Rearrangement of 21-hydroxylase genes in disease-associated MHC supratypes.

Human cDNA probes for 21-hydroxylase (21-OH) and for complement component C4 are used on restriction digests of the members of several families with interesting supratypes. The presence of two Taq I fragments of 3.7 kb and 3.2 kb in size with a 21-OH probe is confirmed in most individuals who show no evidence of C4 deletions or 21-OH deficiency. Most individuals also show a doublet of weakly hybridizing bands at approximately 2.5 kb, the smaller of which is part of the 21 A gene. The arrangement of the 21-OH genes on disease-associated supratypes was examined, and it is shown that copies of the same supratype from unrelated individuals are usually identical. Evidence is provided for deletions of 21A on the B8, C4AQ0, C4B1, BfS, DR3 and B18, C4A3, C4BQ0, BfF1, DR3 supratypes and a duplication of 21A on the B14, C4A2, C4B1/B2, BfS supratype. Gene rearrangements may be relevant to diseases such as juvenile onset diabetes mellitus.