文昌鱼胚胎发育过程中Goosecoid基因的表达分析

Expression pattern of Goosecoidgene during amphioxus embryogenesis

为更详细地了解Goosecoid(Gsc)基因在文昌鱼中的表达情况,研究通过实时荧光定量PCR(real-time quantitative polymerase chain reaction,RT-qPCR)和整胚原位杂交(whole mount in situ hybridization,WISH)对Gsc基因在白氏文昌鱼不同发育时期胚胎的时空表达谱进行了分析。RT-qPCR结果表明,文昌鱼Gsc基因为非母源表达,其合子表达起始于囊胚期,并在原肠胚中期达到峰值,至神经胚早期该基因的表达量显著下降,但仍处于较高的表达水平。此后,随着胚胎发育,基因表达量逐渐下降,到幼体早期只能检测到微弱的表达信号。原位杂交结果显示,Gsc最早表达于囊胚背侧的细胞,原肠胚期基因表达集中在背部中内胚层(该区域对应脊椎动物组织者区域),神经胚早期基因表达向轴中胚层(将来发育成脊索)集中,神经胚中期,除近尾端区域外,该基因在轴中胚层的表达完全消失,此时又在咽区的背面、消化道的两侧和腹侧、神经管的腹侧检测到该基因的表达信号,至神经胚晚期和幼体早期,仅在尾端脊索中胚层区域检测到该基因的表达信号。本研究为进一步研究Gsc基因在文昌鱼中的功能奠定了基础。

To illustrate expression pattern of Goosecoid （Gsc） in amphioxus more clearly, we analyzed Gsc expression pattern in different embryonic stages of Branchiostoma belcheri using both real-time quantitative polymerase chain reaction （RT-qPCR） and whole mount in situ hybridization （WISH） methods. RT-qPCR results indicate that Gsc is not a maternal-expressed gene and can only be detected when the embryos develop into blastula. But its expression level increases dramatically afterwards and peaks at the midgasteula stage. In the subsequent stages, the expression level starts to decline gradually and become very low at early-larva stage. WISH confirms the result of RT-qPCR and localizes its initial expression in the primitive dorsal region of the blastula. At the midgatrula stage, Gsc transcripts are found specially in the dorsal lip of the blastopore （homologous region of vertebrate organizer）. At the early neural stage, the gene is expressed transiently in the axial mesoderm and declined from the region rapidly in the following stages. At the mid-neurula, Gsc expression in the axial mesoderm is only remained in the tail bud region, but new expression domains in the dorsal pharyngeal endoderm, the floor plate and the lateral digestive tract are found. In the following stages till mid-larvae, Gsc expression in most of the above regions becomes underdetectable and only remains in the tail bud. The study will provide essential clues for uncovering the function of Gsc in amphioxus development.