Fish, like many other animals, have two major cell lineages, namely the germline and soma. The germ-soma separation is one of the earliest events of embryonic development. Germ cells can be specifically labeled and isolated for culture and transplan-tation, providing tools for reproduction of endangered species in close relatives, such as surrogate production of trout in salmon. Haploid cell cultures, such as medaka haploid embryonic stem cells have recently been obtained, which are capable of mimicking sperm to produce fertile offspring, upon nuclear being directly transferred into normal eggs. Such fish originated from a mosaic oocyte that had a haploid meiotic nucleus and a transplanted haploid mitotic cell culture nucleus. The first semi-cloned fish is Holly. Here we review the current status and future directions of understanding and manipulating fish germ cells in basic research and reproductive technology.
XU HongYan1, LI MingYou1, GUI JianFang2 & HONG YunHan1,2 1Department of Biological Sciences, National University of Singapore, Singapore 119260, Singapore
Aquaculture has been believed to be a major Chinese contribution to the world. In recent 20 years, genome and other genetic technologies have promoted significant advances in basic studies on molecular basis and genetic improvement of aquaculture animals, and complete genomes of some main aquaculture animals have been sequenced or announced to be sequenced since the beginning of this century. Here, we review some significant breakthrough progress of aquaculture genetic improvement technologies including genome technologies, somatic cell nuclear transfer and stem cell technologies, outline the molecular basis of several economically important traits including reproduction, sex, growth, disease resistance, cold tolerance and hypoxia tolerance, and present a series of candidate trait-related genes. Finally, some application cases of genetic improvement are introduced in aquaculture animals, especially in China, and several development trends are highlighted in the near future.
A unisexual species is generally associated with polyploidy, and reproduced by a unisexual reproduction mode, such as gyno- genesis, hybridogenesis or parthenogenesis. Compared with other unisexual and polyploid species, gibel carp (Carassius au- ratus gibelio) has a higher ploidy level of hexaploid. It has undergone several successive rounds of genome polyploidy, and experienced an additional, more recent genome duplication event. More significantly, the dual reproduction modes, including gynogenesis and sexual reproduction, have been demonstrated to coexist in the polyploid gibel carp. This article reviews the genetic basis concerning polyploidy origin, clonal diversity and dual reproduction modes, and outlines the progress in new va- riety breeding and gene identification involved in the reproduction and early development. The data suggests that gibel carp are under an evolutionary trajectory of diploidization. As a novel evolutionary developmental (Evo-Devo) biology model, this work highlights future perspectives about the functional divergence of duplicated genes and the sexual origin of vertebrate animals.
