Bi-directional effects of vitamin B12 and methotrexate on Daphnia magna fitness and genomic methylation

Abstract

Here we interrogated, using three separate but complementary experimental approaches, the impact of vitamin B12 availability and methotrexate exposure on Daphnia magna, which we hypothesised should have an opposite effect on One carbon metabolism (OCM). OCM is a vital biological process supporting a variety of physiological processes, including DNA methylation. Contrary to mammalian models, this process remains largely unexplored in invertebrates. The purpose of this study was to elucidate the impact of OCM short-term alteration on the fitness and epigenome of the keystone species, Daphnia. We used maternal age at reproduction, brood size and survival rates in combination with DNA methylation sensitive comet assay to determine the effects of vitamin B12 or MTX on fitness and the epigenome. Vitamin B12 had a positive influence on Daphnia fitness and we provide evidence demonstrating that this may be associated with an increased level of genome-wide DNA methylation. Conversely, exposing D. magna to MTX negatively influenced the fitness of the animals and was associated with loss of global DNA methylation, translating in decreased fitness. These results highlight the potential importance of OCM in invertebrates, providing novel evidence supporting a potential role for epigenetic modifications to the genome in D. magna environmental adaptability.

Multigenerational Exposures of Daphnia Magna to Pristine and Aged Silver Nanoparticles: Epigenetic Changes and Phenotypical Ageing Related Effects

“…The average number of offspring per control daphnid was around 6 neonates per brood (Tables S1–4, Supporting Information) leading to cumulative totals of 27–30 offspring over the 5 broods, which was comparable with other studies using the same strain of Daphnia . [ 30 ]…”

Folate, genomic stability and colon cancer: The use of single cell gel electrophoresis in assessing the impact of folate in vitro, in vivo and in human biomonitoring

“…variation of the SCGE assay has been described previously. This assay compared with other methods is simpler and more cost-effective [26][27][28][29]. For this modification, two isoschizomer endonucleases (HpaII and MspI) that share the same restriction site in CpG islands are deployed separately in the assay at the post-lysis step.…”

Transcriptomic Response of Daphnia Magna to Nitrogen or Phosphorus Limited Diet

“…Methylation is an important way for Daphnia to response and adapt to environmental stress [15]. It is also closely related to cell growth and tissue differentiation of metazoans and could be induced by nutrient restriction [16]. Therefore, in our study, the increased degradation of methionine and SAM: SAH ratio may promote the methylation level and stimulate the development (or growth) of D. magna with Nlimited diet.…”