Rodríguez-Seguel Elisa, Alarcón Pilar, Gómez-Skarmeta José Luis
Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, Carretera de Utrera Km1, 41013 Sevilla, Spain.
Dev Biol. 2009 May 15;329(2):258-68. doi: 10.1016/j.ydbio.2009.02.028. Epub 2009 Mar 4.
The Iroquois (Irx) genes encode homeoproteins conserved during evolution. Vertebrate genomes contain six Irx genes organized in two clusters, IrxA (which harbors Irx1, Irx2 and Irx4) and IrxB (which harbors Irx3, Irx5 and Irx6). To determine the precise role of these genes during development and their putative redundancies, we conducted a comparative expression analysis and a comprehensive loss-of-function study of all the early expressed Irx genes (Irx1-5) using specific morpholinos in Xenopus. We found that the five Irx genes display largely overlapping expression patterns and contribute to neural patterning. All Irx genes are required for proper formation of posterior forebrain, midbrain, hindbrain and, to a lesser an extent, spinal cord. Nevertheless, Irx1 and Irx3 seem to have a predominant role during regionalization of the neural plate. In addition, we find that the common anterior limit of Irx gene expression, which will correspond to the future border between the prethalamus and thalamus, is defined by mutual repression between Fezf and Irx proteins. This mutual repression is likely direct. Finally, we show that Arx, another anteriorly expressed repressor, also contribute to delineate the anterior border of Irx expression.
易洛魁（Irx）基因编码在进化过程中保守的同源结构域蛋白。脊椎动物基因组包含六个Irx基因，它们以两个基因簇的形式组织，即IrxA（包含Irx1、Irx2和Irx4）和IrxB（包含Irx3、Irx5和Irx6）。为了确定这些基因在发育过程中的精确作用及其可能存在的冗余性，我们利用非洲爪蟾中的特异性吗啉代寡核苷酸对所有早期表达的Irx基因（Irx1 - 5）进行了比较表达分析和全面的功能丧失研究。我们发现这五个Irx基因表现出很大程度上重叠的表达模式，并对神经模式形成有贡献。所有Irx基因对于前脑后部、中脑、后脑以及在较小程度上对脊髓的正常形成都是必需的。然而，Irx1和Irx3在神经板区域化过程中似乎起主要作用。此外，我们发现Irx基因表达的共同前界，即对应于未来丘脑前核和丘脑之间的边界，是由Fezf和Irx蛋白之间的相互抑制所定义的。这种相互抑制可能是直接的。最后，我们表明，另一种在前部表达的抑制因子Arx也有助于划定Irx表达的前界。
