Androgen and progesterone receptor knockouts in Danio rerio affect aggression and social dominance (part 1)

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Matthew W Chilton (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: It is well known that competition for the basic resources of food , shelter , and mates will always exist in nature. The most prevalent method of competing for such resources is aggression and social dominance. There is overwhelming circumstantial evidence that androgens , like testosterone , play a role in the onset of aggression. Generating an androgen receptor knockout (ARKO) should reduce the effects of androgens throughout the entire organism. It is hypothesized that a system-wide knockout of androgen receptors will diminish the levels of aggression in Zebrafish (Danio rerio). Furthermore , some evidence has shown , though disputed , that a knockout of the nuclear progesterone receptor will result in an increase of aggression. The purpose of this study is to observe how aggression levels as well as the formation and maintenance of social dominance in male zebrafish is altered in Androgen Receptor (AR) and Progesterone Receptor (PGR) knockouts. Wild type (WT) , AR Knockouts , and PGR knockouts were isolated for one week to remove preexisting social behaviors. After the isolation period , males were paired with another of the same genotype with similar age and size. During the two-week pairing period , each pair of fish was observed for five minutes. During observation , fish attacks and retreats were recorded. Filming of pairs occurred on the first and last day of pairing. Motion tracking analysis was used to generate heat maps of the swimming patterns and localization of fish in the tank. Observational data shows a significant decrease of attacks in ARKO fish compared to wildtype fish. We have reason to believe there is an increase in attacks in PGRKO fish compared to wildtype fish; however , more data needs to be collected to confirm this result. Preliminary video analysis indicates that the swimming behaviors of ARKO fish do not indicate the formation of a robust social hierarchy. Androgen Receptor Knockout males were overall less aggressive than the wild types. Progesterone receptor knockout males showed a correlation towards higher aggression , however , there is not enough data to draw a conclusion at this time. Less aggressive ARKO males supports current theories on the effects that male sex hormones have on the body. This knowledge has implications when studying human and animal development , diet , medicine , and more. Insights on nutrition recommendations are gained , as different foods contain precursors to hormones. Many medicines are also designed to resolve hormonal issues or even regulate normal processes such as in both male and female birth control. Investigation of these extremely vital hormones could give insight to the psychological side effects of such drugs. Currently , new methods are being developed to further characterize the observed behavior changes. Experiments to elucidate potential pathways that are responsible for the observed behavior change in the ARKO males are being conducted by a fellow Honors College Member. The Zhu and Issa labs of ECU are excited to uncover new behavior changes that result from androgen and progesterone receptor knockouts.

Additional Information

Publication

Thesis

Language: English

Date: 2018

Keywords

Biology, Biochemistry, Behavior, Zebrafish, Genetics, Steroids, Receptors, Aggression

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