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鈥檛 get an active copy of Mest from
their fathers were much more likely to die (Nature Genetics, vol 20, p
163).
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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鈥攁nd 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鈥檛 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 鈥減arental gene warfare鈥�, says Keverne
(see 鈥淲here did you get your brains?鈥�, 快猫短视频, 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. 鈥淚t is in the mother鈥檚 interest to be a good mother but
you could argue it is far more in the father鈥檚 interest if the father is
investing nothing but his genetic activity,鈥� Keverne says.
But David Haig of Harvard University in Cambridge, Massachusetts, who
developed the parental gene war theory, says 鈥渋t doesn鈥檛 fit at first sight with
the hypothesis鈥� since both males and females need their grandchildren to have
good parents. Still, Haig found it to be 鈥渁 fascinating paper鈥� and said it was
鈥渢he first clear demonstration鈥� 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. 鈥淚s the same gene involved in
both maternal and paternal care, or do separate genes regulate the parental
responses of each sex?鈥