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Tomayto, tomahto: Separate genes exert control over differential male and female behaviors

Sparks flew at a symposium hosted by the Stanford Center for Health Research on Women & Sex Differences in Medicine, which I attended yesterday. One invited speaker -Louann Brizendine, MD, of the University of California at San Francisco - is the author of a couple of books titled The Male Brain and The Female Brain. Another invited speaker - neuroscientist Daphna Joel, PhD, who'd flown in from the University of Tel Aviv, in Israel - emphatically maintained that there is no such thing as a "male" brain or a "female" brain. "What we know," she said bluntly, "is that males have brains and females have brains."

Whatever the semantics of that debate, two things are pretty clear any way you slice it. First, male and female brains are mostly alike. Second, there are measurable and meaningful differences in what goes on inside male versus female brains. As another neuroscientist, UCLA's Art Arnold, PhD, put it: "Every cell in a female's brain expresses a set of genes that the cells in a male's brain express at much lower levels, if at all."

Adding heft to Arnold's comment was a presentation by Nirao Shah, MD, PhD, of UCSF. The neuroanatomist showcased research in his lab that had pinpointed specific genes whose activity levels differed significantly in the brains of male and female mice. Many of these genes, he noted, have human analogs that have been implicated in alcoholism, autism, breast and prostate cancers, and more. By conducting rigorous experiments with mice in which one or another of such genes had been put out of commission, Shah and his colleagues were able to tease out the behavioral consequences of specific genes' inactivation. For example, knocking out a particular gene in female mouse moms results in a massive dimunition in their willingness to defend their nests from intruders - a maternal mandate that normal female mice observe rigorously - yet has no other observable effect on their maternal or sexual behavior. Torpedoing a different gene radically reduces Minnie Mouse's mating mood; but the Mickeys in which this gene has been trashed "are completely normal, as far as we can tell," Shah said.

The upshot: Yes, there are significant differences in behavior (and therefore in brain action) and in gene activity in the brain cells of males and females. Those of male and female mice, that is. What about humans'?

Well, nobody was talking about knocking any genes out of people to see if the men indulge in fewer barroom brawls and the women start laughing off their babies' cries of distress. But there are certainly some strong hints of medically significant differences: The ratio of men to women with autism run somewhere in the neighborhood of 8:1 or even 16:1. Depression is twice as common among women as among men - but only between menarche and menopause. Alzheimer's disease abounds more in women, even after taking into consideration women's greater longevity (itself a medically important difference), as does autoimmunity. On the other hand, Parkinson's and schizophrenia preferentially affect men. There seems to be more at work here than the simple "absorption of gender stereotypes," and it's good to see hardcore biologists attacking the problem with all the scientific rigor at their disposal.

Let's not call the whole thing off.

Previously: A call to advance research on women's health issues
Photo by namuit

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