Significant structural differences in the brains of males and females may result from selective cell death orchestrated by just a single gene during early development, according to a new study.Researchers at the University of Massachusetts Amherst in the US examined the brains of mice lacking a gene called Bax and found that some sex differences that are obvious in normal mice were completely absent. It has been known since the late 1970s that certain well-defined clusters of brain cells known as nuclei differ markedly in males and females, either in overall size or in the total number of cells present. For example, in adult rodents, the bed nucleus of the stria terminalis, or BNST, is 75% larger and contains many more cells in males than in females. The opposite pattern is seen in a region known as the anteroventral periventricular nucleus, or AVPV, which is both larger and richer in cells in females than in males.
