Genotypic and Phenotypic Characteristics of 29 Patients With Rare Types of Osteogenesis Imperfecta: Average 5 Years of Follow-Up

Genetic landscape and phenotypic spectrum of osteogenesis imperfecta in the Kazakhstani pediatric population

This study investigates the genetic landscape and phenotypic spectrum of osteogenesis imperfecta (OI) in the Kazakhstani pediatric population, focusing on 40 children diagnosed and treated at the "University Medical Center" Corporate Fund from July 2021 to June 2023. Genetic analysis was conducted using whole-genome sequencing for 22 participants at the "National Laboratory Astana" (Nazarbayev University, Astana, Kazakhstan) and whole-exome sequencing for 18 participants in private laboratories. Clinically significant genetic variants were found in 35 cases (87.5%). Mutations in the COL1A1 and COL1A2 genes were detected in 24 cases (68.6%), among them 5 variants were described for the first time. Among the rare cases of OI, variants in the IFITM5 (n = 2), SERPINF1 (n = 7), and SERPINH1 (n = 1) genes were identified. At the same time, seven unrelated cases had identical variants in the SERPINF1 gene (c.907C > T, 6 of which in the homozygous and 1 in the compound heterozygous state) and two cases in the IFITM1 gene (c.-14C > T). Novel disease-causing variants were identified in 17% of cases, and a higher proportion of collagen defects were seen. The relatively high proportion of autosomal recessive inherited OI determined in the current study should be investigated at the population level in Kazakhstan and in the countries of Central Asia. Moreover, this study described the genotype-phenotype correlation, which complements and expands the existing knowledge about the OI.

Identification of a family with van der Hoeve's syndrome harboring a novel COL1A1 mutation and generation of patient-derived iPSC lines and CRISPR/Cas9-corrected isogenic iPSCs

Van der Hoeve's syndrome, also known as osteogenesis imperfecta (OI), is a genetic connective tissue disorder characterized by fragile, fracture-prone bone and hearing loss. The disease is caused by a gene mutation in one of the two type I collagen genes COL1A1 or COL1A2. In this study, we identified a novel frameshift mutation of the COL1A1 gene (c.1607delG) in a family with OI using whole-exome sequencing, bioinformatics analysis and Sanger sequencing. This mutation may lead to the deletion of a portion of exon 23 and the generation of a premature stop codon in the COL1A1 gene. To further investigate the impact of this mutation, we established two induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells of OI patients carrying a novel mutation in the COL1A1 gene. Osteoblasts (OB) derived from OI-iPSCs exhibited reduced production of type I collagen and diminished ability to differentiate into osteoblasts. Using a CRISPR-based homology-directed repair strategy, we corrected the OI disease-causing COL1A1 novel mutations in iPSCs generated from an affected individual. Our results demonstrated that the diminished expression of type I collagen and osteogenic potential were enhanced in OB induced from corrected OI-iPSCs compared to those from OI-iPSCs. Overall, our results provide new insights into the genetic basis of Van der Hoeve's syndrome and highlight the potential of iPSC technology for disease modeling and therapeutic development.