Mutations in SERPINF1 cause osteogenesis imperfecta type VI

Osteogenesis imperfecta (OI) is a spectrum of genetic disorders characterized by bone fragility. It is caused by dominant mutations affecting the synthesis and/or structure of type I procollagen or by recessively inherited mutations in genes responsible for the posttranslational processing/trafficking of type I procollagen. Recessive OI type VI is unique among OI types in that it is characterized by an increased amount of unmineralized osteoid, thereby suggesting a distinct disease mechanism. In a large consanguineous family with OI type VI, we performed homozygosity mapping and next‐generation sequencing of the candidate gene region to isolate and identify the causative gene. We describe loss of function mutations in serpin peptidase inhibitor, clade F, member 1 (SERPINF1) in two affected members of this family and in an additional unrelated patient with OI type VI. SERPINF1 encodes pigment epithelium–derived factor. Hence, loss of pigment epithelium–derived factor function constitutes a novel mechanism for OI and shows its involvement in bone mineralization. © 2011 American Society for Bone and Mineral Research     

Risk of new vertebral fractures in patients with adrenal incidentaloma with and without subclinical hypercortisolism: A multicenter longitudinal study

In patients with adrenal incidentalomas (AIs), cross‐sectional studies suggested the presence of an association between subclinical hypercortisolism (SH) and an increased prevalence of vertebral fractures (VFx) and spinal deformity index (SDI), which is a clinical index of bone quality. No longitudinal studies investigated the incidence of VFx and SDI changes over time in SH. The aim of this study was to evaluate VFx risk and SDI changes in SH over time. One‐hundred‐three consecutive AI patients were studied at baseline and after 12 and 24 months. Patients were divided into SH⁺ (n = 27) and SH^– (n = 76) groups on the basis of the presence of two or more among urinary free cortisol greater than 70 µg/24 hours, serum cortisol after 1‐mg dexamethasone suppression test greater than 3.0 µg/dL, and adrenocorticotropic hormone (ACTH) less than 10 pg/mL in 2 or more of the 3 evaluations. At baseline and after 24 months, bone mineral density (BMD) by dual‐energy X‐ray absorptiometry and the presence of VFx and SDI by summing the grade of deformity for each vertebra were evaluated. At the end of follow‐up, the SH⁺ group showed a higher prevalence of VFx (81.5%) as compared with baseline (55.6%, p = .04) and a worsening of SDI (2.11 ± 1.85 versus 1.11 ± 1.47, p = .032) associated with SH regardless of age, gender, body mass index , BMD, baseline SDI, menopause duration [odds ratio (OR) = 12.3, 95% confidence interval (CI) 4.1–36.5, p = .001]. The incidence of new vertebral fractures was higher in the SH⁺ group (48%) than in the SH^– group (13%; p = .001). It is concluded that subclinical hypercortisolism is associated with an increased risk of VFx and a possible deterioration of bone quality. © 2011 American Society for Bone and Mineral Research     

COL1A1新发突变致儿童成骨不全症 1 例报道并文献复习

目的分析一例I型成骨不全症(osteogenesis imperfecta,OI)患儿的临床特点,并研究患者及其家系的基因突变情况及致病性鉴定。方法详细询问病史,分析骨转换指标、骨密度、骨骼X线特点。采用高通量测序法,对患儿骨病检测包225个相关致病基因各外显子编码区域的序列变异情况进行检测分析,采用PCR结合Sanger测序的方法验证突变位点变异情况。结果骨标志物提示高转换水平,影像学提示骨量低下,四肢长骨纤细、骨皮质变薄,基因检测发现患儿COL1A1基因编码区杂合变异c.2911_2912insAG(p.G971Efs*138),经Mutation Taster预测显示为致病性突变。先证者母亲、父亲以及妹妹均未携带该突变基因。结论发现了OI患者COL1A1基因新的突变位点c.2911_2912insAG(p.G971Efs*138),丰富了中国人OI群体COL1A1基因致病突变谱。     

The identification of novel mutations in COL1A1, COL1A2, and LEPRE1 genes in Chinese patients with osteogenesis imperfecta

