Histone epigenetic marks in heterochromatin and euchromatin of the Chagas' disease vector, Triatoma infestans

Triatoma infestans, a vector of Chagas' disease, shows several particular cell biology characteristics, including the presence of conspicuous heterochromatic bodies (chromocenters) where DNA methylation has not been previously detected. Whether histone modifications contribute to the condensed state of these bodies has not yet been studied. Here, we investigated epigenetic modifications of histones H3 and H4 and presence of the non-histone heterochromatin protein (HP1-alpha) in the chromocenters and euchromatin of T. infestans cell nuclei, using immunocytochemistry. The effect of different concentrations of the histone deacetylase inhibitors valproic acid (VPA) and sodium butyrate (NaBt) on chromocenter condensation was visually examined; in VPA-treated specimens, this effect was also analyzed by image analysis. Trimethylated H3K9 signals, which were revealed in chromocenter and non-chromocenter areas, were strongest in chromocenters, whereas selected acetylated histone marks and mono- and dimethylated H3K9 and H4K20 signals were detected only in euchromatin. Weak trimethylated H4K20 signals and variable distribution of HP1-alpha were detected in chromocenters of part of the cellular population analyzed. Although specific VPA and NaBt treatment conditions affected the heterochromatin condensation pattern, they did not induce a decrease in survival and molting rates of the T. infestans nymphs. The VPA-induced chromatin remodeling was not accompanied by induction of H3K9 acetylation in chromocenters. Present findings regarding histone modifications and effects following VPA or NaBt treatments did not yet solve the question of which factors are responsible for maintenance of the condensed state of chromocenters in T. infestans. A possibility requiring further investigation remains on histone methylation marks and/or non-histone proteins. (C) 2016 Elsevier GmbH. All rights reserved.