Learning to mother: Epigenetic mechanisms drive plasticity in the maternal neural circuit - Danielle Stolzenberg

Tuesday, 2 September, 2014 - 11:30 to 12:30
Mothering involves complex behavioral modifications aimed at ensuring the survival of progeny. Most female mammals learn to mother. Although the hormonal events of gestation, birth, and lactation typically coincide with the onset of mothering, these events only partially overlap with maternal responsiveness. Instead, the experience of becoming a mother results in a sustained sensitivity toward offspring long after these hormone-mediated events have waned. Critical questions are what neural mechanisms initiate and sustain the constant display of maternal caregiving behaviors? Maternal experiences are likely consolidated in the neural circuits that regulate maternal behavior. The medial preoptic area (MPOA) of the hypothalamus plays a central role in these circuits, integrating hormonal and infant-related information from all sensory modalities and regulating maternal behavior responses through activation of the mesolimbic dopamine system. Maternal experience induces plastic changes in this circuit. One hypothesis is that alterations in the structure of chromatin (DNA and its supporting proteins, histones) affect gene expression in MPOA neurons. Thus,
maternal experience may alter the way in which MPOA neurons respond to offspring because the pattern of gene expression that supports maternal responsiveness has been altered by structural remodeling of the chromatin. This level of transcriptional regulation, which occurs "above" the level of the genome, is referred to as epigenetic. Using a rodent model, my laboratory has explored the idea that epigenetic processes set new programs of gene expression into motion, which may underlie the plastic reorganization of the maternal circuit. In support of this idea, post-translational modifications of histones by histone acetyltransferase (HAT) enzymes leave “epigenetic marks" that control gene expression in the MPOA. For example, maternal experience is associated with increased expression of specific genes and the recruitment of CREB binding protein, a HAT, to their promoter regions. Further, increasing HAT activity facilitates maternal learning in inexperienced female mice. Finally, the extent to which epigenetic modifications of MPOA produce effects on maternal learning through an interaction with the mesolimbic dopamine system will be discussed.