Production of somatic and germline chimeras in the chicken by transfer of early blastodermal cells

Cells were isolated from stage X embryos of a line of Barred Plymouth Rock chickens (that have black pigment in their feathers due to the recessive allele at the I locus) and injected into the subgerminal cavity of embryos from an inbred line of Dwarf White Leghorns (that have white feathers due to the dominant allele at the I locus). Of 53 Dwarf White Leghorn embryos that were injected with Barred Plymouth Rock blastodermal cells, 6 (11.3%) were phenotypically chimeric with respect to feather colour and one (a male) survived to hatching. The distribution of black feathers in the recipients was variable and not limited to a particular region although, in all but one case, the donor cell lineage was evident in the head. The male somatic chimera was mated to several Barred Plymouth Rock hens to determine the extent to which donor cells had been incorporated into his testes. Of 719 chicks hatched from these matings, 2 were phenotypically Barred Plymouth Rocks demonstrating that cells capable of incorporation into the germline had been transferred. Fingerprints of the blood and sperm DNA from the germline chimera indicated that both of these tissues were different from those of the inbred line of Dwarf White Leghorns. Bands that were present in fingerprints of blood DNA from the chimera and not present in those of the Dwarf White Leghorns were observed in those of the Barred Plymouth Rocks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production of functional spermatids from mouse germline stem cells in ectopically reconstituted seminiferous tubules

Testicular germ cell transplantation into the seminiferous tubules is at present the only way to induce spermatogenesis from a given source of spermatogonial stem cells. Here we show an alternative method that harnesses the self-organizing ability of testicular somatic cells. The testicular cells of embryonic or neonatal mice or rats and of newborn pigs were dissociated into single cells. Each of them reorganized into a tubular structure following implantation into the subcutis of immunodeficient mice. When mouse germline stem (GS) cells derived from spermatogonial stem cells and expanded in culture were intermingled with testicular cells of rodents, they were integrated in the reconstituted tubules and differentiated beyond meiosis into spermatids. Normal offspring were produced by the microinjection of those spermatids into oocytes. This method could be applicable to various mammalian species and useful for producing functional gametes from GS cells in a xenoectopic environment.     

Lessons from the adrenomedullin knockout mouse

Because vasolidator peptide adrenomedullin (AM) exhibits complicated action, we developed AM knockout mice in order to elucidate the physiological and pathophysiological role of AM. The AM(-/-) mice were embryonic lethal, so we could not evaluate directly the role of AM in this mutant mice. Thus, we loaded angiotensin II (AngII) and salt in AM(+/-) mice, which were viable and fertile. As a result, AngII and salt loading caused coronary vascular damage and left ventricular hypertrophy in AM(+/-) mice more greatly than AM(+/+) mice. Moreover, cuff placement of femoral artery stimulated intimal thickening more severely. This treatment increased local AM levels in AM(+/+) mice but not in AM(+/-) mice. The accelerated organ damage in AM(+/-) mice was accompanied with enhanced production of oxidative stress. Thus, our data suggest that intrinsic AM play a vascular protective role.     

Production of virus-free seronegative pups from murine embryos arising from in vitro fertilization with mouse minute virus-exposed spermatozoa

In the present study, the risk of transmission of mouse minute virus (MMV) to recipients of murine embryos arising from in vitro fertilization (IVF) of oocytes with MMV-exposed spermatozoa and to resulting pups was evaluated. Also, the time of seroconversion of recipients and pups was investigated. To achieve this goal, IVF of oocytes with cryopreserved spermatozoa from the inbred C3HeB/FeJ mouse strain was performed, and the resulting embryos were transferred to suitable Swiss recipients. Three groups were investigated: 1) oocytes or the developing embryos were continuously exposed to 10(4) TCID(50) MMVp per milliliter in the fertilization (human tubal fluid [HTF]), culture (KSOM), and embryo transfer (M2) media (positive control); 2) oocytes and spermatozoa were exposed to MMVp in the HTF medium only and transferred after a standard washing procedure with 10 washing steps in virus-free KSOM and M2; and 3) oocytes and spermatozoa were exposed to virus-free HTF, KSOM, and M2 (negative control). To detect antibodies to MMV in recipients and progeny, serological analyses were performed by ELISA on Days 14, 21, 28, and 42, and on Days 42 and 63, respectively, after embryo transfer. The presence of MMV in the washing drops was analyzed by PCR and an in vitro infectivity assay, while organs of some recipients and pups were analyzed by PCR. Using 10(4) of the tissue culture infective dose of MMVp per millilitre in the fertilization medium only, the present results demonstrate that 10 washing steps in the IVF-ET procedure are sufficient to remove the virus to a noninfectious dose, producing MMV-free seronegative recipients and pups. As such, there is minimal risk of transmission of MMV to recipients and pups if spermatozoa become contaminated with such viral loads.     

