Intracellular transport and sorting of actin mRNAs in osteoblasts.

肌动蛋白异构体分选已被证明发生在各种细胞类型的培养。在这个列表中，我们添加了成骨细胞，我们通过原位杂交显示-肌动蛋白主要分布在细胞过程中，在细胞核的一侧，而-肌动蛋白分布在核周围。来自骨骼突变无牙（tl）的成骨细胞，在相同条件下评估，不能区分这些肌动蛋白同种异构体，并表现出弥漫性标记作为其主要表现。对肌动蛋白mrna的诺森分析显示正常和突变培养之间没有差异。最近在tl突变体中证实了成骨细胞寿命缩短和不能直接破骨细胞介导的骨吸收。目前的结果表明，成骨细胞对肌动蛋白mrna的分类失败可能与该突变中的一种或两种病理放大有关，并且据我们所知，这是首次纠正哺乳动物疾病中肌动蛋白mrna分类异常。由于骨吸收和形成是高度相互依赖的，并且注射生长因子CSF-1，我们在体外研究了CSF-1治疗对肌动蛋白mrna分选能力的影响。新生儿CSF-1突变体治疗可恢复老骨表面的成骨细胞，促进体外突变成骨细胞β -肌动蛋白mRNA的正常分选，但不使γ -肌动蛋白分布正常化。这些数据表明，成骨细胞中β -肌动蛋白mRNA和γ -肌动蛋白mRNA的分选机制不同，β -肌动蛋白mRNA的分选差异与成骨细胞应力纤维的特征性极化有关。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.