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Comparative transcriptomic analysis of follicle-enclosed oocyte maturational and developmental competence acquisition in two non-mammalian vertebrates.

Gohin M, Bobe J, Chesnel F - BMC Genomics (2010)

Bottom Line: We have successfully identified orthologous genes exhibiting conserved expression profiles in the ovarian follicle during late oogenesis in both trout and Xenopus.While some identified genes were previously uncharacterized during Xenopus late oogenesis, the nature of these genes has pointed out molecular mechanisms possibly conserved in amphibians and teleosts.It should also be stressed that in addition to the already suspected importance of steroidogenesis in maturational competence acquisition, our approach has shed light on other regulatory pathways which may be involved in maturational and developmental competence acquisitions that will require further studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNRS/IGDR (UMR 6061), IFR140 GFAS, Université de Rennes I, 2, Avenue du Pr, Léon Bernard, 35043 Rennes Cedex, France. Julien.bobe@rennes.inra.fr.

ABSTRACT

Background: In vertebrates, late oogenesis is a key period during which the oocyte acquires its ability to resume meiosis (i.e. maturational competence) and to develop, once fertilized, into a normal embryo (i.e. developmental competence). However, the molecular mechanisms involved in these key biological processes are far from being fully understood. In order to identify key mechanisms conserved among teleosts and amphibians, we performed a comparative analysis using ovarian tissue sampled at successive steps of the maturational competence acquisition process in the rainbow trout (Oncorhynchus mykiss) and in the clawed toad (Xenopus laevis). Our study aimed at identifying common differentially expressed genes during late oogenesis in both species. Using an existing transcriptomic analysis that had previously been carried out in rainbow trout, candidate genes were selected for subsequent quantitative PCR-based comparative analysis.

Results: Among the 1200 differentially expressed clones in rainbow trout, twenty-six candidate genes were selected for further analysis by real-time PCR in both species during late oogenesis. Among these genes, eight had similar expression profiles in trout and Xenopus. Six genes were down-regulated during oocyte maturation (cyp19a1, cyp17a1, tescalcin, tfr1, cmah, hsd11b3) while two genes exhibited an opposite pattern (apoc1, star). In order to document possibly conserved molecular mechanisms, four genes (star, cyp19a1, cyp17a1 and hsd11b3) were further studied due to their known or suspected role in steroidogenesis after characterization of the orthology relationships between rainbow trout and Xenopus genes. Apoc1 was also selected for further analysis because of its reported function in cholesterol transport, which may modulate steroidogenesis by regulating cholesterol bioavailability in the steroidogenic cells.

Conclusions: We have successfully identified orthologous genes exhibiting conserved expression profiles in the ovarian follicle during late oogenesis in both trout and Xenopus. While some identified genes were previously uncharacterized during Xenopus late oogenesis, the nature of these genes has pointed out molecular mechanisms possibly conserved in amphibians and teleosts. It should also be stressed that in addition to the already suspected importance of steroidogenesis in maturational competence acquisition, our approach has shed light on other regulatory pathways which may be involved in maturational and developmental competence acquisitions that will require further studies.

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apoC1 amino acid sequence alignments among vertebrates. Amino acid sequence alignments between human APOC-I (NP_001636.1, H. sapiens), mouse APOC-I (NP_031495.1, M. musculus), rat APOC-I (NP-036956.1, R. norvegicus), the clawed toad apoC1 (CF547196, X. laevis), tetraodon apoC1 (CAF95503, T. nigroviridis), the gilthead seabream apoc1 (AAT45249.1, S. auratus) and the deduced amino acid sequence of rainbow trout apoC1 (CA353171, O. mykiss). Multiple amino acid sequence alignments were constructed using ClustalW software. The signal peptide is indicated.
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Figure 5: apoC1 amino acid sequence alignments among vertebrates. Amino acid sequence alignments between human APOC-I (NP_001636.1, H. sapiens), mouse APOC-I (NP_031495.1, M. musculus), rat APOC-I (NP-036956.1, R. norvegicus), the clawed toad apoC1 (CF547196, X. laevis), tetraodon apoC1 (CAF95503, T. nigroviridis), the gilthead seabream apoc1 (AAT45249.1, S. auratus) and the deduced amino acid sequence of rainbow trout apoC1 (CA353171, O. mykiss). Multiple amino acid sequence alignments were constructed using ClustalW software. The signal peptide is indicated.

Mentions: Finally, our phylogenetic analysis clearly demonstrated the orthology relationship of rainbow trout and Xenopus ApoC1 genes [see Additional file 5]. At the amino acid level, rainbow trout and Xenopus sequences share 36% of identity. The trout sequence is 23% identical to the human protein, while Xenopus sequence is 29% identical to the human protein (Fig. 5).


