Molecular evolution of zebrafish dnmt3 genes and thermal plasticity of their expression during embryonic development

• Published in: Gene 2012-05, Vol.500 (1), p.93-100
• Main Authors: Campos, Catarina, Valente, Luisa M.P., Fernandes, Jorge M.O.
• Format: Article
• Language: English
• Subjects: adults; Animals; Bayesian theory; Danio rerio; DNA; DNA (Cytosine-5-)-Methyltransferases - genetics; early development; embryogenesis; Embryonic development; Epigenetic regulation; epigenetics; Evolution, Molecular; Female; gene expression regulation; Gene Expression Regulation, Developmental; genes; gonads; Humans; long term effects; Male; mammals; messenger RNA; methylation; Methyltransferases; mouth; Phylogeny; Positive selection; temperature; Terminology as Topic; Zebrafish - embryology; Zebrafish - genetics
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2012.03.041

DNA reprogramming by DNA (cytosine-5)-methyltransferases (dnmts) after fertilisation is a dynamic mechanism that is essential for early development. Amongst the three types of dnmt genes in vertebrates, dnmt3 is the one involved in de novo methylation and comprises three related genes, termed dnmt3a, dnmt3b and dnmt3L in mammals. Zebrafish (Danio rerio) has six dnmt3 paralogues, which have hitherto been termed dnmt3 to dnmt8. Bayesian inference of phylogeny and synteny analysis revealed that dnmt6 and dnmt8 are in fact duplicated dnmt3a genes, whereas the other paralogues are closely related to dnmt3b. Hence, we propose a revised nomenclature that more accurately reflects the relationship amongst zebrafish dnmt3 genes. Both dnmt3a genes were ubiquitously expressed in adult tissues, whilst the various dnmt3b paralogues were differentially expressed, with notably high expression levels in the gonads. The influence of embryonic temperature on dnmt3 expression was investigated, since it is known to have a significant impact in early development and a long-term effect on growth in some teleost species. Embryos were incubated at 23, 27 or 31°C and samples collected at six developmental stages from blastula until protruding mouth. Dnmt3 expression during early development was remarkably dynamic. In particular, mRNA levels of the two dnmt3a genes showed a marked increase throughout development and several significant differences in dnmt3a and dnmt3b transcript levels were found between temperatures at the same developmental point. Taken together, our data indicate that dnmt3 paralogues are diverging and that dnmt3a and dnmt3b may play different roles in thermal epigenetic regulation of gene expression during early development. [Display omitted] ► Zebrafish has two dnmt3a and four dnmt3b paralogues. ► Dnmt3a is ubiquitously expressed whereas dnmt3b has differential tissue distribution. ► Dnmt3 genes show a dynamic expression pattern during zebrafish development. ► Embryonic temperature influences dnmt3 transcript levels. ► Dnmt3 paralogues are evolving at different rates, indicating subfunctionalisation.