## Description and display conventions

NumtS (Nuclear mitochondrial sequences) are mitochondrial fragments inserted in nuclear genomic sequences. The most credited hypothesis concerning their generation suggests that in presence of mutagenic agents, or under stress conditions, fragments of mtDNA escape from mitochondria, reach the nucleus and insert into chromosomes during break repair; although NumtS can also derive from duplication of genomic fragments. NumtS may be a cause of contamination during human mtDNA sequencing and hence frequent false low heteroplasmic evidences have been reported. The Bioinformatics group chaired by M. Attimonelli (University of Bari, Italy) has produced the RMmsNumtS (Reference Mus musculus NumtS) compilation annotating 148 Mouse assembled NumtS. To allow the scientific community to access the compilation and to perform genomics comparative analyses inclusive of the NumtS data, the group has designed the Mouse NumtS tracks described below.

The NumtS tracks show nuclear and mitochondrial regions, based on the High Score Pairs (HSPs) obtained by aligning the mitochondrial reference genome (NC_005089) with the mm9 assembly of the mouse genome.

1. "NumtS (Nuclear mitochondrial Sequences)" Track

   The "NumtS mitochondrial sequences" track shows the mapping of the HSPs returned by BlastN on the nuclear genome. The shading of the items reflect the similarity returned by BlastN, and the direction of the arrows is concordant with the strand of the alignment. For every item, a link pointing to the mitochondrial mapping is provided, thus allowing a fast cross among the NumtS genomic contexts.

2. "NumtS assembled" Track

   The "NumtS assembled" track shows items obtained by assembling HSPs annotated in the "NumtS" track fulfilling the following conditions:

   - The orientation of their alignments must be concordant.
   - The distance between them must be less than 2 kb, on the mitochondrial genome as well as on the nuclear genome.

   Exceptions for the second condition arise when a long repetitive element is present between two HSPs.

3. "NumtS on mitochondrion" Track

   The "NumtS on mitochondrion" track shows the mapping of the HSPs on the mitochondrial genome. The shading of the items reflects the similarity returned by BlastN, and the direction of the arrows is concordant with the strand of the alignment. For every item, a link pointing to the nuclear mapping is provided.

4. "Mouse NumtS on mitochondrion SNP" Track

   The "Mouse NumtS SNP" shows the mapping of the HSPs on the mitochondrial genome, with the SNPs which fall within, derived from comparison with the mm9 assembly. No shading is here provided. For every item, a link pointing to the nuclear mapping is provided.

## Methods

NumtS mappings were obtained by running Blast2seq (program: BlastN) between each chromosome of the Mouse Genome (mm9 assembly) and the mouse mitochondrial reference sequence (AC: NC_005089), fixing the e-value threshold to 1e-03. The assembling of the HSPs was performed with spreadsheet interpolation and manual inspection. BED format is used for the first three annotation tracks, while for the last one the SAM/BAM format is preferred.

## Credits

These data were provided by Francesco Maria Calabrese, Domenico Simone and Marcella Attimonelli from the Department of Biochemistry and Molecular Biology "Ernesto Quagliariello" (University of Bari, Italy). Manual inspection and format details are carried out by Francesco Maria Calabrese, Domenico Simone and Luana Raddi.

## References

Simone D, Calabrese FM, Lang M, Gasparre G, Attimonelli M: Validation and UCSC tracks of the extended RHNumtS compilation (submitted).

Lascaro D, Castellana S, Gasparre G, Romeo G, Saccone S, Attimonelli M. The RHNumtS compilation: features and bioinformatics approaches to locate and quantify Human NumtS. BMC Genomics. 2008 June 3;9:267.