# What are the coordinates of the extended major histocompatibility complex (xMHC) in GRCh38?

Is there an accepted boundary of the extended major histocompatibility complex (xMHC) in human? Specifically, I am interested in the boundary coordinates for Genome Reference Consortium Human Build 38 (GRCh38 / hg38).

I'd like to use these coordinates to query MyGene.info to retrieve a list of genes in the xMHC. For example, King et al 2019 used the following definition:

we excluded drugs with nonhuman or xMHC gene targets. We considered xMHC to include HIST1H2AA and KIFC1 and all genes between them (Chromosome 6 25.7 Mb-33.4 Mb).

But I was curious whether there was an authoritative definition of the xMHC region in humans that would specify down the the base pair rather than just megabase pair.

• This is an extremely good question, these genomic coordinates of course exist, the only thing is MHC ... would include mice as well as humans. The HLA.is very well defined but I think you need to ask an immunologist because it is common knowledge, but I don't think any one here knows.
– M__
Oct 29 '20 at 1:53

• Here is a MyGene.info query that returns all NCBI gene IDs and symbols in between chr6:25,726,063-33,410,226 for GRCh38. I like these boundaries since KIFC1 extends past RPL12P1. For some reason RPL12P1 is not included in the MyGene results. Not sure why. It is a pseudogene, but other pseudogenes are included. The MyGene query currently returns 318 genes. Nov 2 '20 at 22:56
• The approved symbol for ncbigene:221613 is now H2AC1 rather than HIST1H2AA. KIFC1 is ncbigene:3833. RPL12P1 is ncbigene:729727. Nov 2 '20 at 23:18