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Validation and Classification of Atypical Splicing Variants Associated With Osteogenesis Imperfecta.

ABSTRACT: Osteogenesis Imperfecta (OI) is a rare inherited bone dysplasia, which is mainly caused by mutations in genes encoding type I collagen including COL1A1 and COL1A2. It has been well established to identify the classical variants as well as consensus splicing-site-variants in these genes in our previous studies. However, how atypical variants affect splicing in OI patients remains unclear. From a cohort of 867 OI patients, we collected blood samples from 34 probands which contain 29 variants that are located close to splice donor/acceptor sites in either COL1A1 or COL1A2. By conducting minigene assay and sequencing analysis, we found that 17 out of 29 variants led to aberrant splicing effects, while no remarkable aberrant splicing effect was observed in the remaining 12 variants. Among the 17 variants that affect splicing, 14 variants led to single splicing influence: 9 led to exon skipping, 2 resulted in truncated exon, and 3 caused intron retention. There were three complicated cases showing more than one mutant transcript caused by recognition of several different splice sites. This functional study expands our knowledge of atypical splicing variants, and emphasizes the importance of clarifying the splicing effect for variants near exon/intron boundaries in OI.

SUBMITTER: Li L

PROVIDER: S-EPMC6832110 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Validation and Classification of Atypical Splicing Variants Associated With Osteogenesis Imperfecta.

Li Lulu L Cao Yixuan Y Zhao Feiyue F Mao Bin B Ren Xiuzhi X Wang Yanzhou Y Guan Yun Y You Yi Y Li Shan S Yang Tao T Zhao Xiuli X

Frontiers in genetics 20191018

Osteogenesis Imperfecta (OI) is a rare inherited bone dysplasia, which is mainly caused by mutations in genes encoding type I collagen including <i>COL1A1</i> and <i>COL1A2</i>. It has been well established to identify the classical variants as well as consensus splicing-site-variants in these genes in our previous studies. However, how atypical variants affect splicing in OI patients remains unclear. From a cohort of 867 OI patients, we collected blood samples from 34 probands which contain 29 ...[more]

PMID: 31737030

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Project description:Osteogenesis imperfecta (imperfect osteogenesis in the Russian literature) is the most common hereditary form of bone fragility, it is a genetically and clinically heterogeneous disease with a wide range of clinical severity, often leading to disability from early childhood. It is based on genetic disorders leading to a violation of the structure of bone tissue, which leads to frequent fractures, impaired growth and posture, with the development of characteristic disabling bone deformities and associated problems, including respiratory, neurological, cardiac, renal impairment, hearing loss. Osteogenesis imperfecta occurs in both men and women, the disease is inherited in both autosomal dominant and autosomal recessive types, there are sporadic cases of the disease due to de novo mutations, as well as X-linked forms. The term "osteogenesis imperfecta" was coined by W. Vrolick in the 1840s. The first classification of the disease was made in 1979 and has been repeatedly reviewed due to the identification of the molecular cause of the disease and the discovery of new mechanisms for the development of osteogenesis imperfecta. In the early 1980s, mutations in two genes of collagen type I (COL1A1 and COL1A2) were first associated with an autosomal dominant inheritance type of osteogenesis imperfecta. Since then, 18 more genes have been identified whose products are involved in the formation and mineralization of bone tissue. The degree of genetic heterogeneity of the disease has not yet been determined, researchers continue to identify new genes involved in its pathogenesis, the number of which has reached 20. In the last decade, it has become known that autosomal recessive, autosomal dominant and X-linked mutations in a wide range of genes, encoding proteins that are involved in the synthesis of type I collagen, its processing, secretion and post-translational modification, as well as in proteins that regulate the differentiation and activity of bone-forming cells, cause imperfect osteogenesis. A large number of causative genes complicated the classical classification of the disease and, due to new advances in the molecular basis of the disease, the classification of the disease is constantly being improved. In this review, we systematized and summarized information on the results of studies in the field of clinical and genetic aspects of osteogenesis imperfecta and reflected the current state of the classification criteria for diagnosing the disease.

Project description:IntroductionDentinogenesis imperfecta type 1 (OIDI) is considered a relatively rare genetic disorder (1:5000 to 1:45,000) associated with osteogenesis imperfecta. OIDI impacts the formation of collagen fibrils in dentin, leading to morphological and structural changes that affect the strength and appearance of teeth. However, there is still a lack of understanding regarding the nanoscale characterization of the disease, in terms of collagen ultrastructure and mechanical properties. Therefore, this research presents a qualitative and quantitative report into the phenotype and characterization of OIDI in dentin, by using a combination of imaging, nanomechanical approaches.MethodsFor this study, 8 primary molars from OIDI patients and 8 primary control molars were collected, embedded in acrylic resin and cut into longitudinal sections. Sections were then demineralized in 37% phosphoric acid using a protocol developed in-house. Initial experiments demonstrated the effectiveness of the demineralization protocol, as the ATR-FTIR spectral fingerprints showed an increase in the amide bands together with a decrease in phosphate content. Structural and mechanical analyses were performed directly on both the mineralized and demineralized samples using a combination of scanning electron microscopy, atomic force microscopy, and Wallace indentation.ResultsMesoscale imaging showed alterations in dentinal tubule morphology in OIDI patients, with a reduced number of tubules and a decreased tubule diameter compared to healthy controls. Nanoscale collagen ultrastructure presented a similar D-banding periodicity between OIDI and controls. Reduced collagen fibrils diameter was also recorded for the OIDI group. The hardness of the (mineralized) control dentin was found to be significantly higher (p<0.05) than that of the OIDI (mineralized) dentine. Both the exposed peri- and intratubular dentinal collagen presented bimodal elastic behaviors (Young's moduli). The control samples presented a stiffening of the intratubular collagen when compared to the peritubular collagen. In case of the OIDI, this stiffening in the collagen between peri- and intratubular dentinal collagen was not observed and the exposed collagen presented overall a lower elasticity than the control samples.ConclusionThis study presents a systematic approach to the characterization of collagen structure and properties in OIDI as diagnosed in dentin. Structural markers for OIDI at the mesoscale and nanoscale were found and correlated with an observed lack of increased elastic moduli of the collagen fibrils in the intratubular OIDI dentin. These findings offer an explanation of how structural changes in the dentin could be responsible for the failure of some adhesive restorative materials as observed in patients affected by OIDI.

Dataset Information

Validation and Classification of Atypical Splicing Variants Associated With Osteogenesis Imperfecta.

Publications

Validation and Classification of Atypical Splicing Variants Associated With Osteogenesis Imperfecta.

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