Cloning and expression of pluripotent factors around the time of gastrulation in the porcine conceptus

Doctor of PhilosophyDepartment of Animal Sciences and IndustryDavid M. GriegerEarly in embryonic development a series of events occur whereby pluripotent cells undergo differentiation to give rise to the three germ layers and extraembryonic tissues of the developing conceptus. Nanog, Sox-2, and Oct-4 genes have been identified as having key roles in maintaining pluripotency in undifferentiated human and mouse cells but recent evidence suggests they may have different roles in farm animals. We cloned the coding sequence for porcine Nanog including 452 base pairs of the Nanog promoter, and partial coding sequences of Oct-4 and Sox-2. Embryos were flushed from sows 10, 12, 15, and 17 days post insemination. RNA was isolated from whole d-10 and -12 conceptuses, d-15 embryonic disk, distal and proximal extraembryonic tissue, and d-17 embryonic disk, distal and proximal extraembryonic tissue, and allantois for real-time PCR. RNA from d-40 maternal myometrium and endometrium, fetal placenta, and liver were also used in real-time PCR. The homeodomain and c-terminal tryptophan repeats are highly conserved in porcine Nanog compared to the mouse, human and bovine. In the promoter, the highly conserved Octamer and Sox binding sequences are also present. The Nanog expression pattern was different when compared to Oct-4 and Sox-2. Day-40 tissues demonstrated the highest expression including endometrium (7 fold) fetal liver (27 fold), placenta (40 fold) and myometrium (72 fold) when compared to day 15 distal extraembryonic tissue. Oct-4 and Sox-2 expression was lowest in d-40 tissues except for fetal liver which was 20 and 71 fold, respectively, higher than endometrium. Oct-4 levels were consistent in d-10, -12, and -15 conceptuses and disk but dropped 3 fold in d-17 disk. On the other hand, Sox-2 was upregulated a 1000 fold in the d-15 disk and 2000 fold in the d-17 disk when compared to the d-12 conceptus. Nanog may have other roles in than maintenance of pluripotency including a possible role in multipotent or progenitor stem cells. Expression of all 3 markers in fetal liver suggests a more primitive cell type is present such as hematopoietic stem cells

Follicular expression of follicle stimulating hormone receptor variants in the ewe

Background: Several alternatively-spliced mRNA transcripts of the follicle stimulating hormone receptor (FSHR) have been identified in sheep, including FSHR-1 (G protein-coupled form), FSHR-2 (dominant negative form), and FSHR-3 (growth factor type-1 form). Our objective was to determine which of these variants is predominantly expressed in follicles collected from ewes at various times after estrus. Methods: Suffolk-cross ewes (n = 8) were allowed to come into estrus naturally and were euthanized 24 (n = 3), 36 (n = 3), or 48 (n = 2) hours after the onset of estrus. All visible follicles were measured, aspirated and pooled according to follicular diameter: small ( = 6.1 mm). Aspirated cells were separated from follicular fluid by centrifugation. Total RNA was extracted from cell pellets and reverse transcribed. The resulting cDNA was subjected to qPCR, using primer sets designed to amplify each variant specifically. Gene expression was normalized to that of beta–actin within samples, and compared by analysis of variance with the level of significant differences set at p < .05. Results: Relative expression of FSHR-3 exceeded that of both FSHR-1 and FSHR-2 in medium follicles, and tended to be higher in small follicles (p = .09) regardless of time after onset of estrus, and thus results from different time points were pooled. Expression of FSHR-3 was greater than that of FSHR-2 and luteinizing hormone receptor (LHR) in small and medium follicles. Expression of LHR was greatest in preovulatory follicles. Conclusions: These experiments show that in addition to the well characterized G protein-coupled form of the FSHR, alternatively spliced variants of the FSHR may participate in follicular dynamics during follicular waves of the sheep estrous cycle. Furthermore, these results indicate that an “alternatively” spliced form of the FSHR (FSHR-3) is the predominant form of the FSHR in the sheep