Tet2调节骨髓间充质干细胞功能

Tet2(Tet家族成员2)在DNA去甲基化修饰、表观遗传调控及骨髓造血中起着重要作用。笔者课题组前期研究发现,随着年龄增长,Tet2敲除小鼠逐步发展为淋系白血病和髓系白血病。但Tet2在骨髓微环境中的作用仍不清楚。进一步研究发现,Tet2敲除的骨髓间充质干细胞(Mesenchymal stem cells,MSC)更多处于G2/M分裂期,其细胞分裂时间缩短,生长速度加快。长周期培养-起始细胞实验表明,Tet2敲除的MSC支持造血干细胞扩增和髓系分化的能力增强。通过点杂交实验发现,Tet2敲除后,骨髓细胞DNA总甲基化水平升高。对Tet2缺失的骨髓细胞进行甲基化测序,结果表明:基因组转录调控区域等多个功能性结构域的甲基化水平明显升高。同时,敲除Tet2的MSC分泌IL-8、IL-18等炎性细胞因子的能力下降;敲除Tet2的MSC更多分泌促进造血干细胞髓系分化的GM-CSF和CCL-3等细胞因子。Tet2可以影响间充质干细胞造血支持作用,进而调节造血。

Tet2 Regulates Osteoclast Differentiation by Interacting with Runx1 and Maintaining Genomic 5-Hydroxymethylcytosine(5hmC)

As a dioxygenase. Ten-Eleven Translocation 2 （TET2） catalyzes subsequent steps of 5-methylcytosine （5mC） oxidation. TET2 plays a critical role in the self-renewal, proliferation, and differentiation of hei-natopoietic stem cells, but its impact on mature hematopoietic cells is not well-characterized. Here we show that Tet2 plays an essential role in osteoclastogenesis. Dele- tion of Tet2 impairs the differentiation of osteoclast precursor cells （macrophages） and their matu- ration into bone-resorbing osteoclasts in vitro. Furthermore, Tet2 / mice exhibit mild osteopetrosis, accompanied by decreased number of osteoclasts in vivo. Tet2 loss in macrophages results in the altered expression of a set of genes implicated in osteoclast differentiation, such as Cehpa, Mafb, and Nfkbiz. Tet2 deletion also leads to a genome-wide alteration in the level of 5-hydroxymethylcytosine （ShmC） and altered expression of a specific subset of macrophage genes associated with osteoclast differentiation. Furthermore, Tet2 interacts with Runxl and negatively modulates its transcriptional activity. Our studies demonstrate a novel molecular mechanism controlling osteoclast differentiation and function by Tet2, that is, through interactions with Runxl and the maintenance of genomie 5hmC. Targeting Tet2 and its pathway could be a potential therapeutic strategy for the prevention and t,＇eatment of abnormal bone mass caused by the deregulation of osteoclast activities.

Novel diagnostic approaches for Fanconi anemia (FA) by single-cell sequencing and capillary nano-immunoassay

Next-generation sequencing technology has been widely utilized for the diagnosis of Fanconi anemia(FA).However,mixed cell sequencing and chimerism of FA patients may lead to unconfirmed genetic subtypes.Herein,we introduced two novel diagnostic methods,including single-cell sequencing and capillary nano-immunoassay.One FA case with FANCM c.4931G>A p.R1644Q and FANCD1 c.6325G>A p.V2109I was studied.The DNA of 28 cells was amplified and eight types of cells were observed after Sanger sequencing.There were two homozygous mutations(FANCM/FANCD1).Furthermore,the capillary nano-immunoassay was conducted to analyze the expression profile of FA-associated proteins.Abnormal FANCM and FANCD1 expressions simultaneously existed.This case was thus diagnosed as FA-D1/FA-M dual subtype.Compared with mixed cell sequencing,single-cell sequencing data shows more accuracy for the FA subtype evaluation,while the capillary nano-immunoassay is a good method to detect the expression profile of abnormal or modified FA protein.

