Calvaria Bone Transcriptome in Mouse Models of Osteogenesis Imperfecta.

Pierre Moffatt,Ghalib Bardai,Iris Boraschi-Diaz,Frank Rauch,Juliana Marulanda

doi:10.3390/ijms22105290

Abstract

Osteogenesis imperfecta (OI) is a bone fragility disorder that is usually caused by mutations affecting collagen type I. We compared the calvaria bone tissue transcriptome of male 10-week-old heterozygous Jrt (Col1a1 mutation) and homozygous oim mice (Col1a2 mutation) to their respective littermate results. We found that Jrt and oim mice shared 185 differentially expressed genes (upregulated: 106 genes; downregulated: 79 genes). A total of seven genes were upregulated by a factor of two or more in both mouse models (Cyp2e1, Slc13a5, Cgref1, Smpd3, Ifitm5, Cthrc1 and Rerg). One gene (Gypa, coding for a blood group antigen) was downregulated by a factor of two or more in both OI mouse models. Overrepresentation analyses revealed that genes involved in ‘ossification’ were significantly overrepresented among upregulated genes in both Jrt and oim mice, whereas hematopoietic genes were downregulated. Several genes involved in Wnt signaling and transforming growth factor beta signaling were upregulated in oim mice, but less so in Jrt mice. Thus, this study identified a set of genes that are dysregulated across various OI mouse models and are likely to play an important role in the pathophysiology of this disorder.

Highlights

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder that is clinically characterized by low bone mass, bone fragility, long bone deformity, scoliosis, discolored sclera and dentinogenesis imperfecta [1]
Low bone mass in OI is likely caused by dysregulation of bone cell activity rather than the incapacity of osteoblasts to produce enough organic bone matrix
In accordance with the biological processes identified by the overrepresentation analyses, several genes involved in Wnt signaling and TGF-beta signaling were upregulated in oim mice, but not, or to a lesser extent, in Jrt mice (Figure 4)

Summary

Introduction

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder that is clinically characterized by low bone mass, bone fragility, long bone deformity, scoliosis, discolored sclera and dentinogenesis imperfecta [1]. (Cyp2e1, Slc13a5, Cgref, Smpd, Ifitm, Cthrc and Rerg), and one (Gypa, coding for a blood group antigen) was downregulated (Table 3) The results for these eight genes were validated by RT-PCR (Figure 3). In accordance with the biological processes identified by the overrepresentation analyses, several genes involved in Wnt signaling and TGF-beta signaling were upregulated in oim mice, but not, or to a lesser extent, in Jrt mice (Figure 4). Among the strongly upregulated genes that are shared between Jrt and oim mice, Cyp2e1, Slc13a5, Cgref and Rerg have not previously been implicated in OI pathophysiology to our knowledge. Cthrc codes for a secreted osteoblast product that decreases bone resorption [31] Regarding downregulated genes, those involved in ‘myeloid cell differentiation’ were overrepresented in both the Jrt and the oim model.

Materials and Methods

Sample Preparation

Library Preparation and RNA Sequencing

Real-Time PCR Validation