Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
Dev Biol. 2012 Feb 1;362(1):11-23. doi: 10.1016/j.ydbio.2011.10.036. Epub 2011 Nov 18.
The T-box transcription factor Eomesodermin (Eomes) has been implicated in patterning and morphogenesis in frog, fish and mouse. In zebrafish, one of the two Eomes homologs, Eomesa, has been implicated in dorsal-ventral patterning, epiboly and endoderm specification in experiments employing over-expression, dominant-negative constructs and antisense morpholino oligonucleotides. Here we report for the first time the identification and characterization of an Eomesa mutant generated by TILLING. We find that Eomesa has a strictly maternal role in the initiation of epiboly, which involves doming of the yolk cell up into the overlying blastoderm. By contrast, epiboly progression is normal, demonstrating for the first time that epiboly initiation is genetically separable from progression. The yolk cell microtubules, which are required for epiboly, are defective in maternal-zygotic eomesa mutant embryos. In addition, the deep cells of the blastoderm are more tightly packed and exhibit more bleb-like protrusions than cells in control embryos. We postulate that the doming delay may be the consequence both of overly stabilized yolk cell microtubules and defects in the adhesive properties or motility of deep cells. We also show that Eomesa is required for normal expression of the endoderm markers sox32, bon and og9x; however it is not essential for endoderm formation.
T 盒转录因子 Eomesodermin（Eomes）在青蛙、鱼类和小鼠的模式形成和形态发生中起作用。在斑马鱼中，两个 Eomes 同源物之一 Eomesa，在过表达、显性负构建体和反义 morpholino 寡核苷酸实验中，被认为与背腹模式形成、胚外膜和内胚层特化有关。在这里，我们首次报道了通过 TILLING 产生的 Eomesa 突变体的鉴定和表征。我们发现 Eomesa 在胚外膜的起始中具有严格的母源性作用，这涉及到卵黄细胞向上覆盖的胚胎隆起。相比之下，胚外膜的进展是正常的，这首次表明胚外膜的起始在遗传上可以与进展分开。胚外膜所需的卵黄细胞微管在母-合子 eomesa 突变体胚胎中存在缺陷。此外，胚胎的深层细胞比对照胚胎中的细胞更紧密地堆积，并且表现出更多的泡状突起。我们推测，隆起的延迟可能是卵黄细胞微管过度稳定以及深层细胞的粘附特性或运动性缺陷的结果。我们还表明，Eomesa 对于内胚层标记物 sox32、bon 和 og9x 的正常表达是必需的；然而，它对内胚层形成不是必需的。
