Maternal Oct-4 is a potential key regulator of the developmental competence of mouse oocytes.
BACKGROUND
The maternal contribution of transcripts and proteins supplied to the zygote is crucial for the progression from a gametic to an embryonic control of preimplantation development. Here we compared the transcriptional profiles of two types of mouse MII oocytes, one which is developmentally competent (MIISN oocyte), the other that ceases development at the 2-cell stage (MIINSN oocyte), with the aim of identifying genes and gene expression networks whose misregulated expression would contribute to a reduced developmental competence.


RESULTS
We report that: 1) the transcription factor Oct-4 is absent in MIINSN oocytes, accounting for 2) the down-regulation of Stella, a maternal-effect factor required for the oocyte-to-embryo transition and of which Oct-4 is a positive regulator; 3) eighteen Oct-4-regulated genes are up-regulated in MIINSN oocytes and are part of gene expression networks implicated in the activation of adverse biochemical pathways such as oxidative phosphorylation, mitochondrial dysfunction and apoptosis.


CONCLUSIONS
The down-regulation of Oct-4 plays a crucial function in a sequence of molecular processes that leads to the developmental arrest of MIINSN oocytes. The use of a model study in which the MII oocyte ceases development consistently at the 2-cell stage has allowed to attribute a role to the maternal Oct-4 that has never been described before. Oct-4 emerges as a key regulator of the molecular events that govern the establishment of the developmental competence of mouse oocytes.
Zuccotti
Maurizio
M
Sezione di Istologia ed Embriologia, Dipartimento di Medicina Sperimentale, Universita' degli Studi di Parma, Parma, Italy. maurizio.zuccotti@unipv.it
Merico
Valeria
V
Sacchi
Lucia
L
Bellone
Michele
M
Brink
Thore C
TC
Bellazzi
Riccardo
R
Stefanelli
Mario
M
Redi
Carlo Alberto
CA
Garagna
Silvia
S
Adjaye
James
J
D000818:Animals; D002868:Chromosomal Proteins, Non-Histone; D002970:Cleavage Stage, Ovum / Q000378:metabolism / Q000502:physiology; D016000:Cluster Analysis; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D008677:Metaphase / Q000235:genetics / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D009865:Oocytes / Q000254:growth & development* / Q000378:metabolism; D023121:RNA, Messenger, Stored / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology
D002868:Chromosomal Proteins, Non-Histone; C462180:Dppa3 protein, mouse; D050814:Octamer Transcription Factor-3; D023121:RNA, Messenger, Stored; D012097:Repressor Proteins