Somatic mutagenesis of mitochondrial cytochrome b gene from hippocampus of Wistar rats

Abstract

One of the most interesting findings in Systems biology is the discovery of negative correlation between gene expression levels and evolutionary rates of genes. Biological explanations of this correlation are still debated. Recently the hypothesis of Drummond and Wilke became increasingly popular. The hypothesis suggests that errors of translation with subsequent misfolding of proteins are the universal factor limiting the rate of protein evolution because this misfolding causes premature cell death. The mitochondrial somatic mutations are the promising tool to examine this hypothesis: damaging mutations in a gene cannot cause the complete lack of the corresponding protein product because animal mitochondria contain many copies of chromosomes (5–15 copies per mitochondria) in somatic tissues. We analyzed somatic mutations in the mitochondrial cytb gene from hippocampus of Wistar rats. We did not find any indication of purifying selection in the cytb gene. Absence of selection does not support the Drummond-Wilke hypothesis which postulates strong purifying selection eliminating errors that cause protein misfolding. This result questions applicability of the Drummond-Wilke hypothesis to mitochodrial proteins.