Bluefin tuna sperm production is hastened by surrogacy in small Euthynnus.

Pacific bluefin tuna (Thunnus orientalis) remains heavily depleted due to overexploitation. Aquaculture and stock enhancement based on artificial seedlings could be effective solutions to this problem. However, widespread adoption of seedling production is limited because spawning in captivity of bluefin tuna, a large pelagic top predator, requires much space, time, cost, and labour.

Production of Germ Cell-Less Rainbow Trout by dead end Gene Knockout and their Use as Recipients for Germ Cell Transplantation.

In germ cell transplantation experiments, the use of sterile recipients that do not produce their own gametes is an important prerequisite. Triploidization and dnd gene knockdown (KD) methods have been widely used to produce sterile fish. However, triploidization does not produce complete sterility in some fish species, and gene KD is labor and time intensive since it requires microinjection into individual fertilized eggs.

Characterization of a vasa homolog in Mekong giant catfish (Pangasianodon gigas): Potential use as a germ cell marker.

For the long-term preservation of the genetic resources of endangered fish species, a combination of germ cell cryopreservation and transplantation can be an effective technique. To optimize these techniques, it is important to identify undifferentiated germ cells possessing transplantability, such as primordial germ cells, type A spermatogonia (ASGs), and oogonia. In this study, a homolog of vasa cDNA in Mekong giant catfish (MGC-vasa) (Pangasianodon gigas), which is an endangered species inhabiting the Mekong river, was cloned and characterized for use as a putative germ cell marker.

Aging- and temperature-related activity of spermatogonial stem cells for germ cell transplantation in medaka.

Spermatogonial transplantation can contribute to developing a novel method of producing seedlings for both aquaculture and biotic conservation. This study's purpose was to investigate aging- and temperature-related changes in the numbers and stem cell functions of type-A spermatogonia (ASG) in the model fish medaka (Oryzias latipes). The ASG numbers in medaka of different ages were quantified via histological observation and enzymatic dissociation of vasa-Gfp medaka testes.

Enrichment of transplantable germ cells in salmonids using a novel monoclonal antibody by magnetic-activated cell sorting.

In the fish germ cell transplantation system, only type A spermatogonia (ASGs) and oogonia are known to be incorporated into the recipient genital ridges, where they undergo gametogenesis. Therefore, high colonization efficiency can be achieved by enriching undifferentiated germ cells out of whole testicular cells. In this study, we used magnetic-activated cell sorting (MACS) for enriching undifferentiated germ cells of rainbow trout using a monoclonal antibody that recognizes a specific antigen located on the germ cell membrane.

Establishment of novel monoclonal antibodies for identification of type A spermatogonia in teleosts†.

We recently established a germ cell transplantation system in salmonids. Donor germ cells transplanted into the body cavity of recipient embryos migrate toward and are incorporated into the recipient gonad, where they undergo gametogenesis. Among the various types of testicular germ cells, only type A spermatogonia (A-SG) can be incorporated into the recipient gonads.

Characterization and expression of a vasa homolog in the gonads and primordial germ cells of the striped catfish (Pangasianodon hypophthalmus).

The analysis of early gonadogenesis during larval development requires a molecular marker that is specifically expressed in the germ cell lineage, such as the vasa gene. In this study, we cloned and characterized vasa in the striped catfish (Pangasianodon hypophthalmus), and designated this as Phy-vasa. Phy-vasa contained all of the predicted consensus motifs that are shared among the vasa genes in other fish species, including RG and RGG repeats, ATPase motifs, and a DEAD-box, and phylogenetic analysis using various DEAD-box family proteins demonstrated that the Phy-vasa protein clustered within the Vasa family.

Specific visualization of live type A spermatogonia of Pacific bluefin tuna using fluorescent dye-conjugated antibodies†.

During our previous work toward establishing surrogate broodstock that can produce donor-derived gametes by germ cell transplantation, we found that only type A spermatogonia (ASGs) have the potency to colonize recipient gonads. Therefore, the ability to visualize ASGs specifically would allow the sequential analysis of donor cell behavior in the recipient gonads. Here we produced monoclonal antibodies that could recognize the cell surface antigens of ASGs in Pacific bluefin tuna (Thunnus orientalis), with the aim of visualizing live ASGs.

Flow-cytometric enrichment of Pacific bluefin tuna type A spermatogonia based on light-scattering properties.

We previously established surrogate broodstock in which the donor germ cells transplanted into the peritoneal cavities of xenogeneic recipients were capable of developing into functional eggs and sperm in teleost fish. In this transplantation system, only the undifferentiated germ cells such as type A spermatogonia (ASG) or a portion of the ASG population were capable of being incorporated into the genital ridges of the recipients and undergo gametogenesis. Therefore, the use of enriched ASGs can be expected to achieve efficient donor-cell incorporation.

Characterization of a vasa homolog in the brown-marbled grouper (Epinephelus fuscoguttatus) and its expression in gonad and germ cells during larval development.

The vasa gene is specifically expressed in the germ cell lineage, and its expression has been used to study germline development in many organisms, including fishes. In this study, we cloned and characterized vasa as Efu-vasa in the brown-marbled grouper (Epinephelus fuscoguttatus). Efu-vasa contained predicted regions that shared consensus motifs with the vasa family in teleosts, including arginine- and glycine-rich repeats, ATPase motifs, and a DEAD box.

Functional Sperm of the Yellowtail (Seriola quinqueradiata) Were Produced in the Small-Bodied Surrogate, Jack Mackerel (Trachurus japonicus).

Production of xenogeneic gametes from large-bodied, commercially important marine species in closely related smaller surrogates with short generation times may enable rapid domestication of the targeted species. In this study, we aimed to produce gametes of Japanese yellowtail (Seriola quinqueradiata) using jack mackerel (Trachurus japonicus) as a surrogate with a smaller body size and shorter maturation period. Donor spermatogonia were collected from the testes of yellowtail males and transferred into the peritoneal cavity of 10- and 12-day-old jack mackerel larvae.