Analysis of differential morphology of the anterior fontanelle in an embryonic avian model of induced thyrotoxicosis

Abstract

Craniosynostosis (CS) occurs when the cranial sutures of the skull fuse prematurely, and this results in intracranial pressure during development and skull deformities. Maternal hyperthyroidism during embryonic development has been linked to the development of CS. Our lab is currently establishing a model of thyroxine-induced CS to study the mechanism involved in thyroxine-enhanced cranial ossification. Two groups of fertilized chicken eggs were injected with saline or 25 ng T4 into the air cell on embryonic days 11 and 15. Skulls from each group were collected on embryonic days 17 through 19 (n = 17-21 per day). They were fixed in formalin and processed using Alizarin Red whole-mount staining to image and quantify any morphological differences in the ossifying membrane of the anterior fontanelle between the treatment and control groups. We hypothesize that thyroxine exposure will alter skull morphology. Geometric morphometric analysis using MorphoJ was performed to identify shape variation between treatment groups of the fibrous space and ossifying region of the anterior fontanelle. Significance was determined by Procrustes ANOVA. Results demonstrated a significant variation in shape of the fibrous gap between developing sutures on embryonic days 17, 18 and 19 (p<0.05) and a significant variation in the shape of the ossifying region on embryonic days 18 and 19 (p<0.001). In conclusion, we determined our model of induced thyrotoxicosis successfully altered skull morphology visualized in the anterior fontanelle. These findings support that our model is successful in promoting the fusing of the cranial bones with thyroxine exposure in our avian model.
 Acknowledgment of NASA West Virginia Space Grant Consortium (Grant #80NSSC20M0055) and the Genomics Core Facility and WV-INBRE (NIH grant P20GM103434).