Transcription factor Hoxb5 reprograms B cells into functional T lymphocytes [RNA-Seq]

Natural hematopoietic stem cells are currently the only cell resource to generate entire T lymphopoiesis in vivo. Altenatively, functional and non-tumorigenic T lymphocytes converted from the other cell types remain unsuccessful. Evidence is still lacking about the concept that ''lineage-switching factors'' (LSFs) exist in HSC, whose re-activation in progeny cells can accomplish lineage conversions. Here we show that upon ectopic expression of Hoxb5(a HSC-specific transcription factor), the Pro-/Pre-B cells were induced into functional early T cell progenitors(iETPs) in vivo. The reprogramming process initiated in the bone marrow and accomplished in the thymus at ETP stage. Strikingly, the T lymphocytes derived from iETPs resemble their natural counterparts in transcriptome pattern, hierarchical differentiation, tissue distribution and immune functions. Our observations pave the way for achieving lineage regeneration by direct reprogramming autologous somatic cells in vivo. Further, our success in haematopoietic system may build a paradigm for LSF-mediated regeneration of other tissues. Overall design: Mus musculus mRNA profiles of 24 cell types, including HSC, MPP, Mature lineage cells (T cells_B cells_Myeloid cells), Pro-_Pre-_B cells, BM-ETPs, BM-iETPs, Thy-ETPs, Thy-iETPs, DN1, DN2, DN3, DN4, DP, CD4-SP,CD8-SP, iDN1, iDN2, iDN3, iDN4, iDP, iCD4-SP and iCD8-SP. 1000 of each cell type was sorted for RANseq analysis refered to published protocol (PMID:20203668).天然造血干细胞（hematopoietic stem cell, HSC）是目前唯一可在体内介导完整T淋巴细胞生成过程的细胞资源。与之相对的是，通过其他细胞类型转化获得的非致瘤性功能性T淋巴细胞仍未实现成功构建。目前，关于“造血干细胞中存在谱系转换因子（lineage-switching factors, LSFs），且其在子代细胞中重新激活可完成谱系转换”这一概念，仍缺乏相关证据支持。本研究显示，在异位表达造血干细胞特异性转录因子Hoxb5后，Pro-/Pre-B细胞可在体内被诱导为功能性早期T细胞前体（early T cell progenitors, iETPs）。该重编程过程始于骨髓，并在胸腺内的ETP阶段完成。值得注意的是，由iETPs分化而来的T淋巴细胞在转录组模式、层级分化、组织分布及免疫功能上，均与天然T淋巴细胞高度相似。本研究结果为通过体内直接重编程自体体细胞实现谱系再生铺平了道路。此外，我们在造血系统中取得的成功，可为通过谱系转换因子介导的其他组织再生研究构建范式。实验整体设计：对24种细胞类型的小家鼠（Mus musculus）mRNA转录组进行分析，涵盖造血干细胞（HSC）、多能造血祖细胞（MPP）、成熟谱系细胞（T细胞、B细胞、髓系细胞）、Pro-/Pre-B细胞、骨髓来源ETPs（BM-ETPs）、骨髓来源iETPs（BM-iETPs）、胸腺来源ETPs（Thy-ETPs）、胸腺来源iETPs（Thy-iETPs）、DN1、DN2、DN3、DN4、DP、CD4单阳性（CD4-SP）、CD8单阳性（CD8-SP）、iDN1、iDN2、iDN3、iDN4、iDP、iCD4-SP及iCD8-SP。每种细胞分选1000个，参照已发表的实验方案（PMID:20203668）进行RNA测序分析。