Scharberg Erwin A, Green Carole, Daniels Geoff, Richter Ekkehard, Klüter Harald, Bugert Peter
Red Cross Blood Service of Baden-Württemberg-Hessen, Institute Baden-Baden, Germany.
Transfusion. 2005 Aug;45(8):1314-8. doi: 10.1111/j.1537-2995.2005.00200.x.
The JAHK antigen was first described in 1995 as a low-frequency red blood cell antigen. Family studies confirmed the association of the antigen with the rare r(G) phenotype of the Rh blood group system, which is associated with weak expression of C and e, but normal G expression. JAHK was allocated the Rh number RH53. The serologic findings indicated the location of the antigen on the RhCE protein, although the molecular basis for JAHK has not been known.
The RHCE gene of eight persons from three unrelated families was analyzed by exon amplification and direct sequencing. Four of the samples were JAHK+ the remaining four were JAHK-. In one JAHK+ sample, the entire RHCE gene was sequenced. The remaining samples were sequenced for exons 1 to 3. A polymerase chain reaction procedure with sequence specific primers was developed for the specific detection of the JAHK allele.
Analysis of the entire RHCE gene of one JAHK+ sample showed the expected CcEe-specific nucleotide sequences and revealed an additional nucleotide change (365C>T) in exon 3. This change represented a missense mutation, which led to an amino acid substitution from serine to leucine at position 122 of the RhCE protein. Three JAHK+ samples from two other unrelated families showed the 365C>T mutation and confirmed the association of the Ser122Leu substitution with the JAHK+ phenotype.
The molecular basis of the JAHK antigen (RH53) is defined by a 365C>T mutation in exon 3 of the RHCE gene leading to the amino acid substitution Ser122Leu. Because the position 122 is predicted to be located in the transmembrane region adjacent to the second loop, the substitution of the neutral serine by the hydrophobic leucine seems to be the cause of the JAHK antigen by a conformational change of the RhCE protein. This structural change may also cause the weakened expression of the C and e antigens observed in JAHK+ individuals. Based on our results it is concluded that the JAHK-specific mutation is associated with a dCe haplotype.
JAHK抗原于1995年首次被描述为一种低频红细胞抗原。家系研究证实该抗原与Rh血型系统中罕见的r(G)表型相关，r(G)表型与C和e抗原的弱表达相关，但G抗原表达正常。JAHK被赋予Rh编号RH53。血清学研究结果表明该抗原位于RhCE蛋白上，尽管JAHK的分子基础尚不清楚。
对来自三个无关家系的8人的RHCE基因进行外显子扩增和直接测序分析。其中4个样本为JAHK阳性，其余4个为JAHK阴性。对1个JAHK阳性样本的整个RHCE基因进行测序，其余样本对第1至3外显子进行测序。开发了一种序列特异性引物的聚合酶链反应程序用于JAHK等位基因的特异性检测。
对1个JAHK阳性样本的整个RHCE基因分析显示出预期的CcEe特异性核苷酸序列，并在外显子3中发现了一个额外的核苷酸变化（365C>T）。这种变化代表一个错义突变，导致RhCE蛋白第122位氨基酸由丝氨酸替换为亮氨酸。来自另外两个无关家系的3个JAHK阳性样本显示出365C>T突变，并证实了Ser122Leu替换与JAHK阳性表型相关。
JAHK抗原（RH53）的分子基础由RHCE基因外显子3中的365C>T突变定义，该突变导致氨基酸替换Ser122Leu。由于预测第122位位于与第二个环相邻的跨膜区域，中性丝氨酸被疏水性亮氨酸替换似乎通过RhCE蛋白的构象变化导致了JAHK抗原的产生。这种结构变化也可能导致在JAHK阳性个体中观察到的C和e抗原表达减弱。基于我们的结果得出结论，JAHK特异性突变与dCe单倍型相关。