Production of germline chimeras by transfer of chicken gonadal primordial germ cells maintained in vitro for an extended period

We previously reported that germline chimeras could be produced by transfer of chicken gonadal primordial germ cells (gPGCs) cultured for a short term (5 days). This study was subsequently undertaken to examine whether gPGCs maintained in vitro for an extended period could retain their specific characteristics to induce germline transmission. Chicken (White Leghorn, WL) gPGCs were retrieved from embryos at stage 28 (5.5 days of incubation) and continuously cultured for 2 months in modified Dulbecco's minimal essential medium without subpassage and changing of the feeder cell layer. After the identification of gPGC characteristics using Periodic acid-Shiff's (PAS) reaction and anti stage-specific embryonic antigen-1 (SSEA-1) antibody staining at the end of the culture, cultured gPGCs were injected into the dorsal aorta of Korean Ogol Chicken (KOC) recipient embryos at stage 17 (2.5 days of incubation). Nineteen chickens (13 males and 6 females) were hatched, grown to sexual maturity, and subsequently subjected to testcross analysis employing artificial insemination with adult KOC. Of these, four (three males and one female) hatched chickens with white coat color. The percentage of germline chimerism was 21% (4/19). The results of this study demonstrated that gPGCs could maintain their specific characteristics for up to 2 months in vitro, resulting in the birth of germline chimeras following transfer to recipient embryos.     

Production of quail (Coturnix japonica) germline chimeras by transfer of gonadal primordial germ cells into recipient embryos

The possibility of producing quail germline chimeras by the transfer of gonadal primordial germ cells (gPGCs) into recipient embryos was investigated. Japanese quail of the black (D: homozygous for the autosomal incomplete dominant gene D) and wild-type plumage (WP: d+/d+) strains were used as donors and recipients, respectively. Gonadal cells were retrieved from the gonads of 5-day-old D embryos, and gPGCs were enriched by magnetism-activated cell sorting. Fresh (noncultured) gPGCs or those isolated after culture for 3 days with gonadal stromal cells present in the mixed cell population were introduced into the dorsal aorta of 2-day-old recipient WP embryos. Hatchability of the recipient embryos was 23.7% (31/131) and 34.4% (31/90) for those transfused with cultured or noncultured gPGCs, respectively. Of the hatched quail, 28 acquired sexual maturity; among these animals, 7.1% (1/14) and 21.4% (3/14) of those that received cultured or noncultured gPGCs, respectively, were proved to be germline chimeras. The percentage of germline transmission to the donor-derived gametes in the chimeras that received cultured and noncultured gPGCs were 1.9 and 2.2-4.7%, respectively. In conclusion, quail gPGCs retrieved from 5-day-old embryos were thus transmitted in the germline after their transfer to quail embryos of a different strain. This property of the gPGCs was not adversely affected by culture for up to 3 days.     

Production and properties of mouse trisomy 15 ⟷ diploid chimeras

Mouse trisomy 15 ? 2n aggregation chimeras have been produced and analyzed at 19 days of gestation. We have found that these chimeras are viable and in most instances normal in external appearance, unlike trisomy (Ts)-15 embryos which are severely growthretarded and die midway through gestation. Trisomic cells were found in all tissues of fetal chimeras, with proportions not significantly different from those of the controls in kidney, heart, liver, and brain, but significantly reduced in thymus and spleen. Ts-15 cells do not, therefore, exhibit a proliferative advantage during fetal development of tissues susceptible to Ts-15-related lymphoid malignancies. However, the presence of Ts-15 cells in the placenta may be associated with placental overgrowth. One fetus containing a monosomy 3 cell population was also observed, the first term fetal chimera with monosomic cells that has been detected.     

