Daddy knows best

New Scientist, 03 October 1998

EVEN if a male mouse never meets his offspring, he still has a hand in how well they raise his grandchildren. A gene essential for normal maternal behaviour comes from the father, say researchers in Britain and Canada.

Genes are inherited in pairs, one from the father and one from the mother. Most are equally active, but some are biochemically labelled, or imprinted, to determine which of the two copies of a gene will be expressed. Researchers have now found a gene that appears to be essential for females to respond appropriately to their young. But surprisingly, because of imprinting, only the gene that comes from the father is expressed.

Azim Surani and Eric Keverne at the University of Cambridge, Louis Lefebvre of Mount Sinai Hospital in Toronto and their colleagues engineered male mice that lacked a gene called Mest. They mated them with healthy females and then looked at how the female offspring raised their own young. They found that the pups of females that didn't get an active copy of Mest from their fathers were much more likely to die (Nature Genetics, vol 20, p 163).

In more than 80 per cent of the litters, for instance, at least one newborn was abandoned, left unfed and tangled in its umbilical cord and placenta—and sometimes all the pups were left this way. None of the mothers with a working Mest gene neglected their pups.

Mutant mothers also failed in other measures of maternal behaviour, such as how long it took them to retrieve a straying pup and how quickly they built a nest from available wood chips. Normal mothers collected their pup within 10 minutes, but Mest-deficient mothers didn't manage it at all during the 15 minutes they were given. And while normal mothers immediately got stuck into nest building, only three out of eight mutant mothers could be bothered.

The finding may have implications for the theory of "parental gene warfare", says Keverne (see "Where did you get your brains?", New Scientist, 3 May 1997, p 34). Some researchers think that imprinting exists because males and females have different interests and try to influence their offspring through a battle of the genes. "It is in the mother's interest to be a good mother but you could argue it is far more in the father's interest if the father is investing nothing but his genetic activity," Keverne says.

But David Haig of Harvard University in Cambridge, Massachusetts, who developed the parental gene war theory, says "it doesn't fit at first sight with the hypothesis" since both males and females need their grandchildren to have good parents. Still, Haig found it to be "a fascinating paper" and said it was "the first clear demonstration" of imprinted genes affecting adult behaviour.

The new findings will also help researchers unravel the interactions of other genes known to influence parental behaviour, says Robert Bridges, a behavioural scientist at Tufts University in Massachusetts. "Is the same gene involved in both maternal and paternal care, or do separate genes regulate the parental responses of each sex?"