Iwaki D David, Lengyel Judith A
Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, CA 90095-1606, USA.
Mech Dev. 2002 Jun;114(1-2):71-84. doi: 10.1016/s0925-4773(02)00061-8.
The Drosophila hindgut develops three morphologically distinct regions along its anteroposterior axis: small intestine, large intestine and rectum. Single-cell rings of 'boundary cells' delimit the large intestine from the small intestine at the anterior, and the rectum at the posterior. The large intestine also forms distinct dorsal and ventral regions; these are separated by two single-cell rows of boundary cells. Boundary cells are distinguished by their elongated morphology, high level of both apical and cytoplasmic Crb protein, and gene expression program. During embryogenesis, the boundary cell rows arise at the juxtaposition of a domain of Engrailed (En)- plus Invected (Inv)-expressing cells with a domain of Delta (Dl)-expressing cells. Analysis of loss-of-function and ectopic expression phenotypes shows that the domain of Dl-expressing cells is defined by En/Inv repression. Further, Notch pathway signaling, specifically the juxtaposition of Dl-expressing and Dl-non-expressing cells, is required to specify the rows of boundary cells. This Notch-induced cell specification is distinguished by the fact that it does not appear to utilize the ligand Serrate and the modulator Fringe.
小肠、大肠和直肠。“边界细胞”的单细胞环在前部分隔大肠和小肠，在后部分隔直肠和大肠。大肠还形成了明显的背侧和腹侧区域；这些区域由两排单细胞的边界细胞分隔开。边界细胞的特征在于其细长的形态、高水平的顶端和细胞质Crb蛋白以及基因表达程序。在胚胎发育过程中，边界细胞排出现在表达Engrailed（En）和Invected（Inv）的细胞区域与表达Delta（Dl）的细胞区域的并置处。功能丧失和异位表达表型分析表明，表达Dl的细胞区域由En/Inv抑制定义。此外，Notch信号通路，特别是表达Dl和不表达Dl的细胞的并置，是确定边界细胞排所必需的。这种Notch诱导的细胞特化的特点是，它似乎不利用配体锯齿蛋白和调节因子边缘蛋白。
