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Development of Laser Capture Microdissection to study the gene expression of the sheep early ovarian folliculogenesis

ABSTRACT: Background Correct achievement of early ovarian folliculogenesis is a crucial phase for further ovarian function. This process is closely regulated by cell-cell interactions and coordinated expression of genes from oocyte and granulosa cells. But, despite of the large number of studies, little is known about the precise gene expression patterns driving early folliculogenesis. The experimental limitations concerned the very small size of these follicles and the mixture of the different developmental stages within an ovary that make the study of isolated follicular components much more difficult. The recently developed laser capture microdissection (LCM) technique coupled with microarrays experiments is promising in addressing the molecular specificity of each follicular compartment. Nevertheless, the isolation of unique cells or group of cells is still challenging to maintain RNA quality during this process and to obtain sufficient amount of RNA. In this study, we described a method allowing the analysis of oocyte and granulosa cells gene expression during the first stages of sheep early folliculogenesis. Results First we developed a new fixation protocol using a frizzed 70% ethanol fixation solution that ensures correct single cell capture and RNA integrity during microdissection time. After LCM capture of the compartments and follicular stages, RNA extraction and amplification, the expression of 6 oocyte-specific genes (SOHLH2, MAEL, MATER, VASA, GDF9, BMP15) and 3 granulosa cell-specific genes (KITLG, GATA4, AMH) confirmed the purity of the samples and documented their ovine expression profiles. Then, using bovine Affymetrix chip, we identified for the first time, a global gene expression for each follicular compartment during early developmental stages. Particularly the granulosa cell data set is quite unique. 1050 granulosa cell specific transcripts compared to oocyte and 759 oocyte specific transcripts were detected. The analysis of the expression of 2 genes (SIRT7, FST) confirmed this specificity of expression. Finally, the integration of the data stated the 3 main physiological events involved in early folliculogenesis and provided descriptive elements that confirmed the relevance and the potential of the LCM-derived RNAs. Conclusions This method should contribute through an additional genome wide expression profiling to give insights on molecular mechanisms involved in stage transitions and cell type interplays.

ORGANISM(S): Bos taurus Ovis aries

PROVIDER: GSE25652 | GEO | 2011/07/01

SECONDARY ACCESSION(S): PRJNA133909

REPOSITORIES: GEO

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Project description:Background Correct achievement of early ovarian folliculogenesis is a crucial phase for further ovarian function. This process is closely regulated by cell-cell interactions and coordinated expression of genes from oocyte and granulosa cells. But, despite of the large number of studies, little is known about the precise gene expression patterns driving early folliculogenesis. The experimental limitations concerned the very small size of these follicles and the mixture of the different developmental stages within an ovary that make the study of isolated follicular components much more difficult. The recently developed laser capture microdissection (LCM) technique coupled with microarrays experiments is promising in addressing the molecular specificity of each follicular compartment. Nevertheless, the isolation of unique cells or group of cells is still challenging to maintain RNA quality during this process and to obtain sufficient amount of RNA. In this study, we described a method allowing the analysis of oocyte and granulosa cells gene expression during the first stages of sheep early folliculogenesis. Results First we developed a new fixation protocol using a frizzed 70% ethanol fixation solution that ensures correct single cell capture and RNA integrity during microdissection time. After LCM capture of the compartments and follicular stages, RNA extraction and amplification, the expression of 6 oocyte-specific genes (SOHLH2, MAEL, MATER, VASA, GDF9, BMP15) and 3 granulosa cell-specific genes (KITLG, GATA4, AMH) confirmed the purity of the samples and documented their ovine expression profiles. Then, using bovine Affymetrix chip, we identified for the first time, a global gene expression for each follicular compartment during early developmental stages. Particularly the granulosa cell data set is quite unique. 1050 granulosa cell specific transcripts compared to oocyte and 759 oocyte specific transcripts were detected. The analysis of the expression of 2 genes (SIRT7, FST) confirmed this specificity of expression. Finally, the integration of the data stated the 3 main physiological events involved in early folliculogenesis and provided descriptive elements that confirmed the relevance and the potential of the LCM-derived RNAs. Conclusions This method should contribute through an additional genome wide expression profiling to give insights on molecular mechanisms involved in stage transitions and cell type interplays. The 2 ovine follicular compartments (i.e. granulosa cells (G) and oocytes (O) were captured using LCM technology for each early stage (primordial (Pd), primary (Pm), secondary (Sec) follicles. The RNA of each group was extracted using Picopure RNA Isolation kit (Arcturus) and subjected to 2 round T7 amplification (RiboAmp®HS PLUS kit, Arcturus). Ovine microarray experiments were performed using the Affymetrix Bovine Expression Array. First the quality of the cross-species hybridizations was checked by comparison of hybridization data of ovine fetal ovary RNA with bovine fetal ovary ones, generated with the Affymetrix standard protocol (protocole 1). Then, three biotin-labeling protocols were compared from ovine fetal ovary total RNA: protocol 1; protocol 2 (Biotin-labeled cRNAs were synthesized following Affymetrix protocol using the second-round cDNAs from RiboAmp®HS kit as templates); protocol 3 (Arcturus biotin turboTM labeling kit from aRNA after the 2 round amplification using RiboAmp®HS kit). Last , one LCM-derived aRNA sample of each group was labeled using the Arcturus biotin turboTM labeling kit (protocol 3) and hybridized to Affymetrix Bovine Expression arrays. Images were interpreted using Microarray Suite version 5.0 (MAS 5.0) in GCOS with scaling (100) and without normalization.

Project description:In mammals, the capacity of the female germ cell, the oocyte, to develop into embryo is acquired throughout meiotic maturation. Immature oocyte cannot be fertilized while mature oocyte is apt to accept spermatozoa and to develop an embryo. In a follicle, the oocyte is surrounded by mural granulosa cells (GC) and is physically and metabolically coupled with specialized granulosa cumulus cells (CC) which play an important role in oocyte maturation and fertilization. Factors expressing in GC and CC during maturation may reflect the oocyte quality, i.e. its capacity to be fertilized and assure early embryo development. However, the modifications of the content and the amount of peptide/proteins in the oocyte and the surrounding CC during oocyte maturation are mostly unknown and so there is not an accurate way of evaluating/monitoring how different in vitro maturation (IVM) protocols being in use in assisted reproduction technologies, can affect the process. In this context, Intact Cell MALDI-TOF Mass Spectrometry (ICM-MS) was applied to bovine follicular cells (bovine single oocytes, cumulus cells and granulosa cells) in order to characterize proteomic changes that occur in the follicle during female gamete development. In order to characterize finely endogenous molecular species observed on ICM-MS profiles and to identify markers of interest with their post-translational modifications, we carried out top-down proteomic on the different follicular cells from oocyte, oocyte-cumulus complexes, cumulus cells and granulosa cells protein extracts. Prior to top-down MS using a dual linear ion trap Fourier Transform Mass Spectrometer LTQ Orbitrap Velos, depending on the amount of available biological material, we employed three analytic strategies as a direct infusion, a mono-dimensional liquid chromatography (µLC-1D-MS/MS) and an off-line multi-dimensional liquid chromatography combining four fractionations (based on reverse phase or gel filtration LC) to µLC-MS/MS. Here, we deposited our dataset from µLC-1D-MS/MS (analyses of oocytes, oocyte-cumulus complexes, cumulus cells and granulosa cells protein extracts) and MDLC-MS/MS (analyses of granulosa cells protein extract).

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Development of Laser Capture Microdissection to study the gene expression of the sheep early ovarian folliculogenesis

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