斑马鱼Pu.1和Fms协同调控髓系至破骨细胞分化的研究

Bone development is precisely regulated in the balance of formation by osteoblasts and resorption by osteoclasts. Osteoclasts are originated from blood recruited myeloid cells to the bone surface where they undergo differentiation. It is known that the transcription factor Pu.1 can regulate fms in myelopoiesis. However, the cooperation of these two genes on osteoclast development is still unclear. By utilizing pu.1G242D or fmsj4e1 zebrafish mutants, we found that pu.1G242D or fmsj4e1 single mutants had significantly increased bone mineral density and severely reduced marrow cavity area compared with the wild-type, and double mutant showed severer phenotypes than single mutant. Moreover, we confirmed that the decreased resorption function of osteoclast was causative for the abnormity of bone development in single mutants. All these suggested that pu.1 and fms may cooperatively promote osteoclast development. In this proposal, we are going to elucidate the genetic and molecular relationship between pu.1 and fms during osteoclast development.

骨发育的顺利进行依赖于成骨和破骨两种细胞的平衡。破骨细胞来源于血液中的髓系细胞，已知转录因子PU.1（急性髓系白血病因子）以及原癌基因fms（集落刺激因子1受体)在早期髓系发育及破骨细胞发育中起到关键作用，然而pu.1和fms在调控破骨细胞发育的分子细胞机理以及相互作用方式仍不明确。我们前期工作中鉴定斑马鱼pu.1G242D突变体与fmsj4e1突变体的表型，发现pu.1G242D 和fmsj4e1 单突变体和pu.1G242D；fmsj4e1双突变体骨密度增加、骨髓腔减小等骨发育异常，但是双突变体的表型最为严重。并且，单突变体中的破骨细胞发育异常而成骨细胞发育不受影响，提示pu.1和fms可能协同调控破骨细胞的发育。本项目拟运用细胞学、遗传学及分子生物学等方法来研究pu.1和fms在调控髓系至破骨细胞发育的细胞学机理、遗传互作关系及分子机制。

破骨细胞是髓系来源的骨吸收细胞。破骨细胞缺陷会导致骨硬化症的发生，这是一种以骨硬化为特征的遗传疾病，目前尚无有效的药物治疗。众所周知，Pu1和Fms是髓系发生的关键调节因子，其在小鼠体内的缺陷可导致破骨细胞数量减少，进而导致骨硬化。然而，Pu1和Fms在破骨细胞发育和骨病发病机制中的相互作用关系仍不清楚。在本研究中，我们对pu.1G242D;fmsj4e1双缺陷斑马鱼进行了描述，发现与pu.1G242D和fmsj4e1单缺陷斑马鱼相比，pu.1G242D;fmsj4e1双缺陷斑马鱼表现出更严重的功能性破骨细胞缺失和骨硬化表型。提示Pu1和Fms在调节破骨细胞发育方面具有协同作用。我们进一步发现，Pu1更多的在破骨细胞形成中起主导作用，而Fms则更多的在破骨细胞成熟中起主导作用。重要的是，我们发现临床药物维甲酸可以通过增加功能性破骨细胞的数量来显著缓解这些模型中不同程度的骨硬化症状。综述所述，我们建立了有价值的不同程度的骨硬化症动物模型，同时，我们的研究结果将为骨硬化症的药物开发提供新的策略，研究论文于2020年10月在线发表在J Genet Genomics （https://doi.org/10.1016/j.jgg.2020.09.002）。