Maturation and Developmental Competence of Selectively Enucleated Germinal Vesicle Oocytes of Mammals upon nuclear transfer
Pages : 292-299
Interaction between the donor nuclei and the recipient cytoplasts is considered as one of the fundamental questions in the field of assisted reproductive technology. The resulting artificial oocytes might be used for embryonic/somatic cloning or treatment of infertility. Because of difficulties in co-operation between donor nuclei (embryonic & somatic) and recipient cytoplasts (Metaphase II), trials were carried out to investigate maturation and developmental competence of fully grown germinal vesicle (GV) cytoplasts upon reconstitution with germ or embryonic or somatic nuclei. In order to obtain the recipient cytoplasts, fully grown germinal vesicle (GV) oocytes were completely or selectively enucleated. For complete enucleation of GV oocyte, the whole nuclei were removed, and for selective enucleation of GV oocyte, nuclear sap and nucleoli were leaked into the cytoplasts and the nuclear envelope with the attached chromatin was removed. Reconstruction of complete or selective GV cytoplasts with germ or embryonic or somatic donor nuclei at different stages of cell cycle was done to investigate maturation and further developmental competence in some studies. These studies indicated that maturation and developmental competence were affected by the recipient cytoplasts and donor nuclei. Although the embryonic or somatic nuclei were abnormal in their maturation and further development, however, the germ cells were able to mature and develop to offspring. Selective GV cytoplasts enhanced proper pronuclei formation and further developmental competence. Several studies showed that germinal vesicle materials are essential for remodeling the introduced somatic nuclei into proper pronuclei and their further developmental competence. Furthermore, the cumulus cells and the nucleolus are the factors compromised the developmental competence of the reconstituted oocytes. In this article, manipulations of GV oocytes in addition to their maturation and developmental competency upon nuclear transfer were addressed. Moreover, the effects of GV materials, nucleoli and cumulus cells on maturation and developmental competence of reconstituted GV cytoplasts upon nuclear transfer were discussed.
Keywords: Maturation; selective enucleation, nucleolus
Article published in International Journal of Current Engineering and Technology, Vol.4,No.1 (Feb- 2014)