GSE160662
Paternal hypoxia exposure primes offspring for increased hypoxia resistance
Environmental challenges experienced by an organism can have multiple effects at an individual level, with recent work also suggesting these challenges may affect their unexposed offspring. In a time of rapid environmental change, understanding whether environmental challenges experienced by organisms could increase the fitness of future generations to survive these same stressors, is critically needed. Low dissolved oxygen is a common environmental challenge that aquatic organisms encounter, resulting in numerous physiological, phenotypic, and epigenetic changes. In this study, we use zebrafish (Danio rerio) as a model to investigate how paternal hypoxia experience impacts subsequent progeny. Males were exposed to moderate hypoxia (11-13 kPA) for 2 weeks, bred to create an F1 generation, and progeny underwent an acute hypoxia (0-1 kPA) tolerance assay. Using time to loss of equilibrium and loss of equilibrium frequency as measured of hypoxia resistance, we show that paternal exposure to hypoxia endow offspring with a greater tolerance to acute hypoxia, compared to offspring of unexposed males, though there are strong family x treatment effects. In addition to phenotypic alternations, we also investigated changes in gene expression in offspring. We conducted RNA-Seq on whole fry and detected 91 differentially expressed genes, including two hemoglobin genes that are significantly upregulated by more than 4-fold in the offspring of hypoxia exposed males. Moreover, the offspring which maintained equilibrium the longest showed the greatest upregulation in hemoglobin expression. Paternal exposures to physiological challenges are thus able to impact the phenotype and gene expression of their unexposed progeny. We conducted whole genome bisulfite sequencing (WGBS) on the sperm of parental males to assess whether changes in progeny phenotype and gene expression are underpinned by changes in DNA methylation. While we observed coupling of methylation levels in the parental sperm and gene expression in progeny overall, we did not detect differential methylation at any of the differentially expressed genes, suggesting that another epigenetic mechanism is responsible for the observed changes in gene expression. Overall, our findings suggest that a 'memory' of past hypoxia exposure is maintained and that this environmentally induced information is transferred to subsequent generations, pre-acclimating progeny to cope with hypoxic conditions. Overall design: Zebrafish males were exposed to moderate hypoxia (11-13 kPA) for 2 weeks and bred to create an F1 generation. To evaluate changes in gene expression, we conducted RNA-Seq on 20 day old fry from control and hypoxia treated males. Additionally, to evaluate changes in DNA methylation patterns we conducted whole genome bisulfite sequencing (WGBS) on the sperm of parental males.