Investigation of changes in global gene expression in the frontal cortex of early-weaned and socially isolated piglets using microarray and quantitative real-time RT-PCR

We hypothesize that early-weaned piglets experience aberrant expression of stress-responsive genes in the frontal cortex, a key brain area involved in cognitive function and behavior organization. To test this hypothesis, female early-weaned piglets (EW; n = 6) were weaned 10 days after birth, while non-weaned piglets (NW; n = 6) were left with their dams. Half of EW (n = 3) and NW (n = 3) animals were socially isolated (SI) for 15 min at 12 days of age, when all animals (n = 12) were euthanized and tissue collected. The effects of EW and SI were examined by gene expression profiling using cDNA microarray hybridizations, generated from a porcine brain cDNA library. A total of 103 genes were differentially expressed (P < 0.05, fold change >1.25) among four direct comparisons. Forty-two genes had known functions, from which 24 showed relevant brain-related functions. Quantitative real-time polymerase chain reaction (Q-RT-PCR) was used to confirm regulation of expression of a subset of 6 genes with important brain functions, selected from the microarray outcomes. In non-weaned animals, a significant suppression of mRNA abundance for carboxypeptidase E, 14-3-3 protein and phosphoprotein enriched in astrocytes 15 kDa was observed in response to SI. Also, in early-weaned animals, diazepam binding inhibitor and actin-related protein 2/3 complex mRNA levels were suppressed in response to SI. Results suggest that social isolation of non- and early-weaned piglets may impact expression of genes involved in regulation of neuronal function, development, and protection in the frontal cortex of young pigs.