Survey of mitochondrial sequences integrated into the bovine nuclear genome

Nuclear copies of the mitochondrial DNA (NUMTs) have already been described in several species. In this context, we identified and analysed 166 bovine NUMT regions with a total length of 430 kbp, representing about 0.02% of the cattle nuclear genome. Copies of all mitochondrial regions were detected in the nuclear genome, with distinct degrees of sequence similarity to the mitogenome. Some NUMT regions include large mitogenome segments and show high similarity to the organelle genome sequence. NUMT regions are frequently modified by insertion of repetitive sequences and by sequence rearrangements. We confirmed the existence of 29 NUMT regions by PCR amplification using DNA from the cow (Dominette) which was used to generate the bovine genome reference sequence, ruling out the possibility that these NUMTs could be artifacts of the genome assembly. As there are NUMT regions with high similarity to the mitogenome, special care is needed when designing primers for mitochondrial DNA amplification. Our results can therefore be used to avoid co-amplification of bovine nuclear sequences similar to mitochondrial DNA.