Genetics of Social Behavior - Social Influences On Gene Expression

Social Influences On Gene Expression

In songbirds, egr1 is a transcription factor encoding gene that is active in the auditory forebrain when hearing a song from another songbird. The strength of the expression of egr1 has much variability, dependent on the nature of the song. Songs previously unheard result in strong responses whereas familiar songs result in little or no response. Pure tones or white noise do not evoke any response. It is thought that the purpose of this genetic response to social stimuli is to update the brain's catalog of the changing natural environment. For example, it would be advantageous for a songbird to express more egr1 in a situation where there is a new song heard (a potential intruder) compared to the familiar song of a known individual. In contrast, for the species of highly social cichlid fish A. burtoni, the egr1 gene plays an indirect role in reproduction. In this species, there is an established social dominance hierarchy and an individual's position determines their access to resources for reproduction. If the alpha male is removed from the group, a previous subordinate starts exhibiting dominant behavior and egr1 is expressed in hypothalamus neurons that are responsible for producing a neuropeptide linked to sexual reproduction. Overall, the role of transcription factor egr1 in the context of social behavior clearly shows the link between genes and behavior. As a corollary to that described above, given an environmental cue egr1 will induce or suppress the transcription of other genes. Egr1 shows how social experience may trigger changes in the brain's gene networks. With higher capacity screening techniques, the expression of many genes simultaneously in response to social stimuli will provide a more complete picture.