Kyung Je Park

Reproduction of Wild Birds via Interspecies Germ Cell Transplantation

Abstract The present study was conducted to apply an interspecies germ cell transfer technique to wild bird reproduction. Pheasant (Phasianus colchicus) primordial germ cells (PGCs) retrieved from the gonads of 7-day-old embryos were transferred to the bloodstream of 2.5-day-old chicken (Gallus gallus) embryos. Pheasant-to-chicken germline chimeras hatched from the recipient embryos, and 10 pheasants were derived from testcross reproduction of the male chimeras with female pheasants. Gonadal migration of the transferred PGCs, their involvement in spermatogenesis, and production of chimeric semen were confirmed. The phenotype of pheasant progenies derived from the interspecies transfer was identical to that of wild pheasants. The average efficiency of reproduction estimated from the percentage of pheasants to total progenies was 17.5%. In conclusion, interspecies germ cell transfer into a developing embryo can be used for wild bird reproduction, and this reproductive technology may be applicable in conserving endangered bird species..

Migration and Proliferation of Intact and Genetically Modified Primordial Germ Cells and the Generation of a Transgenic Chicken

Abstract This study evaluated gonadal migration and postmigratory proliferation of intact and genetically modified chicken primordial germ cells (PGCs). A randomized, controlled trial was conducted with the gonadal population of PGCs and transgenic chicken production as major parameters. PGCs (0, 90, 900, 1800, or 3000 cells) were transferred into 53-h-old embryos. The percentage of PGCs migrating on Day 6 of development was highest (35.8%) following the transfer of 900 PGCs and did not change with increases in transferred PGCs. The number of migrating PGCs gradually increased (P = 0.0001) as the number of transferred PGCs was increased. Gonadal migration was detected after the transfer of intact and genetically modified PGCs, but prominent decreases in PGC migration (from 21.9% to 0.38%) and chimera ratio (from 0.4 to 0.007) occurred with genetically modified PGCs. However, subsequent vigorous proliferation of the modified PGCs (3.67-fold increase from transferred number) led to the derivation of a germline chimera and produced a transgenic hatchling. In conclusion, the number of migrating PGCs increased as the number of transferred cells increased. Vigorous proliferation after transfer compensated for the decreased migration capacity of genetically modified PGCs and resulted in the production of a transgenic chicken.

Expression pattern of meiosis associated SYCP family members during germline development in chickens.

Synaptonemal complexes (SCs) are associated with synapsis of homologous chromosomes, chiasmata distribution, recombination and segregation of chromosomes during the extended prophase of meiosis I. Three isoforms of SC proteins, SYCP1, SYCP2 and SYCP3, were identified as the structural proteins of SCs, and may be involved in the assembly and disassembly of SCs. The aim of this present study is to determine the pattern of expression of chicken homologues of SYCP family members during ovarian and testicular development. Protein sequence analysis using CLUSTAL X revealed that the sequences and potential phosphorylation sites of chicken SYCP family proteins were highly conserved with mammalian homologues of SYCP family proteins. Quantitative real-time-PCR and in situ hybridisation analysis revealed that chicken SYCP family members were differentially expressed during ovarian and testicular development. During ovarian development, all chicken SYCP family members were detected in primordial germ cells (PGCs) until embryonic day (E) 8.0; the expression continued in proliferating pre-meiotic oogonia until E15.5 and was upregulated in meiotic prophase I oocytes until hatching. After hatching, all chicken SYCP family members were detected at a low level until 24-weeks-old. During testicular development, all chicken SYCP family members were detected in PGCs until E13.0; the expression continued in pro-spermatogonia and proliferating spermatogonia for up to 8 weeks, and was upregulated in meiotic prophase I spermatocytes in adults. Our data demonstrate the expression pattern of meiosis associated SYCP family members during ovarian and testicular development in chickens.

Physiological Effects of Diethylstilbestrol Exposure on the Development of the Chicken Oviduct

Estrogen has dramatic effects on the development and function of the reproductive tract in mammals. Although diethylstilbestrol (DES) triggers the development of reproductive organs in immature animals, continued exposure to DES induces dysfunction of the female reproductive tract in mice. To investigate the effects of neonatal estrogen exposure on the reproductive tract of female chickens, we implanted DES pellets into the abdominal region of immature female chicks and then examined the effects of DES on the oviducts of both immature chicks and sexually mature chickens (30 weeks old). DES induced mass growth and differentiation of the oviduct in immature chicks. The chick oviduct increased by 2.7- and 29-fold in length and weight, respectively, following primary DES stimulation. In secondary DES stimulation, the length and weight of the chick oviduct increased by 4.5- and 74-fold, respectively. Additionally, DES treatments caused abnormal development of the infundibulum and magnum in hen oviducts. Furthermore, infundibulum abnormality gave rise to unusual ovulation of follicles and resulted in infertility and dysfunction of the magnum, such as less production of egg white proteins. Our results indicate that DES exposure during early developmental stages in chickens has detrimental effects on the development and maintenance of the female reproductive tract after sexual maturation.

