Effect of immunosuppressants on a mouse model of osteogenesis imperfecta type V harboring a heterozygous Ifitm5 c.-14C\u2009>\u2009T mutation

Nobutaka Hanagata,Toshiaki Koda,Keiko Kamimura,Taro Takemura

doi:10.1038/s41598-020-78403-1

Nobutaka Hanagata, Toshiaki Koda + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-78403-1

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Abstract

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.

Highlights

Interferon-induced transmembrane protein 5 (IFITM5) is a type II (N-in/C-out) transmembrane protein, the amino terminus of which is located inside the cell and the carboxyl terminus is located e xtracellularly[1]
osteogenesis imperfecta (OI) type V is thought to be caused by the mutated interferon-induced transmembrane protein 5 gene (IFITM5) (MALEP-IFITM5) in which these 5 amino acids are added to the amino terminus of IFITM5, the mechanism of its onset is unknown at present
In osteoblasts isolated from mouse calvaria, 20 μg/ml FK506 considerably suppressed the expression of Ifitm[5] (Fig. 1A)

Summary

Introduction

Interferon-induced transmembrane protein 5 (IFITM5) is a type II (N-in/C-out) transmembrane protein, the amino terminus of which is located inside the cell and the carboxyl terminus is located e xtracellularly[1]. Following reports stating that no major abnormality is seen in the osteogenesis of Ifitm5-deficient mice, many research groups have reported that patients with osteogenesis imperfecta (OI) type V have a heterozygous point mutation (c.-14C > T) in the 5 ’ untranslated region of the IFITM5 gene[5,6,7,8,9,10,11,12,13,14,15,16]. OI type V is an autosomal dominant condition and is distinguished from other types of OI by features such as forearm interosseous membrane calcification, hyperplastic callus formation, and radial head. The absence of major skeletal abnormalities in Ifitm5-deficient mice leads to the possibility that OI type V may be treatable by suppressing the expression of both wild-type (WT) and c.-14C > T mutant Ifitm[5], which is a similar condition to that in Ifitm5-deficient mice

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