Loss of Tet2 affects platelet function but not coagulation in mice

Ten-eleven translocation 2(TET2)functions as a methylcytosine dioxygenase that catalyzes the iterative oxidation of 5-methylcytosine to 5-hydroxymethylcytosine,5-formylcytosine and 5-carboxylcytosine.TET2 has been shown to be crucial for the maintenance and differentiation of hematopoietic stem cells,and its deletion and/or mutations results in the expansion of HSPCs,and leads to hematological malignancies.TET2 mutations were found in a variety of hematological disorders such as CMML(60%),MDS(30%),MPN(13%)and AML(20%).Interestingly,it was shown that CMML patients with TET2 mutation exhibited fewer platelets than CMML patients without TET2 mutation.However,the role and function of TET2 in platelet hemostasis and thrombogenesis is not well defined.Here in this study,using a genetically engineered Tet2 deletion mouse model,we found that the absence of Tet2 caused a decrease in the proportion of MEP cells and hyperploid megakaryocytes.Additionally,Tet2-deficient mice displayed impaired platelet activation and aggregation under stimulation of ADP and low concentrations of thrombin,although the modestly compromised platelet function and MEP differentiation in Tet2-deficient mice could be compensated without affecting blood coagulation function.Our study indicate that Tet2 deficiency leads to mild impairment of platelet function and thrombopoiesis in mice.

Passion for moments and compassion for patients: in memory of Dr. Jianfeng Zhou (1966–2022)

At 11:37 on March 27,2022,Dr.Jianfeng Zhou,a renowned hematologist in China and a leader in the field of CAR-T treat-ment in hematological tumors,died unexpectedly at the age of 56 because of sudden coronary dissection rupture(acute myo-cardial infarction secondary to spontaneous coronary artery dissection).I have known Jianfeng for>20 years(Figs.1 and 2),he was one of the most outstanding,compassionate,and hard-work-ing clinician-scientist I have come across with.He dedicated his career to improving healthcare outcomes for every patient in his care,as well as to medical innovations that brought novel treatments to hundreds of thousands more patients.

DNAH2 facilitates the homologous recombination repair of Fanconi anemia pathway through modulating FANCD2 ubiquitination

Fanconi anemia(FA),an X-linked genetic or autosomal recessive disease,exhibits complicated pathogenesis.Previously,we detected the mutated Dynein Axonemal Heavy Chain 2(DNAH2)gene in 2 FA cases.Herein,we further investigated the potential association between DNAH2 and the homologous recombination repair pathway of FA.The assays of homologous recombination repair,mitomycin C(MMC)sensitivity,immunofluorescence,and ubiquitination modification were performed in U2OS and DR-U2OS cell lines.In MMC-treated U2OS cells,the downregulation of the DNAH2 gene increased the sensitivity of cells to DNA inter-strand crosslinks.We also observed the reduced enrichment of FANCD2 protein to DNA damage sites.Furthermore,the ubiquitination modification level of FANCD2 was influenced by the deficiency of DNAH2.Thus,our results suggest that DNAH2 may modulate the cell homologous recombination repair partially by increasing the ubiquitination and the enrichment to DNA damage sites of FANCD2.DNAH2 may act as a novel co-pathogenic gene of FA patients.

Colony-stimulating factor 3 receptor (CSF3R) M696T mutation does not impact on clinical outcomes of a Ph+ acute lymphoblastic leukemia patient

Colony-stimulating factor 3 receptor(CSF3R)mutations have been identified in a variety of myeloid disorders.Although CSF3R point mutations(eg,T618I)are emerging as key players in chronic neutrophilic leukemia/atypical chronic myelogenous leukemia,the significance of rarer CSF3R mutations is unknown.Here,we report a 32-year-old female who was diagnosed as Philadelphia chromosome-positive acute lymphoblastic leukemia(Ph^(+)ALL)with the CSF3R M696T mutation and was undergone unrelated donor hematopoietic stem cell transplantation.The patient achieved complete remission with chemotherapy in combination with tyrosine kinase inhibitor(TKI)and long-term survival by unrelated donor transplantation.Meanwhile,we performed a series of experiments using murine interleukin 3(IL-3)-dependent Ba/F3 cell line to evaluate the transforming capacity of the CSF3R M696T mutation.We confirmed the presence of a CSF3R M696T germline mutation in this patient which was inherited from her mother.The in vitro experiment results showed that the CSF3R M696T mutation contributes marginally to the tumor transformation of Ba/F3 cells,indicating that CSF3R M696T mutation was neutral in tumor transformation ability.We concluded that TKI is effective in patients with the CSF3R M696T mutation in Ph+ALL and donors with CSF3R M696T mutation might still be selected as the candidate for transplantation.