Positive selection on gene expression in the human brain

(copulation and egg-laying, respectively; Figure 1 experiments 6 and 13, and [1]). Silencing the fru GAL4 neurons in fru M virgin females does not induce egg-laying, as it does in wild-type (fru F) females (Figure 1C, experiment 7). Thus, Fru M appears to reconfigure the circuit for male rather than female behaviour in a way that cannot be explained entirely by altered patterns of neuronal activity. We infer from these data that the distinct reproductive behaviours of males and females are mediated by a common fru GAL4 neural circuit (Figure 2). Activation of this circuit is required for mating behaviour, which is manifested as male behaviour in fru M males and females, but as female behaviour in fru F females. In females, the transition from pre-mating to post-mating behaviour is triggered experimentally by silencing these neurons (Figure 1), or naturally by the sex peptide transferred in the male's seminal fluid [5,6]. Sex peptide may therefore promote post-mating behaviours by modulating the activity of the fru GAL4 circuit in females. (2000). Spatial, temporal, and sexually dimorphic expression patterns of the fruitless gene in the Drosophila central nervous system. (2003). The sex peptide of Drosophila melanogaster: female post-mating responses analyzed by using RNA interference. Proc. Natl. Figure 2. Control of sexual behavior by fru GAL4 neurons. Model for the role of fru GAL4 neurons in Drosophila sexual behaviour, based on the results presented in Figure 1 for female behaviours and in [1] for male behaviours. Male mating behaviour is observed in both males and females, provided Fru M is present. Virgin and mated female behaviours are only observed in females (they are not anatomically possible in males). Flies in which the Fru M neurons are both silenced and masculinized perform neither male behaviour, virgin female behaviour, nor mated female behaviour, irrespective of their sex. The editors of Current Biology welcome correspondence on any article in the journal, but reserve the right to reduce the length of any letter to be published. All Correspondence containing data or scientific argument will be refereed. Recent work has shown that the expression levels of genes transcribed in the brains of humans and chimpanzees have changed less than those of genes transcribed in other tissues [1]. However, when gene expression changes are mapped onto the evolutionary lineage in which they occurred, the brain shows more changes than other tissues in the human lineage compared to the chimpanzee …