March
2007
Memories are made of this0
Links to free teaching resources for the science story below:
Teaching resources (UK US) designed specifically for this story at www.realscience.org.uk
Set of lessons on gene inheritance: Students learn how genes are passed from one generation to the next. They explore meiosis, which divides the genetic material of an individual in half to produce the sperm or egg cells. They explore how genetic diseases are passed from one generation to the next. A coin-toss exercise demonstrates the odds of parents passing mutated genes to their offspring. Two videos illustrate positive, negative and neutral effects of mutations. From Teachers’ Domain. Simple registration required.
“A mysterious biological mechanism that subtly changes the way people’s genes behave may account for many of the surprising differences between identical twins…” Washington Post. Background on epigenetics.
“Recent revisions to the basic mechanisms of modern genetics violate many long held ideas of inheritance.” Teacher background, since “older textbooks will not have references for these genetic surprises.”
“If you thought that DNA has no secrets left to surrender, think again. The sequencing of the human genome may have heralded a new era for genetic research, but the unravelling DNA story still has a twist in its tail. The new buzzword in many corners of the establishment is epigenetics…”
“How does the environment alter the phenotype? Identical twins are not interesting merely because they are different: everybody’s different. Instead, they are interesting because they show how the same genome can unfold differently with slightly different conditions.” Prominent scientist weblog touching on epigenetics.
“The only important thing about DNA is its sequence, right? Wrong.” Teacher background on epigenetics and methylation.
Activities and instruction on how memory works, and on Alzheimer’s disease. From PBS.
Activity page on memory, with: a minds-on and hands-on experience; an opportunity to compare memory tricks; tools and ideas for improving memory.
The story:
University of Alabama: 14-Mar-2007, 12:00 Eastern US Time, Eurekalert.
Memories are made of this
Scientists have discovered a mechanism by which the constantly changing brain makes its memories—from a dog-bite to that first kiss.
It’s the same mechanism that cells use to alter their genes during development of the embryo.
Neurobiologists Courtney Miller and David Sweatt report their findings in the March 15, 2007 issue of the journal Neuron.
Their studies were aimed at exploring if a process called DNA methylation plays a role in making memories.
In methylation, molecules called methyl groups are attached to genes. This switches them off. Cells use methylation when the embryo is developing to switch off particular genes. This lets the cells specialize into different types – skin, bones, hair, etc – as the embryo grows and develops.
The name for this process is “epigenetic”. Epi means “above” or “in addition”. So epigenetic means that something is happening in addition to the normal action of the genes.
During development of the embryo, methylation causes a permanent change in the activity of genes. Previous studies had hinted that methylation stays active into the adult brain. But it wasn’t thought to be a mechanism for making long-term memories.
On the other hand, mistakes in DNA methylation are seen in some brain disorders, such as schizophrenia.
So Miller and Sweatt designed experiments to test if methylation helps make memories. In their experiments they produced fearful memories in rats. They gave the animals mild shocks when they were in a particular training chamber.
They could then test if the rats remembered, by noticing if they froze when placed in that chamber.
Then they gave the animals drugs that inhibit methylation. This was to test if methylation was needed for the rats to form these memories.
The researchers found that it was. They also found that methylation directly controls the activity of two genes. One of these prevents memories being formed. It is called protein phosphatase 1. The other helps memories form. It is called reelin.
DNA methylation was once thought to be a static process after cell differentiation – when cells had become part of the different organs of the body. This study is the first to find evidence, say the scientists, that instead it is “dynamically regulated in the adult nervous system”, and “plays an integral role in memory formation.”
The new findings show that DNA methylation is used by the central nervous system. This is a key step in controlling gene activity to make memories.
In terms of possible applications of the work, epigenetic errors have been seen in cancer, some types of autism and schizophrenia. So the new findings could improve our understanding of the causes of those disorders.
More broadly, the findings show the importance of DNA methylation in changes in the brain caused by events in the environment
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The researchers include Courtney A. Miller and J. David Sweatt of University of Alabama at Birmingham in Birmingham, AL.
This work was supported by the NIMH, NINDS, American Health Assistance Foundation, and the Evelyn F. McKnight Brain Research Foundation. C.A.M. is a Civitan Emerging Scholar.
Miller et al.: “Covalent Modification of DNA Regulates Memory Formation.” Publishing in Neuron 53, 857–869, March 15, 2007. DOI 10.1016/j.neuron.2007.02.022. www.neuron.org.
