No abstract

Approximately 100 species become extinct a day. Despite increasing interest in using cloning to rescue endangered species, successful interspecies nuclear transfer has not been previously described, and only a few reports of in vitro embryo formation exist. Here we show that interspecies nuclear transfer can be used to clone an endangered species with normal karyotypic and phenotypic development through implantation and the late stages of fetal growth. Somatic cells from a gaur bull (Bos gaurus), a large wild ox on the verge of extinction, (Species Survival Plan Ͻ 100 animals) were electrofused with enucleated oocytes from domestic cows. Twelve percent of the reconstructed oocytes developed to the blastocyst stage, and 18% of these embryos developed to the fetal stage when transferred to surrogate mothers. Three of the fetuses were electively removed at days 46 to 54 of gestation, and two continued gestation longer than 180 (ongoing) and 200 days, respectively. Microsatellite marker and cytogenetic analyses confirmed that the nuclear genome of the cloned animals was gaurus in origin. The gaur nuclei were shown to direct normal fetal development, with differentiation into complex tissue and organs, even though the mitochondrial DNA (mtDNA) within all the tissue types evaluated was derived exclusively from the recipient bovine oocytes. These results suggest that somatic cell cloning methods could be used to restore endangered, or even extinct, species and populations. 79

The objectives of the present experiment were to compare survival after transfer of bovine embryos produced in vivo with those produced in vitro and to examine the physical characteristics of fetuses produced from these transfers. Embryos produced in vivo (Holstein x Angus) were recovered from uterine flushings of superovulated heifers 7 days after first artificial insemination, and embryos produced in vitro (Holstein x beef breeds) were collected 7 days after insemination. Embryos were paired by source (in vivo, in vitro), stage (compact morula, blastocyst), and quality grade (excellent = 1, good = 2), and transferred nonsurgically to recipient heifers on Day 7 (+/- 1 day) of the estrous cycle. Pregnancy status was monitored by determination of serum progesterone concentrations, ultrasonography, and palpation through 7 mo of gestation, at which time fetuses were recovered. In comparison with grade 1 embryos produced in vivo, the risk of embryonic death after transfer was similar for grade 2 embryos produced in vivo (p = 0.56) and for grade 1 embryos produced in vitro (p = 0.88). By contrast, grade 2 embryos produced in vitro were at greater (p = 0.04) risk of embryonic death. Embryo loss was associated (p = 0.01) with increased serum concentrations of progesterone in recipients at the time of transfer. At 7 mo of gestation, fetuses from embryos produced in vitro were heavier (p = 0.02) than fetuses from embryos produced in vivo and had skeletal measurements that were disproportionate (p < or = 0.04) to body weight.

No abstract

The trophoblastic interferons ovine and bovine trophoblast protein-1 (oTP-1 and bTP-1, respectively) have been implicated as mediators of maternal recognition of pregnancy in sheep and cattle. The objective of this study was to describe the onset and duration of gene expression for oTP-1 and bTP-1 in preimplantation ovine and bovine conceptuses by in situ hybridization and Northern analysis. Sections from paraffin-embedded ovine conceptuses, collected on Days 10, 11, 12, 13, and 15 of gestation (n = 1, 3, 3, 2, 2), and bovine conceptuses, collected on Days 12/13, 15/16, and 19 (n = 2, 4, 5), were hybridized to specific [35S]-labeled cDNA probes. Two different probes, one encompassing bases 442-918 and representing both coding and 3'-untranslated regions, and a second 3'-specific probe (bases 650-912) were used to detect oTP-1 mRNA. At all stages examined, oTP-1 mRNA was confined to trophectoderm of ovine conceptuses. Consistent with earlier studies, expression increased markedly at Day 13. oTP-1 mRNA was detected at low levels in seven of seven ovine conceptuses prior to Day 13 when the longer probe was employed. With the 3'-specific probe, however, oTP-1 mRNA was detected in only one of the seven ovine conceptuses prior to Day 13. Thus, although low amounts of oTP-1 mRNA may be present in ovine conceptuses prior to Day 13, massive induction of this mRNA occurs on Day 13 coincident with the initiation of maternal recognition of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)