Directed Differentiation of Zebrafish Pluripotent Embryonic Cells to Functional Cardiomyocytes

RCAN family member 3 deficiency contributes to noncompaction of the ventricular myocardium

Noncompaction of the ventricular myocardium (NVM), the third most diagnosed cardiomyopathy, is characterized by prominent trabeculae and intratrabecular recesses. However, the genetic etiology of 40%-60% of NVM cases remains unknown. Here, we identify two infants with NVM, in a nonconsanguineous family, with a typical clinical presentation of persistent bradycardia since the prenatal period. A homozygous missense variant (R223L) of RCAN family member 3 (RCAN3) is detected in both infants using whole-exome sequencing. In the zebrafish model, marked cardiac dysfunction is detected in rcan3 deficiency (MO-rcan3ATG-injected) and rcan-/- embryos. Developmental dysplasia of both endocardial and myocardial layers is also detected in rcan3-deficient embryos. RCAN3 R223L variant mRNAs can not rescue heart defects caused by rcan3 knockdown or knockout; however, hRCAN3 mRNAs rescue these phenotypes. RNA-seq experiments show that several genes involved in cardiomyopathies are significantly regulated through multiple signaling pathways in the rcan3-knockdown zebrafish model. In human cardiomyocytes, RCAN3 deficiency results in reduced proliferation and increased apoptosis, together with an abnormal mitochondrial ultrastructure. Thus, we suggest that RCAN3 is a susceptibility gene for cardiomyopathies, especially NVM and that the R223L mutation is a potential loss-of-function variant.

Defining the Pluripotent Marker Genes for Identification of Teleost Fish Cell Pluripotency During Reprogramming

Pluripotency is a transient state in early embryos, which is regulated by an interconnected network of pluripotency-related genes. The pluripotent state itself seems to be highly dynamic, which leads to significant differences in the description of induced pluripotent stem cells from different species at the molecular level. With the application of cell reprogramming technology in fish, the establishment of a set of molecular standards for defining pluripotency will be important for the research and potential application of induced pluripotent stem cells in fish. In this study, by BLAST search and expression pattern analysis, we screen out four pluripotent genes (Oct4, Nanog, Tdgf1, and Gdf3) in zebrafish (Danio rerio) and crucian carp (Carassius). These genes were highly expressed in the short period of early embryonic development, but significantly down-regulated after differentiation. Moreover, three genes (Oct4, Nanog and Tdgf1) have been verified that are suitable for identifying the pluripotency of induced pluripotent stem cells in zebrafish and crucian carp. Our study expands the understanding of the pluripotent markers of induced pluripotent stem cells in fish.

Fish Pluripotent Stem-Like Cell Line Induced by Small-Molecule Compounds From Caudal Fin and its Developmental Potentiality

The technique of induced pluripotent stem cells has significant application value in breeding and preserving the genetic integrity of fish species. However, it is still unclear whether the chemically induced pluripotent stem cells can be induced from non-mammalian cells or not. In this article, we first verify that fibroblasts of fish can be chemically reprogrammed into pluripotent stem cells. These induced pluripotent stem-like cells possess features of colony morphology, expression of pluripotent marker genes, formation of embryoid bodies, teratoma formation, and the potential to differentiate into germ cell-like cells in vitro. Our findings will offer a new way to generate induced pluripotent stem cells in teleost fish and a unique opportunity to breed commercial fish and even save endangered fish species.

The effect of Activin pathway modulation on the expression of both pluripotency and differentiation markers during early zebrafish development compared with other vertebrates

Activin-like factors control many developmental processes, including pluripotency maintenance and differentiation. Although Activin-like factors' action in mesendoderm induction has been demonstrated in zebrafish, their involvement in preserving the stemness remains unknown. To investigate the role of maternal Activin-like factors, their effects were promoted or blocked using synthetic human Activin A or SB-431542 treatments respectively until the maternal to zygotic transition. To study the role of zygotic Activin-like factors, SB-431542 treatment was also applied after the maternal to zygotic transition. The effect of the pharmacological modulations of the Activin/Smad pathway was then studied on the mRNA expressions of the ndr1, ndr2, tbxta (no tail/ntl) as the differentiation index, mych, nanog, and oct4 (pou5f3) as the pluripotency markers of the zebrafish embryonic cells as well as sox17 as a definitive endoderm marker. Expression of the target genes was measured at the 16-cell, 256-cell, 1K-cell, oblong, dome, and shield stages using the real-time quantitative polymerase chain reaction (RT-qPCR). Activation of the maternal Activin signaling pathway led to an increase in zygotic expression of the tbxta, particularly marked at the oblong stage. In other words, promotion of the maternal Activin/Smad pathway induced differentiation by advancing the major peaks of ndr1 and nanog, thereby eliciting tbxta expression. Whereas suppression of the maternal or zygotic Activin/Smad pathway sustained the pluripotency by preventing the major peaks of ndr1 and nanog as well as tbxta encoding.

