Irvine K D, Wieschaus E
Department of Molecular Biology, Princeton University, NJ 08544, USA.
Development. 1994 Apr;120(4):827-41. doi: 10.1242/dev.120.4.827.
After the onset of gastrulation, the Drosophila germband undergoes a morphological change in which its length along the anterior-posterior axis increases over two-and-a-half fold while its width along the dorsal-ventral axis simultaneously narrows. The behavior of individual cells during germband extension was investigated by epi-illumination and time-lapse video microscopy of living embryos. Cells intercalate between their dorsal and ventral neighbors during extension, increasing the number of cells along the anterior-posterior axis while decreasing the number of cells along the dorsal-ventral axis. Mutations that reduce segmental subdivision of the embryo along the anterior-posterior axis decrease both germband extension and its associated cell intercalation. In contrast, cell intercalation and germband extension are still detected in embryos that lack dorsal-ventral polarity. Characterization of germband extension and cell intercalation in mutant embryos with altered segmentation gene expression indicates that these processes are regionally autonomous and are dependent upon the establishment of striped expression patterns for certain pair-rule genes. Based on these observations, we propose a model for germband extension in which cell intercalation results from the establishment of adhesive differences between stripes of cells by pair-rule genes.
原肠胚形成开始后，果蝇胚带经历形态变化，其沿前后轴的长度增加超过两倍半，而沿背腹轴的宽度同时变窄。通过对活胚胎进行落射照明和延时视频显微镜观察，研究了胚带延伸过程中单个细胞的行为。在延伸过程中，细胞在其背侧和腹侧邻居之间插入，增加沿前后轴的细胞数量，同时减少沿背腹轴的细胞数量。沿前后轴减少胚胎节段细分的突变会减少胚带延伸及其相关的细胞插入。相反，在缺乏背腹极性的胚胎中仍可检测到细胞插入和胚带延伸。对具有改变的体节基因表达的突变胚胎中胚带延伸和细胞插入的特征分析表明，这些过程是区域自主的，并且依赖于某些成对规则基因条纹状表达模式的建立。基于这些观察结果，我们提出了一个胚带延伸模型，其中细胞插入是由成对规则基因在细胞条纹之间建立粘附差异导致的。
