Craniofacial Growth in Giant Transgenic Rodents

Shea, Brian

Abstract

The objective of this pilot research is to examine growth of the craniofacial complex in giant transgenic mice. These mice are characterized by marked increases in circulating growth hormone and overall body weight relative to littermate controls. Unlike many previous studies, this analysis is specifically designed to distinguish between those general craniodental size and shape changes in the transgenic mice that are merely a function of increased body size, and those alterations in skull morphology or tooth size that reflect regional and specific growth perturbations. The hypothesis is that the transgenic mice will exhibit some special growth changes in the face that are not simple correlates of overall weight gain. This study will combine allometric analysis of true cross-sectional growth data with Wright's (1932) hierarchy of general, group, and special size factors to test this hypothesis. This research will elucidate aspects of the hormonal control of skull growth and tooth size, and thus contribute to our understanding of normal and abnormal craniofacial growth. Changes in skull form and tooth size or eruption rate frequently characterize various endocrine disorders, and orthodontists are often involved in the ramifications of growth hormone therapies. This involvement will probably increase dramatically in the future, as the availability of hGH from bacterial DNA cloning rises. The transgenic mouse, with its """"""""naturally"""""""" produced high levels of circulating growth hormone, provides an important model for the study of the effects of gigantism, growth hormone therapies, and endocrine disorders on the craniofacial complex.