Site-specific Wnt signalling explains regional differences in bone physiology – Evidence from a cross-species RNA-Seq study comparing osteocyte transcriptomes in the tibia and skull

Local site-specific differences between bones in different regions of the skeleton account for their different properties and functions. To identify mechanisms behind these differences, we have performed a cross-species study comparing RNA transcriptomes of cranial and tibial osteocytes, from bones with very different primary functions and physiological responses, collected from the same individual mouse, rat and rhesus macaque. Bioinformatic analysis was performed to identify 32 genes changed in the same direction between sites and shared across all three species. Several well-established key genes in bone growth and remodelling were upregulated in the tibias of all three species (BMP7, DKK1, FGF1, FRZB, SOST). Many of them associate or crosstalk with the canonical Wnt signalling pathway. These results suggest Wnt signalling-related candidates for different control of regulatory mechanisms in bone homeostasis in the skull and tibia and indicate a different balance between genetically determined structure and feedback mechanisms to strains induced by mechanical loading at the different sites. mRNA profile comparison of osteocytes in skull and long bone. It's a cross species study involving mouse, rat and rhesus macaques