Novel Technique for Visualizing Primordial Germ Cells in Sturgeons (Acipenser ruthenus, A. gueldenstaedtii, A. baerii, and Huso huso)1

Abstract

Primordial germ cells (PGCs) are the origin of all germ cells in developing embryos. In the sturgeon embryo, PGCs develop from the vegetal hemisphere, which mainly acts as an extraembryonic source of nutrition. Current methods for studying sturgeon PGCs require either killing the fish or using costly and time-consuming histological procedures. Here, we demonstrate that visualization of sterlet (Acipenser ruthenus>) PGCs in vivo is feasible by simply labeling the vegetal hemisphere with fluorescein isothiocyanate (FITC)-dextran. We injected FITC-dextrans, with molecular weights varying between 10 000 and 2 000 000, into the vegetal pole of 1- to 4-cell stage embryos. At the neurula to tail-bud developmental stages, FITC-positive PGC-like cells appeared ventrally around the developing tail bud in the experimental group that received a high-molecular-weight FITC-dextran. The highest average number of FITC-positive PGC-like cells was observed in embryos injected with FITC-dextran having a molecular weight of 500 000 (FD-500). The pattern of migration of the labeled cells was identical to that of PGCs, clearly indicating that the FITC-positive PGC-like cells were PGCs. Labeled vegetal cells, except for the PGCs, were digested and excreted before the embryos starting feeding. FITC-labeled PGCs were observed in the developing gonads of fish for at least 3 mo after injection. We also found that FD-500 could be used to visualize PGCs in other sturgeon species. To the best of our knowledge, this report is the first to demonstrate in any animal species that PGCs can be visualized in vivo for a long period by the injection of a simple reagent.

Nuclear DNA markers for identification of Beluga and Sterlet sturgeons and their interspecific Bester hybrid

“…Acipenser ruthenus is used as a model species in sturgeon research due to ease of handling, short maturation time, and its routine reproduction in captivity 20, 21 . The marker for A .…”

Identification and sexually dimorphic expression of vasa isoforms in Dabry′s sturgeon (Acipenser dabryanus), and functional analysis of vasa 3′-untranslated region

“…Moreover, a PGC transplantation assay between sturgeon and goldfish proved that PGC migration machinery is conserved between these two distantly related species (Saito et al 2014). The ability of chimeric mRNA to label and trace PGCs in Dabry's sturgeon is extremely useful for PGC cryopreservation and the conservation of endangered species by germ cell transplantation technologies (Okutsu et al 2006;Psenicka et al 2015;Saito and Psenicka 2015;Yoshizaki et al 2005).…”

Biotechnology applied to fish reproduction: tools for conservation

“…Despite the great advances provided by this approach to germ cell transplantation technique in fish and mainly for the understanding of PGC biology and physiology (Nikolic et al 2015;Robles et al 2016), some problems still prevailed with regard to fish conservation purposes. The technique's performance involves steps that can make it unsuitable to be conducted in many fish species, such as the preparation of a strain containing germline cells labeled by GFP as performed by Linhartová and colleagues in the tench Tinca tinca (Linhartova et al 2014) and Saito and Psenicka in sturgeons (Saito and Psenicka 2015). For these purposes, in vitro reproduction of parental fish is necessary, which could be extremely difficult for some species.…”