Functional genomics of social recognition.

Although various types of group living are widespread in mammals, including humans, the study of the hormonal and genetic underpinnings of nonsexual social behaviour, is in its infancy compared to the analysis of sexual behaviour mechanisms. Oxytocin, vasopressin and gonadal hormones certainly play an important role. Social recognition, where animals identify and recognize other individual conspecifics, is a crucial prerequisite for the occurrence of a wide range of social behaviours. Social recognition is also important for coping with one major cost of life in a group: the increased risk of exposure to parasites and infection. We review recent functional genomic studies on the involvement of oxytocin and oestrogen-receptor genes in the regulation of social recognition in mice and in the ecologically relevant context of parasite recognition and avoidance. Based on quantitative studies of social recognition with gene-knockout mice and with antisense DNA, we propose a four-gene micronet contributing to social recognition. This micronet involves the genes coding for oestrogen receptors alpha (ER-alpha), beta (ER-beta), oxytocin and the oxytocin receptor. In this model, circulating oestrogens promote transcription of (i) oxytocin in the paraventricular nucleus of the hypothalamus through ER-beta and (ii) oxytocin receptor in the amygdala through ER-alpha. This model forms the core around which increasingly complex genetic, hormonal and neural interactions associated with social behaviours and recognition can be organized.