The Epigenetics Revolution: How Modern Biology is Rewriting Our Understanding of Genetics, Disease and Inheritance

The babies who were born small stayed small all their lives, with lower obesity rates than the general population.

Deaths through drowning are most common when sales of suntan lotion are highest. From this one could infer that sun tan lotions have some effect on people that makes them more likely to drown. The reality of course is that sales of suntan lotion rise during hot weather, which is also when people are most likely to go swimming. The more people who swim, the greater the number who will drown, on average. There is a correlation between the two factors we have monitored (sales of sun block and deaths by drowning) but this isn’t because one factor causes the other.

The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ (I found it!) but ‘That’s funny …’
Isaac Asimov

There is a well-known scientific proverb: absence of evidence is not the same as evidence of absence.

Thomas Henry Huxley. He was Darwin’s great champion in the 19th century and it was Huxley who first described ‘the slaying of a beautiful hypothesis by an ugly fact’.

DNA alone isn’t carrying all the necessary information for the creation of new life. Something else must be required in addition to the genetic information. Something epigenetic.

In full-blown cancer the cells don’t just divide too often, they are also abnormal and can start to invade other tissues.

A mole is a benign tumour. So is a little outgrowth in the inside of the large intestine, called a polyp. Neither a mole nor a polyp is dangerous in itself. The problem is that the more of these moles or polyps you have, the greater the likelihood that one of them will go the next step, and develop an abnormality that will take it further along the path towards full-blown cancer

So there is a consistent finding. Our two unrelated compounds, which control growth of cancer cells in culture and which have now been licensed for use in human treatment, inhibit epigenetic enzymes. In doing so, they both drive up gene expression which raises the obvious question of why this is useful for treating cancer.

Proto-oncogenes and tumour suppressors are not intrinsically good or bad. In healthy cells, the activities of these two classes of genes balance each other. But when regulation of these networks goes wrong, cell proliferation may become mis-regulated. If a proto-oncogene becomes over-active, it may push a cell towards a cancerous state. Conversely, if a tumour suppressor gets inactivated, it will no longer act as a brake on cell division. The outcome is the same in both cases – the cell may begin to proliferate too rapidly

When the DNA of a CpG island is heavily methylated, the gene controlled by that promoter is switched off. In other words, DNA methylation is a repressive modification. DNMT activity increases DNA methylation and therefore represses gene expression