The early development of many animals relies on the posttranscriptional regulations of maternally stored mRNAs. In particular, the translation of maternal mRNAs is tightly controlled during oocyte maturation and early mitotic cycles in Xenopus . The Embryonic Deadenylation ElemeNt (EDEN) and its associated protein EDEN-BP are known to trigger deadenylation and translational silencing to several mRNAs bearing an EDEN. This Xenopus RNA-binding protein is an ortholog of the human protein CUG-BP1/CELF1. Five mRNAs, encoding cell cycle regulators and a protein involved in the notch pathway, have been identified as being deadenylated by EDEN/EDEN-BP. To identify new EDEN-BP targets, we immunoprecipitated EDEN-BP/mRNA complexes from Xenopus tropicalis egg extracts. We identified 153 mRNAs as new binding targets for EDEN-BP using microarrays. Sequence analyses of the 3′ untranslated regions of the newly identified EDEN-BP targets reveal an enrichment in putative EDEN sequences. EDEN-BP binding to a subset of the targets was confirmed both in vitro and in vivo . Among the newly identified targets, Cdk1, a key player of oocyte maturation and cell cycle progression, is specifically targeted by its 3′ UTR for an EDEN-BP-dependent deadenylation after fertilization.

Cytoplasmic control of the adenylation state of mRNAs is a critical post-transcriptional process involved in the regulation of mRNAs stability and translational efficiency. The early development of Xenopus laevis has been a major model for the study of such regulations. We describe here a microarray analysis to identify mRNAs that are regulated by changes in their adenylation state during oogenesis and early development of the diploid frog Xenopus tropicalis. The microarray data were validated using qRT–PCR and direct analysis of the adenylation state of endogenous maternal mRNAs during the period studied. We identified more than 500 mRNAs regulated at the post-transcriptional level among the 3000 mRNAs potentially detected by the microarray. The mRNAs were classified into nine different adenylation behavior categories. The various adenylation profiles observed during oocyte maturation and early development and the analyses of 3′-untranslated region sequences suggest that previously uncharacterized sequence elements control the adenylation behavior of the newly identified mRNAs. These data should prove useful in identifying mRNAs with important functions during oocyte maturation and early development.

The U6 snRNA, the core catalytic component of the spliceosome, is extensively modified post-transcriptionally, with 2’-O-methylation being most common. However, how U6 2’-O-methylation is regulated remains largely unknown. Here we report that TFIP11, the human homolog of the yeast spliceosome disassembly factor Ntr1, localizes to nucleoli and Cajal Bodies and is essential for the 2’-O-methylation of U6. Mechanistically, we demonstrate that TFIP11 knockdown reduces the association of U6 snRNA with fibrillarin and associated snoRNAs, therefore altering U6 2′-O-methylation. We show U6 snRNA hypomethylation is associated with changes in assembly of the U4/U6.U5 tri-snRNP leading to defects in spliceosome assembly and alterations in splicing fidelity. Strikingly, this function of TFIP11 is independent of the RNA helicase DHX15, its known partner in yeast. In sum, our study demonstrates an unrecognized function for TFIP11 in U6 snRNP modification and U4/U6.U5 tri-snRNP assembly, identifying TFIP11 as a critical spliceosome assembly regulator.

The specific interactions between RNA-binding proteins and their target RNAs are an essential level to control gene expression. By combining ultra-violet cross-linking and immunoprecipitation (CLIP) and massive SoliD sequencing we identified the RNAs bound by the RNA-binding protein CELF1, in human HeLa cells. The CELF1 binding sites deduced from the sequence data allow characterizing specific features of CELF1-RNA association. We present therefore the first map of CELF1 binding sites in human cells.

Unlike mammals, some nonmammalian species recruit Müller glia for retinal regeneration after injury. Identifying the underlying mechanisms may help to foresee regenerative medicine strategies. Using a Xenopus model of retinitis pigmentosa, we found that Müller cells actively proliferate upon photoreceptor degeneration in old tadpoles but not in younger ones. Differences in the inflammatory microenvironment emerged as an explanation for such stage dependency. Functional analyses revealed that enhancing neuroinflammation is sufficient to trigger Müller cell proliferation, not only in young tadpoles but also in mice. In addition, we showed that microglia are absolutely required for the response of mouse Müller cells to mitogenic factors while negatively affecting their neurogenic potential. However, both cell cycle reentry and neurogenic gene expression are allowed when applying sequential pro- and anti-inflammatory treatments. This reveals that inflammation benefits Müller glia proliferation in both regenerative and nonregenerative vertebrates and highlights the importance of sequential inflammatory modulation to create a regenerative permissive microenvironment.