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PLoS One October 22, 2010; 5 (10): e13532.

Aging of Xenopus tropicalis eggs leads to deadenylation of a specific set of maternal mRNAs and loss of developmental potential.

Kosubek A , Klein-Hitpass L , Rademacher K , Horsthemke B , Ryffel GU .

As first shown more than 100 years ago, fertilization of an aged (overripe) egg increases the rate of malformations and embryonic loss in several vertebrates, including possibly humans as well. Since the molecular events in aging eggs may be similar in these species, we established in the frog Xenopus tropicalis a defined protocol for delayed fertilization of eggs. A three-hour delayed fertilization led to a dramatic increase in malformation and mortality. Gene expression profiling revealed that 14% of the polyadenylated maternal transcripts were downregulated upon aging. These transcripts were not degraded, but rather deadenylated as shown for specific maternal mRNAs. The affected transcripts are characterized by a relatively short 3''UTR and a paucity of cytoplasmic polyadenylation elements (CPE) and polyadenylation signals (PAS). Furthermore, maternal mRNAs known to be deadenylated during egg maturation as well as after fertilization were preferentially deadenylated in aged eggs. Taken together our analysis of aging eggs reveals that unfertilized eggs are in a dynamic state that was previously not realized. On the one hand deadenylation of transcripts that are typically deadenylated during egg maturation continues and this implies overripeness of the aged egg in the truest sense of the word. On the other hand transcripts that normally are deadenylated after fertilization loose their poly(A) in the aged egg and this implies that the egg awaiting fertilization starts processes that are normally only observed after fertilization. Based on our novel finding we postulate that the imbalance of the polyadenylated maternal transcripts upon egg aging contributes to the loss of developmental potential. Based on this hypothesis the developmental consequences of downregulation of specific transcripts can be analyzed in future.

PubMed ID: 21042572
PMC ID: PMC2962626
Article link: PLoS One

Species referenced: Xenopus
Genes referenced: atp5f1a eno1 mrpl22 nop58 pelo sdhb slc34a2 tpi1 tubb2b ube2k

GEO Series: GSE21109: NCBI

Article Images: [+] show captions
References [+] :
Aegerter, Messenger RNA stockpile of cyclin B, insulin-like growth factor I, insulin-like growth factor II, insulin-like growth factor receptor Ib, and p53 in the rainbow trout oocyte in relation with developmental competence. 2003, Pubmed