Dominant inheritance of osteogenesis imperfecta (OI) is caused by mutations in COL1A1 or COL1A2, the genes that encode type I collagen, and CRTAP, LEPRE1, PPIB, FKBP10, SERPINH1, and SP7 mutations were recently detected in a minority of patients with autosomal recessive OI. However, these findings have been mostly restricted to Western populations. The proportion of mutations and the correlations between genotype and phenotype in Chinese patients with OI are completely unknown. In this study, mutation analyses were performed for COL1A1, COL1A2, CRTAP, and LEPRE1 in a cohort of 58 unrelated Chinese patients with OI; the relationship between collagen type I mutations and clinical features was examined. A total of 56 heterozygous mutations were identified in COL1A1 and COL1A2, including 43 mutations in COL1A1 and 13 mutations in COL1A2. Among the 56 causative COL1A1 and COL1A2 mutations, 24 novel mutations were found, and 25 (44.6%) resulted in the substitution of a glycine within the Gly-X-Y triplet domain of the triple helix. Compared with COL1A1 haploinsufficiency (n?=?23), patients with mutations affecting glycine residues had a severe skeletal phenotype. In patients 18?years of age or older, on average patients with COL1A1 haploinsufficiency were taller and had higher femoral neck bone mineral density than with patients with helical mutations. Interestingly, we found two novel compound heterozygous mutations in the LEPRE1 gene in two unrelated families with autosomal recessive OI. Although the genotype?Cphenotype correlation is still unclear, our findings are useful to understand the genetic basis of Chinese patients with OI.     

Changes in bone biomarker concentrations and musculoskeletal symptoms among breast cancer patients initiating aromatase inhibitor therapy and women without a history of cancer

The objectives of this study were to examine: (1) changes in bone formation (osteocalcin) and bone resorption (cross-linked N-telopeptides of bone type I collagen [NTXs]) markers, as well as calcium, phosphorus, and intact parathyroid hormone, over the first 6 months of aromatase inhibitor (AI) therapy among a cohort of breast cancer patients compared with a group of unexposed women without a history of cancer; and (2) whether bone marker changes were associated with musculoskeletal pain. Eligible breast cancer patients (n = 49) and postmenopausal women without a history of cancer (n = 117) were recruited and followed for 6 months. At baseline, 3 months, and 6 months, a questionnaire was administered to assess pain and medication use, and a blood sample was drawn. Results showed that, among the breast cancer patients, calcium concentrations decreased significantly (−7.8% change; p = 0.013) and concentrations of NTXs increased significantly from baseline to 6 months (9.6% change; p = 0.012). Changes were not observed for women in the comparison group. Statistically significant differences in percent change between the breast cancer patients and the women in the comparison group were observed for calcium at 6 months (−7.8% versus 0.0%; p = 0.025), phosphorus at 6 months (−5.1% versus 16.7%; p = 0.003), NTXs at 6 months (9.6% versus −0.7%; p = 0.017), and osteocalcin at 6 months (11.5% versus −3.6%; p = 0.016). No statistically significant associations were observed between bone turnover marker changes and musculoskeletal pain among the breast cancer patients, although baseline NTXs were higher among women with onset or increase in pain compared with those reporting no pain (p = 0.08). Findings from this study suggest that AIs cause changes in bone turnover during the first 6 months of treatment; however, these changes are not associated with musculoskeletal pain. Breast cancer patients initiating AI therapy should be assessed and monitored for fracture risk using known clinical risk factors, including bone density, and managed appropriately. © 2012 American Society for Bone and Mineral Research.     

A scoring system for the assessment of clinical severity in osteogenesis imperfecta

Introduction  

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility and fractures. Patients with OI have clinical features that may range from mild symptoms to severe bone deformities and neonatal lethality. Numerous approaches for the classification of OI have been published. The Sillence classification is the most commonly used. In this study, we aimed at developing a more refined sub-classification by applying a proposed scoring system for the quantitative assessment of clinical severity in different types of OI.     

Osteogenesis imperfecta without features of type V caused by a mutation in the IFITM5 gene

Osteogenesis imperfecta (OI) is typically caused by mutations in type 1 collagen genes, but in recent years new recessive and dominant forms caused by mutations in a plethora of different genes have been characterized. OI type V is a dominant form caused by the recurrent (c.‐14C > T) mutation in the 5'UTR of the IFITM5 gene. The mutation adds five residues to the N‐terminus of the IFITM5, but the pathophysiology of the disease remains to be elucidated. Typical clinical features present in the majority of OI type V patients include interosseous membrane calcification between the radius and ulna and between the tibia and fibula, radial head dislocation, and significant hyperplastic callus formation at the site of fractures. We report a 5‐year‐old child with clinical features of OI type III or severe OI type IV (characteristic facies, gray sclerae, typical fractures) and absence of classical features of OI type V with a de novo recurrent IFITM5 mutation (c.‐14C > T), now typical of OI type V. This highlights the variability of OI caused by IFITM5 mutations and suggests screening for mutations in this gene in most cases of OI where type 1 collagen mutations are absent. © 2013 American Society for Bone and Mineral Research.     