Compensatory proliferation of endogenous chicken primordial germ cells after elimination by busulfan treatment

IntroductionPrimordial germ cells (PGCs) are the major population of cells in the developing bilateral embryonic gonads. Little is known about the cellular responses of PGCs after treatment with toxic chemicals such as busulfan during embryo development. In this study, we investigated the elimination, restorative ability, and cell cycle status of endogenous chicken PGCs after busulfan treatment.MethodsBusulfan was emulsified in sesame oil by a dispersion-emulsifying system and injected into the chick blastoderm (embryonic stage X). Subsequently, we conducted flow cytometry analysis to evaluate changes in the PGC population and cell cycle status, and immunohistochemistry to examine the germ cell proliferation.ResultsResults of flow cytometry and immunohistochemistry analyses after busulfan treatment showed that the proportion of male PGCs at embryonic day 9 and female PGCs at embryonic day 7 were increased by approximately 60% when compared with embryonic day 5.5. This result suggests the existence of a compensatory mechanism in PGCs in response to the cytotoxic effects of busulfan. Results of cell cycling analysis showed that the germ cells in the G0/G1 phase were significantly decreased, while S/G2/M-phase germ cells were significantly increased in the treatment group compared with the untreated control group in both 9-day-old male and female embryos. In addition, in the proliferation analysis with 5-ethynyl-2′-deoxyuridine (EdU) incorporation, we found that the proportion of EdU-positive cells among VASA homolog-positive cells in the 9-day embryonic gonads of the busulfan-treated group was significantly higher than in the control group.ConclusionsWe conclude that PGCs enter a restoration pathway by promoting their cell cycle after experiencing a cytotoxic effect.

The distribution of neuron-specific gene family member 1 in brain and germ cells: Implications for the regulation of germ-line development by brain

Vesicular acidification at early endosomes dissociates endocytosed receptor‐ligand complexes. The ligands, receptors, or both are then directed to late endosomes for degradation or recycled back to the plasma membrane. Of neuron‐specific gene (NSG) family members, early endosomal protein neuron‐specific gene family member 1 (NSG1) is the most important in receptor recycling. In this study, we characterized chicken NSG1 (cNSG1). We found several functional sites related to endocytotic machinery in cNSG1 that were highly conserved with most other vertebrate NSG1 proteins. We examined the tissue and duration specificity and the temporal and spatial patterns of cNSG1 expression. cNSG1 expression was preferentially located in all regions of the brain, neuroendocrine glands, and spinal cord. Unexpectedly, cNSG1 expression was strongly detected during male and female germ‐line development. Expression of NSG1 in two apparently unrelated cell types such as neurons and germ cells suggests NSG1 roles in neurons and germ‐cells chemotaxis and endocytotic machinery. Developmental Dynamics 240:850–861, 2011.

Precise gene editing of chicken Na+/H+ exchange type 1 (chNHE1) confers resistance to avian leukosis virus subgroup J (ALV-J)

Avian leukosis virus subgroup J (ALV-J), first isolated in the late 1980s, has caused economic losses to the poultry industry in many countries. As all chicken lines studied to date are susceptible to ALV infection, there is enormous interest in developing resistant chicken lines. The ALV-J receptor, chicken Na+/H+ exchange 1 (chNHE1) and the critical amino acid sequences involved in viral attachment and entry have already been characterized. However, there are no reported attempts to induce resistance to the virus by targeted genome modification of the receptor sequences. In an attempt to induce resistance to ALV-J infection, we used clustered regularly interspaced short palindromic repeats (CRISPR)-associated (CRISPR/Cas9)-based genome editing approaches to modify critical residues of the chNHE1 receptor in chicken cells. The susceptibility of the modified cell lines to ALV-J infection was examined using enhanced green fluorescent protein (EGFP)-expressing marker viruses. We showed that modifying the chNHE1 receptor by artificially generating a premature stop codon induced absolute resistance to viral infection, with mutations of the tryptophan residue at position 38 (Trp38) being very critical. Single-stranded oligodeoxynucleotide (ssODN)-mediated targeted recombination of the Trp38 region revealed that deletions involving the Trp38 residue were most effective in conferring resistance to ALV-J. Moreover, protein structure analysis of the chNHE1 receptor sequence suggested that its intrinsically disordered region undergoes local conformational changes through genetic alteration. Collectively, these results demonstrate that targeted mutations on chNHE1 alter the susceptibility to ALV-J and the technique is expected to contribute to develop disease-resistant chicken lines.

Effects of Gamma-Irradiation on the Sterilization of Primordial Germ Cells in Quail

Quail is a very useful animal model for studying vertebrate development because of its small body size and unique reproductive traits. This species is also ideal model for producing germline chimeras via transferring exogenous primordial germ cells (PGCs) into the recipient embryo. To increase the contribution efficiency of donor PGCs into recipients’ tissues, decreasing the population of endogenous PGCs has been rate-limiting factor. We therefore conducted this study to investigate if gamma (γ)-irradiation depletes endogenous PGCs in developing quail embryo. Firstly, freshly laid stage X quail embryos were irradiated with various output of γ-irradiation and its teratogenic effect on the embryo was evaluated. Although a dose-dependent increase in the number of embryo showing malformation was found as the output increased (0, 250, 500, 750, and 1,000 rads), only a maximum of 10.1% of embryos were abnormal in 1,000 rads. Immunocytochemical analysis using the QCR1 antibody, which is specific marker for quail PGCs, was conducted to analyze the effect of sterilization. As results, γ-rays at a dose-rate of 500 rads/73 sec onto undeveloped stage X embryo significantly reduced the number of germ cells to an average of 75.55 % and 82.03 % in male and female embryos, respectively. We conclude that γ-ray selectively targets PGCs while affects minimally to the somatic development in quail embryo. Our results will not only provide important data for germline chimera production but can be used for analyzing the effect of ionized rays on the differentiating germ cells in various stages during animal development.