WNT4 EXPRESSION IN OVARIAN GRANULOSA CELL PRECURSORS IS REQUIRED FOR FOLLICLE FORMATION
Notice bibliographique
Résumé
Wnt4 is a small glycoprotein signaling molecule whose importance to the proper embryonic development of the ovary is now well established. However, recent studies have shown that Wnt4 is also expressed in the postnatal mouse ovary, localizing to granulosa cell precursors during follicle formation and subsequently in granulosa cells until preantral stages of follicular development. We have found a similar pattern of ovarian expression for beta-catenin, a Wnt signaling effector that is stabilized and translocates to the nucleus in response to Wnt ligand, suggesting that Wnt4 signals via the “canonical” Wnt/beta-catenin pathway in granulosa cells. While these results demonstrate that Wnt signaling occurs in postnatal ovarian granulosa cells, its physiological roles remain to be defined. Wnt4-null mice could not be used to elucidate the roles of Wnt4 in follicle development, as these die shortly after birth due to developmental kidney defects. A conditional gene targeting approach using Cre-lox technology was therefore devised so as to inactivate Wnt4 in granulosa cell precursors. A mouse strain bearing a floxed Wnt4 allele was created using standard gene targeting techniques, and this allele was found to function normally prior to Cre-mediated recombination. Granulosa cell-specific inactivation of Wnt4 was then achieved by crossing Wnt4 floxed mice with previously-described Amhr2Cre/+ mice, in which Cre transgene expression begins in granulosa cell precursors during the perinatal period. The fertility of the resulting Wnt4flox/−;Amhr2Cre/+ female offspring was assessed by housing them with wild-type males for a six month period. Wnt4flox/−;Amhr2Cre/+ females produced a similar number of litters than control animals lacking the Cre transgene, but average litter size was significantly smaller (3.86 ±0.38 vs 7.16 ±0.64, mean±SEM, n=4 animals/group, P < 0.05). Gross examination of adult Wnt4flox/−;Amhr2Cre/+ ovaries revealed that they were significantly smaller than those from Wnt4flox/− littermates [2.56mg ± 0.25mg (n=18) vs 4.22mg ± 0.39mg (n=10), mean±SEM, P < 0.05]. Histological evaluations showed that all stages of follicular development and corpora lutea could be identified in Wnt4flox/−;Amhr2Cre/+ ovaries, but all were present in lower numbers than in control ovaries. Efficiency of Cre-mediated recombination was assessed by semi-quantitative RT-PCR, and Wnt4 mRNA levels were found to be reduced by 50% on average in Wnt4flox/−;Amhr2Cre/+ ovaries compared to controls, mirroring the reductions in fertility and ovary size. Importantly, a small subset (5–10%) of postpubertal Wnt4flox/−;Amhr2Cre/+ ovaries featured a near-complete abrogation of Wnt4 expression as a result of high-efficiency recombination of the floxed allele. These ovaries were far smaller (<1mg), and contained only a small number of apparently unhealthy primary follicles. Ovaries from older (>6mo) Wnt4flox/−;Amhr2Cre/+ mice with high recombination efficiency were completely devoid of follicles. Based on these findings we propose that Wnt4 expression in granulosa cell precursors is required for follicle formation to occur properly. (poster)
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».