The genetic background of the high prevalence red blood cell antigen AnWj has remained unresolved since its identification in 1972, despite reported associations with both CD44 and Smyd1 histone methyltransferase. Development of anti-AnWj, which may be clinically significant, is usually due to transient suppression of antigen expression, but a small number of individuals with persistent, autosomally recessive inherited AnWj-negative phenotype have been reported. Whole-exome sequencing of individuals with the rare inherited AnWj-negative phenotype revealed no shared mutations in CD44H or SMYD1; instead, we discovered homozygosity for the same large exonic deletion in MAL, which was confirmed in additional unrelated AnWj-negative individuals. MAL encodes an integral multipass membrane proteolipid, myelin and lymphocyte protein (Mal), which has been reported to have essential roles in cell transport and membrane stability. AnWj-positive individuals were shown to express full-length Mal on their red cell membranes, which was not present on the membranes of AnWj-negative individuals, regardless of whether from an inherited or suppression background. Furthermore, binding of anti-AnWj was able to inhibit binding of anti-Mal to AnWj-positive red cells, demonstrating the antibodies bind to the same molecule. Overexpression of Mal in an erythroid cell line resulted in the expression of AnWj antigen, regardless of the presence or absence of CD44, demonstrating that Mal is both necessary and sufficient for AnWj expression. Our data resolve the genetic background of the inherited AnWj-negative phenotype, forming the basis of a new blood group system, further reducing the number of remaining unsolved blood group antigens.

中文翻译：

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MAL 基因的缺失导致 Mal 蛋白丢失，定义了罕见的遗传性 AnWj 阴性血型表 型


自 1972 年被发现以来，高流行率红细胞抗原 AnWj 的遗传背景一直未得到解决，尽管据报道与 CD44 和 Smyd1 组蛋白甲基转移酶有关。抗 AnWj 的发展可能具有临床意义，通常是由于抗原表达的短暂抑制，但也有少数个体具有持续的常染色体隐性遗传性 AnWj 阴性表型。对具有罕见遗传性 AnWj 阴性表型的个体进行全外显子组测序，显示 CD44H 或 SMYD1 没有共同突变;相反，我们在 MAL 中发现了相同的大外显子缺失的纯合性，这在其他无关的 AnWj 阴性个体中得到了证实。MAL 编码完整的多通道膜蛋白脂、髓鞘和淋巴细胞蛋白 （Mal），据报道，它在细胞转运和膜稳定性中起着重要作用。AnWj 阳性个体显示在其红细胞膜上表达全长 Mal，而 AnWj 阴性个体的膜上不存在，无论来自遗传背景还是抑制背景。此外，抗 AnWj 的结合能够抑制抗 Mal 与 AnWj 阳性红细胞的结合，表明抗体与同一分子结合。在红系细胞系中过表达 Mal 会导致 AnWj 抗原的表达，无论 CD44 的存在与否，这表明 Mal 对于 AnWj 表达既必要又充分。我们的数据解析了遗传性 AnWj 阴性表型的遗传背景，形成了新血型系统的基础，进一步减少了剩余未解决的血型抗原的数量。