Meeting Abstract

P3.70  Friday, Jan. 6  Expression patterns of germline specific markers indicate a preformation mechanism of germ cell development in cephalochordates WU, H.R.; ZHANG, Q.J.; CHEN, Y.T.; YU, J.K.*; ICOB, Academia Sinica; Fujian Normal University; ICOB, Academia Sinica; ICOB, Academia Sinica jkyu@gate.sinica.edu.tw

The segregation of germline cells from somatic cells is a critical step in metazoan animal development. In recent years, comparative studies in diverse organisms using conserved germ-cell specific markers, such as Vasa and Nanos gene products, have provided interesting insights into the evolution of germ cell specification mechanisms. We previously showed that the gene products of Vasa and Nanos become localized to the vegetal side during oogenesis in the cephalochordate amphioxus Branchiostoma floridae. These co-localized Vasa and Nanos maternal transcripts aggregate into a compact granule after fertilization, suggesting a preformation mechanism of germ cell development. In addition to the localized maternal transcripts, Vasa and Nanos are also expressed zygotically in the posterior growth zone in amphioxus embryos, suggesting they may also function in highly proliferating somatic stem cells. Here we further characterize expression of B. floridae homologs of Piwi and Tudor, both genes are known for playing important roles in germline development in diverse metazoan animals. We identified multiple Piwi-like genes and Tudor domain containing genes from the amphioxus draft genome. Within the two amphioxus Piwi-like homologs, one displays maternal and zygotic expression patterns identical to those of Vasa and Nanos, suggesting it may also function in both germline and somatic stem cells. More interestingly, we found one of the Tudor genes is only expressed maternally and co-localized with Vasa/Nanos maternal transcripts in the putative germline progenitor cell, suggesting that it may function exclusively in germ cell formation in amphioxus. Therefore, our results demonstrate the molecular distinction between the amphioxus germline stem cells and somatic stem cells.