It has been clear for many years that we are not just genetic machines. Epigenetic changes - alterations to the chemical marks that accumulate around genes, regulating their 'switching on' (expression) and 'switching off' (silencing) - can be induced by environmental factors such as such as diet, drugs and exercise. The question generating most controversy is whether such epigenetic modifications can be passed from generation to generation. With regard to epigenetics, the expression 'sins of the father' might be reconceived as 'sins of the mother' or even 'sins of the grandmother'. There is growing evidence that both DNA and the inherited epigenetic landscape can contribute to regulation of gene expression in the offspring, and further that they are crucial to development and survival.
Working with fruit flies, this German research team used fruit flies to investigate the transmission of a particular epigenetic mark from mother to embryo. They focused on an epigenetic histone methylation referred to as H3K27me3 - also found in humans - that affects chromatin structure. DNA winds around molecular spools called histones (the DNA and histones are referred to as chromatin) as it wraps into the chromosome. Altering chromatin structure can influence gene expression, with closed chromatin leading to gene silencing and open chromatin leading to gene expression. By using a green staining technique, researchers were able to determine that whilst other epigenetic marks had been erased from the embryo after fertilisation (the epigenetic barcode thus essentially reset) H3K27me3 modifications remained. Further study demonstrated that removal of the H3K27me3 during early development led to failure of embryonic development, thus epigenetic modifications are important for embryonic development.