. © 2016 Wiley Periodicals, Inc.

An atypical fracture in male patient with osteogenesis imperfecta

So-called atypical fractures have been related to prolonged treatment with bisphosphonates. Although there remain unanswered questions with respect to their etiology and physiopathology, it does appear to be a causal relationship. There are many references in the literature about this problem in patients in whom these drugs have been used to treat osteoporosis, but few reports in patients who have received this therapy for the management of osteogenesis imperfecta. The Authors describe a case of a young male patient with osteogenesis imperfecta with a number of historical fractures, and who received treatment with these drugs, initially parenterally and subsequently orally, presenting as a complication of the treatment, an atypical diaphyseal femoral fracture. The characteristics of the fracture are consistent with the updated diagnostic criteria of the American Society for Bone and Mineral Research. The clinical case, its treatment, both surgically and metabolically with teriparatide, and its development over a year, are analysed. The case is notable for, on the one hand, the significance of the presence of this type of fracture in a young patient with this disease, and on the other, because of the administration of teriparatide outside its established clinical indications, with twin objectives: to improve the bone structure of the patient's underlying disease, and to counteract the harmful effects which bisphosphonates may have on this bone.