多重引物HRMA对成骨不全患者COL1A1/2基因突变的筛查与分析

目的建立多重引物高分辨熔解曲线分析(high resolution melting analysis,HRMA)方法并运用该方法筛查两例成骨不全(osteogenesis imperfecta,OI) COL1A1/2的突变基因。方法收集两例OI患者临床资料,采集患者及50例正常对照的血液标本。设计COL1A1、COL1A2基因103个外显子所对应的引物,将满足一定条件的两对引物相互配对,与单份样本DNA混合作为扩增体系。运用HRMA筛查产物突变情况,基因测序确定突变位点。结果本研究中共涉及到COL1A1和COL1A2的103个外显子,其中成功配对39对,未配对成功的有3个COL1A1外显子和22个COL1A2外显子,成功率为75. 73%。先证者1筛查结果 HRMA熔解曲线在COL1A1 41号外显子上存在异常,测序结果为c.2877delT杂合突变,即c DNA2 877位碱基T缺失,编码的缬氨酸变成色氨酸。先证者2筛查结果 HRMA熔解曲线在COL1A1 16号外显子上存在异常,测序结果为c.1028delC杂合突变,即c DNA1 028位碱基C缺失,编码的脯氨酸变成亮氨酸。两种突变类型在中国人群中均未见报道,为新发现的两种剪切突变,且与传统HRMA筛查结果一致。结论多重引物HRMA方法在传统HRMA基础上进行了创新,将两对引物与单份样本DNA混合作为扩增体系,HRMA筛查产物突变情况,且与传统HRMA筛查结果一致,具有一定创新性和可行性,为成骨不全患者基因突变及其他遗传病致病基因的筛查提供了新的思路。     

Two Rare Mutations in the COL1A2 Gene Associate With Low Bone Mineral Density and Fractures in Iceland

We conducted a genome‐wide association study of low bone mineral density (BMD) at the hip and spine utilizing sequence variants found through whole‐genome sequencing of 2636 Icelanders. We found two rare missense mutations, p.Gly496Ala and p.Gly703Ser, in the COL1A2 gene that associate with measures of osteoporosis in Icelanders. Mutations in COL1A2 are known to cause the autosomal dominant disorder osteogenesis imperfecta. Both variants associate with low BMD and with osteoporotic fractures. p.Gly496Ala (frequency of 0.105%) shows the strongest association with low BMD at the spine (p = 1.8 × 10^?7, odds ratio [OR] = 4.61 [95% confidence interval (CI) 2.59, 8.18]), whereas p.Gly703Ser (frequency of 0.050%) is most strongly associated with low BMD at the hip (p = 1.9 × 10^?8, OR = 9.34 [95% CI 4.28, 20.3]). Association with fractures was p = 2.2 × 10^?5, OR = 3.75 (95% CI 2.03, 6.93) and p = 0.0023, OR = 4.32 (95% CI 1.69, 11.1), respectively. The carriers of these variants do not have signs of osteogenesis imperfecta other than low BMD, demonstrating that similar mutations in COL1A2 can affect skeletal phenotypes in more than one way. © 2015 American Society for Bone and Mineral Research.     

Ultrastructural localization of proteoglycans in bone in osteogenesis imperfecta as demonstrated by Cuprolinic Blue staining

 The role of proteoglycans in bone in osteogenesis imperfecta (OI) has been examined. Using Cuprolinic Blue staining of whole fetal bone tissue and examining the tissue in the transmission electron microscope, the presence of proteoglycans was observed. Quantitative comparative image-analysis of the proteoglycans from electron micrographs was performed, with measurement of sizes and number of proteoglycan particles. A significant increase in the total number of proteoglycan particles in OI bone osteoid was observed when compared with normal, matched controls. The area of the proteoglycan particles, as measured by pixel-area, using image analysis, was also increased in OI bone osteoid. These findings further suggest a role for proteoglycans in mineral formation by the possible inhibition of mineral growth and alteration of collagen nucleation sites. The increased number and size of proteoglycan particles may be a contributing factor to the previously reported poor mineral formation with subsequent loss of bone strength, making it more prone to fracture, in OI. Received: August 28, 2001 / Accepted: February 8, 2002     

Skeletal Characteristics of WNT1 Osteoporosis in Children and Young Adults

WNT proteins comprise a 19‐member glycoprotein family that act in several developmental and regenerative processes. In bone, WNT proteins regulate osteoblast differentiation and maintain bone health by activating the canonical WNT/β‐catenin pathway. We reported a heterozygous missense mutation c.652T>G (p.C218G) in WNT1 exon 4 as the cause for severe early‐onset, autosomal dominant osteoporosis. The initial study concerned a large Finnish family with 10 affected adults. Here we report clinical findings of the WNT1 osteoporosis in 8 children and young adults (median age 14 years; range 10 to 30 years) in two families, all with the p.C218G mutation in WNT1. Clinical assessments showed no apparent dysmorphia or features similar to typical osteogenesis imperfecta (OI). Biochemistry revealed no changes in parameters of calcium metabolism and bone turnover markers. Fracture frequencies varied, but all subjects had sustained at least one fracture and 4 had a pathological fracture history. Plain radiographs showed osteopenic appearance, loss in vertebral height, and thin diaphyses of the long bones. Bone densitometry showed the BMD to be below normal median in all subjects and the bone mass deficit seemed to be more severe in older participants. Bone histomorphometry revealed a low turnover osteoporosis in 2 subjects at ages 14 and 16 years. These findings are congruent with earlier findings in adult patients and indicate that WNT1 osteoporosis causes significant skeletal changes already in early childhood and impairs bone mass gain during pubertal years. Genetic testing of children or close relatives of affected individuals is recommended for appropriate preventive measures. © 2016 American Society for Bone and Mineral Research.     

