Role of Oct-4 during acquisition of developmental competence in mouse oocyte

Meiotic arrest with roscovitine and sexual maturity improve competence of mouse oocytes by regulating expression of competence-related genes

We have studied the mechanisms by which meiotic arrest maintenance (MAM) with roscovitine, female sexual maturity, and the surrounded nucleoli (SN) chromatin configuration improve the competence of mouse oocytes by observing the expression of oocyte competence-related genes in non-surrounded nucleoli (NSN) and SN oocytes from prepubertal and adult mice following maturation with or without MAM. The results demonstrated that MAM with roscovitine significantly improved the developmental potential of adult SN and prepubertal NSN oocytes, but had no effect on that of prepubertal SN oocytes. Without MAM, while 40% of the 2-cell embryos derived from prepubertal SN oocytes developed into 4-cell embryos, none of the 2-cell embryos derived from prepubertal NSN oocytes did, and while 42% of the 4-cell embryos derived from adult SN oocytes developed into blastocysts, only 1% of the 4-cell embryos derived from prepubertal SN oocytes developed into blastocysts. Furthermore, MAM with roscovitine, SN configuration, and female sexual maturity significantly increased the mRNA levels of competence-beneficial genes and decreased those of competence-detrimental genes. In conclusion, our results suggest that MAM with roscovitine, SN chromatin configuration, and female sexual maturity improve oocyte competence by regulating the expression of competence-related genes, suggesting that Oct4, Stella, Mater, Zar1, Mapk8, and Bcl2 are oocyte competence-beneficial genes, whereas Foxj2, Ship1, and Bax are competence-detrimental genes.

Bone morphogenetic protein 15 induces differentiation of mesenchymal stem cells derived from human follicular fluid to oocyte-like cell

Follicular fluid (FF) is essential for developing ovarian follicles. Besides the oocytes, FF has abundant undifferentiated somatic cells containing stem cell properties, which are discarded in daily medical procedures. Earlier studies have shown that FF cells could differentiate into primordial germ cells via forming embryoid bodies, which produced oocyte-like cells (OLC). This study aimed at isolating mesenchymal stem cells (MSC) from FF and evaluating the impacts of bone morphogenetic protein 15 (BMP15) on the differentiation of these cells into OLCs. Human FF-derived cells were collected from 78 women in the assisted fertilization program and cultured in human recombinant BMP15 medium for 21 days. Real-time polymerase chain reaction and immunocytochemistry staining characterized MSCs and OLCs. MSCs expressed germline stem cell (GSC) markers, such as OCT4 and Nanog. In the control group, after 15 days, OLCs were formed and expressed zona pellucida markers (ZP2 and ZP3), and reached 20-30 µm in diameter. Ten days after induction with BMP15, round cells developed, and the size of OLCs reached 115 µm. A decrease ranged from 0.04 to 4.5 in the expression of pluripotency and oocyte-specific markers observed in the cells cultured in a BMP15-supplemented medium. FF-derived MSCs have an innate potency to differentiate into OLCs, and BMP15 is effective in promoting the differentiation of these cells, which may give an in vitro model to examine germ cell development.

Distribution pattern of cytoplasmic organelles, spindle integrity, oxidative stress, octamer-binding transcription factor 4 (Oct4) expression and developmental potential of oocytes following multiple superovulation

The aim of the present study was to determine the effects of repeated superovulation on oocyte quality and embryo developmental potential. Female Swiss albino mice were injected with 5IU pregnant mare's serum gonadotropin followed 48h by 10IU human chorionic gonadotropin. Mice were superovulated up to four times with a gap of 7 days between each superovulation cycle. Ovarian weight increased significantly with an increasing number of superovulation cycles. Although the first stimulation cycle resulted in a threefold increase in the number of oocytes, the number of oocytes decreased gradually after subsequent stimulations. Increased cytoplasmic fragmentation, abnormal mitochondrial distribution, aggregation of Golgi apparatus, spindle damage, increased intracellular oxidative stress and a decrease in expression of octamer-binding transcription factor 4 (Oct4) expression were observed in these oocytes. Further, embryos derived from mice subjected to multiple stimulation cycles exhibited a low blastocyst rate, decreased hatching rate and increased apoptosis in blastocysts. In conclusion, the present study demonstrates that repeated superovulation adversely affects mouse oocyte quality by altering the distribution of cytoplasmic organelles, increasing oxidative stress and decreasing Oct4 expression, resulting in poor developmental potential of the embryos.

STELLA collaborates in distinct mesendodermal cell subpopulations at the fetal-placental interface in the mouse gastrula

The allantois-derived umbilical component of the chorio-allantoic placenta shuttles fetal blood to and from the chorion, thereby ensuring fetal-maternal exchange. The progenitor populations that establish and supply the fetal-umbilical interface lie, in part, within the base of the allantois, where the germ line is claimed to segregate from the soma. Results of recent studies in the mouse have reported that STELLA (DPPA-3, PGC7) co-localizes with PRDM1 (BLIMP1), the bimolecular signature of putative primordial germ cells (PGCs) throughout the fetal-placental interface. Thus, if PGCs form extragonadally within the posterior region of the mammal, they cannot be distinguished from the soma on the basis of these proteins. We used immunohistochemistry, immunofluorescence, and confocal microscopy of the mouse gastrula to co-localize STELLA with a variety of gene products, including pluripotency factor OCT-3/4, mesendoderm-associated T and MIXl1, mesendoderm- and endoderm-associated FOXa2 and hematopoietic factor Runx1. While a subpopulation of cells localizing OCT-3/4 was always found independently of STELLA, STELLA always co-localized with OCT-3/4. Despite previous reports that T is involved in specification of the germ line, co-localization of STELLA and T was detected only in a small subset of cells in the base of the allantois. Slightly later in the hindgut lip, STELLA+/(OCT-3/4+) co-localized with FOXa2, as well as with RUNX1, indicative of definitive endoderm and hemangioblasts, respectively. STELLA was never found with MIXl1. On the basis of these and previous results, we conclude that STELLA identifies at least five distinct cell subpopulations within the allantois and hindgut, where they may be involved in mesendodermal differentiation and hematopoiesis at the posterior embryonic-extraembryonic interface. These data provide a new point of departure for understanding STELLA's potential roles in building the fetal-placental connection.

A hypothetical relationship between the nuclear reprogramming factors for induced pluripotent stem (iPS) cells generation--bioinformatic and algorithmic approach

A hypothetical evolutionary relationship was generated between the nuclear reprogramming factors for induced pluripotent stem (iPS) cells generation. Utilizing bioinformatics techniques, sequence analyses and phylogenetic tree algorithms, a comparative study has been performed to understand the evolutionary relationship of human nuclear reprogramming factors of induced pluripotent stem cells (iPSCs) generation. Among the total six nuclear reprogramming factors, the four reprogramming factors (SOX2, C-MYC, KLF4, and LIN28) have significant evolutionary origin. Our study shows SOX2 and C-MYC have evolutionary relationship and common point of origin. Likewise, KLF4 and LIN28 are having evolutionary relationship and have common point of origin. Based on these evidences, we propose that our study may be a great help to the future researchers to understand the mechanism(s) as well as pathway of nuclear reprogramming process.