Intracellular transport and sorting of actin mRNAs in osteoblasts.

肌动蛋白同种型分选已显示在培养物中的多种细胞类型中发生。在此列表中，我们添加成骨细胞，其中我们通过原位杂交显示，β-肌动蛋白主要分布在细胞过程中，并且在细胞核的一侧，γ-肌动蛋白具有核周分布。骨骼突变无牙（tl）的成骨细胞，在相同条件下评估，不能区分这些肌动蛋白亚型，并表现出弥散标记作为其主要表现。肌动蛋白mRNA的Northan分析显示正常和突变培养物之间没有差异。成骨细胞寿命缩短和不能直接破骨细胞介导的骨吸收最近已被证明在tl突变体。目前的结果表明，成骨细胞的肌动蛋白mRNA排序失败可能与一个或两个这些病理放大在这种突变，并代表，据我们所知，第一次纠正肌动蛋白mRNA排序异常与哺乳动物疾病。由于骨吸收和骨形成是高度相互依赖的，并且注射CSF-1（一种生长因子），我们研究了CSF-1治疗对体外分选肌动蛋白mRNA能力的影响。新生儿CSF-1治疗突变体恢复成骨细胞在较老的骨表面，促进正常分选β-肌动蛋白mRNA在体外突变成骨细胞没有正常化γ-肌动蛋白分布。这些数据表明成骨细胞中的β和γ-肌动蛋白mRNA通过不同的机制进行分选，并且β-肌动蛋白mRNA的差异分选与成骨细胞中应力纤维的特征极化有关。该实验系统可用于探索细胞和组织生物学这些方面的关系和调节。

Actin isoform sorting has been shown to occur in a variety of cell types in culture. To this list we add osteoblasts, in which we show by in situ hybridization that beta-actin is distributed primarily in cell process and on one side of the nucleus and gamma-actin has a perinuclear distribution. Osteoblasts from the skeletal mutation toothless(tl), evaruated under identical conditions, fail to sort these actin isoforms differentially and exhibit diffuse labeling as their major manifestation. Northan analyses of actin mRNAs showed no differences between normal and mutant cultures. Shortened osteoblast life span and an inability to direct osteoclast-mediated bone resorption have recently been demonstrated in tl mutants. The present results suggest that a failure of osteoblasts to sort actin mRNAs may be related to one or both of these pathological magnifestation in this mutation and represent, to our knowledge, the first correction of an actin mRNA-sorting abnormality with a mammalian disease. Because bone resorption and formation are highly interdependent and injections of CSF-1, a growth factor, we examined the effects of CSF-1 treatment on ability to sort actin mRNAs in vitro. Neonatal CSF-1 treatment of mutants restores osteoblasts on older bone surfaces, promotes normal sorting of beta-actin mRNA in mutant osteoblasts in vitro without normalizing gamma-actin distribution. These data suggest the beta and gamma-actin mRNAs in osteoblasts are sorted by different mechanisms and that the differential sorting of beta-actin mRNA is related to the characteristic polarization of stress fibers in osteoblasts. This experimental system can be used to explore the relationships and regulation of these aspects of cell and tissue biology.