Kaur Amanpreet, Desikan Harini, Pagnucco Grace, Kandarpa Malathi, Talpaz Moshe, Raghavan Malini
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI.
Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Rogel Cancer Center, Ann Arbor, MI.
bioRxiv. 2025 Jun 27:2025.06.24.661416. doi: 10.1101/2025.06.24.661416.
Calreticulin (CRT) is important for human leukocyte antigen (HLA) class I assembly. Somatic mutations of the CRT gene () in hematopoietic lineage cells cause myeloproliferative neoplasms (MPNs). Typically, MPN patient cells have one copy each of the wild-type and mutant allele. We find that heterozygous knock-in of a MPN mutation into human cell lines maintains or slightly induces surface expression of HLA class I allotypes. However, full deficiency of wild-type CRT variably reduces the surface expression of HLA class I allotypes, and MPN CRT mutants fail to restore expression for all tested allotypes. Consistent with the largely heterozygous nature of mutations in MPN, surface HLA class I expression in platelets and monocytes from MPN patients with mutations generally falls within the normal range, with higher average expression measured in monocytes from patients treated with interferon alpha compared with other treatments. Overall, the studies indicate that loss of HLA class I expression in cells deficient in wild-type CRT (the CRT dependency) is allele-dependent and correlates with known effects of the assembly factor tapasin. Furthermore, heterozygous knock-in of a MPN-linked mutation has no effect on some allotypes and slightly induces HLA class I expression for CRT-dependent allotypes.
钙网蛋白（CRT）对人类白细胞抗原（HLA）I类组装很重要。造血谱系细胞中CRT基因的体细胞突变会导致骨髓增殖性肿瘤（MPN）。通常，MPN患者细胞具有野生型和突变型等位基因各一个拷贝。我们发现，将MPN突变杂合敲入人类细胞系可维持或轻微诱导HLA I类同种异型的表面表达。然而，野生型CRT的完全缺失会不同程度地降低HLA I类同种异型的表面表达，并且MPN CRT突变体无法恢复所有测试同种异型的表达。与MPN中突变主要为杂合性质一致，具有突变的MPN患者血小板和单核细胞表面HLA I类表达通常在正常范围内，与其他治疗相比，用α干扰素治疗的患者单核细胞中平均表达更高。总体而言，这些研究表明，野生型CRT缺陷细胞中HLA I类表达的丧失（CRT依赖性）是等位基因依赖性的，并且与组装因子塔帕辛的已知作用相关。此外，与MPN相关的突变杂合敲入对某些同种异型没有影响，并且对CRT依赖性同种异型轻微诱导HLA I类表达。
