Male and female brains have evolutionarily conserved sexual signatures

Male and female brains have evolutionarily conserved sexual signatures

An article published in the open-access journal PLoS Genetics reports that male and female primates and humans have hundreds of biological differences that are evident in gene expressions in the cerebral cortex. The Uppsala University, Karolinska Institute, and University of Chicago researchers maintain that some of these differences first appeared a very long time ago. Notably, evolution has preserved these differences that indicate particular sex differences in the brain.

Although clear differences between males and females - like average body size, weight, and genitalia design - have been sustained during primate evolution, this new study has analyzed gene expression within the cerebral cortex. This part of the brain is responsible for complex functions in primates, including humans, such as memory, attentiveness, thought processes, and language.

Björn Reinius (Department of Development and Genetics, Uppsala University, Uppsala, Sweden) and colleagues conducted their study by measuring gene expression in the brains of male and female humans, macaques, and marmosets. The researchers took the products of genes (RNA) from each animal's brain and hybridized them to microarrays that consisted of thousands of DNA clones, coding for thousands of genes. The between-sex analysis required the authors to focus on DNA sequence differences for genes presenting different expression levels.

Co-author Professor Elena Jazin (Uppsala University) specifies that, "Knowledge about gender differences is important for many reasons. For example, this information may be used in the future to calculate medical dosages, as well as for other treatments of diseases or damage to the brain."

The authors found that, "Genes with conserved sexual gene expression dimorphism in the brain also evolve under more evolutionary constraint, compared with other genes, suggesting that they may have important roles during evolution of sex in primates. Moreover, we found higher evolutionary constrains in the coding regions of female-biased genes as compared to both male-biased and non sex-biased brain expressed genes." They believe that the insights provided by this study may help explain some of the psychiatric diseases with differences in males and females.

Reinius adds that future studies will be required to answer questions regarding whether these differences in gene expression are functionally significant.

An Evolutionarily Conserved Sexual Signature in the Primate Brain

Reinius B, Saetre P, Leonard JA, Blekhman R, Merino-Martinez R, et al.

PLoS Genetics . 4(6):e1000100.


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