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Stapleford, United Kingdom

Bakst M.R.,U.S. Department of Agriculture | Wade A.J.,Ew Group
Avian Biology Research | Year: 2014

The normal developmental sequence of the turkey embryo from the initial cleavage divisions through hypoblast formation has been described previously in 11 separate stages based on the progressive morphological differentiation of the embryo (Gupta and Bakst, Turkey embryo staging from cleavage through hypoblast formation. J. Morphol., 217, 313-325, 1993). However, in recent preliminary studies, our attempts to apply this stage table to describe the stages of embryo development were not successful. Therefore, we re-evaluated the development sequence of the turkey using eggs obtained from modern day commercial lines. Embryos from unincubated eggs and eggs incubated at different time intervals up to 25 hour were examined. In contrast to the observations by Gupta and Bakst, embryos from unincubated eggs lack an area pellucida (AP) but are characterised by dense clusters of cells that do not begin to dissipate and begin forming the AP until after 3-4 hours of incubation. Koller's sickle may or may not be present prior to and during hypoblast formation. Based on these new observations, a revised stage table including the above observations is presented to reflect more accurately the development of the modern commercial turkey embryo. Source


Wade A.J.,Ew Group | French N.A.,Aviagen | Ireland G.W.,University of Manchester
Poultry Science | Year: 2014

Diseases such as avian influenza can destroy turkey flocks, potentially resulting in the loss of valuable or rare genetic material. Consequently, there is an urgent need to develop a means to archive such germplasm. Germline chimeras produced by intravascular transfer of primordial germ cells (PGC) have been reported in other avian species but not turkeys. This study examined the feasibility of both establishing an archive of frozen PGC, and producing germline chimeras by injecting the thawed PGC into host embryos. To meet these aims, the following experiments were performed: (1) PGC identification within turkey embryos; (2) development of an efficient method for isolation of turkey PGC; (3) demonstration that PGC can be cryopreserved, recovered, and retain viability; (4) reinjection into embryos and detection of injected PGC. Primordial germ cells were identified using periodic acid- Schiff reagent and the immunological marker OLP-1. Bloodstream PGC were isolated using Ficoll density gradient centrifugation with PGC recovery peaking at stages 13, 14, and 15 with 32 ± 4.9, 33 ± 6.4, and 26 ± 5.4 PGC recovered, respectively. Primordial germ cells were frozen using Dulbecco's modified Eagle medium, 20% fetal calf serum, and 10% dimethylsulfoxide and demonstrated 90 ± 1.7% viability after 3 mo frozen in liquid nitrogen. Freshly isolated and frozen thawed DiI- and Q-Tracker-labeled PGC repopulated stage 30 gonads after vascular transfer into ex ovo cultured embryos. The DiI-labeled cells repopulated gonads less frequently, with 36 ± 13.2% of gonads containing the DiI-labeled PGC, and 7 ± 3.8% of reinjected PGC reaching the gonads of positive embryos. The Q-tracker- labeled cells were detected more frequently in embryos, with 67 ± 21.1% having positive signals, and 44 ± 4.9% of reinjected Q-tracker-labeled PGC colonized the gonads of positive embryos. This study demonstrated the feasibility of using turkey PGC to archive turkey germplasm from different strains because frozen PGC reintroduced into host embryos can colonize the host gonads, suggesting the possibility of producing turkey germline chimeras. © 2014 Poultry Science Association Inc. Source


Tyack S.G.,CSIRO | Tyack S.G.,Ew Group | Jenkins K.A.,CSIRO | O'Neil T.E.,CSIRO | And 10 more authors.
Transgenic Research | Year: 2013

Traditional methods of avian transgenesis involve complex manipulations involving either retroviral infection of blastoderms or the ex vivo manipulation of primordial germ cells (PGCs) followed by injection of the cells back into a recipient embryo. Unlike in mammalian systems, avian embryonic PGCs undergo a migration through the vasculature on their path to the gonad where they become the sperm or ova producing cells. In a development which simplifies the procedure of creating transgenic chickens we have shown that PGCs are directly transfectable in vivo using commonly available transfection reagents. We used Lipofectamine 2000 complexed with Tol2 transposon and transposase plasmids to stably transform PGCs in vivo generating transgenic offspring that express a reporter gene carried in the transposon. The process has been shown to be highly effective and as robust as the other methods used to create germ-line transgenic chickens while substantially reducing time, infrastructure and reagents required. The method described here defines a simple direct approach for transgenic chicken production, allowing researchers without extensive PGC culturing facilities or skills with retroviruses to produce transgenic chickens for wide-ranging applications in research, biotechnology and agriculture. © 2013 Springer Science+Business Media Dordrecht. Source

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