Cowing D, Kenyon C
Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143-0554, USA.
Nature. 1996 Jul 25;382(6589):353-6. doi: 10.1038/382353a0.
The Hox genes are expressed in a conserved sequence of spatial domains along the anteroposterior (A/P) body axes of many organisms. In Drosophila, position-specific signals located along the A/P axis establish the pattern of Hox gene expression. In the nematode Caenorhabditis elegans, it is not known how the pattern of Hox gene expression is established. C. elegans uses lineal control mechanisms and local cell interactions to specify early blastomere identities. However, many cells expressing the same Hox gene are unrelated by lineage, suggesting that, as in Drosophila, domains of Hox gene expression may be defined by cell-extrinsic A/P positional signals. To test this, we have investigated whether posterior mesodermal and ectodermal cells will express their normal posterior Hox gene when they are mispositioned in the anterior. Surprisingly, we find that correct Hox gene expression does not depend on cell position, but is highly correlated with cell lineage. Thus, although the most striking feature of Hox gene expression is its positional specificity, in C. elegans the pattern is achieved, at least in part, by a lineage-specific control system that operates without regard to A/P position.
Hox基因在许多生物体沿前后（A/P）体轴的空间结构域的保守序列中表达。在果蝇中，沿A/P轴定位的特异性信号建立了Hox基因的表达模式。在秀丽隐杆线虫中，尚不清楚Hox基因的表达模式是如何建立的。秀丽隐杆线虫利用线性控制机制和局部细胞相互作用来确定早期卵裂球的身份。然而，许多表达相同Hox基因的细胞在谱系上并无关联，这表明，与果蝇一样，Hox基因的表达结构域可能由细胞外A/P位置信号所定义。为了验证这一点，我们研究了后中胚层和外胚层细胞在前部位置错误时是否会表达其正常的后部Hox基因。令人惊讶的是，我们发现正确的Hox基因表达并不依赖于细胞位置，而是与细胞谱系高度相关。因此，尽管Hox基因表达最显著的特征是其位置特异性，但在秀丽隐杆线虫中，这种模式至少部分是由一个不考虑A/P位置的谱系特异性控制系统实现的。
