Epigenetics--a helpful tool to better understand processes in clinical nephrology?

Epigenetics (literally in addition to the genetic sequence) is a novel discipline that has languished in the shadow of its genomic big brother that has attracted little interest among nephrologists. By tradition, phenotypic variations are divided into a genetic and an environmental component (Figure 1). There is no doubt that variations within the genome may have an impact on the phenotype in chronic kidney disease (CKD) 1. However, as epigenetic mechanisms due to environmental factors are also critical for normal functioning of the genome 2, the associations between the unphysiological uraemic environment and the epigenotype should be of interest to study in this patient group. Indeed, as the epigenotype is transmitted to daughter cells, and epigenetic changes may endure in subsequent cell generations, this discipline could bring a new perspective to the study of all physiological processes. The epigenetic state, and thus the interpretation of the genome is based on the recognition by proteins involved in transcription of specific genomic loci. Chromatin consists of DNA wrapped around cores of histones. The specific enzymatic modifications of DNA and histones are specific for a given locus in a given cell type at a given time and under defined outer influences. The unique structure of chromatin formed at specific loci provides the specificity of the genome to transcription required to acquire and maintain cell-specific phenotypes. The modifications that can occur in eukaryotes include methylation at the 5-carbon position of cytosines in CG (CpG) dinucleotide sequences. The mammalian epigenome denotes properties of the genome that are not explained by the primary DNA sequence but