Isolation and physical localization of new chromosome-specific centromeric repeats in farm animals

In this study, new classes of tandemly repeated DNA sequences in the centromeric regions of three farm animal species are reported. Pericentromeric regions of bovine chromosome X, porcine chromosome 14 and equine chromosome I were microdissected by laser and amplified by DOP-PCR. Painting probes showed strong hybridization signals on their corresponding centromeres. Specific DNA fragments were isolated by cloning and sequenced. For each species, high homology level was found among the sequences. The presence of specific repeats within each sequence allows us to consider them as monomeric units or parts of longer tandemly repeated monomeric units that generate a specific higher-order repeat. In this respect, the isolation of new centromeric sequences enriches the genetic map of these three species and represents a useful tool for FISH analysis, thus expanding our knowledge on centromeres of farm animal species.