A striking feature of the nervous system pertains to the appearance of different neural cell subtypes at different axial levels. Studies in the Drosophila central nervous system reveal that one mechanism underlying such segmental differences pertains to the segment-specific removal of cells by programmed cell death (PCD). One group of genes involved in segment-specific PCD is the Hox homeotic genes. However, while segment-specific PCD is highly precise, Hox gene expression is evident in gradients, raising the issue of how the Hox gene function is precisely gated to trigger PCD in specific segments at the outer limits of Hox expression. The Drosophila Va neurons are initially generated in all nerve cord segments but removed by PCD in posterior segments. Va PCD is triggered by the posteriorly expressed Hox gene Abdominal-B (Abd-B). However, Va PCD is highly reproducible despite exceedingly weak Abd-B expression in the anterior frontiers of its expression. Here, we found that the transcriptional cofactor Dachshund supports Abd-B-mediated PCD in its anterior domain. In vivo bimolecular fluorescence complementation analysis lends support to the idea that the Dachshund/Abd-B interplay may involve physical interactions. These findings provide an example of how combinatorial codes of transcription factors ensure precision in Hox-mediated PCD in specific segments at the outer limits of Hox expression.

中文翻译：

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腊肠犬与 Abdominal-B 一起作用，在 Abd-B 表达的边界触发果蝇中枢神经系统的程序性细胞死亡

神经系统的一个显着特征与在不同轴向水平出现不同神经细胞亚型有关。对果蝇中枢神经系统的研究表明，这种节段性差异背后的一种机制与通过程序性细胞死亡 (PCD) 进行的节段特异性细胞去除有关。参与片段特异性 PCD 的一组基因是 Hox 同源基因。然而，虽然片段特异性 PCD 非常精确，但 Hox 基因表达在梯度中很明显，这引发了 Hox 基因功能如何精确门控以在 Hox 表达外部限制的特定片段中触发 PCD 的问题。果蝇_Va 神经元最初在所有神经索节段中生成，但在后节段中被 PCD 移除。Va PCD 由后向表达的 Hox 基因Abdominal-B ( Abd-B ) 触发。然而，Va PCD 具有高度可重复性，尽管其表达的前边界中的 Abd-B 表达极其微弱。在这里，我们发现转录辅因子 Dachshund 在其前域支持 Abd-B 介导的 PCD。体内双分子荧光互补分析支持 Dachshund/Abd-B 相互作用可能涉及物理相互作用的观点。这些发现提供了一个示例，说明转录因子的组合代码如何确保 Hox 表达外部限制的特定片段中 Hox 介导的 PCD 的精确性。