Selleck M A, Hayamizu T F, Ohsugi K, Bronner-Fraser M, Bryant S V
Developmental Biology Center, University of California at Irvine 92717, USA.
Dev Biol. 1996 Jan 10;173(1):318-26. doi: 10.1006/dbio.1996.0026.
It is well established that Hensen's nodes can induce the formation of supernumerary digits after grafting into the anterior margin of the developing limb bud. The recent finding that distinct mesodermal cell populations are segregated within the node has made it possible to isolate different prospective cell types in an attempt to correlate digit-inducing ability with cell fate. We find that the prospective notochord cells contained within Hensen's node are able to induce supernumerary digits, whereas presumptive somite cells cannot. This early difference in inducing ability persists into later stages of development: epithelial somites are unable to induce while notochord from all lengths of the neuraxis continues to induce. Using probes to retinoic acid receptor-beta 2 and sonic hedgehog (shh) we find no evidence to support the idea that inducing tissues generate extra digits by releasing retinoic acid into adjacent limb tissue but find that the inducing ability of a tissue correlates with its expression of shh.
亨氏结移植到发育中的肢芽前缘后可诱导额外指（趾）的形成，这一点已得到充分证实。最近的研究发现，不同的中胚层细胞群在结内被分隔开来，这使得分离不同的预期细胞类型成为可能，以便将指（趾）诱导能力与细胞命运联系起来。我们发现，亨氏结中所含的预期脊索细胞能够诱导额外指（趾）的形成，而假定的体节细胞则不能。这种诱导能力的早期差异在发育后期仍然存在：上皮体节无法诱导，而来自神经轴各长度的脊索则继续诱导。使用视黄酸受体-β2和音猬因子（shh）的探针，我们没有发现证据支持诱导组织通过向相邻肢体组织释放视黄酸来产生额外指（趾）的观点，但发现组织的诱导能力与其shh表达相关。
