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 (2008). 4(6):e1000100.

doi:10.1371/journal.pgen1000100

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Written by: Peter M Crosta