Nanotechnology Innovation Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
Graduate School of Life Science, Hokkaido University, N10 W8, Kitaku, Sapporo, 060-0810, Japan.
Sci Rep. 2020 Dec 3;10(1):21197. doi: 10.1038/s41598-020-78403-1.
Osteogenesis imperfecta (OI) type V is an autosomal dominant disorder caused by the c.-14C > T mutation in the interferon-induced transmembrane protein 5 gene (IFITM5), however, its onset mechanism remains unclear. In this study, heterozygous c.-14C > T mutant mice were developed to investigate the effect of immunosuppressants (FK506 and rapamycin) on OI type V. Among the mosaic mice generated by Crispr/Cas9-based technology, mice with less than 40% mosaic ratio of c.-14C > T mutation survived, whereas those with more than 48% mosaic ratio exhibited lethal skeletal abnormalities with one exception. All heterozygous mutants obtained by mating mosaic mice with wild-type mice exhibited a perinatal lethal phenotype due to severe skeletal abnormalities. Administration of FK506, a calcineurin inhibitor, in the heterozygous fetuses improved bone mineral content (BMC) of the neonates, although it did not save the neonates from the lethal effects of the mutation, whereas rapamycin, an mTOR inhibitor, reduced BMC, suggesting that mTOR signaling is involved in the bone mineralization of heterozygous mutants. These findings could clarify certain aspects of the onset mechanism of OI type V and enable development of therapeutics for this condition.
成骨不全症（OI）类型 V 是一种常染色体显性遗传病，由干扰素诱导跨膜蛋白 5 基因（IFITM5）中的 c.-14C > T 突变引起，但其发病机制尚不清楚。在本研究中，构建了杂合 c.-14C > T 突变的小鼠模型，以研究免疫抑制剂（FK506 和雷帕霉素）对 OI 类型 V 的影响。在基于 Crispr/Cas9 技术的嵌合体小鼠中，只有不到 40%嵌合率的 c.-14C > T 突变小鼠能够存活，而嵌合率超过 48%的小鼠则表现出致死性骨骼异常，只有一例例外。通过将嵌合体小鼠与野生型小鼠交配获得的所有杂合突变体均因严重的骨骼异常而表现出围产期致死表型。在杂合胎儿中给予钙调神经磷酸酶抑制剂 FK506 可改善新生儿的骨矿物质含量（BMC），尽管它不能使新生儿免受突变的致死影响，而 mTOR 抑制剂雷帕霉素则降低了 BMC，提示 mTOR 信号通路参与杂合突变体的骨矿化。这些发现可以阐明 OI 类型 V 发病机制的某些方面，并为该疾病的治疗方法的开发提供依据。
