Friday, September 13, 2013

The non-nuclear genome: including a mitochondrial genome in GRCh38

The GRC maintains and improves the reference nuclear assembly only. The MITOMAP ( group has served a similar function curating genetic variation of  the mitochondrial genome. When the GRC released GRCh37 we only released the nuclear genome, as we didn't think we could distribute the sequence representing the mitochondrial (MT) reference (which we did not produce) as part of the GRCh37 reference. Not distributing an MT sequence with reference nuclear assembly led to some confusion in the research community as different groups adopted different versions of the MT sequence records to use as their reference.
The current MT reference sequence is the Revised Cambridge Reference Sequence (rCRS) represented by GenBank accession number J01415.2 and RefSeq accession number NC_012920.1. The MITOMAP group has graciously allowed the GRC to distribute their annotated version of the rCRS MT reference sequence with the nuclear assembly and this sequence was added to GRCh37 with the second patch release. This same MT reference sequence will be included in the GRCh38 assembly release.