Hambardzumyan Dolores, Sergent-Tanguy Solène, Thinard Reynald, Bonnamain Virginie, Masip Manuel, Fabre Annabelle, Boudin Hélène, Neveu Isabelle, Naveilhan Philippe
INSERM U643, Nantes, France.
J Neurosci Res. 2009 May 1;87(6):1296-309. doi: 10.1002/jnr.21957.
Posttranscriptional events such as RNA stabilization are important for cell differentiation, but little is known about the impact of AU-rich binding proteins (AUBPs) on the fate of neural cells. Expression of destabilizing AUBPs such as AUF1 and neuronal-specific stabilizing proteins such as HuB, HuC and HuD was therefore analyzed in the developing central nervous system. Real-time RT-PCR indicated a specific developmental pattern in the postnatal cerebellum, with a progressive down-regulation of AUF1 from P1, whereas HuB was strongly up-regulated at about P7. These changes were accompanied by a progressive increase in AUF1p45 and the disappearance of one HuB isoform from P15, suggesting particular roles for these AUBPs in the developing cerebellum. AUF1 was detected in the three main cerebellar layers, whereas Hu proteins were found only in postmitotic neurons. A role for Hu proteins in the early stages of neuronal differentiation is further supported by arrest of cell proliferation following induction of HuB or HuD expression in a neural stem cell line. The decrease in nestin expression suggest that HuD, but not HuB, favors the transition of neural progenitors into early neuroblasts, but other factors are most probably required for their full differentiation into neurons, insofar as GAP-43 was not detected in HuD-transfected cells. These data suggest critical roles for HuB at the very earliest stages of neuronal differentiation, such as cell cycle exit, and HuD might also be involved in the transition of neural progenitors into early neuroblasts. Taken together, the present results strengthen the importance of AUBPs in brain ontogenesis.
诸如RNA稳定化等转录后事件对细胞分化很重要，但关于富含AU元件的结合蛋白（AUBP）对神经细胞命运的影响却知之甚少。因此，我们分析了发育中的中枢神经系统中不稳定的AUBP（如AUF1）和神经元特异性稳定蛋白（如HuB、HuC和HuD）的表达情况。实时逆转录聚合酶链反应（RT-PCR）显示，出生后小脑呈现出特定的发育模式，从出生后第1天（P1）开始，AUF1逐渐下调，而HuB在大约P7时强烈上调。这些变化伴随着AUF1 p45的逐渐增加以及一种HuB异构体从P15开始消失，这表明这些AUBP在发育中的小脑中具有特定作用。在小脑的三个主要层中均检测到AUF1，而Hu蛋白仅在有丝分裂后的神经元中发现。在神经干细胞系中诱导HuB或HuD表达后细胞增殖停滞，这进一步支持了Hu蛋白在神经元分化早期阶段的作用。巢蛋白表达的降低表明，HuD而非HuB有利于神经祖细胞向早期神经母细胞的转变，但由于在转染HuD的细胞中未检测到生长相关蛋白-43（GAP-43），它们完全分化为神经元很可能还需要其他因素。这些数据表明，HuB在神经元分化的最早阶段（如细胞周期退出）发挥关键作用，HuD可能也参与神经祖细胞向早期神经母细胞的转变。综上所述，目前的结果强化了AUBP在脑发育过程中的重要性。
