Runx1 Control of Bone Resorption during Fracture Repair

描述（由申请人提供）：我们产生的初步证据表明，与野生型窝仔相比，Runx1单倍不足小鼠骨折老茧中的破骨细胞数量增加。此外，我们发现在破骨细胞前体中靶向删除Runx1导致小梁骨量减少25-30%，骨吸收增加40-50%。最后，我们在体外确定Runx1抑制破骨细胞特异性基因的表达。因此，我们假设Runx1抑制髓系前体细胞分化为成熟的破骨细胞，并以此方式改变骨骼稳态和修复。我们建议：1。评估Runx1在骨重塑和骨折修复过程中调节破骨细胞的作用。(目标1)。我们打算确定：(i) Runx1是体内破骨细胞分化和功能的转录抑制因子；（ii）在前体而非成熟破骨细胞中条件缺失Rux1是否会损害骨折愈合。2. 明确runx1介导的破骨细胞发生抑制的机制。(目标2)。我们建议确定(i) Runx1是否对早期而非晚期破骨细胞分化至关重要；（ii）检验rux1介导的破骨细胞生成抑制是否依赖于rank信号的抑制；（iii） Runx1通过调节关键基因改变破骨细胞前体谱系的承诺和分化；（iv） Runx1调节髓系前体对各种谱系命运的承诺。我们提出的实验将为骨骼再生和修复过程中破骨细胞分化的转录抑制提供一种新颖而综合的机制见解。

DESCRIPTION (provided by applicant): We generated preliminary evidence showing that the number of osteoclasts in the fracture calluses of mice haploinsufficient for Runx1 is increased compared to wild type littermates. Furthermore, we found that targeted deletion of Runx1 in osteoclast precursors led to 25-30% decrease in trabecular bone mass and a 40-50% increase in bone resorption. Finally, we determined that Runx1 inhibits the expression of osteoclast specific genes in vitro. Thus, we hypothesized that Runx1 inhibits myeloid precursor cell differentiation into mature osteoclasts and in this way alters skeletal homeostasis and repair. We propose to: 1. Evaluate the role of Runx1 in regulating osteoclasts during bone remodeling and fracture repair. (Aim 1). We propose to determine whether: (i) Runx1 is a transcriptional repressor of osteoclast differentiation and function in vivo and (ii) if conditional deletion of Rux1 in precursors but not mature osteoclasts will impair fracture healing. 2. Define the mechanisms underlying Runx1-mediated inhibition of osteoclastogenesis. (Aim 2). We propose to determine whether (i) Runx1 is critical for early but not late osteoclast differentiation; (ii) examine if Rux1-mediated inhibition of osteoclastogenesis depends on inhibition of RANK-signaling; (iii) Runx1 alters osteoclast precursor lineage commitment and differentiation by regulating critical genes; (iv) Runx1 regulates myeloid precursor commitment towards various lineage fates. Our proposed experiments will provide a novel and integrated mechanistic insight into the transcriptional repression of osteoclast differentiation during skeletal regeneration and repair.