The absence of 21-OH A and C4 B genes is a constant characteristic of the "Sardinian" HLA extended haplotype A30 Cw5 B18 BfF1 DR3 DRw52 DQw2.
The genomic DNA of 25 unrelated individuals with HLA haplotype A30 Cw5 B18 BfF1 DR3 D w52 DQw2 was digested with the restriction enzyme Taq I and hybridized with cDNA probes for C4 and 21-OH genes. Eighteen individuals and a non-Sardinian reference cell (DUCAF) were homozygous for the entire extended haplotype, six individuals were heterozygous for the HLA-A locus and homozygous for the rest of the same haplotype. All of the 18 homozygous individuals, four of the six heterozygous subjects and the DUCAF cell revealed the absence of two fragments at 3.2 and 2.4 kb corresponding to the 21-OH A gene, and the absence of fragments corresponding to the C4 B "long" or "short" gene. The contemporary absence of the 21-OH A and C4 B genes seems to be a constant characteristic of this extended haplotype in the Sardinian population and suggests that this and other extended haplotypes bearing C4 A or C4 B null alleles could be ancestral haplotypes which never duplicated at these loci.
Carcassi
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C
Institute of Clinical Medicine, Cagliari University, Italy.
Porcella
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R
Manca
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ML
Orrù
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S
La Nasa
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G
Contu
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L
D000483:Alleles; D015139:Blotting, Southern; D015935:Complement C4b / Q000235:genetics*; D004247:DNA / Q000235:genetics; D005796:Genes; D006680:HLA Antigens / Q000235:genetics*; D015234:HLA-A Antigens / Q000235:genetics; D015235:HLA-B Antigens / Q000235:genetics; D015236:HLA-C Antigens / Q000235:genetics; D006681:HLA-D Antigens / Q000235:genetics; D006683:HLA-DQ Antigens / Q000235:genetics; D006684:HLA-DR Antigens / Q000235:genetics; D006239:Haplotypes / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007558:Italy; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D013250:Steroid Hydroxylases / Q000235:genetics*
D006680:HLA Antigens; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015236:HLA-C Antigens; D006681:HLA-D Antigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D015935:Complement C4b; D004247:DNA; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase