Collaborative Research: Determining the Mechanisms by which Parental Testosterone Biases the Ratio of Male to Female Birds

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

Female birds determine the sex of offspring because they are heterogametic, but they also control the ratio of male to female offspring, the sex ratio, in response to environmental variables. Recent work shows that testosterone (T) treatment induces male-biased sex ratios in multiple species, and that it may do so by influencing which sex chromosome is retained in the oocyte during meiosis I (i.e. segregation distortion). The idea that a hormone can influence the genetic material inherited by offspring has enormous potential not only for understanding sex ratio adjustment in all vertebrate systems, but also when considering the inheritance of other genetic traits that determine offspring phenotype. The work will advance understanding of how the environment and endocrine system work together to determine genetic inheritance, as well as the cellular dynamics of meiosis. The researchers will also generate educational modules for both high school students and teachers and collaborate on potential applications of this work to poultry production. The research will also afford research training opportunities to numerous undergraduate and graduate students and continue their participation in programs geared towards involving under-represented groups in science. The results of previous data support the hypothesis that T stimulates male-biased sex ratios through segregation distortion of sex chromosomes during meiosis. To further analyze the effects of maternal testosterone, studies are planned to: test for the presence of androgen receptors on the germinal disc and follicle cells near the time of meiotic segregation; test for changes in the expression of genes involved in spindle fiber formation and chromosome movement in oocytes collected from T-treated hens; and to determine whether T elevations at meiotic segregation are necessary for sex ratio biases. Histologic, endocrine, and transcriptomic analyses are planned in association with the studies. The research is expected to reveal the intracellular pathway responsible for segregation distortion, to identify key points of regulation, and to determine how the pathways respond to changes in environmental and social conditions shown to influence offspring sex ratios. Results from the studies will be published in peer-reviewed journals and presented at regional and national scientific meetings.