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View Full Version : HLA-DR7 : distribution map, subtypes, SNPs and associated medical conditions



Maciamo
20-01-16, 11:47
Here is a map showing the allele frequency of HLA-DR7 (http://en.wikipedia.org/wiki/HLA-DR7). The maximum frequencies are observed in the Basque country (26 to 31%), northern Catalonia (23%), the Balearic Islands (22%), Cantabria (20%), Tunisia (19%), Saudi Arabia (18%), Andalusia (17.5%), Libya (17%), and in Ireland (16%). You can visualise the data by country on this table of HLA-DR frequencies (http://www.eupedia.com/genetics/HLA-DR_allele_frequencies_by_country.shtml).

Outside Europe and the Mediterranean, frequencies above 20% were also reported in Bashkortostan (south-west Siberia), the Buryat Republic (south-east Siberia), India, Bangladesh, Sri Lanka, Sudan, Ethiopia, the Central African Republic, and Burkina Faso.

Only two populations lack DR7 almost completely: the Saami and the Sardinians. This is odd considering that DR7 reaches extremely high frequencies among the Basques (usually closely related to the Sardinians) and the Siberians (where the Saami originated).

http://cdn.eupedia.com/images/content/HLA-DR7.png


It is hard to find any correlation between HLA-DR7 and haplogroups or autosomal admixture, apart maybe for mtDNA haplogroup J1, which is also high in Arabia, North Africa, Iberia and Celtic Northwest Europe and at the same time low in the Balkans and absent among the Saami. The Sardinians have 12.5% of mtDNA J, but 8.5% of it is J2, so the correlation with J1 also works to some extends.

Apart from the regions occupied by Y-haplogroup J1 (Arabia, North Africa, Sudan), HLA-DR7 is also found in regions with high frequencies of R1b (Ireland, Wales, Brittany, Basque country, Catalonia, Bashkortostan) and R1a (Poland, Ukraine, Russia, Indian subcontinent).

Interestingly, the Sahel region, where HLA-DR7 is found (from the Sudan to Burkina Faso) also happens to be a region high in both Y-haplogroups J1 and R1b, but also a region where mt-haplogroup J1b1a is found. Nowadays J1b1a is found chiefly in western Europe and India. In my history of haplogroup R1b (http://www.eupedia.com/europe/Haplogroup_R1b_Y-DNA.shtml#mtDNA) I have explained how J1b1a was very probably one of the maternal lineages associated with R1b1* (P25) people in northern Mesopotamia during the Early Neolithic, before R1b people migrated to the Pontic Steppe and North Africa with their herds of cattle. It is not entirely unreasonable to imagine that HLA-DR7 could have been found originally among tribes belonging to mt-haplogroup J1, and that it was spread in great part of J1b people (R1b Indo-Europeans, R1b North Africans, but also J1 Arabs). Remarkably, J1b1b happens to be found both in India and among the Buryats ! Other J1b subclades (J1b2 to J1b8) are found in the Middle East and North Africa.


Medical associations

HLA-DR7 is associated with psoriasis (https://en.wikipedia.org/wiki/Psoriasis_vulgaris), Type 2 diabetes, asparaginase allergies, and to T. cruzi infection with cardiomyopathy (https://en.wikipedia.org/wiki/Cardiomyopathy) (aka Chaga's cardiomyopathy (https://en.wikipedia.org/wiki/Chaga%27s_cardiomyopathy)).

The haplotype DR7-DQA1*0201 / DQB1*0202 is associated with Graves' disease (https://en.wikipedia.org/wiki/Graves%27_disease).

The DR7-DQ2 (https://en.wikipedia.org/wiki/HLA-DQ#DQ2) + DR5 (https://en.wikipedia.org/wiki/HLA-DR5)-DQ7 (https://en.wikipedia.org/wiki/HLA-DQ#DQ7) phenotype is the primary risk DQ isoform in celiac disease (https://en.wikipedia.org/wiki/Celiac_disease).


SNP's

You can verify if you carry HLA-DR7 by checking your raw data from 23andMe, Geno 2.0 or FamilyFinder. There exists over 50 subclades, but the vast majority of Europeans belong to DRB1*07:01.

- DRB1*07:01 : rs7745002, rs2647087, rs241398

You normally need to be positive for all three alleles.

LeBrok
20-01-16, 16:42
Perhaps it came from West Africa to Europe through Gibraltar, after LGM, and expanded through Europe with WHGs?

Maciamo
20-01-16, 18:22
Perhaps it came from West Africa to Europe through Gibraltar, after LGM, and expanded through Europe with WHGs?

Possible, but considering the high frequency in Russia, Siberia and South Asia it looks like a long shot. A Middle Eastern point of origin is more likely.