In-Silico Epigenetic Analysis of a Cluster of Genes on BTA2 in a Region with Imprinted QTL Effects on Postnatal Bovine Growth

Genomic imprinting is preferential expression of one of two alleles of a gene in offspring based on parental origin. In spite of recent evidence that hundreds of genes may be imprinted in mammals, the number of known imprinted genes in cattle remains very few. The growing significance of imprinted genes on the architecture of complex traits increases the need to identify and understand their biology in other mammals. We recently identified a 6-cM [9-Mb] region on bovine chromosome 2 region with parent-of-origin effect on postnatal growth in cattle in a genome scan. In search for positional candidates, we performed some in-silico analysis of 6 out of the 47 genes found in this region. We found that RRAGC is incorrectly assigned to Bta2 instead of Bta1. The CpG islands of all genes analyzed (except MAP3K2) coincided with Weisman evolutionary CpG islands. Evolutionary CpG islands in ERCC and IWS1 overlap promoter regions, exon 1 and intron 1 and highly conserved in cattle, human and mouse. The PROC gene appears to share a common CpG island between cattle and human. MAP3K2 appears to be influenced only by its methylation status in mouse but not in human due to absence of CpG islands, but in cattle the CpG island is located 15 kb upstream of the transcriptional start site. Our results suggest that some CpG islands may have functional roles in genes in this region, and it appears that cattle and human share more common CpG islands than between human and mouse.