http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Temporal Expression of RNA Polymerase II in Porcine Oocytes and Embryos
Oqani, Reza,Lee, Min Gu,Tao, Lin,Jin, Dong Il The Korean Society of Animal Reproduction 2012 Reproductive & developmental biology Vol.36 No.4
Embryonic genome activation (EGA) is the first major transition that occurs after fertilization, and entails a dramatic reprogramming of gene expression that is essential for continued development. Although it has been suggested that EGA in porcine embryos starts at the four-cell stage, recent evidence indicates that EGA may commence even earlier; however, the molecular details of EGA remain incompletely understood. The RNA polymerase II of eukaryotes transcribes mRNAs and most small nuclear RNAs. The largest subunit of RNA polymerase II can become phosphorylated in the C-terminal domain. The unphosphorylated form of the RNA polymerase II largest subunit C-terminal domain (IIa) plays a role in initiation of transcription, and the phosphorylated form (IIo) is required for transcriptional elongation and mRNA splicing. In the present study, we explored the nuclear translocation, nuclear localization, and phosphorylation dynamics of the RNA polymerase II C-terminal domain in immature pig oocytes, mature oocytes, two-, four-, and eight-cell embryos, and the morula and blastocyst. To this end, we used antibodies specific for the IIa and IIo forms of RNA polymerase II to stain the proteins. Unphosphorylated RNA polymerase II stained strongly in the nuclei of germinal vesicle oocytes, whereas the phosphorylated form of the enzyme was confined to the chromatin of prophase I oocytes. After fertilization, both unphosphorylated and phosphorylated RNA polymerase II began to accumulate in the nuclei of early stage one-cell embryos, and this pattern was maintained through to the blastocyst stage. The results suggest that both porcine oocytes and early embryos are transcriptionally competent, and that transcription of embryonic genes during the first three cell cycles parallels expression of phosphorylated RNA polymerase II.
Oqani, Reza K.,Zhang, Jin Yu,Lee, Min-Gu,Diao, Yun Fei,Jin, Dong-Il Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.6
Fertilization of the oocyte commences embryogenesis during which maternally inherited mRNAs are degraded and the embryonic genome is activated. Transcription of embryonic mRNA is initiated by embryonic genome activation (EGA). RNA polymerase II (RNA Pol II) is responsible for the synthesis of mRNAs and most small nuclear RNAs, and consists of 12 subunits, the largest of which characteristically harbors a unique C-terminal domain (CTD). Transcriptional activity of RNA Pol II is highly regulated, in particular, by phosphorylation of serine residues in the CTD. Here, we have shown the presence of RNA Pol II CTD phosphoisoforms in porcine oocytes and preimplantation embryos. The distribution pattern as well as phosphorylation dynamics in germinal vesicles and during embryogenesis differed in developmental stages with these isoforms, indicating a role of RNA Pol II CTD phosphorylation at the serine residue in transcriptional activation during both oocyte growth and embryonic genome activation. We additionally examined the effects of the RNA Pol II inhibitor, ${\alpha}$-amanitin, on embryo development. Our results show that inhibition of polymerase, even at very early stages and for a short period of time, dramatically impaired blastocyst formation. These findings collectively suggest that the functionality of maternal RNA Pol II, and consequently, expression of early genes regulated by this enzyme are essential for proper embryo development.
Effects of CDK inhibitors on the maturation, transcription, and MPF activity of porcine oocytes
Oqani, Reza K.,Lin, Tao,Lee, Jae Eun,Kim, So Yeon,Kang, Jung Won,Jin, Dong Il Elsevier 2017 Reproductive biology Vol.17 No.4
<P><B>Abstract</B></P> <P>In mammals, cyclin-dependent kinases (CDKs) are involved in regulating both the cell cycle and transcription. Although CDK1 is known to act as the kinase subunit of maturation-promoting factor (MPF), the roles of the other CDKs in mammalian oocyte maturation are not yet understood. Here, we show that inhibition of various CDKs by small molecule inhibitors has different effects on the maturation and transcriptional activity of pig oocytes in vitro. Inhibition of CDK1 did not significantly affect cumulus cell expansion, but its kinase activity was necessary for germinal vesicle breakdown (GVBD). The inhibitions of CDK2, CDK4, or CDK6 had no effect on cumulus expansion or GVBD. The catalytic activity of CDK7 was crucial for GVBD but less important for cumulus expansion, whereas inhibition of CDK9 severely blocked both cumulus cell expansion and GVBD. CDK1, -2, -4, and -6 appeared to be dispensable for nuclear transcription, as their inhibitions did not affect nascent RNA production in oocytes. However, inhibition of CDK7 or CDK9 dramatically decreased the transcriptional activity in oocytes. Finally, we found that the GVBD arrest triggered by CDK9 inhibition was not due to altered MPF activity, but rather the inhibition of transcription. Overall, our results show that CDK7 and CDK9 are important for the nuclear maturation and transcriptional activity of pig oocytes.</P>
General Transcription Factors and Embryonic Genome Activation
Oqani, Reza K.,Kang, Jung Won,Lin, Tao,Lee, Jae Eun,Jin, Dong-Il The Korean Society of Animal Reproduction 2014 Reproductive & developmental biology Vol.38 No.1
Embryonic genome activation (EGA) is a highly complex phenomenon that is controlled at various levels. New studies have ascertained some molecular mechanisms that control EGA in several species; it is apparent that these same mechanisms regulate EGA in all species. Protein phosphorylation, DNA methylation and histone modification regulate transcriptional activities, and mechanisms such as ubiquitination, SUMOylation and microRNAs post-transcriptionally regulate development. Each of these regulations is highly dynamic in the early embryo. A better understanding of these regulatory strategies can provide the possibility to improve the reproductive properties in mammals such as pigs, to develop methods of generating high-quality embryos in vitro, and to find markers for selecting developmentally competent embryos.
Halogenated nucleotide labeling of nascent RNAs reveals dynamic transcription in growing pig oocytes
Oqani, Reza K.,Lee, Min Gu,Diao, Yun Fei,Han, Rong Xun,Jin, Dong Il Wiley‐Liss, Inc. 2013 Developmental dynamics Vol.242 No.1
<P><B>Abstract</B></P><P><B>Background</B>: Germ cells differentiate into oocytes in females and are arrested at the first meiotic prophase. However, during arrest, oocytes undergo a growth phase leading to a dramatic increase in size, which is under control of transcription events. In the current study, we examined the transcriptional activity of growing pig oocytes using an immunocytochemical approach. Our data showed that fluorouridine (FU), a halogenated nucleotide, can be successfully incorporated into synthesizing RNAs and detected using a specific monoclonal antibody. <B>Results</B>: Using this method, we identified dynamic changes in transcriptional activity patterns in growing pig oocytes. Oocytes obtained from small follicles exhibited the highest level of transcription, while at the final phase of growth, transcription was no longer detected. These transcriptional changes were concomitant with chromatin compaction resulting in a tightly packed ring‐like chromatin conformation surrounding the nucleolar structure. Also, FU incorporation appeared sensitive to the biochemical manipulation of transcription, because transcriptional inhibitors induced a decrease in signal intensity from FU labeling and transcriptional activation caused an increase in FU signal intensity. <B>Conclusions</B>: Our data collectively support that a direct link exists between chromatin configuration and transcriptional activity in pig oocytes, and support the suitability of FU for studies on transcription‐related events in mammalian oocytes. Developmental Dynamics 242:16–22, 2013. © 2012 Wiley Periodicals, Inc.</P>