SUNDAY, 26 FEBRUARY 2012Nirao Shah’s laboratory has recently discovered molecular events that may underlie behavioural differences between males and females. Some of the most pronounced sex differences arise in sexual and parenting characteristics, which have previously been linked to an area of the brain known as the hypothalamus. The researchers therefore searched for genes that were expressed to differing degrees in the hypothalamus of male and female mice. They identified sixteen such genes, which also demonstrated differing levels of expression in another brain region – the amygdala, associated with emotions.
The genes could be switched on or off in the brain by the sex hormones testosterone, oestrogen, and progesterone. To better understand their function, the researchers observed the behaviour of mice lacking some of the genes. When only one gene was missing, overall behaviour seemed normal. However, closer study revealed significant differences in sex-related behavior, for example, motivation to mate, or the length of time taken by females to defend their pups from intruders.
Scientists are unclear as to how exactly the genes might give rise to this behavioural variation, but many of them have been implicated in communication between neurons. Further investigation is also required to determine how social relations affect the expression of the genes.
These findings, published in Cell, could explain some of the behavioural differences typically seen between males and females. They may also contribute to the variation seen within each sex, for example, in levels of aggression or maternal/paternal tendencies. While these genes are likely to be only part of the story, they certainly appear to be involved.
Written by Ayesha Sengupta