Application of interspecific Somatic Cell Nuclear Transfer (iSCNT) in sturgeons and an unexpectedly produced gynogenetic sterlet with homozygous quadruple haploid

Effect of appropriate extenders to maintain sperm functionality during short-term storage of sterlet (Acipenser ruthenus) sperm with fertilization assay under hatchery conditions

Short-term storage and management of sperm in vitro is an easy and economical process in which suitable extenders can be utilized to extend the storage period and prevent sperm function impairment. Therefore, the current study aimed to evaluate the effect of suitable extenders during the short-term storage of sterlet sperm and determine their fertilizing capacity and hatching success. Three extenders containing a composition of 16, 20, and 24 mM NaCl, 1 mM KCl, 0.1 mM CaCl2, 10 mM Tris, pH 8.0 with osmolarity of 46, 55, and 62 mOsm/kg, were used to dilute the sperm of four sexually mature sterlet males (n = 4). Using a CASA system, the motility and velocity of undiluted and diluted sperm with extenders (E1 - E3) were assessed over 6 days at 0-2 °C. The short-term stored diluted sperm was then used in the fertilization and hatching assay, and undiluted fresh and stored sperm was used as a control. A two-way factorial analysis of variance (ANOVA) model confirmed significant effects on sperm motility, curvilinear velocity (VCL), and straight-line velocity (VSL) (P < 0.001), as well as their interaction with the extender. The model was decomposed into a one-way ANOVA to examine the impacts of extenders and storage time. With increasing storage periods, the sperm motility and velocity gradually decreased for diluted sperm with three extenders (E1-E3) but sharply decreased for undiluted sperm (Control). The motility of undiluted sperm was found 3.77 ± 4.09% at 4 days, whereas sperm diluted with extenders showed 57.57 ± 12.33% (E1), 64.34 ± 11.86% (E2), and 61.40 ± 12.41% (E3) motility at 6 days. This study explored extenders optimized with higher osmolarity (39-62 mOsm/kg) and lower K+ (1 mmol/L) as the most suitable medium for storing sterlet sperm for 6 days. After 6 days post storage, sperm diluted with extenders E1-E3 achieved a fertilization rate of 31.29 ± 14.2%, 31.66 ± 8.84%, and 30.67 ± 10.02%, respectively, and hatching success of 29.58 ± 13.4%, 30.50 ± 7.89%, and 27.95 ± 9.62%, respectively with freshly ovulated eggs.

Quantitative analysis of mitochondrial DNA in porcine-mouse cloned embryos

The aim of the research is to identify that porcine oocytes can function as recipients for interspecies cloning and have the ability to develop to blastocysts. Furthermore each mitochondrial DNA (mtDNA) in interspecises cloned embryos was analyzed. For the study, mouse-porcine and porcine-porcine cloned embryos were produced with mouse fetal fibroblasts (MFF) and porcine fetal fibroblasts (PFF), respectively, introduced as donor cells into enucleated porcine oocytes. The developmental rate and cell numbers of blastocysts between intraspecies porcine-porcine and interspecies mouse-porcine cloned embryos were compared and real-time polymerase chain reaction (PCR) was performed for the estimate of mouse and porcine mtDNA copy number in mouse-porcine cloned embryos at different stages.There was no significant difference in the developmental rate or total blastocyst number between mouse-porcine cloned embryos and porcine-porcine cloned embryos (11.1 ± 0.9%, 25 ± 3.5 vs. 10.1 ± 1.2%, 24 ± 6.3). In mouse-porcine reconstructed embryos, the copy numbers of mouse somatic cell-derived mtDNA decreased between the 1-cell and blastocyst stages, whereas the copy number of porcine oocyte-derived mtDNA significantly increased during this period, as assessed by real-time PCR analysis. In our real-time PCR analysis, we improved the standard curve construction-based method to analyze the level of mtDNA between mouse donor cells and porcine oocytes using the copy number of mouse beta-actin DNA as a standard. Our findings suggest that mouse-porcine cloned embryos have the ability to develop to blastocysts in vitro and exhibit mitochondrial heteroplasmy from the 1-cell to blastocyst stages and the mouse-derived mitochondria can be gradually replaced with those of the porcine oocyte in the early developmental stages of mouse-porcine cloned embryos.

