Transgenic rhesus monkeys carrying the green fluorescent protein (GFP) gene were produced by injecting pseudotyped replication-defective retroviral vector into the perivitelline space of 224 mature rhesus oocytes, later fertilized by intracytoplasmic sperm injection. Of the three males born from 20 embryo transfers, one was transgenic when accessible tissues were assayed for transgene DNA and messenger RNA. All tissues that were studied from a fraternal set of twins, miscarried at 73 days, carried the transgene, as confirmed by Southern analyses, and the GFP transgene reporter was detected by both direct and indirect fluorescence imaging.

No abstract

Manipulations of DNA and cellular structures are essential for the propagation of genetically identical animals by nuclear transfer. However, none of the steps have been optimized yet. This study reports a protocol that improves live dynamic imaging of the unfertilized bovine oocyte's meiotic spindle microtubules with microinjected polymerization-competent X-rhodamine-tubulin and/or with vital long-wavelength excited DNA fluorochrome Sybr14 so that the maternal chromosomes can be verifiably removed to make enucleated eggs the starting point for cloning. Suitability of the new fluorochromes was compared to the conventional UV excitable Hoechst 33342 fluorochrome. Enucleation removed the smallest amount of cytoplasm (4-7%) and was 100% efficient only when performed under continuous fluorescence, i.e., longer fluorescence exposure. This was in part due to the finding that the second metaphase spindle is frequently displaced (60.7 +/- 10%) from its previously assumed location subjacent to the first polar body. Removal of as much as 24 +/- 3% of the oocyte cytoplasm underneath the polar body, in the absence of fluorochromes, often resulted in enucleation failure (36 +/- 6%). When labeled oocytes were exposed to fluorescence and later activated, development to the blastocyst stage was lowest in the group labeled with Hoechst 33342 (3%), when compared to Sybr14 (19%), rhodamine-tubulin (23%), or unlabeled oocytes (37%). This suggests that longer wavelength fluorochromes can be employed for live visualization of metaphase spindle components, verification of their complete removal during enucleation, and avoidance of the confusion between artifactual parthenogenesis versus "cloning" success, without compromising the oocyte's developmental potential after activation.