Some lessons from the tissue transglutaminase knockout mouse

Transglutaminase 2 (TG2) is an inducible transamidating acyltransferase that catalyzes Ca²⁺-dependent protein modifications. It acts as a G protein in transmembrane signaling and as a cell surface adhesion mediator, this distinguishes it from other members of the transglutaminase family. The sequence motifs and domains revealed in the TG2 structure, can each be assigned distinct cellular functions, including the regulation of cytoskeleton, cell adhesion, and cell death. Though many biological functions of the enzyme have already been described or proposed previously, studies of TG2 null mice by our laboratory during the past years revealed several novel in vivo roles of the protein. In this review we will discuss these novel roles in their biological context.     

Production of chimeras by aggregation of embryonic stem cells with diploid or tetraploid mouse embryos

The production of mouse chimeras is a common step in the establishment of genetically modified animal strains. Chimeras also provide a powerful experimental tool for following cell behavior during both prenatal and postnatal development. This protocol outlines a simple and economical technique for the production of large numbers of mouse chimeras using traditional diploid morula<-->diploid embryonic stem (ES) cell aggregations. Additional steps are included to describe the procedures necessary to produce specialized tetraploid chimeras using tetraploid morula<-->diploid ES cell aggregations. This increasingly popular form of chimera produces embryos of nearly complete ES cell derivation that can be used to speed transgenic production or ask developmental questions. Using this protocol, mouse chimeras can be generated and transferred to pseudopregnant surrogate mothers in a 5-d period.     

All-or-none craniorachischisis in Loop-tail mutant mouse chimeras

Mouse embryos homozygous for the mutant gene Loop-tail (Lp) are characterized by craniorachischisis, an open neural tube extending from the midbrain to the tail. In the present study, experimental chimeric mice containing mixtures of genetically mutant (from Lp/+ x Lp/+ matings) and genetically normal cells were produced. Our aim was to determine whether a 'rescue,' phenotypic gradient, or intermediate expression (i.e. alternating areas of open and closed neural tube) would be observed in these chimeras. We report our analyses of Loop-tail mutant chimeras (n = 82) by gross examination, progeny testing and quantitative analysis of glucose phosphate isomerase (GPI) isozyme levels. An all-or-none craniorachischisis in Loop-tail mutant chimeras was observed. Two multicolored adult chimeras, without any gross evidence of a neural tube defect, were shown to be homozygous Loop-tail chimeras (Lp/Lp in equilibrium +/+) by progeny testing. These results indicate that the normal phenotype can be expressed in the presence of mutant cells. Conversely, six neonates with craniorachischisis were shown to be chimeras by GPI analyses. These results show that the full mutant phenotype can be expressed even when one-third to one-half of the cells are genotypically wild-type. This study did not determine which tissue is primarily responsible for the defective neurulation in this mutant, but suggests that a 'threshold' mechanism underlies the Loop-tail mutant phenotype. In some chimeras that threshold is not reached and the neural tube remains open, whereas in other chimeras the threshold is reached and the neural tube closes completely.     

Nest-building by the virgin female mouse exposed to ultrasound from inaccessible pups

When a naïve virgin female mouse is exposed to an inaccessible litter so that it perceives the odour and the ultrasounds from the pups, its nest-building behaviour undergoes changes that are different from changes occurring in a control condition providing exposure to an inaccessible adult female. Virgin females exposed to a litter built their nest as near as possible to the pups. Other characteristics of their nest-building behaviour were influenced differently according to the type of ultrasound that the pups were emitting. In a condition where pups were mainly calling in response to cold, virgin females built heavier nests than control females. When mainly calls in response to handling were given by the pups, the females built lighter nests than control females. Finally, there was also some suggestion that the females exposed to ultrasounds from handled pups tended to chew the nest-material more than either control females or females exposed to ultrasound from cooled pups.     

