COL1A1 and osteogenesis imperfecta: To determine whether a variant has an impact on splicing efficiency, we selected 34 OI probands carrying 29 different variants which were located close to the splicing sites in introns or exons of COL1A1 or COL1A2. Based on minigene assays and sequence analysis, 17 variants showed aberrant splicing effects while 12 variants presented no splicing consequences.