A team of scientists has discovered rare cells in the brains of mice; one set is only found in males, and another set is found only in females in an area that helps control mating and aggression. The findings have been reported in Cell.
"The results show that there are differences between male and female mammalian brains at the level of cellular composition as well as gene expression but that those differences are subtle, and their functional significance remains to be explained," said Professor David Anderson, the Tianqiao and Chrissy Chen Institute for Neuroscience Leadership Chair and a Howard Hughes Medical Institute Investigator.
The brain contains various cell types including neurons, which transmit information, and various types of glial cells that help support and protect neurons. All cells in the body, including neuronal cells, carry an organism’s genome in its nucleus. The genes that are expressed in those cells give them their identity and help them carry out their roles.
One small region of the brain, the hypothalamus, is found in all vertebrates and plays a vital role in a variety of critical functions, including the regulation of body temperature, appetite, and emotional responses. It also produces and releases several essential hormones. Within one section of the hypothalamus called the ventrolateral subdivision of the ventromedial hypothalamus (VMHvl), there are cells that are known to play a direct role in controlling mating behaviors and aggression.
Previous research that studied these cells in the VMHvl showed that when the neurons are strongly stimulated, female and male mice will immediately become aggressive even when no threat is present. When the cells are weakly stimulated, the mice will initiate mating behaviors.
This new study analyzed gene expression in the VMHvl cells using cutting edge genomic tools that can identify the genes that are active in these cells - the cells’ transcriptome. While previous work has studied transcriptomics in this region, only about ten percent of the gene transcripts were assessed. By looking at more transcripts, the researchers were able to determine that there are more than seventeen types of cells in this small area of the brain. The research also indicated that some types of these cells are present in higher levels in male mice, and others were only identified in female mice.
Professor Anderson is featured discussing neuronal circuitry in the video above.
It’s known that there are sex differences in gene expression. This is the first time that different kinds of cells can be found in male or female brains, however. The scientists plan on continuing this work to learn more about what these different kinds of cells are doing.