Variation of Metallothionein I and II Gene Expression in the Bank Vole (Clethrionomys glareolus) Under Environmental Zinc and Cadmium Exposure

Abstract

The main idea of the study was to assess how environmental metal pollution activates defence responses at transcription levels in the tissues of bank voles (Clethrionomys glareolus). For this purpose, the metallothioneine (MT) genes expression (a well known biomarker of exposure and response to various metals) was measured. The real-time PCR method was used for relative quantification of metallothionein I and metallothionein II expressions in the livers, kidneys and testes of bank voles from six populations exposed to different contaminants, mainly zinc, cadmium and iron. The assessment of Zn, Cu and Fe concentrations in the tissues allowed to study the MTs gene expression responses to these metals. ANOVA analysis showed differences between populations in terms of metal concentration in tissues, livers and kidneys. Student T test showed significant differences in metal concentration between unpolluted and polluted sites only for the liver tissue: significantly lower Zn levels and significantly higher Fe levels in the unpolluted sites. Kruskal–Wallis test performed on C T data shows differences in the gene expressions between populations for both MT genes for liver and testes. In the liver metallothionein I gene expression was upregulated in populations considered as more polluted (up to 7.5 higher expression in Miasteczko Śląskie comparing to Mikołajki). Expression of metallothionein II revealed a similar pattern. In kidneys, differences in expression of both MT genes were not that evident. In testes, MT upregulation in polluted sites was noted for metallothionein II. For metallothionein however, we found downregulation in populations from more contaminated sites. The expressions of both MTs were positively influenced by cadmium in kidney (concentration data from the previous study) and zinc and copper in liver, while cadmium had effects only on the liver MT II gene expression. Positive relationship was obtained for lead and metallothionein II expression in the liver.

Gene Expression Variation of Candidate Endogenous Control Genes Across Latitudinal Populations of the Bank Vole (Clethrionomys glareolus)

“…Over the past years, several traditional housekeeping (e.g., Actb, Gapdh, Rn18s, or Tuba1a) have been used for RT-qPCR data normalization in the bank vole in order to assess gene expression patterns implicated in the susceptibility to PUUV infection (Dubois et al, 2018;Müller et al, 2019), in the cellular response to the chronic exposure to ionizing radiation (Mustonen et al, 2018) or environmental heavy metal contamination (Świergosz-Kowalewska and Holewa, 2007;Zarzycka et al, 2016;Mikowska et al, 2018), and to measure PUUV viral RNA load in bank vole tissues (Guivier et al, 2014). However, the common RGs may show high expression variability in different tissues or experimental settings and other genes may thus present suitable alternatives (Hernandez-Santana et al, 2016).…”