Lockwood Wendy K, Bodmer Rolf
Department of Cell, Developmental and Neural Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109-1048, USA.
Mech Dev. 2002 Jun;114(1-2):13-26. doi: 10.1016/s0925-4773(02)00044-8.
Two secreted signaling molecules, wingless (wg) and decapentaplegic (dpp), are required to specify the heart in Drosophila. wg and dpp are also required to specify other cell types within the mesoderm and in many other regions of the embryo. Because the spatial patterns of wg and dpp are dynamic, different populations of mesodermal cells are exposed to different combinations of wg and/or dpp at different times. To determine whether the patterns of wg and dpp expression provide unique positional information for the specification of heart precursors, we altered these patterns. Our data suggest that wg and dpp contribute progressively to the elaboration of the expression pattern of the mesoderm-specific homeobox-containing gene tinman (tin), and that the overlap of wg and dpp at an early stage (9) as well as at a later stage (11) in the presence of tin-expressing cells directs cardiac-specific differentiation. Furthermore, ectopic tin expression in the ectoderm at wg/dpp intersects (the primordia of the thoracic imaginal disks) also leads to cardiac-specific differentiation, suggesting that tin confers mesoderm-specificity to the wg/dpp response. We conclude that ectopic heart can be generated by altering the patterns of wg and dpp within the tin-expressing mesoderm, or by ectopic induction of tin within the wg- and dpp-expressing ectoderm.
在果蝇中，指定心脏需要两种分泌性信号分子，即无翅（wg）和五体不全（dpp）。wg和dpp在中胚层以及胚胎的许多其他区域指定其他细胞类型时也是必需的。由于wg和dpp的空间模式是动态的，不同群体的中胚层细胞在不同时间会接触到wg和/或dpp的不同组合。为了确定wg和dpp的表达模式是否为心脏前体的指定提供独特的位置信息，我们改变了这些模式。我们的数据表明，wg和dpp逐渐促进中胚层特异性含同源框基因tinman（tin）表达模式的细化，并且在存在tin表达细胞的早期阶段（9）以及后期阶段（11），wg和dpp的重叠引导心脏特异性分化。此外，在wg/dpp相交处（胸节成虫盘的原基）的外胚层中异位表达tin也会导致心脏特异性分化，这表明tin赋予wg/dpp反应中胚层特异性。我们得出结论，通过改变表达tin的中胚层内wg和dpp的模式，或通过在表达wg和dpp的外胚层内异位诱导tin，可以产生异位心脏。
