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Effect of GnRH injection timing in the production of pronuclear-stage zygotes used for DNA microinjection

Published online by Cambridge University Press:  08 October 2004

Hernan Baldassarre
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada
Bin Wang
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada
Melanie Gauthier
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada
Nathalie Neveu
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada
Anthoula Lazaris
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada
Costas N. Karatzas
Affiliation:
Nexia Biotechnologies Inc., Vaudreuil-Dorion, Quebec, Canada

Abstract

This study was aimed at developing a hormonal treatment protocol in order to optimize the proportion of pronuclear-stage embryos to be used for DNA microinjection in a goat transgenic founder production programme. A total of 46 adult BELE® and 47 adult standard goats (1–5 years old) were used as donors and recipients, respectively. They were heat-synchronized using intravaginal sponges containing 60 mg medroxyprogesterone acetate for 10 days with an injection of 125 μg cloprostenol on the morning of the eighth day. Recipients were injected with 400 IU eCG at the time of sponge removal while donors received a total of 133 mg NIH-FSH-P1 (Folltropin-V) given twice daily in decreasing doses over 3 days starting 48 h before sponge removal. Ovulation was induced in donors by injecting 100 μg of GnRH at 24 h (GnRH24) or 36 h (GnRH36) after sponge removal. Embryo recovery was performed by oviduct flushing following a standard mid-ventral laparotomy procedure. The proportion of embryos in the pronuclear stage of development was higher in the GnRH36 group (90% vs 34%, p<0.01). Embryos were microinjected with a DNA expression cassette followed by transfer to the oviduct of synchronized recipients. A higher, yet not statistically significant, pregnancy rate was found in the recipients transferred with pronuclear-stage embryos compared with those transferred with 2-cell-stage embryos (64% vs 37%, chi-square p=0.06). One transgenic female founder was produced from the group of recipients transferred with pronuclear-stage microinjected embryos.

Type
Research Article
Copyright
2004 Cambridge University Press

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