Young Mok Lee

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..

A Testis-Mediated Germline Chimera Production Based on Transfer of Chicken Testicular Cells Directly into Heterologous Testes

Abstract In this study, we proposed a testis-mediated germline chimera production system based on the transplantation of testicular cells directly into heterologous testes. The testicular cells of juvenile (4-wk-old) or adult (24-wk-old) Korean Ogol chickens with a recessive pigmentation inhibitory gene, with or without prior culture, were injected (2 × 107 cells/head) into the seminiferous tubules of juvenile or adult recipients with White Leghorn with a dominant pigmentation inhibitory gene in a 2 × 2 factorial arrangement. The localization of transplanted cells into the inner space of the seminiferous tubules was confirmed within 24 h after injection. Subsequent testcross analyses showed that 7.8% (5/64) of the recipients had chimeric status in their testes. The periods of time from transfer to hatching of the first progeny with black feathers were 38 and 45 days for adult cells transplanted into an adult recipient, 188 days for adult cells into a juvenile recipient, and 137 days for juvenile cells into a juvenile recipient. Culture of the testicular cells derived both colony-forming and monolayer-forming cells. The colony-forming cells were stained positively for periodic acid Schiff solution, and further reacted with anti-SSEA-1, anti-SSEA-3, and anti-SSEA-4 antibodies both before and after culture for 15 days. In conclusion, it may be possible to develop the testis-mediated germline chimera production technique, which extends the feasibility of genetic manipulations in avian species.

Identification, Culture, and Characterization of Germline Stem Cell-Like Cells in Chicken Testes

Abstract We recently succeeded in inducing germline transmission by transferring chicken testicular cells into heterologous testes. This study was designed subsequently to identify pluripotent cells in the testicular cells, which would induce the germline transmission. Testicular cells retrieved from juvenile (4-wk-old) or adult (24-wk-old) White Leghorn (WL) chickens were stained with germ cell-specific markers anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-EMA1, anti-ITGA6, and anti-ITGB1 antibodies; 2C9; and lectin-Solanum tuberosum agglutinin (STA). The percentages of the cells that were positive for each marker were within the ranges of 0.33%–0.44% and 0.029%–0.072% of the total testicular cell population in the juvenile and adult, respectively, and significant (P < 0.0002) differences were detected between the ages. When 1 × 106 testicular cells were cultured in Dulbecco minimum essential medium-based medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (FGF2), and/or insulinlike growth factor 1 (IGF1), colony formation was detected only in LIF++FGF2-containing or LIF+FGF2+IGF1-containing medium during primary culture, and the supplementation of LIF+FGF2+IGF1 was the most efficient for maintaining the colony-forming cells through subculture. The established cells retrieved at the end of the primary culture or the 20th subpassage were positive for chicken germ cell-specific periodic acid-Schiff (PAS), EMA1, 2C9, SSEA1, SSEA3, SSEA4, ITGA6, and ITGB1; and lectin-STA markers (evaluated after 11th subpassage). Double staining of lectin-STA with anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-ITGA6, and anti-ITGB1 also was possible. They differentiated spontaneously into embryoid bodies after being cultured in LIF-free medium. We conclude that germline stem cell-like cells are present in chicken testicular cells retrieved from both juvenile and adult testes, which can be identified with the specific markers for primordial germ cells or embryonic germ cells.

The reversible developmental unipotency of germ cells in chicken.

We recently developed bimodal germline chimera production approaches by transfer of primordial germ cells (PGCs) or embryonic germ cells (EGCs) into embryos and by transplantation of spermatogonial stem cells (SSCs) or germline stem cells (GSCs) into adult testes. This study was undertaken to investigate the reversible developmental unipotency of chicken germ cells using our established germline chimera production systems. First, we transferred freshly isolated SSCs from adult testis or in vitro cultured GSCs into stage X and stage 14-16 embryos, and we found that these transferred SSCs/GSCs could migrate to the recipient embryonic gonads. Of the 527 embryos that received SSCs or GSCs, 135 yielded hatchlings. Of 17 sexually mature males (35.3%), six were confirmed as germline chimeras through testcross analysis resulting in an average germline transmission efficiency of 1.3%. Second, PGCs/EGCs, germ cells isolated from embryonic gonads were transplanted into adult testes. The EGC transplantation induced germline transmission, whereas the PGC transplantation did not. The germline transmission efficiency was 12.5 fold higher (16.3 vs 1.3%) in EGC transplantation into testis (EGCs to adult testis) than that in SSC/GSC transfer into embryos (testicular germ cells to embryo stage). In conclusion, chicken germ cells from different developmental stages can (de)differentiate into gametes even after the germ cell developmental clock is set back or ahead. Use of germ cell reversible unipotency might improve the efficiency of germ cell-mediated germline transmission.