Comparative transcriptomic analysis of follicle-enclosed oocyte maturational and developmental competence acquisition in two non-mammalian vertebrates.

Gohin M, Bobe J, Chesnel F - BMC Genomics (2010)

apoC1 amino acid sequence alignments among vertebrates. Amino acid sequence alignments between human APOC-I (NP_001636.1, H. sapiens), mouse APOC-I (NP_031495.1, M. musculus), rat APOC-I (NP-036956.1, R. norvegicus), the clawed toad apoC1 (CF547196, X. laevis), tetraodon apoC1 (CAF95503, T. nigroviridis), the gilthead seabream apoc1 (AAT45249.1, S. auratus) and the deduced amino acid sequence of rainbow trout apoC1 (CA353171, O. mykiss). Multiple amino acid sequence alignments were constructed using ClustalW software. The signal peptide is indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2821372&req=5

Figure 5: apoC1 amino acid sequence alignments among vertebrates. Amino acid sequence alignments between human APOC-I (NP_001636.1, H. sapiens), mouse APOC-I (NP_031495.1, M. musculus), rat APOC-I (NP-036956.1, R. norvegicus), the clawed toad apoC1 (CF547196, X. laevis), tetraodon apoC1 (CAF95503, T. nigroviridis), the gilthead seabream apoc1 (AAT45249.1, S. auratus) and the deduced amino acid sequence of rainbow trout apoC1 (CA353171, O. mykiss). Multiple amino acid sequence alignments were constructed using ClustalW software. The signal peptide is indicated.
Mentions: Finally, our phylogenetic analysis clearly demonstrated the orthology relationship of rainbow trout and Xenopus ApoC1 genes [see Additional file 5]. At the amino acid level, rainbow trout and Xenopus sequences share 36% of identity. The trout sequence is 23% identical to the human protein, while Xenopus sequence is 29% identical to the human protein (Fig. 5).

Bottom Line: We have successfully identified orthologous genes exhibiting conserved expression profiles in the ovarian follicle during late oogenesis in both trout and Xenopus.While some identified genes were previously uncharacterized during Xenopus late oogenesis, the nature of these genes has pointed out molecular mechanisms possibly conserved in amphibians and teleosts.It should also be stressed that in addition to the already suspected importance of steroidogenesis in maturational competence acquisition, our approach has shed light on other regulatory pathways which may be involved in maturational and developmental competence acquisitions that will require further studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNRS/IGDR (UMR 6061), IFR140 GFAS, Université de Rennes I, 2, Avenue du Pr, Léon Bernard, 35043 Rennes Cedex, France. Julien.bobe@rennes.inra.fr.

ABSTRACT

Background: In vertebrates, late oogenesis is a key period during which the oocyte acquires its ability to resume meiosis (i.e. maturational competence) and to develop, once fertilized, into a normal embryo (i.e. developmental competence). However, the molecular mechanisms involved in these key biological processes are far from being fully understood. In order to identify key mechanisms conserved among teleosts and amphibians, we performed a comparative analysis using ovarian tissue sampled at successive steps of the maturational competence acquisition process in the rainbow trout (Oncorhynchus mykiss) and in the clawed toad (Xenopus laevis). Our study aimed at identifying common differentially expressed genes during late oogenesis in both species. Using an existing transcriptomic analysis that had previously been carried out in rainbow trout, candidate genes were selected for subsequent quantitative PCR-based comparative analysis.

Results: Among the 1200 differentially expressed clones in rainbow trout, twenty-six candidate genes were selected for further analysis by real-time PCR in both species during late oogenesis. Among these genes, eight had similar expression profiles in trout and Xenopus. Six genes were down-regulated during oocyte maturation (cyp19a1, cyp17a1, tescalcin, tfr1, cmah, hsd11b3) while two genes exhibited an opposite pattern (apoc1, star). In order to document possibly conserved molecular mechanisms, four genes (star, cyp19a1, cyp17a1 and hsd11b3) were further studied due to their known or suspected role in steroidogenesis after characterization of the orthology relationships between rainbow trout and Xenopus genes. Apoc1 was also selected for further analysis because of its reported function in cholesterol transport, which may modulate steroidogenesis by regulating cholesterol bioavailability in the steroidogenic cells.

Conclusions: We have successfully identified orthologous genes exhibiting conserved expression profiles in the ovarian follicle during late oogenesis in both trout and Xenopus. While some identified genes were previously uncharacterized during Xenopus late oogenesis, the nature of these genes has pointed out molecular mechanisms possibly conserved in amphibians and teleosts. It should also be stressed that in addition to the already suspected importance of steroidogenesis in maturational competence acquisition, our approach has shed light on other regulatory pathways which may be involved in maturational and developmental competence acquisitions that will require further studies.

Show MeSH