Rogulja-Ortmann Ana, Renner Simone, Technau Gerhard M
Institute of Genetics, University of Mainz, 55099 Mainz, Germany.
Development. 2008 Oct;135(20):3435-45. doi: 10.1242/dev.023986. Epub 2008 Sep 17.
The generation of morphological diversity among segmental units of the nervous system is crucial for correct matching of neurons with their targets and for formation of functional neuromuscular networks. However, the mechanisms leading to segment diversity remain largely unknown. We report here that the Hox genes Ultrabithorax (Ubx) and Antennapedia (Antp) regulate segment-specific survival of differentiated motoneurons in the ventral nerve cord of Drosophila embryos. We show that Ubx is required to activate segment-specific apoptosis in these cells, and that their survival depends on Antp. Expression of the Ubx protein is strongly upregulated in the motoneurons shortly before they undergo apoptosis, and our results indicate that this late upregulation is required to activate reaper-dependent cell death. We further demonstrate that Ubx executes this role by counteracting the function of Antp in promoting cell survival. Thus, two Hox genes contribute to segment patterning and diversity in the embryonic CNS by carrying out opposing roles in the survival of specific differentiated motoneurons.
神经系统节段性单元之间形态多样性的产生，对于神经元与其靶标正确匹配以及功能性神经肌肉网络的形成至关重要。然而，导致节段多样性的机制在很大程度上仍不为人知。我们在此报告，Hox基因超双胸（Ubx）和触角足（Antp）调节果蝇胚胎腹神经索中分化运动神经元的节段特异性存活。我们表明，Ubx是激活这些细胞中节段特异性凋亡所必需的，并且它们的存活依赖于Antp。Ubx蛋白的表达在运动神经元即将发生凋亡前不久强烈上调，我们的结果表明这种晚期上调是激活依赖于收割者的细胞死亡所必需的。我们进一步证明，Ubx通过抵消Antp在促进细胞存活中的功能来执行这一作用。因此，两个Hox基因通过在特定分化运动神经元的存活中发挥相反作用，有助于胚胎中枢神经系统的节段模式形成和多样性。
