One in three adults in the U.S. has high blood pressure (hypertension). Although men and women are just as likely to develop hypertension during their lifetimes, men younger than 45 have hypertension more often than women that age do. Scientists wondered if this difference is because the male hormone testosterone affects physiological processes differently than the female hormone estrogen does. In the case of hypertension, the suspicion was correct, but it wasn’t the entire story. Recent studies have shown that the gene that gives men the physiological traits to produce testosterone—the SRY gene—may influence blood pressure, too.
Called the sex-determining region of the Y chromosome, SRY is found only on the Y chromosome and carries out its main job after conception when the embryo is developing. SRY turns on the genes involved in the development of male sex organs, triggering the testes to develop and produce the male hormone testosterone. Females don’t have a Y chromosome, nor the SRY gene. Instead, they develop ovaries and produce the female hormone estrogen.
SRY is part of a family of genes whose job is to turn other genes on or off. It is directly related to another gene found on the X chromosome, SOX3. Men have both SRY and SOX3, while women only have SOX3. However, because SRY and SOX3 are from the same family, they control the same genes. In a new study in Physiological Genomics, researchers wanted to know if SRY and SOX3 controlled the genes involved in blood pressure regulation in the same way: Did both of them turn on the genes or did one turn off and the other turn on the genes?
The researchers found that SRY and SOX3 had the same effects on several blood pressure genes except for one gene that produced renin, a protein that raises blood pressure. SRY turned renin production on, while SOX3 turned it off. SRY’s protein was also found in male rats’ kidneys, where renin is made, while SOX3’s was not. This led researchers to believe that renin is only controlled by SRY in males and that blood pressure is controlled differently in men, offering an explanation for why hypertension risks are different between the sexes.