Fish primary embryonic pluripotent cells assemble into retinal tissue mirroring in vivo early eye development

Organoids derived from pluripotent stem cells promise the solution to current challenges in basic and biomedical research. Mammalian organoids are however limited by long developmental time, variable success, and lack of direct comparison to an in vivo reference. To overcome these limitations and address species-specific cellular organization, we derived organoids from rapidly developing teleosts. We demonstrate how primary embryonic pluripotent cells from medaka and zebrafish efficiently assemble into anterior neural structures, particularly retina. Within 4 days, blastula-stage cell aggregates reproducibly execute key steps of eye development: retinal specification, morphogenesis, and differentiation. The number of aggregated cells and genetic factors crucially impacted upon the concomitant morphological changes that were intriguingly reflecting the in vivo situation. High efficiency and rapid development of fish-derived organoids in combination with advanced genome editing techniques immediately allow addressing aspects of development and disease, and systematic probing of impact of the physical environment on morphogenesis and differentiation.

Generation of Stable Induced Pluripotent Stem-like Cells from Adult Zebra Fish Fibroblasts

Induced pluripotent stem (iPS) cells provide a powerful platform for the study of development, regeneration, and disease. Although many stable iPS cell lines have been established for mammals, few attempts have been made to induce iPS cells in nonmammalian species. Because of technical advantages over other vertebrates on stem cells, induced pluripotent stem cells from fish could be of value for research. In this paper, stable iPS-like cell lines were generated from adult zebra fish fibroblasts by combining the doxycycline inducible lentiviral delivery system and chemical treatment. RT-PCR analysis, alkaline phosphatase staining, and immunofluorescence indicated that adult zebra fish fibroblasts were successfully reprogrammed into iPS-like cells (ziPSCs). The ziPSCs exhibited stable growth and manifested many features of fish embryonic stem cells with pluripotency in vitro and in vivo. Because of easy maintenance, the developed technology in this study for generating zebra fish iPS-like cells could be extended to investigating other genera of fish.

Fish, the better model in human heart research? Zebrafish Heart aggregates as a 3D spontaneously cardiomyogenic in vitro model system

The zebrafish (ZF) has become an essential model for biomedical, pharmacological and eco-toxicological heart research. Despite the anatomical differences between fish and human hearts, similarities in cellular structure and conservation of genes as well as pathways across vertebrates have led to an increase in the popularity of ZF as a model for human cardiac research. ZF research benefits from an entirely sequenced genome, which allows us to establish and study cardiovascular mutants to better understand cardiovascular diseases. In this review, we will discuss the importance of in vitro model systems for cardiac research and summarise results of in vitro 3D heart-like cell aggregates, consisting of myocardial tissue formed spontaneously from enzymatically digested whole embryonic ZF larvae (Zebrafish Heart Aggregate - ZFHA). We will give an overview of the similarities and differences of ZF versus human hearts and highlight why ZF complement established mammalian models (i.e. murine and large animal models) for cardiac research. At this stage, the ZFHA model system is being refined into a high-throughput (more ZFHA generated than larvae prepared) and stable in vitro test system to accomplish the same longevity of previously successful salmonid models. ZFHA have potential for the use of high-throughput-screenings of different factors like small molecules, nucleic acids, proteins and lipids which is difficult to achieve in the zebrafish in vivo screening models with lethal mutations as well as to explore ion channel disorders and to find appropriate drugs for safety screening.

Isolation and characterization of string-forming female germline stem cells from ovaries of neonatal mice

Germline stem cells are essential in the generation of both male and female gametes. In mammals, the male testis produces sperm throughout the entire lifetime, facilitated by testicular germline stem cells. Oocyte renewal ceases in postnatal or adult life in mammalian females, suggesting that germline stem cells are absent from the mammalian ovary. However, studies in mice, rats, and humans have recently provided evidence for ovarian female germline stem cells (FGSCs). A better understanding of the role of FGSCs in ovaries could help improve fertility treatments. Here, we developed a rapid and efficient method for isolating FGSCs from ovaries of neonatal mice. Notably, our FGSC isolation method could efficiently isolate on average 15 cell "strings" per ovary from mice at 1-3 days postpartum. FGSCs isolated from neonatal mice displayed the string-forming cell configuration at mitosis (i.e. a "stringing" FGSC (sFGSC) phenotype) and a disperse phenotype in postnatal mice. We also found that sFGSCs undergo vigorous mitosis especially at 1-3 days postpartum. After cell division, the sFGSC membranes tended to be connected to form sFGSCs. Moreover, F-actin filaments exhibited a cell-cortex distribution in sFGSCs, and E-cadherin converged in cell-cell connection regions, resulting in the string-forming morphology. Our new method provides a platform for isolating FGSCs from the neonatal ovary, and our findings indicate that FGCSs exhibit string-forming features in neonatal mice. The sFGSCs represent a valuable resource for analysis of ovary function and an in vitro model for future clinical use to address ovarian dysfunction.

Beyond organoids: In vitro vasculogenesis and angiogenesis using cells from mammals and zebrafish

The ability to culture complex organs is currently an important goal in biomedical research. It is possible to grow organoids (3D organ-like structures) in vitro; however, a major limitation of organoids, and other 3D culture systems, is the lack of a vascular network. Protocols developed for establishing in vitro vascular networks typically use human or rodent cells. A major technical challenge is the culture of functional (perfused) networks. In this rapidly advancing field, some microfluidic devices are now getting close to the goal of an artificially perfused vascular network. Another development is the emergence of the zebrafish as a complementary model to mammals. In this review, we discuss the culture of endothelial cells and vascular networks from mammalian cells, and examine the prospects for using zebrafish cells for this objective. We also look into the future and consider how vascular networks in vitro might be successfully perfused using microfluidic technology.