LAUSR

Embryonic movement is important for establishing shape in the developing skeleton. Previous work on the limb showed that shape is a result of interplay between molecular and mechanical cues, and when movement is reduced multiple aspects of morphology are altered (Nowlan et al 2010) and temporal and spatial changes in gene expression occur (Rolfe et al 2014). Much less is known about the effect of movement on jaw morphogenesis although work in chick, mouse and zebrafish indicates that movement is important for normal development (Hall and Herring 1990, Rot-Nikcevic et al 2007, Brunt et al 2015). The cellular and molecular basis of these changes in the jaw is unknown and no quantitative comparative shape analysis has been performed. A rigid-paralysis chick model treated with DMB to induce immobilisation and a muscle-less Tbx1 mouse model are being used to examine jaw development in altered mechanical environments. Immobilised chicks, muscle-less mice and their respective stage-matched controls are harvested at different embryonic stages. Whole tissue staining for bone and cartilage (Alcian-Alizarin) followed by 3D OPT scanning is then performed. Quantitative comparison of shape changes in the chick and the mouse is being carried out using geometric morphometrics to assess which aspects of morphology are the most affected by lack of movement. Diversity in form and function of vertebrate jaw morphology reflects differences in evolutionary history and developmental processes. Future work will focus on molecular and cellular mechanisms altered during jaw development under differing mechanical regimes, uncovering potential mechanosensitive molecular signalling pathways that interpret the mechanical environment. Differences among mouse strains in bone formation response to mechanical stimulation (Kodama et al 2014) suggests that variable and heritable mechanosensitive genes contribute to phenotypic variation, and understanding the importance of movement for appropriate embryogenesis has important implications for therapeutics as well as morphological evolution.