Epigenetic Factors and Chromosome Organization


The term epigenetics was introduced by C. H. Waddington in 1956 to describe all the interactions between genes and their environment that lead to phenotypic expression. Today it is used to define heritable modifications in gene expression that are not based on changes in nucleotide sequence. In mammalian chromosomes, the commonly reported epigenetic markers are cytosine methylation, histone methylation, histone acetylation, histone methylation and noncoding ribonucleic acid and chromosome association.

Keywords: epigenetics; methylation; acetylation; chromosome; ICF syndrome

Figure 1.

(a) Chromosomes from an ICF patient after in situ hybridization. Probes specific for chromosome 1, classical satellite 2 (green spots) and α‐satellite (red spots). Chromosomes are associated and display a strong decondensation of regions corresponding to classical satellite 2. (b) Chromosomes 1 and 16 methylation patterns after immunofluorescence with 5‐methylcytosine antibody. On the left, normal chromosomes showing an R‐banding‐like pattern and a strong methylation of constitutive heterochromatin. On the right, chromosomes from an ICF patient with the typical undermethylation of classical satellite 2 (arrows).

Figure 2.

Methylation patterns after immunofluorescence with 5‐methylcytosine antibody in normal mouse embryos. (a) Differential methylation of parental chromosome arms observed in zygote. The large arrow indicates methylated chromosomes of maternal origin and the thin arrow indicates the undermethylated chromosomes of paternal origin. (b) Chromosomes from normal mouse embryos during preimplantation development. The asymmetrically methylated chromosomes (arrows) indicate a passive demethylation mechanism.



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Bourc'his, Déborah, and Viegas‐Péquignot, Evani(Jan 2006) Epigenetic Factors and Chromosome Organization. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0005788]