Non-genetic processes in development and heredity

  • Datum:
  • Plats: Lindahlsalen, Norbyvägen 18A, Uppsala
  • Doktorand: Silva, Willian T. A. F.
  • Om avhandlingen
  • Arrangör: Evolutionsbiologi
  • Kontaktperson: Silva, Willian T. A. F.
  • Disputation

Disputation

There is a swiftly increasing amount of empirical evidence that non-genetic factors, such as DNA methylation and small RNAs, play an important role not only in development but also in heredity and, therefore, evolutionary dynamics. One of the most interesting aspects of non-genetic processes is their responsiveness to environmental conditions, which has been shown to affect not only the phenotype and fitness of the individuals directly exposed to the stimulus, but also their offspring even when the stimulus is no longer present, indicating that the transmission of non-genetic factors across generations might work analogously to immunization against recurring conditions. In this thesis, I explored the effects and consequences of non-genetic processes in development and heredity, from both theoretical and experimental perspectives. In Article I, I created a mathematical model of DNA methylation dynamics during the maternal-to-zygotic transition, leading to the zygotic genome activation. I found that there is a developmental constraint on the transition between different cell lineages, with an increasing flexibility of active methylation and decreasing flexibility of maintenance (de-)methylation. In Article II, we explored the dynamics of small RNA production throughout development, including their amplification, transgenerational transmission and responsiveness to environmental conditions. Responsiveness of small RNA production resulted in greater benefits when soma and germline are both responsive, especially in highly correlated environmental conditions. In Article III, I carried out experiments on zebrafish to explore the effects of the male social environment on sperm production in terms of sperm morphology and DNA quality. Males exposed to different social treatments produced sperm with different morphologies and DNA integrity levels. In Article IV, we used the same experimental design to look at the effects of the male social environment on offspring development in terms of differential gene expression patterns. Males exposed to different social treatments sired offspring that showed different expression patterns of genes involved in post-transcriptional processes of gene expression regulation.  Our findings shed light on the importance of non-genetic processes in development and heredity and contributes to the current knowledge about which and how non-genetic mechanisms can potentially affect evolutionary dynamics.