What are the coordinates of the extended major histocompatibility complex (xMHC) in GRCh38?
Here is one definition of the classical MHC region: https://www.ncbi.nlm.nih.gov/grc/human/regions/MHC?asm=GRCh38.p13
which defines it as the 5mb region chr6:28510120-33480577 in GRCh38 coordinates.
The &quot;extended MHC&quot; defined here [1] is 7.2 mb and encompasses an additional &quot;extended Class I&quot; region upstream of the region given above. The xMHC is defined in [1] as the regions between HIST1H2AA and RPL12P1 genes, which would give you chr6:25726063-33400644 in Grch38. This is very similar to your HIST1H2AA - KIFC1 definition (chr6:25726063-33410226). Of course if you're trying to reproduce a result, probably better to use the original paper's definition.
[1] https://www.nature.com/articles/nrg1489