Sexual dimorphism at the molecular level

Men and women were "separated" by 6,500 genes

Denis Strigun, Naked Science

Figure from the Weizmann Institute Researchers Identify 6,500 Genes press release
That Are Expressed Differently in Men and Women – VM.

Studying how different genes are expressed in men and women is important for understanding human evolution and developing new therapeutic strategies. An example of such specificity is sexual dimorphism: for example, it is expressed in the features of anatomy, structure and work of the brain, behavior and mortality. In 2012, an international team of scientists found that only in B-lymphocytes, about 15 percent of quantitative trait loci (QTLs) affect expression based on gender. At the same time, most of these genes are assumed to be carried by representatives of both sexes, and although mutations in them often accumulate along one line, selection restrictions can lead to the spread of the anomaly to the other sex, increasing the population risk.

In a new paper (Gershoni, Pietrokovski, The landscape of sex-differential transcriptome and its consequent selection in human adults, BMC Biology, 2017), Israeli scientists have fully described the expression of sex-dependent genes in 45 universal tissues. To do this, they studied the results of RNA sequencing of the project for the study of tissue genotypes (Genotype-Tissue Expression, GTEx) on the example of 8555 samples from 357 men and 187 women. The authors evaluated the sexual characteristics of expression by comparing the individual index of 18,670 out of 19,644 protein-coding genes for each tissue. Further comparison between the sexes allowed us to identify over 6,500 genes with high sex specificity, the expression of 650 of which significantly differed in two tissues, and 22 – in nine or more. The most pronounced specificity was demonstrated by 6123 genes in the mammary glands.

Evaluation of gender-specific gene expression (a)
and their number in 45 tissues of men and women (b).
Graph from an article in BMC Biology.

Specific expression of more than a hundred genes was found in skeletal muscles, skin, subcutaneous fat, anterior cingulate cortex (in total – in seven of 13 brain tissues) and the left ventricle of the heart. In particular, in men, the MUCL1 gene was hyperexpressed in the skin, whereas in women – in the mammary glands. Similar differences were characteristic of liver tissues. Additionally, scientists assessed the relationship of genes with the risk of various diseases and the peculiarities of the work of internal organs. The analysis showed that "female" genes positively correlate with glucose metabolism, obesity, muscle diseases and cardiomyopathy. In turn, the "male" genes, in addition to glucose metabolism (also specific), were associated with a different molecular mechanism of muscle contraction.

The authors attributed 1,559 DNA sites to genes whose expression was stronger (by no more than 10 percent) in only one sex. Most of them (82.6 percent) turned out to be "male" and were overexpressed in the testicles. Also, many of these genes were associated with the prostate gland and skin. In women, such genes have been found in the reproductive system and brain tissues. According to scientists, the results confirm the evolutionary importance of differences in the structure and work of the genitals of men and women. In this sense, it is noteworthy that dozens of genes were specifically expressed in men in skin tissues that were not directly related to the function of procreation. The data obtained clarify the genetic differences between the sexes.

Portal "Eternal youth" http://vechnayamolodost.ru  10.05.2017