Aid is a key regulator of myeloid/erythroid differentiation and DNA methylation in murine hematopoietic stem/progenitor cells (RNA-Seq)

Recent studies have uncovered that activation-induced cytidine deaminase (AID) and ten-eleven-translocation (TET) family members regulate active DNA demethylation. Genetic alterations of TET2 in various myeloid malignancies and aberrant hematopoietic stem cell (HSC) self-renewal/differentiation in mice with hematopoietic tissue specific loss of Tet2 have been reported, indicating that TET2 is a master regulator of normal and malignant hematopoiesis. Despite a functional link between AID and TET in epigenetic gene regulation, the role of AID loss in normal hematopoiesis and myeloid transformation remains to be investigated. Here, we show that Aid loss in mice leads to expansion of myeloid cells and contraction in erythroid progenitors resulting in pathologic anemia possibly due to dysregulated expression of Cebpa and Gata1, myeloid/erythroid lineage specific transcription factors. Consistent with data in the murine context, silencing of AID skews differentiation towards myelomonocytic lineage in human BM cells. However, in contrast to Tet2, Aid loss does not contribute to enhanced HSC self-renewal or cooperate with Flt3-ITD in myeloid leukemogenesis. Genome-wide transcription and differential methylation analysis uncover critical role of Aid as a key epigenetic regulator. These results indicate that AID and TET2 share common effects on myeloid and erythroid lineage differentiation, and that their role is non-redundant in regulating HSC self-renewal and in myeloid transformation. Overall design: We utilized germ line Aid knockout mice for our study and examined transcriptome of FACS-sorted LSK populations from WT, Aid(+/-) and Aid(-/-) animals at 12 months of age.

近期研究证实，激活诱导胞苷脱氨酶（activation-induced cytidine deaminase, AID）与十-十一易位（ten-eleven-translocation, TET）家族成员共同调控活性DNA去甲基化过程。已有研究报道，多种髓系恶性肿瘤中存在TET2的遗传变异，且造血组织特异性敲除Tet2的小鼠会出现造血干细胞（hematopoietic stem cell, HSC）自我更新与分化异常，这表明TET2是正常与恶性造血过程的核心调控因子。尽管AID与TET在表观遗传基因调控中存在功能关联，但AID缺失在正常造血及髓系转化中的作用仍有待阐明。本研究发现，小鼠体内Aid缺失会导致髓系细胞扩增、红系祖细胞减少，进而引发病理性贫血，这一现象可能源于髓系/红系谱系特异性转录因子Cebpa与Gata1的表达失调。与小鼠模型的实验结果一致，在人类骨髓（bone marrow, BM）细胞中沉默AID会使细胞分化向髓单核细胞谱系偏移。然而与Tet2不同，Aid缺失并不会增强HSC的自我更新能力，也不会在髓系白血病发生过程中与FMS样酪氨酸激酶3内部串联重复（FMS-like tyrosine kinase 3 internal tandem duplication, Flt3-ITD）发生协同作用。全基因组转录与差异甲基化分析证实，Aid作为关键表观遗传调控因子发挥着重要作用。上述结果表明，AID与TET2在髓系及红系谱系分化中具有共同的调控效应，且二者在调控HSC自我更新及髓系转化过程中的作用并不冗余。实验设计：本研究使用生殖系Aid敲除小鼠开展实验，对12月龄野生型（wild type, WT）、Aid(+/-)及Aid(-/-)小鼠经荧光激活细胞分选术（fluorescence-activated cell sorting, FACS）分离得到的谱系阴性、Sca-1阳性、c-Kit阳性（LSK）细胞群进行转录组分析。