Zebrafish (Danio rerio) vary by strain and sex in their behavioral and transcriptional responses to selenium supplementation

Abstract

We used the Nadia, Gaighatta, Scientific Hatcheries, and TM1 zebrafish (Danio rerio) strains to test the hypothesis that variation among populations influences the behavioral and transcriptional responses to selenium supplementation. When fed a diet with control levels of selenium, zebrafish strains differed significantly in behavior, characterized as their mean horizontal and vertical swimming positions within the tank. The four strains also differed in brain expression of selenoprotein P1a (sepp1a), glutathione peroxidase 3 (gpx3), thioredoxin reductase 1 (txnrd1), and tRNA selenocysteine associated protein 1 (secp43). Iodothyronine deiodinase 2 (dio2) did not differ among strains but showed a sex-specific expression pattern. When supplemented with selenium, all strains spent a greater proportion of time near the front of the tank, but the response of vertical swimming depth varied by strain. Selenium supplementation also caused changes in selenoprotein expression in the brain that varied by strain for sepp1a, secp43, and dio2, and varied by strain and sex for txnrd1. Expression of gpx3 was unaffected by selenium. Our data indicate that selenium homeostasis in the brain may be a regulator of behavior in zebrafish, and the strain-specific effects of selenium supplementation suggest that genetic heterogeneity among populations can influence the results of selenium supplementation studies.

Fig. 1

Strain specific response of Vertical Depth behavior to Se supplementation in zebrafish. Plotted values are least square means ± standard errors. Asterisks (*) indicate significant differences from control values within each strain. Zebrafish strain abbreviations: Gaighatta (G), Nadia (N), Scientific Hatchery (S), TM1 (T). Diet abbreviations: selenomethionine (SeMet), and sodium selenite (NaSel).

Fig. 2

Increase in Horizontal Position behavior (proportion of time nearest the observer) with Se supplementation in zebrafish. a) There was a significant effect of strain on Horizontal Position. b) Both forms of Se supplementation significantly increased Horizontal Position. Different letters denote significantly different least square means (± standard errors). Refer to Fig. 1 for abbreviation definitions.

Fig. 3

Strain specific effects of Se supplementation on brain expression of selenoprotein P1a (sepp1a) in zebrafish. Plotted values are least square means ± standard errors. Asterisks (*) indicate significant differences from control values within each strain. Refer to Fig. 1 for abbreviation definitions.

Fig. 4

Strain variation in brain expression of glutathione peroxidase 3 (gpx3) inzebrafish. Different letters denote significantly different least square means (± standard errors). Refer to Fig. 1 for abbreviation definitions.

Fig. 5

Strain specific effects of Se supplementation on brain expression of tRNA selenocysteine associated protein 1 (secp43) in zebrafish. Plotted values are least square means ± standard errors. Asterisks (*) indicate significant differences from control values within each strain. Refer to Fig. 1 for abbreviation definitions.

Fig. 6

Effect of sex and strain on brain thioredoxin reductase 1 (txnrd1) expression in zebrafish. a) For females, there was a strain specific effect of Se supplementation. Note that the T strain was removed from the analysis due to a male-biased sex ratio in the strain. b) For males, there was also a strain specific effect of Se supplementation. Asterisks (*) indicate significant differences from control values within each sex. Refer to Fig. 1 for abbreviation definitions.

Fig. 7

Effect of sex and strain on brain iodothyronine deiodinase 2 (dio2) expression in zebrafish. a) Male zebrafish had significantly higher brain expression of dio2 than females. Different letters denote significantly different least square means. Note that the T strain was removed from the analysis due to a male-biased sex ratio in the strain. b) Se supplementation significantly increased brain dio2 expression in the N strain. Asterisks (*) indicate significant differences from control values within each strain. Refer to Fig. 1 for abbreviation definitions.