The brains of male and female mice differ in important ways, according to a new study led by researchers at Stanford University Medicine. And, according to experts, these differences are probably reflected in the human brains of women and men as well.
For the experiment, the scientists examined four small structures within the brains of mice that are known to program “rating, dating, mating, and hate” behaviors. These behaviors, such as female receptivity to mating and maternal protection, help animals reproduce and their young survive. They discovered more than 1,000 genes with different levels of activity in the brains of one sex compared to the other.
“Using these genes as entry points, we have identified specific groups of brain cells that orchestrate sex-specific behaviors,” says Nirao Shah, co-author of the paper published in the journal Cell.
Male mice, for example, are quick to distinguish the sex of strangers invading what they consider to be their territory . If the intruder is another male, they immediately attack him. If it is a female, they initiate courtship. Female mice exhibit maternal rather than territorial aggression, attacking anything that threatens their pups. They are more inclined than males to protect their young and retrieve any that stray. And their willingness to mate varies mightily depending on the stage of their cycle. Clearly instinctive behaviors.
The genetic makeup of the brain most likely explains much of the social behaviors typical of sex, which have been built into the brains of animals over millions of years of evolution. These findings help explain sex differences in behavior in mammals .
Experiments with mice therefore suggest that John Gray’s best-seller “Men are from Mars, Women are from Venus” was right . In fact, male and female brains vary in important ways.
The researchers also identified more than 600 differences in gene activation levels between females at different phases of their estrous cycle. (In females, this is known as the menstrual cycle; female mice do not menstruate.) “To find, within these four tiny brain structures, several hundred genes whose activity levels depend only on the stage of the female cycle was completely surprising, ” said Shah, who has dedicated her career to understanding how sex hormones regulate typical sexual behaviors.
” Mice are not human . But it is reasonable to expect that analogous brain cell types will be shown to play a role in our sex-typical social behaviors,” explains Shah.
More research is needed to map in greater detail the sex-related genetic differences between male and female mice, and also to assess the similarities and differences between the mouse and human genomes.
Referencia: A functional cellular framework for sex and estrous cycle-dependent gene expression and behavior
Joseph R. Knoedler
Sayaka Inoue 8
Daniel W. Bayless 8
Charu Ramakrishnan
Karl Deisseroth
Nirao M. Shah 9
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Published:January 21, 2022 CELL DOI:https://doi.org/10.1016/j.cell.2021.12.031
