UCLA is the first to uncover a gender difference in gene expression in fat and muscle tissue. Earlier studies have identified roughly 1,000 sex-biased genes in the liver, and other research has found a combined total of 60 gender-influenced genes in the brain about one-tenth of what the UCLA team discovered in these organs.
Even in the same organ, the researchers identified scores of genes that varied in expression levels between the sexes. Gender consistently influenced the expression levels of thousands of genes in the liver, fat and muscle tissue. This effect was slightly more limited in the brain, where hundreds, not thousands, of genes showed different expression patterns.
"Males and females share the same genetic code, but our findings imply that gender regulates how quickly the body can convert DNA to proteins," said Yang. "This suggests that gender influences how disease develops."
The gender differences in gene expression also varied by tissue. Affected genes were typically those most involved in the organ's function, suggesting that gender influences important genes with specialized roles, not the rank-and-file.
In the liver, for example, the expression of genes involved in drug metabolism differed by sex. The findings imply that male and female livers function the same, but work at different rates.
"Our findings in the liver may explain why men and women respond differently to the same drug," noted Lusis. "Studies show that aspirin is more effective at preventing heart attack in men than women. One gender may metabolize the drug faster, leaving too little of the medication in the system to produce an effect."
"At the genetic level, the only difference between the genders is the sex chromosomes," said Drake. "Out of the more than 30,000 genes that
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Contact: Elaine Schmidt
eschmidt@mednet.ucla.edu
310-794-2272
University of California - Los Angeles
7-Jul-2006