Characterization of missense mutations in the signal peptide and propeptide of FIX in hemophilia B by a cell-based assay
Characterization of missense mutations in the signal peptide and propeptide of FIX in hemophilia B by a cell-based assay
复制标题
通过基于细胞的检测表征血友病 B 中 FIX 信号肽和前肽的错义突变
DOI：
10.1182/bloodadvances.2020002520
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发表时间：
2020-08-11
期刊：
影响因子：
7.5
通讯作者：
Shen, Guomin
中科院分区：
文献类型：
--
作者：
Gao, Wenwen;Xu, Yaqi;Shen, Guomin
Many mutations in the signal peptide and propeptide of factor IX (FIX) cause hemophilia B. A FIX variants database reports 28 unique missense mutations in these regions that lead to FIX deficiency, but the underlying mechanism is known only for the mutations on R43 that interfere with propeptide cleavage. It remains unclear how other mutations result in FIX deficiency and why patients carrying the same mutation have different bleeding tendencies. Here, we modify a cell-based reporter assay to characterize the missense mutations in the signal peptide and propeptide of FIX. The results show that the level of secreted conformation-specific reporter (SCSR), which has a functional gamma-carboxyglutamate (Gla) domain of FIX, decreases significantly in most mutations. The decreased SCSR level is consistent with FIX deficiency in hemophilia B patients. Moreover, we find that the decrease in the SCSR level is caused by several distinct mechanisms, including interfering with cotranslational translocation into the endoplasmic reticulum, protein secretion, gamma-carboxylation of the Gla domain, and cleavage of the signal peptide or propeptide. Importantly, our results also show that the SCSR levels of most signal peptide and propeptide mutations increase with vitamin K concentration, suggesting that the heterogeneity of bleeding tendencies may be related to vitamin K levels in the body. Thus, oral administration of vitamin K may alleviate the severity of bleeding tendencies in patients with missense mutations in the FIX signal peptide and propeptide regions.