Hybrid minigene splicing assay verifies the pathogenicity of a novel splice site variant in the COL1A1 gene of a chinese patient with osteogenesis imperfecta type I

BackgroundOsteogenesis imperfecta (OI) is a rare genetic bone disease associated with brittle bones and fractures. Among all known types, OI type I is the most common type and characterized by increased bone fragility, low bone mass, distinctly blue-gray sclera, and susceptibility to conductive hearing loss beginning in adolescence. Mutations in genes encoding type I collagen (COL1A1 and COL1A2) contribute to the main pathogenic mechanism of OI.MethodsSubtle mutation of the COL1A1 gene in the proband was detected by targeted next-generation sequencing (NGS) and confirmed by Sanger sequencing. We then assessed the effect of the mutation on the splicing of the COL1A1 gene by bioinformatics prediction and hybrid minigene splicing assay (HMSA).ResultsA novel splice site mutation c.1821+1 G>C was discovered in the proband by NGS and further confirmed by Sanger sequencing, which was also simultaneously identified from the proband's mother and elder sister. Bioinformatics predicted that this mutation would result in a disappearance of the 5′ donor splice site in intron 26, thereby leading to abnormal splicing and generation of premature stop codon. The follow-up experimental data generated by HMSA was consistent with this prediction.ConclusionOur study identified a novel splice site mutation that caused OI type I in the proband by abnormal splicing and demonstrated that combined applications of NGS, bioinformatics and HMSA are comprehensive and effective methods for diagnosis and aberrant splicing study of OI.     

A morphological and ultrastructural study of bone in osteogenesis imperfecta

A morphological and electron microscopic study of bone from patients with osteogenesis imperfecta (OI) has been performed. Bone from OI patients from various anatomical sites has been compared with that from normal, age-, site-, and sex-matched controls. The morphology of OI bone appeared variable among patients and sites of bone examined. Immature woven bone and a poor lamellar pattern were the significant morphological features and demonstrated that OI could not be characterized on the basis of a single histological pattern. At the ultrastructural level, a number of previously unreported features were evident. Abnormal collagen fibers and an altered mineral composition were found in many OI patients, however, the panoramic heterogeneity between clinical types and indeed within a single clinical type made it difficult to classify OI in this manner. The presence of intermitochondrial inclusions containing calcium and phosphorus and the presence of a stromal calcification in the bone in some OI patients suggested an abnormal mineral formation. Qualitatively, no obvious difference in the number of osteoblasts or osteoclasts was observed. The morphology and ultrastructure of OI bone were good indicators of the disease and serve a role in assessing the progress of a patient through diagnosis and treatment. This report presents new ultrastructural findings in collagen and in mineral formation in OI compared with normal human bone.     

A case of renal hypouricemia caused by urate transporter 1 gene mutations

Hypouricemia is a common disorder in the general population. Herein, renal hypouricemia caused by human urate transporter 1 (hURAT1) gene mutations in a Japanese patient with intellectual disability is reported. She had compound heterozygous mutations in this gene (W258X and IVS2+1G>A), nevertheless, she showed no clinical manifestations such as urolithiasis and exercise-induced acute renal failure. Restriction enzyme analysis with HphI was useful to screen the IVS2+1G>A mutation in hURAT1 gene.     

Recessive distal renal tubular acidosis in Sarawak caused by AE1 mutations

Mutations of the AE1 (SLC4A1, Anion-Exchanger 1) gene that codes for band 3, the renal and red cell anion exchanger, are responsible for many cases of familial distal renal tubular acidosis (dRTA). In Southeast Asia this disease is usually recessive, caused either by homozygosity of a single AE1 mutation or by compound heterozygosity of two different AE1 mutations. We describe two unrelated boys in Sarawak with dRTA associated with compound heterozygosity of AE1 mutations. Both had Southeast Asian ovalocytosis (SAO), a morphological abnormality of red cells caused by a deletion of band 3 residues 400–408. In addition, one boy had a DNA sequence abnormality of band 3 residue (G701D), which has been reported from elsewhere in Southeast Asia. The other boy had the novel sequence abnormality of band 3 (Q759H) and profound hemolytic anemia.