Meta-analysis of DNA methylation in invertebrates: evolutionary trends and indications for environmental assessment

• Autor(a) principal: Pereira, Bruno Miguel Pacheco
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33239
• topic: Gene body; Evolution; Adaptation; Epigenetics; Meta-analysis; CpG O / E.

The anthropogenic impact in a variety of ecosystems has been increasing significantly in recent decades. This anthropogenic pressure translates into globally spreading phenomena like habitat fragmentation, mass extinction or biodiversity decline, that threaten ecosystem services. The mitigation of such detrimental ecological impacts is largely dependent on our ability to properly assess effects of the pressures on biological systems, i.e., with sufficient resolution levels that allows establishing reliable cause-effect relationships. High-resolution tools to assess these effects have recently been emerging, e.g., tools based in gene expression and the epigenome. The latter is strongly influenced by environmental conditions, with consequences in gene expression. Thus, the epigenome constitutes a new opportunity for the mechanistic understanding of toxic effects of environmental contaminants and for the development of biomarkers of exposure and effect. In this context, the specific objectives of the present dissertation were as follows: (i) to collect reliable genomic data of various invertebrate species representing different environmental compartments; (ii) quantify the distribution of the potential for gene body methylation based on the prevalence of CpG dinucleotides in the genome of each species; (iii) elaborate on the differential ability of invertebrate species to respond or potentially adapt to challenging and/or highly fluctuating environments based on phenotypic plasticity mediated by DNA methylation and/or related mutations; (iv) conclude on the most favourable models to address gene body methylation within an ecotoxicological context. Among the set of 27 species with reliable genomic data publicly available selected for meta-analysis, 11 recorded an observed-to-expected CpG ratio distribution (CpG O/E) that suggest the existence of gene groups with high susceptibility to methylation, and 16 have distributions suggesting that the entire genome is little or very little susceptible to methylation. Patterns of reduced susceptibility to DNA methylation have been identified among phylogenetically closely related species, which supports the theory that DNA methylation may have played a relevant role in species adaptation to new ecological niches, e.g., during the colonization of terrestrial or freshwater environments from primitive marine environments. The concentration of CG dinucleotides in the analysed genomes also allowed to discuss the suitability of different model organisms used in ecotoxicology for the development of biomarkers of exposure or effect based on DNA methylation. In this context, the following species are noteworthy as those presenting higher relative levels of CG dinucleotides in their genome: N. vectensis and T. californicus in the marine environment; D. magna and D. polymorpha in freshwater ecosystems; I. scapularis and H. saltator in the soil compartment; A. albimanus, A. albopictus and N. vitripennis representing aerial species.