A fateful courtship

What really differentiates males from females? Could it be that they both came, after all, from the same planet? And what role do genes, hormones and scents play here?

Men and women sometimes seem to come from different planets, but the male brain and the female brain are similar, in general. So similar, that it is possible to turn peaceful and motherly mice into a kind of "casanovas" - by turning on just one genetic switch. This is according to the research of Dr. Tali Kimchi, who recently joined the Department of Neurobiology at the Weizmann Institute of Science.

During her post-doctoral research in the laboratory of Dr. Catherine Dulac at Harvard University, Dr. Kimhi deciphered mechanisms by which the behavior of mice is controlled by pheromones - odorous substances that animals secrete to communicate with each other and attract the opposite sex. Dr. Kimchi examined female mice that had been genetically modified so that their genetic load lacked the gene responsible for receiving the pheromone signals. The result: the genetically engineered mice neglected their pups and stopped protecting them. In fact, these mice developed sexual behaviors typical of males: they smelled the rears of potential mates and chased them, tried to mount them while making typical pelvic movements, and made courtship whistles that were not typical of females. The male mice that encountered these females seemed quite surprised, and tried to run away from them.

The masculinity of the mice indicates that in their brains there are neural circuits adapted to both male and female behavior, but the pheromones suppress the male behaviors and activate the female behavior style - by regulating male and female neural pathways. The researchers hypothesize that the males' brains also have circuits for both male and female behavior, but the pheromones suppress the female behaviors (such as taking care of puppies). These revolutionary findings on the potential of sexual behavior in the brains of mammals were published in the scientific journal Nature, and received a lot of attention in the world of science and even outside of it.

At the Weizmann Institute of Science, Dr. Kimchi will continue to investigate the role of pheromones in male and female behaviors. She will investigate the genetic, hormonal and neurochemical basis of the activity of pheromones, with an emphasis on social behaviors and those related to reproduction. In her new laboratory, wild mice, which have undergone a process of genetic engineering, will be equipped with electronic chips and antennas. They will live in semi-natural pens containing monitoring equipment. With the help of infrared cameras, the scientists will be able to follow the movement of the mice even at night;

And with the help of microphones they listen to the "conversations" of these animals. Unlike the reality TV programs, which usually block the intimate moments, Dr. Kimchi's "big brother" will focus specifically on the sexual and reproductive activity of the mice. The scientists will try to find out which genes, groups of nerve cells and neural circuits in the brain control actions such as distinguishing between males and females, fighting over desirable mates, and rearing puppies.

Dr. Kimchi prefers to conduct the research on wild mice, even though these mice are much smaller and agile, which makes it difficult to track them. The advantage they bring to research is their relative proximity to nature, both in terms of genetic and physiological makeup and in terms of social behavior. The study focuses on females, who pose a greater challenge to researchers because their behavior is less predictable. For example, it can be expected that a male mouse will always try to attack another male perceived as a rival, and will try to mate with a threatened female. On the other hand, it is difficult to predict in advance how a mouse will react and act in different situations. This is, among other things, because female behavior is affected by the hormonal cycle. Dr. Kimchi says that the behavior of females is more complex compared to male behavior also because it is controlled by a greater number of genetic, hormonal and environmental factors.

These studies may shed new light on the biological roots of behaviors considered characteristic of males or females. For more than fifty years, scientists thought that what differentiates males and females are the sex hormones that control neural circuits in the brain. But studies carried out in recent years by Dr. Kimchi and other scientists offer a different explanation: it is possible that the characteristic behavior of different genders depends less on hormones and more on groups of nerve cells controlled by pheromones or other sensory signals (so, for example, the females with the "masculine" behavior in the study of Dr. Kimchi had completely normal female hormones, and did not receive any male hormones such as testosterone).

In the long term, this research aims to discover new genes and neural circuits that shape the physiology and reproductive behavior of mammals. In particular, Dr. Kimchi strives to understand the genetic and environmental factors that lead to social behavior and unusual breeding practices, such as poor maternal or paternal behavior and even killing puppies, excessive aggression towards neighboring animals, preference for individuals of the same pair (gender), and little success in producing offspring. Such an understanding may help in the study of gender-dependent phenomena and diseases such as autism, schizophrenia, tendency to violence, and environmental anxiety and depression.

personal

When four-year-old Tali Kimchi would go for a walk with her parents, she would stop them from time to time so she could watch the rows of ants crossing the road. Ever since she can remember, she has always wanted to study the behavior of animals and natural phenomena.

In the research work she carried out during her studies in preparation for receiving a doctorate degree in the Department of Zoology at Tel Aviv University, under the guidance of Dr. Yosef Terkel, she came to fascinating insights regarding the navigational ability of a rat, a rodent that is about 25 centimeters long, lives under the ground and looks like a kind of furry cylinder, lacking the ability to see and has sharp front teeth. She discovered that when the rat digs its burrows in search of food and mates, it uses the Earth's magnetic field as a compass to help it choose direction. In addition, the rat manages to dig its burrow around obstacles in the shortest possible indirect way. Dr. Kimchi discovered that in order to do this he relies on a natural "radar": he slams his head against the walls of the burrow to create waves, detects the returning echo using receptors located in his legs, and thus maps the area and chooses the appropriate excavation route.