wnt-NPC1-胆固醇转运信号通路调节造血干细胞自我更新机制的研究

Wnt signaling has repeatedly been implicated in playing important roles on hematopoietic stem cells (HSCs) self renewal.However, the mechanisms under regulation of wnt signaling on HSCs self renewal have not been well understood. We had reported that an unkown wnt signaling involves into maintenace self renewal of a hematopoietic precusor cell line, EML (erythroid myeloid lymphoid).We purified and identified two sub-populations, Lin-Sca-1hiCD34+(CD34+)and Lin-Sca-1loCD34-(CD34-) from EML system.We found that CD34+ cells autonomously renew and differentiate to CD34- cells and balance the renewal and the differentiation. The unknown wnt siganling is required to maintain CD34+ cells renewal.The insights into how the unknown wnt signaling works remains to be invistgated. Our recent evidences suggested that the unknown Wnt signaling upregulates NPC1 expression.NPC1 has capacities to bind cholesterol and transfer cholesterol from endosomes/lysosomes to endoplasmic reticulum and plasma membrane.NPC1 was shown to regulate the functions of the unknown wnt signaling on CD34+ cell renewal. Those evidences indicate that there is Wnt-NPC1-cholesterol trafficking pathway, which performs regulatory functions on HSCs renewal.We now propose to investigate insights into how the unknown wnt signaling regulates NPC1 expression,how NPC1 regulates HSCs renewal and cholterol trafficking regulates HSCs fate.From above studies we can explore the machenisms under the regulatory roles of the unknown wnt signaling on HSCs renewal.

wnt信号通路对调节造血干细胞（hematopoietic stem cells, HSCs）自我更新能力有重要作用，其机制还不完全清楚。我们前期研究报道，EML造血干细胞系存在调节 HSCs自我更新和分化平衡的内在机制，一种新的wnt信号通路对维持HSCs自我更新能力有重要作用，但是，其下游的效应分子有待研究。我们近期的研究发现，wnt信号通路能够调节游离胆固醇转运蛋白NPC1的表达，NPC1在wnt信号通路调节HSCs自我更新过程中起关键作用，提示HSCs可能存在wnt-NPC1-胆固醇转运-HSCs功能的信号途径。本项目将在已有研究结果的基础上，结合建立的细胞模型和正常造血干细胞，通过研究wnt信号通路如何调节NPC1基因表达、NPC1如何维持HSCs自我更新能力、胆固醇转运平衡如何调节HSCs功能，阐明wnt-NPC1-胆固醇信号途径调节HSCs自我更新的机制。

Niemen-Pick disease type C（NPD-C)是一种单基因、隐性遗传性疾病，是由于NPC1（95%）或者NPC2（5%）基因突变所致。NPC1和NPC2在细胞内主要分布在溶酶体、转运摄入的胆固醇到其他细胞器（包括细胞膜），维持胆固醇在细胞内分布的平衡。NPC1或者NPC2功能突变导致胆固醇在溶酶体蓄积、细胞功能障碍，累及全身各器官系统，特别是造血、神经系统，但是，其细胞、分子水平的发病机制还不清楚。本项目通过研究NPC1与Wnt信号通路之间相互作用（cross-talk), 重点研究Wnt信号通路如何调节NPC1基因表达、NPC1如何影响Wnt信号通路转导、NPC1如何调节Wnt信号通路介导的造血干细胞（hematopoietic stem cells, HSCs）自我更新能力等方面，阐明wnt-NPC1-胆固醇转运信号途径调节HSCs功能的机制。通过项目的研究，我们发现1）经典Wnt信号通路在转录水平和转录后水平正向调节NPC1的表达；2）NPC1通过隔离GSK3beta与beta-catenin之间的相互作用，稳定beta-catenin的表达，增强Wnt信号通路的转导；3）NPC1在维持Wnt信号通路调节HSCs自我更新及淋巴系分化能力方面起重要作用。这些研究结果对阐明NPC disease的发病机制及开发新的治疗药物有重要意义。相关研究结果已经发表论文5篇，申请发明专利1项，2次参加国际干细胞研究协会年会、2次参加中国细胞生物学年会交流。