Schlosser G, Northcutt R G
Brain Research Institute, University of Bremen, Bremen, 28334, Germany.
Dev Biol. 2001 Jun 1;234(1):55-71. doi: 10.1006/dbio.2001.0237.
In order to determine the time window for induction of lateral line placodes in the axolotl, we performed two series of heterotopic and isochronic transplantations from pigmented to albino embryos at different stages of embryogenesis and assessed the distribution of pigmented neuromasts in the hosts at later stages. First, ectoderm from the prospective placodal region was transplanted to the belly between early neurula and mid tailbud stages (stages 13-27). Whereas grafts from early neurulae typically differentiated only into epidermis, grafts from late neural fold stages on reliably resulted in differentiation of ectopic pigmented neuromasts. Second, belly ectoderm was transplanted to the prospective placodal region between early neurula and tailbud stages (stages 13-35). Normal lateral lines containing pigmented neuromasts formed in most embryos when grafts were performed prior to early tailbud stages (stage 24) but not when they were performed later. Our findings indicate that lateral line placodes, from which neuromasts originate, are already determined at late neural fold stages (first series of grafts) but are inducible until early tailbud stages (second series of grafts). A further series of heterochronic transplantations demonstrated that the decline of inducibility at mid tailbud stages is mainly due to the loss of ectodermal competence.
为了确定蝾螈侧线基板诱导的时间窗口，我们在胚胎发育的不同阶段进行了从有色胚胎到白化胚胎的两组异位和等时移植，并在后期评估了宿主中有色神经丘的分布。首先，将来自预期基板区域的外胚层移植到神经胚早期和尾芽中期（第13-27阶段）之间的腹部。而来自神经胚早期的移植通常仅分化为表皮，而从神经褶后期开始的移植可靠地导致异位有色神经丘的分化。其次，将腹部外胚层移植到神经胚早期和尾芽阶段（第13-35阶段）之间的预期基板区域。当在尾芽早期（第24阶段）之前进行移植时，大多数胚胎中形成了含有有色神经丘的正常侧线，但在后期进行移植时则不然。我们的研究结果表明，神经丘起源的侧线基板在神经褶后期（第一组移植）就已确定，但直到尾芽早期（第二组移植）仍可诱导。另一组异时移植表明，尾芽中期诱导能力的下降主要是由于外胚层感受态的丧失。
