Distinctive Gene Expression Patterns and Imprinting Signatures Revealed in Reciprocal Crosses Between Cattle Sub-Species.

Background: There are two genetically distinct subspecies of cattle, Bos taurus taurus and Bos taurus indicus, which arose from independent domestication events. The two types of cattle show substantial phenotypic differences, some of which emerge during fetal development and are reflected in birth outcomes, including birth weight. We explored gene expression profiles in the placenta and four fetal tissues at mid-gestation from one taurine ( Bos taurus taurus ; Angus ) and one indicine ( Bos taurus indicus ; Brahman ) breed and their reciprocal crosses. Results: A total of 6,456 differentially expressed genes (DEGs) were identified between the two purebreds in at least one fetal tissue of which 110 genes were differentially expressed in all five tissues examined. DEGs shared across tissues were enriched for pathways related to immune and stress response functions. Only the liver had a substantial number of DEGs when reciprocal crossed were compared among which 310 DEGs were found to be in common with DEGs identified between purebred livers; these DEGs were significantly enriched for metabolic process GO terms. Analysis of DEGs across purebred and crossbred tissues suggested an additive expression pattern for most genes, where both paternal and maternal alleles contributed to variation in gene expression levels. However, expression of 5% of DEGs in each tissue was consistent with parent of origin effects, with both paternal and maternal dominance effects identified. Conclusions: These data identify candidate genes potentially driving the tissue-specific breed differences and provide biological insight into parental genome effects underlying phenotypic differences in bovine fetal development.