Intracytoplasmic sperm injection in sturgeon species: A promising reproductive technology of selected genitors

Sturgeons are the most endangered species group and their wild populations continue to decrease. In this study, we apply intracytoplasmic sperm injection (ICSI), an assisted reproductive technology, for the first time in endangered and critically endangered sturgeons. Using various egg-sperm species combinations we performed different ICSI experiments with immobilized pre- or non-activated spermatozoa, single or many, fresh or cryopreserved. Then we evaluated the fertilization success as well as the paternity of the resultant embryos and larvae. Surprisingly, all experimental groups exhibited embryonic development. Normal-shaped feeding larvae produced in all egg-sperm species-combination groups after ICSI using single fresh-stripped non-activated spermatozoa, in one group after ICSI using single fresh-stripped pre-activated spermatozoa, and in one group after ICSI using multiple fresh-stripped spermatozoa. ICSI with single cryopreserved non-activated spermatozoa produced neurula stage embryos. Molecular analysis showed genome integration of both egg- and sperm-donor species in most of the ICSI transplants. Overall, ICSI technology could be used as an assisted reproduction technique for producing sturgeons to rescue valuable paternal genomes.

Opportunities and Limitations for Reproductive Science in Species Conservation

Reproductive science in the context of conservation biology is often understood solely in terms of breeding threatened species. Although technologies developed primarily for agriculture or biomedicine have a potentially important role in species conservation, their effectiveness is limited if we regard the main objective of animal conservation as helping to support populations rather than to breed a small number of individuals. The global threats facing wild species include the consequences of climate change, population growth, urbanization, atmospheric and water pollution, and the release of chemicals into the environment, to cite but a few. Reproductive sciences provide important and often unexpected windows into many of these consequences, and our aim here is both to demonstrate the breadth of reproductive science and the importance of basic knowledge and to suggest where some of the insights might be useful in mitigating the problems. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 10 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Embryonic fate after somatic cell nuclear transfer in non-enucleated goldfish oocytes is determined by first cleavages and DNA methylation patterns

Reducing the variability in nuclear transfer outcome requires a better understanding of its cellular and epigenetic determinants, in order to ensure safer fish regeneration from cryobanked somatic material. In this work, clones from goldfish were obtained using cryopreserved fin cells as donor and non-enucleated oocytes as recipients. We showed that the high variability of clones survival was not correlated to spawn quality. Clones were then characterized for their first cleavages pattern in relation to their developmental fate up to hatching. The first cell cycle duration was increased in clones with abnormal first cleavage, and symmetric first two cleavages increased clone probability to reach later on 24 h- and hatching-stages. At 24 h-stage, 24% of the clones were diploids and from donor genetic origin only. However, ploidy and genetic origin did not determine clones morphological quality. DNA methylation reprogramming in the promoter region of pou2, nanog, and notail marker genes was highly variable, but clones with the nicest morphologies displayed the best DNA methylation reprogramming. To conclude, non-enucleated oocytes did allow authentic clones production. The first two cell cycles were a critical determinant of the clone ability to reach hatching-stage, and DNA methylation reprogramming significantly influenced clones morphological quality.

Spermatogonial Stem Cells in Fish: Characterization, Isolation, Enrichment, and Recent Advances of In Vitro Culture Systems

Spermatogenesis is a continuous and dynamic developmental process, in which a single diploid spermatogonial stem cell (SSC) proliferates and differentiates to form a mature spermatozoon. Herein, we summarize the accumulated knowledge of SSCs and their distribution in the testes of teleosts. We also reviewed the primary endocrine and paracrine influence on spermatogonium self-renewal vs. differentiation in fish. To provide insight into techniques and research related to SSCs, we review available protocols and advances in enriching undifferentiated spermatogonia based on their unique physiochemical and biochemical properties, such as size, density, and differential expression of specific surface markers. We summarize in vitro germ cell culture conditions developed to maintain proliferation and survival of spermatogonia in selected fish species. In traditional culture systems, sera and feeder cells were considered to be essential for SSC self-renewal, in contrast to recently developed systems with well-defined media and growth factors to induce either SSC self-renewal or differentiation in long-term cultures. The establishment of a germ cell culture contributes to efficient SSC propagation in rare, endangered, or commercially cultured fish species for use in biotechnological manipulation, such as cryopreservation and transplantation. Finally, we discuss organ culture and three-dimensional models for in vitro investigation of fish spermatogenesis.

Optimization of sterlet (Acipenser ruthenus) egg incubation

Sterlet Acipenser ruthenus was used to assess egg and embryo development when incubated at 17 °C in Petri dishes placed in a hatchery tank (300 L recirculating dechlorinated water) with incubation occurring in a static tabletop system in an air-conditioned laboratory, or in a 700 L Q-cell incubator. Eggs in each dish were placed in a plastic box with 300 mL dechlorinated water. Separated eggs from three individual females were fertilized using pooled sperm from four males with there being four replicates. There were no differences (P > 0.05) in mean percentages of neurulation and embryos undergoing cleavage for eggs incubated in the hatchery tank and with use of the static tabletop system. Furthermore, there were no differences (P >  0.05) in percentage of embryos undergoing cleavage, neurulation and hatching for each female when eggs were incubated using the two systems. Results indicate a Petri dish placed in a small plastic box with 300 mL of dechlorinated water was adequate for incubation of sterlet eggs. Results of the study also indicate that with the static system: 1) eggs should be fertilized from each female to retain individual identity; 2) eggs should be dispersed in Petri dishes to avoid clumping; 3) water should be changed at 24 h, but not at 48 h (neurulation) post-fertilization; and 4) embryos that do not optimally develop should be removed the day after neurulation (72 h of post-fertilization period) and water should be exchanged every day subsequent to the 48 h time-point post-fertilization.

