Quantitative Genetic Analysis of Third Metacarpal Morphometry in Baboons (Papio hamadryas)

Osteoporosis is a very disabling disease in humans, and not until recently with the advent of modern technology has it been researched in a manner beneficial to medical applications. Initially, the use of animals in osteoporosis research served primarily as an avenue for testing and research. Recently the use of nonhuman primates has expanded the research potential for such studies on related individuals more similar to humans. Baboon colonies provide researchers with accessible nonhuman primate populations in which pedigrees can be determined and biomedical studies can be performed. This study is based on 186 hand-wrist radiographs of two baboon subspecies, Papio hamadryas cynocephalus and P.h. anubis, collected at the Southwest Foundation for Biomedical Research in San Antonio, Texas. The records of the baboons from which the radiographs were taken were arranged into pedigrees. The third metacarpal of each radiograph was digitized on a video analysis system using x,y coordinates at 1.0 mm intervals to establish cortical bone area measurements. Subsequent analysis of these measurements established first and second moments of area and radii of gyration. Computer analysis using the program "Maxlikh2", similar to Fischer's Fundamental theorem, determined heritability estimates from the measurements along the parameters of the pedigrees for seven quantitative traits. Heritability is a function of degree of genetic inheritance of a complex trait, in this case radii of gyration of cortical bone. Multivariate analysis using variables mean, sex, age, sex/age interaction, and phenotypic variance and yielded heritability and standard error estimates for the quantitative traits kmax, kmin, area, length, subperiosteal-medullary width, kmax\length, and kmin\length. Quantitative traits are significantly heritable. Cortical bone morphology of baboon third metacarpals may provide a methodology for identifying risk factors associated with developing osteoporosis. The study of bone heritability in primates contributes a new application for osteoporosis research. Studies of bone heritability in baboons could lead to the use of such studies as models for human osteoporosis.