In recent years, studies have found that PIG-A mutations can also be detected in normal people, accounting for about 10%. However, no PNH clones and proliferation have been found, and no clinical symptoms of PNH 14. In Shin TH et al 2019, the data gathered about PNH macaque model using CRISPR/Cas9 technology to create model of hematologic disease based on the near phylogenetic/functional similarity between macaque and human was shown that there was no intrinsic clonal amplification of PNH-HSPCs 15. At present, studies reported that immune-escape characteristics 16 17 18, anti-apoptotic properties 19 20, and second gene mutations 21 22 23 may be involved in the amplification of PNH clones. T-lymphocyte immune attack GPI+HSC, and GPI−HSC is less vulnerable to attack. Studies have found that PNH cells are protected from NK/T effector cells due to the lack of GPI-anchored cytomegalovirus ul-16 binding protein (ULBPs) or CD1d restriction 24 25. CD109 has been reported to be a protein in GPI-APs, a TGF-co-receptor, which plays a key role in inhibiting TGF-signal-mediated erythrocyte differentiation. The lack of CD109 may make PIGA-mutated HSPCs more sensitive to TGF-β, leading to more easy differentiation of mutant erythroid progenitors into mature erythrocytes 26. The studies found that PNH clone cells have anti-apoptotic properties. In addition, Bcl-2, Bcl-XL, Bag-1, McL-1 and other anti-apoptotic genes were significantly increased in PNH patients, and played an important role in the anti-apoptotic process 27. The studies also found that PIG-A mutations disrupt lipid raft formation of cell membrane, this change passivation for promoting apoptosis signals or growth inhibition 28. The theory of secondary genetic mutations has been reported since the 1970s 21. Additional mutant genes such as HMGA2 29 30, WT1 31, TET2 32 and RBPJ 33 have been reported in PNH patients. Most cases of PNH can carry additional mutations and these mutations are secondary strikes. PIGA mutation is the initial mutation, the nature of PNH is a single gene disease, and its clinical manifestations are mainly determined by PIGA mutations rather than myeloid gene mutations 34. However, various theories cannot explain all the pathological mechanisms, and PNH clones must be involved in other mechanisms to gain proliferation advantage in patients.
Although LncRNAs do not encode proteins, they play an important role in cell proliferation and differentiation, and are widely studied in oncologic diseases. Not only solid tumors, but also non-solid tumors and even autoimmune diseases have been studied. The LncRNAs LOC101928834, H19, WT1-AS, TCL6, LEF1-AS1, EPB41L4A-AS1, PVT1, GAS5 and ZFAS were found relevant to (myelodysplastic syndromes (MDS) pathogenesis and outcome 35 36. Many LncRNAs such as MALAT1, GAS5, DLEU2, H19 and so on were reported in diagnosis ang progression of multiple myeloma (MM) 37 38. The LncRNAs HOTAIR, LincRNA-p21, LncRNA H19 and MALAT1 play important role in clinical diagnosis ang progression of Rheumatoid arthritis (RA) 39. The mechanism of action of LncRNA is complex. LncRNAs can interact with DNA, RNA, or protein. LncRNAs are involved in various pathways, including p53, NF-κB, PI3K/AKT, Notch and so on.
In our study, the results of RNA sequencing in PNH patients showed a large number of differentially expressed LncRNAs and mRNAs, many of which were involved in cell proliferation, thrombosis, etc. Such results gave us a lot of information, LncRNAs may play an important role in PNH clone proliferation. By verification, we found that the level of LncRNA FAM157C in CD59− cells siginificantly increased, and was positively correlated with the LDH levels and CD59− granulated and monocytes cells ratio. After knockdown of FAM157C gene, it was found that the cells were blocked in G0/G1 phase and S phase, the apoptosis rate increased, the proliferation ability decreased. The FAM157C was expressed in bone marrow, spleen and other organs, and its function has not been reported in the literature. The results of our experiment suggested that FAM157C gene may promote PNH clone proliferation. The mechanism remains to be further studied.