Application of next‑generation sequencing for molecular diagnosis in a large family with osteogenesis imperfecta type I.

Increased bone fragility and low bone mass are common features of osteogenesis imperfecta (OI), which is associated with connective tissue. Its type is distinguished by clinical phenotypes and molecular genetics. Although fifteen types (I‑XV) of OI have been identified at present, the majority of patients are diagnosed as OI type I‑IV. Type I collagen is responsible for OI type I‑IV, consists of α1 (I) and α2 (I) chains and is encoded by COL1A1 and COL1A2. To identify the pathogenic gene of a large Chinese family with OI type I and explain genetic heterogeneity of the patients, next‑generation sequencing (NGS) was conducted in a female with OI type I and her affected niece and daughter to search for the mutation. Subsequently, it was confirmed in other family members by Sanger sequencing. Analysis of COL1A1 gene identified a splicing mutation (c.471+1G>A, also termed IVS5+1G>A) that converted the 5' end of intron 5 from GT to AT. The current study aimed to investigate why there are different phenotypes with the same mutation observed within the same OI pedigree, and the results suggested that there may be environmental factors involved. The present study provided genetic counseling and prenatal diagnosis for the family members, however additionally provided insight into the phenotype‑genotype association in OI.