Targeted Molecular Genetic Diagnosis by Next Generation Sequence Analysis Method and Investigation of Responsible Candidate Genes in Patients with Osteogenesis Imperfecta
Project no. 20185 · Status: Kapanmış · 2018
Summary
Osteogenesis imperfecta (OI) is a phenotypically and molecularly heterogeneous group of inherited connective tissue disorders that share similar skeletal abnormalities causing bone fragility and deformity. About 17 genes responsible for OI have been identified to date. Osteogenesis imperfecta was divided into 4 types clinically, the number of subtypes has increased to 19 in parallel with the genes defined over the years. Mutations in the COL1A1 and COL1A2 genes encoding type I collagen are responsible for approximately 70-80% of the etiology. Apart from these genes, genes involved in posttranslational modification and intracellular transport of type I collagen were also responsible for the disease. The aim of this study was to investigate the molecular genetic etiology and to determine the relationship between genotype and phenotype with targeted next-generation sequence analysis for cases with OI phenotype. Method: Patients with a diagnosis of OI and who had no molecular genetic cause were included in the study. Clinical typing of all patients was performed. Demographic and clinical characteristics were recorded. In the first step, mutations in COL1A1 and COL1A2 genes which are known to be the most responsible for OI were investigated. In the second step, a targeted next-generation sequence analysis panel (Illumina TruSight One) containing genes involved in collagen/bone synthesis was performed on the Illumina Nextseq550 platform in cases with no mutation in these genes. Genes responsible for OI and found in the panel were examined. Pathogenicity of determined variants was determined according to ACMG/AMP criteria. Results: Of the 30 patients (Female/Male: 14/16) included in the study, 8 (25.8%) had a consanguineous marriage between their parents and 13 (41.9%) had a family history of affected individuals. The mean age at admission was 4.09 ± 3.90 years, and the body weight was determined as SDS: -1.68 (-16.16 - 2.5) SD and height as SDS: -2.35 (-15.44 - 1.24) SD. When the cases were grouped according to clinical types; 12 patients (38.7%) were evaluated as type 1, 3 (9.7%) as type 2, 11 (35.5%) as type 3, and 4 (12.9%) as type 4. While bone deformity was detected in 17 (54.8%) of the cases, 16 (51.6%) were evaluated as independently mobile. Blue sclera was detected in 22 (71%) patients, scoliosis in 6 (19.4%), dentinogenesis imperfecta in 4 (12.9%) and hearing loss in 2 (6.5%). Mutation on COL1A1 gene was detected in 16 patients (53.3%), and on COL1A2 gene in 3 patients (10.0%). One (3.3%) patient had a mutation in both genes. In 5 (16.7%) of 10 patients who had no mutations in these genes, 3 different genes’ (SERPINF1, FKBP10, and P3H1) mutations were detected as a result of targeted sequence analysis. Twelve (40%) of the mutations detected in all investigated genes were not previously reported in the literature and were considered to be disease-specific according to in-silico analysis programs. In five (16.7%) patients, a disease-related mutation was not found in a total of 15 genes, which were known to be associated with OI and were included in the panel list. Advanced genetic analyzes are ongoing in cases where no mutation is detected in any gene. Conclusion: This study is a comprehensive research that shows the clinical and molecular characteristics of OI disease and the genetic etiology was determined in 25 (83.3%) of 30 cases by targeted sequence analysis method. In addition, 12 new mutations were detected in OI genes and a significant contribution was made to the literature.