Swartz S Zachary, Chan Xin Yi, Lambert J David
Department of Biology, University of Rochester, Hutchison Hall, River Campus, Rochester, NY 14627-0211, USA.
Dev Genes Evol. 2008 Feb;218(2):107-13. doi: 10.1007/s00427-008-0203-6. Epub 2008 Jan 23.
Members of the Vasa family of helicases are specifically localized to germ line lineages in embryos of many animal groups and, in some cases, have been shown to be required for germ line formation. Despite considerable attention to the embryology of gastropod molluscs, the germ line has not been identified in the early cleavage stages of these embryos. We have cloned a Vasa ortholog in the snail Ilyanassa and examined the distribution of IoVasa mRNA during early cleavage. Initially, the transcript is present in all cells and non-specifically localized to centrosomes in a subset of cells. The IoVasa mRNA becomes progressively more enriched in the dorsal quadrant of the embryo, and then becomes restricted to particular cells in the 4d lineage. At the 64-cell stage, IoVasa mRNA is detected in 4dL11, 4dL12, 4dR11, and 4dR12. Following another round of division in the 4d lineage, the mRNA is restricted to two cells: 4dL121 and 4dR121. By the 108-cell stage, IoVasa mRNA is no longer detectable. Because the germ line is thought to arise from the 4d lineage in spiralians, these data are consistent with the hypothesis that the Ilyanassa germ line is marked by inheritance of IoVasa and derived from the cells 4dL121 and 4dR121. Alternatively, IoVasa may be required in somatic lineages where it is expressed, and the germ line may be specified later in development.
解旋酶瓦萨家族的成员在许多动物类群的胚胎中特异性地定位于生殖细胞谱系，并且在某些情况下，已被证明是生殖细胞形成所必需的。尽管腹足纲软体动物的胚胎学受到了相当多的关注，但在这些胚胎的早期卵裂阶段尚未鉴定出生殖细胞。我们在蜗牛伊利亚纳萨中克隆了一个瓦萨直系同源基因，并研究了伊奥瓦萨信使核糖核酸（IoVasa mRNA）在早期卵裂过程中的分布。最初，该转录本存在于所有细胞中，并非特异性地定位于一部分细胞的中心体。IoVasa mRNA在胚胎的背侧象限中逐渐富集，然后局限于4d谱系中的特定细胞。在64细胞阶段，在4dL11、4dL12、4dR11和4dR12中检测到IoVasa mRNA。在4d谱系进行另一轮分裂后，该信使核糖核酸局限于两个细胞：4dL121和4dR121。到108细胞阶段，不再能检测到IoVasa mRNA。由于在螺旋动物中生殖细胞被认为起源于4d谱系，这些数据与以下假设一致，即伊利亚纳萨的生殖细胞以IoVasa的遗传为标志，并源自4dL121和4dR121细胞。或者，IoVasa可能在其表达的体细胞谱系中是必需的，并且生殖细胞可能在发育后期被指定。
