A SURVEY OF NATURAL SELECTION IN MAMMALIAN IGA MOLECULES

STUDENT SEMINAR IN BIODIVERSITY AND EVOLUTION

IgA is the predominant immunoglobulin isotype in mucosal tissues and external secretions, playing an important role as a first line of defense against pathogens. Considering the complexity of its interactions with the surrounding environment, IgA is a likely target for diversifying selection. To investigate this question, the action of natural selection on IgA was examined using computational methods to detect codon based selection. The analysis of primate and mammals IgA showed that diversifying selection has targeted all three IgA heavy chain constant domains but mostly the Cα1 and Cα2 domains. The structural locations of the identified positively selected codons suggest they indirectly influence the conformation of sites on IgA-Fc that are critical for interaction with host IgA receptors and also with proteins produced by mucosal pathogens that prevent their elimination by IgA-mediated effector mechanisms, emphasizing the importance of IgA in protection against mucosal pathogens.

Ana is a BIODIV PhD student, who is studying the evolution of immunoglobulin genes in mammals with a focus on Leporids under the supervision of Paulo C. Alves (CIBIO-InBIO) and Christian Gortazar (SaBio - IREC (CSIC-UCLM-JCCM).

Image credits: Ana Pinheiro