The egg-to-embryo transition entails transforming a highly differentiated oocyte into totipotent blastomeres, and represents one of the earliest obstacles that must be successfully hurdled for continued development. Degradation of maternal mRNAs (which initiates during oocyte maturation) and reprogramming gene expression (which is clearly evident in 2-cell embryos) lie at the heart of this transition. The overarching objective of the proposed studies is to use mouse as a model system to gain deeper insights into the molecular basis for each of these underlying events, i.e., degradation of maternal mRNA and reprogramming gene expression. An apparently universal feature of the egg-to-embryo transition is degradation of maternal mRNAs either during maturation or shortly after fertilization/genome activation. How mRNAs are degraded is gaining increased attention because mRNA degradation is highly regulated. Moreover, there is growing consensus that degradation of maternal mRNA is essential for the egg-to-embryo transition.
Specific Aim 1 will test the hypothesis that recruitment of maternal mRNAs encoding DCP1A &2 results in the 5'mRNA degradation pathway as the dominant pathway. The proposed studies will also define the role of the maturation-associated phosphorylation of DCP2 in mRNA degradation. Results of these studies will provide a detailed understanding of degradation of maternal mRNAs during the course of oocyte maturation. How reprogramming of gene expression occurs and uses a maternally inherited transcription apparatus remains enigmatic.
Specific Aim 2 will test the hypothesis that recruitment during oocyte maturation of mRNAs encoding chromatin remodelers and transcription factors is essential for reprogramming gene expression. Results of these studies will likely provide a simple and elegant solution to this problem. Post-transcriptional mechanisms are rapidly gaining attention as a major locus of regulation of gene expression, and in particular, the role of microRNAs (miRNA) in mRNA degradation. Although oocytes express a plethora of miRNAs, as well as mediators of their function, miRNA activity that leads to mRNA degradation functions poorly in oocytes and inhibiting miRNA biogenesis has no marked effect on oocyte and preimplantation development.
Specific Aim 3 will identify the molecular basis for failure of miRNAs to promote degradation of their target mRNAs in oocytes. Understanding the basis for this failure will shed further light on the role of small RNAs in oocyte development. Taken together, results of the proposed studies will generate a detailed understanding of two critical processes that underly the egg-to- embryo transition, i.e., maternal mRNA degradation and reprogramming gene expression.

Public Health Relevance

The proposed studies will provide new information regarding molecular mechanisms underlying the egg-to- embryo transition. The results of these studies will provide further insights into how eggs develop into early embryos, and thereby impact the treatment of human infertility and assisted reproduction technologies.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
2R01HD022681-26A1
Application #
8502932
Study Section
Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
Program Officer
Ravindranath, Neelakanta
Project Start
1987-09-01
Project End
2018-04-30
Budget Start
2013-07-01
Budget End
2014-04-30
Support Year
26
Fiscal Year
2013
Total Cost
$314,841
Indirect Cost
$114,841
Name
University of Pennsylvania
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Ma, Jun; Fukuda, Yusuke; Schultz, Richard M (2015) Mobilization of Dormant Cnot7 mRNA Promotes Deadenylation of Maternal Transcripts During Mouse Oocyte Maturation. Biol Reprod 93:48
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Ma, Pengpeng; de Waal, Eric; Weaver, Jamie R et al. (2015) A DNMT3A2-HDAC2 Complex Is Essential for Genomic Imprinting and Genome Integrity in Mouse Oocytes. Cell Rep 13:1552-60
Liu, W; Stein, P; Cheng, X et al. (2014) BRD4 regulates Nanog expression in mouse embryonic stem cells and preimplantation embryos. Cell Death Differ 21:1950-60

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