Researchers have transmitted fear of a specific smell down two generations of mice, using a mechanism of inheritance that responds directly to environmental factors. They say a similar effect may be significant in some human psychiatric disorders.
The study at Emory University in Atlanta is one of the most striking demonstrations so far of “epigenetics”, a phenomenon causing increasing excitement among evolutionary biologists. It involves biochemical marking of DNA in response to experience, in a way that may affect the activity of genes for several generations.
The scientists made laboratory mice fear the odour of acetophenone, which is rather like cherry blossom, by giving them a mild electric shock whenever they were exposed to it. They then found that the offspring of these sensitised mice recoiled when they first smelled it, although they were conceived by in-vitro fertilisation and had no contact with their parents. The sensitivity even appeared in the second generation.
Publishing their results in Nature Neuroscience, the authors suggest that epigenetic inheritance may also be important in humans. “Knowing how the experiences of parents influence their descendants helps us to understand psychiatric disorders that may have a transgenerational basis, and possibly to design therapeutic strategies,” says Kerry Ressler, professor of psychiatry at Emory.
Both mother and father mice passed on acetophenone sensitivity to their biological offspring. But it was not transmitted to fostered pups, showing that social interaction was not involved. Nor were the smell-sensitised offspring more nervous in general.
The scientists do not understand the biochemical mechanism that induces the epigenetic changes in the sperm and eggs of the sensitised mice. But they did find a modification to the DNA of the odour receptor gene that responds to acetophenone.
“There is some evidence that some of the generalised effects of diet and hormone changes, as well as trauma, can be transmitted epigenetically,” Ressler says. “The difference here is that the odour-sensitivity learning process is affecting the nervous system – and apparently, reproductive cells too – in such a specific way.”
Questions remain but scientists who are enthusiastic about epigenetics welcome the results so far. “It is high time public health researchers took human transgenerational responses seriously,” says Marcus Pembrey of University College London.
“I suspect we will not understand the rise in neuropsychiatric disorders or obesity, diabetes and metabolic disruptions generally without taking a multi‑ generational approach.”
Fathers’ diet linked to birth defects
Everyone knows that what the mother eats before conception is very important for the baby’s health. Now a study at McGill University in Montreal suggests that paternal diet plays an important role too.
The research focused on folate, the essential vitamin also known as folic acid. Mothers in the industrialised world are advised that, to avoid miscarriages and birth defects, they must consume enough folate in their diet (through green vegetables, cereals, fruit and meat) or take folate supplements.
Working with mice, the McGill scientists compared the offspring of fathers with sufficient and insufficient folate in their diets.
They found a strong association between insufficiency and birth defects. The study is published in the journal Nature Communications.
“We were very surprised to see that there was an almost 30 per cent increase in birth defects in the litters sired by fathers whose levels of folates were insufficient,” says Romain Lambrot. “We saw some pretty severe skeletal abnormalities.”
The scientists found that these problems resulted from a failure in the epigenomic reprogramming that takes place as sperm develop – the large-scale erasure and re-marking of all the DNA in the paternal genome.
The study confirms other research (including the Emory University study featured on this page) which shows that sperm carries a memory of the father’s environment including diet and lifestyle.
“Fathers need to think about what they put in their mouths, what they smoke and what they drink, and remember they are caretakers of generations to come,” says Sarah Kimmins, the study leader. “Our next step will be to work with a fertility clinic so that we can start assessing the links in men between diet, being overweight and how this information relates to the health of their children.”
Using spiders’ webs to monitor pollution
An electrostatic glue found on the webs of common garden spiders could be used to detect unwanted chemicals in the air, according to research from Oxford University, writes Sarah Spickernell.
The glue is attracted to the electric charge that builds up on insects as they fly past. This helps spiders capture prey by causing their webs to reach out and grab hold of the insects.
“Everything that moves through the air develops static charge, so it’s fascinating to see how spider webs make use of this to actively catch prey,” says Fritz Vollrath, who led the study, published in the journal Naturwissenschaften.
Vollrath and colleagues studied how stretching the web affected the resistance and shape of the glue droplets, discovering that the glue maintained its electrical conductivity even when stretched a considerable distance.
According to the Oxford team, the glue’s characteristics could serve a more industrial purpose, since the particles of pesticides and other pollutants are charged. “Electrical attraction drags these particles to the webs, so you could harvest and test webs to monitor pollution levels,” says Vollrath.
He adds that it would even be possible to identify pollutants by analysing the shapes woven by spiders, which eat their polluted webs after use: “Spiders spin different webs on different drugs, for example creating beautiful webs on LSD and terrible webs on caffeine.”
Mosquito attraction could be blocked
A single group of mosquito cells has been identified as attracting the insects to human skin. The discovery could hold the key to developing new mosquito repellents and controls in the future.
Mosquitoes, which infect humans with diseases such as malaria, dengue fever and West Nile virus, are responsible for killing more people every year than any other living creature.
But the study at the University of California, Riverside, has revealed that certain cells in the mosquitoes’ olfactory system, which controls their sense of smell, could be inhibited to prevent them from being attracted to us.
The cells, called cpA neurones, cause mosquitoes to respond positively to certain human body odours. The study, published in the journal Cell, also identified some odours that have the opposite effect – inhibiting the neurones and removing the attraction.
Anandasankar Ray, who led the study, welcomes the advances that could be made on the back of this research. “These findings open up very realistic possibilities for developing ways to use simple, natural, affordable and pleasant odours to prevent mosquitoes from finding humans,” he says.
The next stage will be to develop the repellents. This should not prove too much of a challenge, given that several compounds that inhibit and deactivate cpA neurones are already known.
“We believe that this study will be the foundation for the discovery of a new generation of mosquito behaviour-modifying approaches,” concludes Ray.