Distribution of androgenetic cells in fetal mouse chimeras

To asses the potential of androgenetic cells to participate in post-midgestation fetal development we have made use of an in situ detectable cell lineage marker in the analysis of chimeric mouse fetuses containing an androgenetic cell lineage. Our results show conclusively that androgenetic cells participate in the formation of derivatives of all lineages and in some tissues may contribute the majority of the total cell population. However, the allocation or persistence of androgenetic cells was non-random. High contribution of androgenetic cells was observed in brown adipose tissue, mesenchyme, smooth muscle, perichondrium, peripheral nerves and epithelia of the intestinal tract and the trachea. Thus, androgenetic cells were able to efficiently populate mesodermal, ectodermal and endodermal derivatives. In contrast, there was a clear prejudice against androgenetic cells in the brain.     

Systematic elimination of parthenogenetic cells in mouse chimeras

The developmental potential of primitive ectoderm cells lacking paternal chromosomes was investigated by examining the distribution of parthenogenetic cells in chimeras. Using GPI-1 allozymes as marker, parthenogenetic cells were detected in most organs and tissues in adult chimeras. However, these cells were under severe selective pressure compared with cells from normal fertilized embryos. In the majority of chimeras, parthenogenetic cells in individual animals were observed in a limited number of tissues and organs and, even in these instances, their contribution was substantially reduced. Nevertheless, parthenogenetic cells were detected more consistently in some organs, especially the brain, heart, kidney and spleen. In contrast, there was apparently a systematic selection against parthenogenetic cells in some tissues, most notably in skeletal muscle, liver and pancreas. These results suggest that paternally derived genes are probably required not only for the development of extraembryonic structures but also for subsequent development of embryonic tissues derived from the primitive ectoderm lineage.     

Zebrafish germline chimeras produced by transplantation of ovarian germ cells into sterile host larvae

High frequency production of zebrafish germline chimeras was achieved by transplanting ovarian germ cells into sterile Danio hybrid recipients. Ovarian germ cells were obtained from 3-mo-old adult Tg(vasa:DsRed2-vasa);Tg(bactin:EGFP) double transgenic zebrafish by discontinuous Percoll gradient centrifugation. An average of 755 ± 108 DsRed-positive germ cells was recovered from each female. For transplantations, a total of approximately 620 ± 242 EGFP-positive cells of which 12 ± 4.7 were DsRed-positive germ cells were introduced into the abdominal cavity under the swim bladder of 2-wk-old sterile hybrid larvae. Six weeks after transplantation, a total of 10 recipients, obtained from 2 different transplantations, were examined, and 2 individuals (20%) were identified that possessed a large number of DsRed- and EGFP-positive cells in the gonadal region. The transplanted ovarian germ cells successfully colonized the gonads and differentiated into sperm in the male hybrid recipients. Of 67 adult recipients, 12 (18%) male chimeric fish reproduced and generated normal offspring when paired with wild-type zebrafish females. The fertilization efficiency ranged from 23% to 56%. Although the fertile male chimeras were generated by transplantation of ovarian germ cells, the F1 generation produced by the male chimeras contained both male and female progeny, indicating that male sex determination in zebrafish is not controlled by sex chromosome heterogamy. Our findings indicate that a population of ovarian germ cells that are present in the ovary of adult zebrafish can function as germline stem cells, able to proliferate and differentiate into testicular germ cells and functional sperm in male recipients. The high frequency of germline chimera formation achieved with the ovarian germ cells and the convenience of identifying the chimeras in the sterile host background should make this transplantation system useful for performing genetic manipulations in zebrafish.     

Long-term proliferation in culture and germline transmission of mouse male germline stem cells

Spermatogenesis is a complex process that originates in a small population of spermatogonial stem cells. Here we report the in vitro culture of spermatogonial stem cells that proliferate for long periods of time. In the presence of glial cell line-derived neurotrophic factor, epidermal growth factor, basic fibroblast growth factor, and leukemia inhibitory factor, gonocytes isolated from neonatal mouse testis proliferated over a 5-month period (>10(14)-fold) and restored fertility to congenitally infertile recipient mice following transplantation into seminiferous tubules. Long-term spermatogonial stem cell culture will be useful for studying spermatogenesis mechanism and has important implications for developing new technology in transgenesis or medicine.