Immunoglobulin Genetics in Non-Eutherian Mammals

University Of New Mexico, Albuquerque NM

Investigators

Abstract

The study of immunoglobulin (Ig) genetics in a wide range of vertebrate species is essential for understanding the evolution and diversity of the adaptive immune responses in vertebrates. Until very recently, information on mammalian Igs has been limited almost exclusively to one of the three mammalian Orders, the eutherians or placental mammals. The overall goal of this study is to describe the genetic organization and mechanisms of expression that shape the antibody repertoires in metatherians (marsupials) and to extend these studies into prototherians (egg laying monotremes). The first specific aim is to determine those sequences in the opossum germline that code for the variable (V), diversity (D), joining (J) and constant (C) regions for Ig heavy chains, and V, J, and C regions for each family of light chains. This will be achieved using cosmid and phage-based cloning strategies. Resulting data will provide necessary information to determine the contributions of combinatorial diversity, somatic mutation and gene conversion for generation of Ig diversity in this species. In addition, although IgM, IgG, IgE, and IgA have been identified in marsupial species, IgD has not. Therefore, the presence and expression of IgD will be determined for the opossum using cosmid based genomic walking. The second specific aim is to characterize the Ig genes of two monotreme species, the platypus and echidna. No Ig gene sequences or their heavy and light chain organization are currently available for these species. Emphasis will be placed on light chains since patterns of light chain duplication are among the most variable across vertebrate orders. The third aim is to analyze Ig sequences from a wide range of marsupials from both the Americas and Australasia to determine patterns of evolution. Preliminary analyses of heavy chain variable region sequences from three marsupial species show an unusual pattern of sequence homogeneity or convergence. The project will provide information on the evolution of the mammalian immune system and will help resolve questions on the systematics of the three mammalian Orders. The results as a whole will provide insights into the genomic evolution of Ig genes in mammals not possible with comparisons of only humans and common laboratory species. The project will involve students at all levels of training: postdoctoral, graduate, and undergraduate. Students will gain research experience, will participate in the publication and presentation of the results, and will have the opportunity to collaborate with colleagues in Australia, New Zealand, and the United States.