Abstract

Childbirth is a period of substantial rapid biological and psychological change and a wide range of psychotic disorders can occur ranging from mild ‘baby blues’ to severe episodes of psychotic illnesses. Puerperal psychosis is the most extreme form of postnatal psychosis, occurring in 1 in 1000 births. In this study, we have used the pig as an animal model for human postnatal psychiatric illness and, in particular, puerperal psychosis. Our aim was to identify quantitative trait loci (QTL) and altered patterns of hypothalamic gene expression associated with maternal (infanticide) sow aggression. This is defined as sows attacking and killing their own newborn offspring within 24 hours of birth. An affected sib pair whole genome linkage analysis was carried out and resulted in mapping 4 QTL on Sus scrofa chromosomes 2 (SSC2), 10 (SSC10) and X (SSCX). The peak regions of these QTL are syntenic to HSA 5q14.3-15, 1q32, Xpter-Xp2.1 and Xq2.4-Xqter respectively. Several potential candidate genes lie in these regions in addition to relevant abnormal behavioural QTL , found in humans and rodents. In parallel, expression analysis using brain-based targeted cDNA microarrays of hypothalamic tissue from aggressive and matched non-aggressive sows was used to identify which genes were over and under-expressed in the abhorrent behavioural phenotype compared to the matched control. This expression analysis suggested which genetic pathways in the hypothalamus are potentially associated with the maternal infanticide behaviour and some of these genes and the pathways in which they are involved were also implicated in the parallel QTL study. This data will provide candidate genes that can be investigated in the analogous human condition for evidence of variation and also single nucleotide polymorphism haplotypes that can be used to predict and manage aggressive sows over the critical postnatal period.