Mechanistic basis of epigenetic switching and memory
2020
Professor Martin Howard
Summary of the science
Epigenetics studies how and why cells switch genes on and off. Epigenetic memory is when the offspring of a cell inherit the same pattern of on/off genes as their parents. This means that events that happened to the parents, which made them turn genes on and off, are 'remembered' by their descendants.
Genes are the instructions for cells which tell them how and when to make different proteins. Genes are stored as strands of DNA in the nucleus, where they’re wrapped around proteins called histones. This system of wrapping means cells can store 2 metres of DNA inside a nucleus that’s too small to see without a microscope.
One way of switching genes on and off is controlling how tightly DNA is wrapped around histones. DNA that is looser is easier to get to, so proteins that read the gene instructions will read these genes more frequently, and make more of those proteins. DNA can be loosened by changing the proteins that are bound to it. Sometimes genes are switched on or off for a long time, which is called epigenetic memory as it helps cells remember events that happened a long time ago. These memories are be passed to daughter cells when the cell divides, which means they often outlive the original cell.
About the research
Epigenetic modifications are stably maintained across a cell's descendent lineage, a phenomenon known as epigenetic memory. The Howard Lab investigates the mechanistic basis of epigenetic memory using the floral regulator FLC as their molecular system of choice. FLC represents an ideal choice as it is epigenetically repressed by cold conditions, with a longer period of cold resulting in quantitatively more loci being repressed, establishing a clear use of memory at the molecular level.
About the illustration
We wanted to have a section of an Arabidopsis root as a central figure of the illustration as it is a common visualisation used by the Howard Lab. The illustration is then completed with strands of histone-DNA complexes which adds texture to the image and clearly capitulates the molecular focus of the research. The histones maintain the same modifications throughout the strands, highlighting the idea of memory.