In the present study we investigated the effect of selection for fertility traits on gene expression in anterior pituitary (AP) of NE selection lines. The objective of this study was to identify differentially expressed genes in the anterior pituitary of sows with different fertility phenotype. A White Composite base population originated two selection lines, one control line and another selected line for prolificacy. Selection was conducted based on an index, in which ovulation rate and embryo survival were included as parameters. Sows from both lines were slaughtered during follicular development phase. Differential display PCR (DD-PCR) was used to search for differences between lines in AP gene expression. Northern analysis and microarray were used to confirm DD-PCR results. Microarray was constructed using swine anterior pituitary clones (from the present study) and follicle clones from a concurrent DD-PCR project. In the expression study, three genes were identified as differentially expressed in the same direction of DD-PCR using Northern hybridizations. Using microarray analysis, 13 genes were differently expressed (P \u3c 0.05) for the two lines. At D2 nine genes were differently expressed, and at D4, the expression of six genes differed between lines. In general, genes differentially expressed are involved in cell growth, iron pool regulation, and energy production. In conclusion, long-term selection for fertility plays an important role in changing gene expression patterns in the anterior pituitary. Selected transcripts isolated from DD-PCR were mapped. Eleven markers were mapped using somatic cell hybrid panel (SCHP). Eight markers were mapped using a radiation hybrid panel (RH). SCHP mapping allows regional assignment of markers to chromosomes, and RH mapping refines mapping location and defines marker order not resolved in the linkage maps of the pig, which is important in finding genes in QTL region, in applying marker-assisted selection, and in increasing gene density in the porcine genomic map. Furthermore, they are useful for development of the porcine transcript map and the high-resolution BAC contig map
