Calvaria Bone Transcriptome in Mouse Models of Osteogenesis Imperfecta

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.

Keywords: RNA sequencing; Wnt signaling; osteogenesis imperfecta; transforming growth factor beta.

Figure 1

Results of RNA sequencing in calvaria of 10-week-old mice. Venn diagram of differentially expressed genes in oim and Jrt mice.

Figure 2

Fold change in Jrt and oim versus WT mice in genes that, when mutated, give rise to OI. The red line indicates parity to WT. Asterisks (*) indicate significant upregulated genes (adjusted p < 0.05, as determined by deseq2).

Figure 3

Real-time PCR results in calvaria RNA of 10-week-old male mice. Results for Jrt are shown in the upper panel, results for oim in the lower panel. Values represent the 2^−∆Ct normalized to Rpl27. Significant differences in gene expression compared to WT mice are indicated by asterisks (one-tailed unpaired t-test): ns, non-significant, * p < 0.05, ** p < 0.01, *** p < 0.001. Error bars represent standard errors.

Figure 4

Fold change in Jrt and oim versus WT mice of genes that are involved in (a) Wnt signaling and (b) TGF-beta signaling. The red line indicates parity to WT. Asterisks (*) indicate significant upregulated genes (adjusted p < 0.05, as determined by deseq2).

Figure 5

Three-dimensional rendering of microCT scans of 10-week-old WT, Jrt and oim mice’s right parietal bones. In Jrt and oim mice, the bone is thinner and contains less bone marrow space (arrows).