Scientists at the University College London (UCL) have discovered new genetic evidence showing why “Men Are from Mars, and Women Are from Venus.” The London scientists have discovered widespread variations in how genes express themselves differently in the male and female brain.
The researchers discovered that between men and women, genes are expressed differently in all major brain regions. These differences involved 2.5% of all the genes expressed in the human brain.
To explore the possibility of sex-biased gene regulatory brain architectures, the investigators conducted a postmortem analysis aimed at finding significant interactions between sex and genotype. The authors found that sex-biased gene expression in the adult human brain is widespread.
Most importantly, they found that in some cases, “molecular differences are likely to have functional consequences relevant to human disease, and that sex biases in expression may reflect sex-biased gene regulatory structures.”
Dr. Mina Ryten, UCL Institute of Neurology and senior author of the paper, said: "There is strong evidence to show that men and women differ in terms of their susceptibility to neurological diseases, but up until now the basis of that difference has been unclear. Our study provides the most complete information so far on how the sexes differ in terms of how their genes are expressed in the brain. We have released our data so that others can assess how any gene they are interested in is expressed differently between men and women."
The NRXN3 Gene is Linked to Autism
Among the many results, the researchers specifically looked at the gene NRXN3, which has been linked to autism-risk. The statistics of autism are alarming. About 1 in 88 children are now identified with an autism spectrum disorder (ASD) according to estimates from the CDC. This number has almost doubled since the year 2000 when only 1 in 150 children were diagnosed with ASD. Autism spectrum disorders are almost 5 times more common among boys (1 in 54) than among girls (1 in 252).
The discovery of variations of the NRXN3 gene could be important in understanding the higher incidence of autism in males. The study suggests that there is a sex-bias in the way that genes are expressed and regulated. This leads to different functionalities and susceptibilities to brain diseases like autism.
The NRXN3 gene is transcribed into two major forms and the study results show that although one form is expressed similarly in both men and women, the other is produced at lower levels in women in the area of the thalamus.
The thalamus (from Greek, "inner chamber") is a midline symmetrical structure between the left and right hemispheres of the cerebrum, situated between the cerebral cortex and the midbrain. Some of its functions are the relaying of sensory and motor signals to the cerebral cortex, and the regulation of consciousness, sleep, and alertness.
Conclusion: Genes Express Themselves Very Differently in Men and Women
This study provides the most complete information so far on how the sexes differ in terms of how their genes are expressed in the brain, according to the researchers.
Mina Ryten emphasizes the importance of genomics in better understanding the molecular basis of sex differences in structure, neurochemistry, behavior, and susceptibility to disease. She concludes, “There is strong evidence to show that men and women differ in terms of their susceptibility to neurological diseases, but up until now the basis of that difference has been unclear.”
If you’d like to read more on this topic please check out my Psychology Today blogs: “Autism Genes Can Disrupt Connections Between Brain Regions”, “Sleep Strengthens Healthy Brain Connectivity”, “The Size and Connectivity of the Amygdala Predicts Anxiety”, "Decoding the Secrets of Brain Connectivity", “How is the Cerebellum Linked to Autism Spectrum Disorders?” and "These are Revolutionary Times for the Biology of Psychology."