Differential gene expression between the growth plate and non-growth plate forming bones in the mouse carpus and tarsus

The pisiform and calcaneus are unique among carpals and tarsals, respectively, because they form a single growth plate and associated secondary ossification center at one end. The pisiform and calcaneus are both important for mammalian locomotion and have evolutionarily relevant changes across different mammalian species, including humans. Little is known about the genes underlying the development and morphology of these bones and their individual growth plates. We used RNA sequencing to determine differentially expressed genes (DEGs) between the pisiform (growth plate forming) and other carpals (non-growth plate forming) as well as the proximal calcaneus (growth plate forming) and distal calcaneus (non-growth plate forming) in 0, 4, and 9 day old mice. Growth plate and non-growth plate forming data were compared within each bone. We also assessed overlap between the pisiform and calcaneus datasets for shared DEGs. There were 63 DEGs in the pisiform/carpal data and 27 DEGs in the calcaneus data that were more highly expressed in the growth plate forming tissue for at least 2 of the 3 ages. In the pisiform, this included genes associated with adipogenesis and cell surface receptor signaling. In the calcaneus, this included genes associated with embryonic development and the retinoic acid signaling pathway. There was overlap between the two datasets for some FGF, Wnt, and retinoic acid pathway genes. This analysis identifies potential genetic targets for formation of growth plates in the pisiform and calcaneus.