Haploid embryonic stem (ES) cells combine haploidy and pluripotency, enabling direct genetic analyses of recessive phenotypes in vertebrate cells. Haploid cells have been elusive for culture, due to their inferior growth and genomic instability. Here, we generated gynogenetic medaka embryos and obtained three haploid ES cell lines that retained pluripotency and competitive growth. Upon nuclear transfer into unfertilized oocytes, the haploid ES cells, even after genetic engineering, generated viable offspring capable of germline transmission. Hence, haploid medaka ES cells stably maintain normal growth, pluripotency, and genomic integrity. Mosaic oocytes created by combining a mitotic nucleus and a meiotic nucleus can generate fertile fish offspring. Haploid ES cells may offer a yeast-like system for analyzing recessive phenotypes in numerous cell lineages of vertebrates in vitro.

Vasa is essential for germline development. However, the precise processes in which vasa involves vary considerably in diverse animal phyla. Here we show that vasa is required for primordial germ cell (PGC) migration in the medakafish. vasa knockdown by two morpholinos led to the PGC migration defect that was rescued by coinjection of vasa RNA. Interestingly, vasa knockdown did not alter the PGC number, identity, proliferation and motility even at ectopic locations. We established a cell culture system for tracing PGCs at the single cell level in vitro. In this culture system, control and morpholino-injected gastrulae produced the same PGC number and the same time course of PGC survival. Importantly, vasa-depleted PGCs in culture had similar motility and locomotion to normal PGCs. Expression patterns of wt1a, sdf1b and cxcr4b in migratory tissues remained unchanged by vasa knockdown. By chimera formation we show that PGCs from vasa-depleted blastulae failed to migrate properly in the normal environment, whereas control PGCs migrated normally in vasa-disrupted embryos. Furthermore, ectopic PGCs in vasa-depleted embryos also retained all the PGC properties examined. Taken together, medaka vasa is cell-autonomously required for PGC migration, but dispensable to PGC proliferation, motility, identity and survival.

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Embryonic stem (ES) cells are pluripotent cells capable of differentiation into various cell types. Haploid ES cells elegantly combine the advantages of haploidy and pluripotency and offer a unique in vitro system for genetic analyses of molecular, cellular and developmental events in various cell lineages. Our recent success in generating haploid ES cell lines from gynogenetic embryos of the medaka fish suggests that haploidy can support ES cell derivation and maintenance in a vertebrate. In this study, we present a step-by-step protocol for derivation and characterization of medaka haploid ES cells. We have used this procedure to produce three haploid ES cell lines from five primary cultures. It takes about 15 weeks to generate stable cultures, 5-8 weeks to obtain pure haploid cells and 5-6 weeks to characterize ES cells in vitro and in vivo.

Tilapia is one of the most important economic and fastest-growing species in aquaculture worldwide. In 2015, an epidemic associated with severe mortality occurred in adult tilapia in Hubei, China. The causative pathogen was identified as Tilapia parvovirus (TiPV) by virus isolation, electron microscopy, experimental challenge, In situ hybridization (ISH), indirect immunofluorescence (IFA), and viral gene sequencing. Electron microscopy revealed large numbers of parvovirus particles in the organs of diseased fish, including kidney, spleen, liver, heart, brain, gill, intestine, etc. The virions were spherical in shape, non-enveloped and approximately 30nm in diameter. The TiPV was isolated and propagated in tilapia brain cells (TiB) and induced a typical cytopathic effect (CPE) after 3 days post-infection (dpi). This virus was used to experimentally infect adult tilapia and clinical disease symptoms similar to those observed naturally were replicated. Additionally, the results of ISH and IFA showed positive signals in kidney and spleen tissues from TiPV-infected fish. To identify TiPV-specific sequences, the near complete genome of TiPV was obtained and determined to be 4269 bp in size. Phylogenetic analysis of the NS1 sequence revealed that TiPV is a novel parvovirus, forms a separate branch in proposed genus Chapparvovirus of Parvoviridae . Results presented here confirm that TiPV is a novel parvovirus pathogen that can cause massive mortality in adult tilapia. This provides a basis for the further studies to define the epidemiology, pathology, diagnosis, prevention and treatment of this emerging viral disease.

Chimera formation is a powerful tool for analyzing pluripotency in vivo. It has been widely accepted that host cell lineages are generally accessible to embryonic stem (ES) cells with the actual contribution depending solely on the intrinsic pluripotency of transplanted donor cells. Here, we show in the fish medaka (Oryzias latipes) that the host accessibility to ES cell contribution exhibits dramatic differences. Specifically, of three albino host strains tested (i 1 , i 3 and af), only strain i 1 generated pigmented chimeras. Strikingly, this accessibility is completely lost in i 1 but acquired in i 3 after host c-irradiation. Host irradiation also differentially affected ES cell contribution to somatic organs and gonad. Therefore, the accessibility of various host cell lineages can vary considerably depending on host strains and cell lineages as well as on irradiation. Our findings underscore the importance of host genotypes for interpreting donor cell pluripotency and for improving ES-derived chimera production.

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Flexible, lightweight, and wearable devices are currently attracting tremendous interest in the field of advanced electronics. In this work, novel 1D, flexible, coaxial-structured, bright and colorful alternating current electroluminescent (ACEL) fibers consisting of AgNW-based electrodes, a ZnS phosphor layer, and silicone dielectric and encapsulation layers are designed and fabricated through a simple protocol. This facile all-solution-based fabrication protocol enables scalable production of long ACEL fibers (>12 cm). Stemming from the rational design and facile fabrication process, the as-prepared ACEL fibers exhibit uniform, bright, and angularly independent luminance (up to 202 cd m −2 @ 195 V and 2 kHz). Benefiting mainly from the robust AgNWbased electrodes and versatile silicone, the ACEL fibers exhibit additionally excellent flexibility and mechanical stability, being capable to maintain ≈91% of luminance after 500 bending-recovery cycles, as well as mitigated luminance degradation after continuous work in ambient. The proper length combined with superb mechanical properties makes the ACEL fibers readily weavable. Most notably, the isolating, hydrophobic, and biocompatible silicone encapsulation layer endows the ACEL fibers unprecedented wearability. Eventually, a proof-of-concept ACEL fabric is demonstrated by weaving the asprepared long ACEL fibers, to show the future perspective of directly weaving ACEL fibers into densely arrayed wearable functional cloths. Flexible Electronics