Polin H, Danzer M, Reiter A, Brisner M, Gaszner W, Weinberger J, Gabriel C
Red Cross Transfusion Service of Upper Austria, Linz, Austria.
Vox Sang. 2014 Nov;107(4):393-8. doi: 10.1111/vox.12168. Epub 2014 Jun 11.
Gene conversion events between GYPA and GYPB or GYPA and GYPE are facilitated by the close chromosomal proximity and high degree of sequence homology and can lead to the formation of GP hybrid genes. Discrepant results between blood group genotyping and haemagglutination in 22 random blood donors induced molecular characterization.
Sequence analysis of GYPA exons 1-7 and GYPB exons 1-5 was performed for gDNA and cDNA. The linkage of the nucleotide alterations was defined by haplotype separation.
DNA analysis demonstrated a normal GYPA haplotype (GYPAN n = 20, GYPAM n = 2) with an altered GP hybrid nucleotide sequence in trans. A GYPB homologue sequence of minimal 10-bp encompassing intron 1 and exon 2 was translated into GYPA, accounting for an amino acid substitution from arginine to glutamic acid at position 13 (38 C>A). Genomic DNA analysis demonstrated the cis-linkage of the hybrid nucleotide sequence with each GYPA(Ser20, Gly24) (n = 20) associated with the expression of M and GYPA(Leu20, Glu24) (n = 2) encoding the N phenotype. The serologic data indicate that the changes do not affect the expression of a normal M and N antigen. cDNA sequences confirmed the gDNA results and furthermore identified a heterozygous deletion of GYPB exon 2 in all probands.
The results document a GYPA-B-A hybrid gene, probably produced via a single unequal homologous recombination event. A segmental transfer of GYPB seems most likely accounting for the allelic dropout.
由于染色体距离接近以及高度的序列同源性，促进了GYPA与GYPB或GYPA与GYPE之间的基因转换事件，这可能导致GP杂交基因的形成。对22名随机献血者进行血型基因分型和血凝反应时出现的差异结果引发了分子特征分析。
对基因组DNA（gDNA）和互补DNA（cDNA）进行GYPA外显子1 - 7和GYPB外显子1 - 5的序列分析。通过单倍型分离确定核苷酸改变的连锁关系。
DNA分析显示一个正常的GYPA单倍型（GYPAN，n = 20；GYPAM，n = 2），与之反式的是一个改变的GP杂交核苷酸序列。一个至少10个碱基对的GYPB同源序列，包含内含子1和外显子2，被转译为GYPA，导致第13位氨基酸从精氨酸替换为谷氨酸（38 C>A）。基因组DNA分析表明杂交核苷酸序列与每个表达M的GYPA(Ser20, Gly24)（n = 20）以及编码N表型的GYPA(Leu20, Glu24)（n = 2）顺式连锁。血清学数据表明这些变化不影响正常M和N抗原的表达。cDNA序列证实了gDNA结果，并且进一步在所有先证者中鉴定出GYPB外显子2的杂合缺失。
这些结果证明了一个GYPA - B - A杂交基因，可能是通过单个不等位同源重组事件产生的。GYPB的片段转移似乎最有可能是导致等位基因缺失的原因。
