Hamada Mayuko, Wada Shuichi, Kobayashi Kenji, Satoh Nori
CREST, Japan Science Technology Agency, Kawaguchi, Saitama 333-0012, Japan.
Differentiation. 2005 Sep;73(7):364-76. doi: 10.1111/j.1432-0436.2005.00037.x.
A novel gene (Ci-Rga) essential for tissue differentiation during embryogenesis of the ascidian Ciona intestinalis is reported here. This gene was identified through functional screening of Ciona genes required for development by translational inhibition experiments with morpholino antisense oligonucleotides. The deduced protein of Ci-Rga contains two copies of a domain with unknown function called the MtN3/saliva domain. Phylogenetic analysis showed that Ci-Rga belongs to the MtN3/saliva family of genes conserved among metazoans and plants, and is an ortholog of mouse Rga (Recombination-activating gene 1 gene activation). During Ciona embryogenesis, both maternal and zygotic transcripts of Ci-Rga were expressed. Translational inhibition of Ci-Rga with specific morpholino resulted in abnormal embryos in which the cleavage pattern became atypical and expression of marker genes for each of the six major tissues, namely the endoderm, muscle, mesenchyme, notochord, neural tissue, and epidermis, was lost or suppressed at the tailbud stage. Although differentiation of all the six major tissues was affected by Ci-Rga knock-down, the degree of abnormalities and the timing of appearance of abnormalities were different among tissues. Expression analysis of developmentally important genes involved in the fate specification, such as Ci-Bra, Ci-Twist-like1a, Ci-Otx, Ci-Fgf9/16/20, Ci-Lhx3, Ci-FoxD, and Ci-Tbx6b, showed that an initial step of the fate specification of notochord, mesenchyme, and neural tissue, but not of endoderm or muscle, is impaired in the knock-down embryo. These results showed that Ci-Rga is a multifunctional gene essential for tissue differentiation during embryogenesis, and is primarily required for the fate specification of notochord, mesenchyme, and neural tissue, and provide some insights into the function of this little-known group of genes.
本文报道了一种在玻璃海鞘胚胎发育过程中对组织分化至关重要的新基因（Ci-Rga）。该基因是通过用吗啉代反义寡核苷酸进行翻译抑制实验，对玻璃海鞘发育所需基因进行功能筛选而鉴定出来的。Ci-Rga推导的蛋白质包含两个拷贝的功能未知结构域，称为MtN3/唾液结构域。系统发育分析表明，Ci-Rga属于后生动物和植物中保守的MtN3/唾液基因家族，是小鼠Rga（重组激活基因1基因激活）的直系同源基因。在玻璃海鞘胚胎发育过程中，Ci-Rga的母体和合子转录本均有表达。用特异性吗啉代抑制Ci-Rga的翻译会导致胚胎异常，其卵裂模式变得不典型，并且在尾芽期，六个主要组织（即内胚层、肌肉、间充质、脊索、神经组织和表皮）各自的标记基因表达缺失或受到抑制。尽管所有六个主要组织的分化都受到Ci-Rga敲低的影响，但不同组织的异常程度和异常出现的时间不同。对参与命运决定的发育重要基因（如Ci-Bra、Ci-Twist-like1a、Ci-Otx、Ci-Fgf9/16/20、Ci-Lhx3、Ci-FoxD和Ci-Tbx6b）的表达分析表明，在敲低胚胎中，脊索、间充质和神经组织（而非内胚层或肌肉）命运决定的初始步骤受到损害。这些结果表明，Ci-Rga是胚胎发育过程中组织分化所必需的多功能基因，主要是脊索、间充质和神经组织命运决定所必需的，并为这一鲜为人知的基因群体的功能提供了一些见解。
