Development

Macho Mice

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Science  16 Oct 2009:
Vol. 326, Issue 5951, pp. 341
DOI: 10.1126/science.326_341a

Male-specific behaviors in mice include mating, aggression, and territorial marking. Development of male-specific behaviors in mice, as well as in humans, requires the testicular hormone testosterone. The hormone estrogen, better known for its function in females, is also required. In males, which lack ovaries, estrogen is produced when the enzyme aromatase converts testosterone to estrogen. Estrogen produced by aromatase-expressing cells in the brain then signals through receptors to affect behavior. Wu et al. have now analyzed the neurons that express aromatase and their connectivity in mice. Although aromatase-expressing neurons represent only a minority of the neurons in the brain, the locations and patterns of these neurons in the adult mouse brain reflect sexual dimorphism. Sexually dimorphic territorial behaviors are also affected by disruption of estrogen-based signaling. The testosterone surge around the time of birth in mice thus seems to direct masculinization of territorial behaviors through aromatization of testosterone into estrogen in key neurons within the the brain, rather than through androgen receptor signaling.

Cell 139, 61, (2009).

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