Aberger F, Weidinger G, Grunz H, Richter K
Institute of Genetics, University of Salzburg, Hellbrunnerstrasse 34, A-5020, Salzburg, Austria.
Mech Dev. 1998 Mar;72(1-2):115-30. doi: 10.1016/s0925-4773(98)00021-5.
In a search for novel developmental genes expressed in a spatially restricted pattern in dorsal ectoderm of Xenopus we have identified XAG-2, a cement gland-specific gene with a putative role in ectodermal patterning. XAG-2 encodes a secreted protein, which is expressed in the anterior region of dorsal ectoderm from late gastrula stages onwards. Activation of XAG-2 transcription is observed in response to organizer-secreted molecules including the noggin, chordin, follistatin and cerberus gene products. Overexpression of XAG-2 but not of the related cement gland marker XAG-1 induces both cement gland differentiation and expression of anterior neural marker genes in the absence of mesoderm formation. Further, we show that XAG-2 signaling depends on an intact fibroblast growth factor (FGF) signal transduction pathway and that XAG-2-induced anterior neural fate of ectodermal cells can be transformed to a more posterior character by retinoic acid. Based on these findings we propose a role for XAG-2 in the specification of dorsoanterior ectodermal fate, i.e. in the formation of cement gland and induction of forebrain fate of Xenopus.
在寻找非洲爪蟾背侧外胚层中以空间限制模式表达的新型发育基因时，我们鉴定出了XAG - 2，这是一种特定于黏着腺的基因，在外胚层模式形成中可能发挥作用。XAG - 2编码一种分泌蛋白，从原肠胚后期开始在背侧外胚层的前部区域表达。观察到XAG - 2转录的激活是对包括头蛋白、脊索蛋白、卵泡抑素和斯芬克斯基因产物在内的组织者分泌分子的反应。在没有中胚层形成的情况下，XAG - 2的过表达而非相关黏着腺标记物XAG - 1的过表达诱导了黏着腺分化和前神经标记基因的表达。此外，我们表明XAG - 2信号传导依赖于完整的成纤维细胞生长因子（FGF）信号转导途径，并且视黄酸可将XAG - 2诱导的外胚层细胞的前神经命运转变为更靠后的特征。基于这些发现，我们提出XAG - 2在背侧前外胚层命运的特化中发挥作用，即在非洲爪蟾黏着腺的形成和前脑命运的诱导中发挥作用。
