Wnt signaling in cranial bones as a proponent of TH-induced craniosynostosis.

Abstract

Craniosynostosis (CS) is the premature fusion of the sutures within the skull during embryonic development. Recently, thyrotoxicosis in pregnant women has been shown to increase the risk of craniosynostosis in the developing fetus, but the specific mechanism relating the accelerated bone development in CS to increased thyroid hormone (TH) is unknown. Different cell signaling pathways, such as Wnt, Ihh, BMP, and IGF-1, have been identified in TH regulated bone development. However, the Wnt pathway has been chosen in this study for its extensive involvement in bone development. It is known that Wnt-signaling increases levels of β-catenin which then drives the transcription of Wnt/β-catenin target genes such as Twist1 and Runx2. When upregulated, these genes have been linked to increased osteoblast differentiation and bone formation. In this study, we aimed to determine the level of Wnt signaling activation, in cranial bones of differing embryonic origins (frontal and parietal bones) from an avian model of thyrotoxicosis. Collected bones were processed for assessing β-catenin protein expression by western blotting and Twist1 and Runx2 gene expression by qRT-PCR. Analysis is currently in progress. We predict that differences will be observed between the parietal and frontal bones as the parietal bones derive from the mesoderm whereas the frontal bones derive from the neural crest.