Somatic cell nuclear transfer in non-enucleated goldfish oocytes: understanding DNA fate during oocyte activation and first cellular division

Nuclear transfer consists in injecting a somatic nucleus carrying valuable genetic information into a recipient oocyte to sire a diploid offspring which bears the genome of interest. It requires that the oocyte (maternal) DNA is removed. In fish, because enucleation is difficult to achieve, non-enucleated oocytes are often used and disappearance of the maternal DNA was reported in some clones. The present work explores which cellular events explain spontaneous erasure of maternal DNA, as mastering this phenomenon would circumvent the painstaking procedure of fish oocyte enucleation. The fate of the somatic and maternal DNA during oocyte activation and first cell cycle was studied using DNA labeling and immunofluorescence in goldfish clones. Maternal DNA was always found as an intact metaphase within the oocyte, and polar body extrusion was minimally affected after oocyte activation. During the first cell cycle, only 40% of the clones displayed symmetric cleavage, and these symmetric clones contributed to 80% of those surviving at hatching. Maternal DNA was often fragmented and located under the cleavage furrow. The somatic DNA was organized either into a normal mitotic spindle or abnormal multinuclear spindle. Scenarios matching the DNA behavior and the embryo fate are proposed.

The N-space Episenome unifies cellular information space-time within cognition-based evolution

Self-referential cellular homeostasis is maintained by the measured assessment of both internal status and external conditions based within an integrated cellular information field. This cellular field attachment to biologic information space-time coordinates environmental inputs by connecting the cellular senome, as the sum of the sensory experiences of the cell, with its genome and epigenome. In multicellular organisms, individual cellular information fields aggregate into a collective information architectural matrix, termed a N-space Episenome, that enables mutualized organism-wide information management. It is hypothesized that biological organization represents a dual heritable system constituted by both its biological materiality and a conjoining N-space Episenome. It is further proposed that morphogenesis derives from reciprocations between these inter-related facets to yield coordinated multicellular growth and development. The N-space Episenome is conceived as a whole cell informational projection that is heritable, transferable via cell division and essential for the synchronous integration of the diverse self-referential cells that constitute holobionts.

A newly developed cloning technique in sturgeons; an important step towards recovering endangered species

Several steps of sturgeon somatic cell nuclear transfer (SCNT) have been recently established, but improvements are needed to make it a feasible tool to preserve the natural populations of this group of endangered species. The donor cell position inside the recipient egg seems to be crucial for its reprogramming; therefore by injecting multiple donor somatic cells instead of a single cell with a single manipulation, we increased the potential for embryo development. Using the Russian sturgeon Acipenser gueldenstaedtii as a multiple cell donor and sterlet Acipenser ruthenus as the non-enucleated egg recipient, we obtained higher proportion of eggs developing into embryos than previously reported with single-SCNT. Molecular data showed the production of a specimen (0.8%) contained only the donor genome with no contribution from the recipient, while two specimens (1.6%) showed both recipient and donor genome. These findings are the first report of donor DNA integration into a sturgeon embryo after interspecific cloning. In all, we provide evidence that cloning with the multiple donor somatic cells can be feasible in the future. Despite the fact that the sturgeon cloning faces limitations, to date it is the most promising technique for their preservation.

Various nuclear reprogramming systems using egg and oocyte materials

Maternal factors stored in eggs and oocytes are necessary for reprogramming sperm for embryonic development. This reprogramming activity of maternal factors also works towards somatic cells, including terminally differentiated cells. Several different experimental systems utilizing egg and oocyte materials have been applied to study nuclear reprogramming by maternal factors. Among these systems, the most widely used is the transfer of a somatic cell nucleus to an oocyte arrested at the metaphase II stage, leading to the production of a cloned animal. Nuclear transfer to an unfertilized oocyte thus provides a unique opportunity to examine reprogramming processes involved in acquiring totipotency. Other experimental systems are also available to study maternal reprogramming, such as nuclear transfer to Xenopus laevis oocytes at the germinal vesicle stage, treatment with extracts obtained from eggs or oocytes, and induced pluripotency with overexpressed maternal factors. Each system can be used for answering different types of scientific questions. This review describes currently available reprogramming systems using egg and oocyte materials and discusses how we can deepen our understanding of reprogramming mechanisms by taking advantage of these various experimental systems.