Environmental factors affect DNA methylation in the marine polychaete Polydora cornuta (Annelida)
LE3 .A278 2017
Bachelor of Science
Maternal environment plays a significant role in influencing offspring phenotype through epigenetic modifications such as DNA methylation. The marine invertebrate, Polydora cornuta (Annelida), has phenotypic plasticity in larval development, producing two distinct morphs of larvae: adelphophagic (non-dispersive) and planktotrophic (dispersive). The objectives of my experiment were to 1) develop a protocol to detect differences in DNA methylation among individuals and 2) determine if DNA methylation is affected by environmental factors. Additionally, methionine was explored as a potential link between maternal environment and DNA methylation, as marine detritivores (including P. cornuta) are thought to be methionine limited. I hypothesized that exposure of females to compounds that cause a shift in larval phenotype (e.g., BPA) would also cause a change to the maternal epigenome (DNA methylation). Adult P. cornuta were cultured in 6 groups: seawater control), BPA, folate/B12, and three concentrations of methionine (10-5, 10-6, 10-7M). Differences in maternal methylation were demonstrated through total genome digestion with isoschizomers HpaII and MspI. Gel electrophoresis was used to generate DNA smear patterns that indicated differential cleavage at methylated CpG dinucleotides. DNA smear patterns were analyzed using ImageJ software to generate intensity plots. The protocol was sensitive enough to detect individual variation in DNA methylation pattern. Exposure to BPA and all three concentrations of methionine significantly reduced DNA methylation relative to the controls. The greatest reduction in methylation was seen in methionine treated worms. Therefore, methionine is potentially an important link between environment and epigenome. Further steps are needed to establish a direct link between DNA methylation and larval phenotype. This study has contributed to a greater understanding of the mechanism underlying epigenetic modification in invertebrates, and its relationship with phenotypic plasticity.
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