Report Visualizing Sexual Dimorphism in the Brain

Summary Dimorphic behaviors may derive from circuits that dif- fer not only anatomically but biochemically. However, Sexually dimorphic behaviors are likely to involve neu- analysis of mRNA populations fails to reveal genes thatral pathways that express the androgen receptor (AR). are expressed solely in male or female neurons. The We have genetically modified the AR locus to visualize only exceptions are the genes on the Y chromosome dimorphisms inneuronal populations thatexpress AR. and Xist RNA, which controls dosage compensation in Analysis of AR-positive neurons reveals both known all cells in the female (Dewing et al., 2003; Eriksson et dimorphisms in the preoptic area of the hypothalamus al., 1999; Lahr et al., 1995; Xu et al., 2002). Since females and the bed nucleus of the stria terminalis as well as expressing transgenic SRY can be masculinized in the novel dimorphic islands in the basal forebrain with a absenceof aY chromosome,it isunlikely thatadditional clarity unencumbered by the vast population of AR-