The equine oocyte: Factors affecting meiotic and developmental competence

Hinrichs, Katrin

doi:10.1002/mrd.21186

Cited by 56 publications

(54 citation statements)

References 92 publications

(136 reference statements)

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“…The early observation that the process of follicle selection would create subordinate follicles containing more competent oocyte was made in the bovine model [32,35], but over the last decade, similar observations were made especially in mono-ovulating species like the horse [36]. The first question that arises from such observation is why would oocytes from dying follicles be better?…”

Section: The Mystery Of Early Atresiamentioning

confidence: 92%

Follicle environment and quality of in vitro matured oocytes

Sirard

2011

J Assist Reprod Genet

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In mammalian reproduction, the oocyte depends on the ovarian follicle for most of its growth. They form a bipolar partnership and the status of one will impact the functioning of the other. When oocytes are removed from their follicle by ovulation, they have normally completed all the steps required to begin their journey into the oviduct and drive the early embryonic development. When oocytes are removed from their follicle before natural ovulation, the process by which they acquire all the important components for their journey might not be completed and their ability to mature, fertilize or develop into embryos or to term might be compromised. Animal models have been useful to define the important steps required for the oocyte's growth phase, and in the mouse, when the oocyte has reached its full size, the program is ready. This is not the case in larger mammals where the completion of growth does not ensure that the oocyte is fully capable of undergoing all the steps to the embryo and to term. The final steps of oocyte preparation also involve a progressive condensation of the chromatin that may facilitate normal maturation but may also indirectly reduce the lifespan of the oocyte. In such a scenario, the oocyte would have an expiration date when fully competent. In humans, a number of indications may justify the aspiration of oocytes from unstimulated patients and the development of an in vitro maturation (IVM) process that would allow fertilization and subsequent development. This objective could be realized by a better understanding of the essential follicular contribution required before removing the oocyte. Therefore, this review will focus on the large animal models where IVM has been used and studied for more than 25 years. The status of the follicle at the time of oocyte recovery and the status of the oocyte's chromatin will be described in detail as they have a significant impact on the outcome.

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Section: The Mystery Of Early Atresiamentioning

confidence: 92%

Follicle environment and quality of in vitro matured oocytes

Sirard

2011

J Assist Reprod Genet

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“…ICSI has become the method of choice for the fertilization of equine oocytes in the laboratory because of the failure of standard IVF in this species (see Hinrichs (2010)). However, success in equine in vitro embryo production is variable, and few laboratories have reported repeatable blastocyst rates of more than 15% per injected oocyte.…”

Section: Introductionmentioning

confidence: 99%

Cell lineage allocation in equine blastocysts produced in vitro under varying glucose concentrations

et al. 2015

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Equine embryos develop in vitro in the presence of high glucose concentrations, but little is known about their requirements for development. We evaluated the effect of glucose concentrations in medium on blastocyst development after ICSI. In experiment 1, there were no significant differences in rates of blastocyst formation among embryos cultured in our standard medium (DMEM/F-12), which contained O16 mM glucose, and those cultured in a minimal-glucose embryo culture medium (!1 mM; Global medium, GB), with either 0 added glucose for the first 5 days, then 20 mM (0-20) or 20 mM for the entire culture period . In experiment 2, there were no significant differences in the rates of blastocyst development (31-46%) for embryos cultured in four glucose treatments in GB (0-10, 0-20, 5-10, or 5-20). Blastocysts were evaluated by immunofluorescence for lineage-specific markers. All cells stained positively for POU5F1. An inner cluster of cells was identified that included presumptive primitive endoderm cells (GATA6-positive) and presumptive epiblast (EPI) cells. The 5-20 treatment resulted in a significantly lower number of presumptive EPI-lineage cells than the 0-20 treatment did. GATA6-positive cells appeared to be allocated to the primitive endoderm independent of the formation of an inner cell mass, as was previously hypothesized for equine embryos. These data demonstrate that equine blastocyst development is not dependent on high glucose concentrations during early culture; rather, environmental glucose may affect cell allocation. They also present the first analysis of cell lineage allocation in in vitro-fertilized equine blastocysts. These findings expand our understanding of the factors that affect embryo development in the horse.

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“…In fact, the analysis of H4K8, H4K12 and H4K16 acetylation pattern revealed that the progressive chromatin rearrangement from fibrillar to condensed configuration is characterized by a decrease of acetylation at K8 and K12 residues and by an increase of acetylation at K16 residue. These data are of particular interest since the process of chromatin remodeling that precedes the resumption of meiosis has been recognized as a marker of oocyte final differentiation and associated with the acquisition of meiotic and developmental competences (De La Fuente, 2006) in several species, including the horse (Hinrichs and Williams, 1997;Hinrichs and Schmidt, 2000;Dell'Aquila et al, 2001;Hinrichs et al, 2005;Hinrichs, 2010). Histone acetylation has been recognized as one of the mechanisms implicated in GV large-scale chromatin remodeling (De La Fuente et al, 2004;Kageyama et al, 2007) and provides an important epigenetic mechanism for the developmental control of global gene expression (De La Fuente, 2006).…”

Section: Discussionmentioning

confidence: 99%

Changes in histone H4 acetylation during in vivo versus in vitro maturation of equine oocytes

Franciosi

Lodde

Goudet

et al. 2011

MHR: Basic Science of Reproductive Medicine

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Epigenetic modifications are established during gametogenesis and preimplantation embryonic development. Any disturbance of the normal natural environment during these critical phases could cause alterations of the epigenetic signature. Histone acetylation is an important epigenetic modification involved in the regulation of chromatin organization and gene expression. The present study was aimed to determine whether the proper establishment of post-translational histone H4 acetylation at lysine 8 (AcH4K8), 12 (AcH4K12) and 16 (AcH4K16) of equine oocytes is adversely affected during in vitro maturation (IVM) when compared with in vivo matured oocytes collected from naturally cycling mares not undergoing ovarian hyperstimulation. The acetylation patterns were investigated by means of indirect immunofluorescence staining with specific antibodies directed against the acetylated lysine residues. Our results indicate that the acetylation state of H4 is dependent on the chromatin configuration in immature germinal vesicle (GV) stage oocytes and it changes in a residue-specific manner along with the increase of chromatin condensation. In particular, the levels of AcH4K8 and AcH4K12 increased significantly, while AcH4K16 decreased significantly from the fibrillar to the condensed state of chromatin configuration within the GV. Moreover, during meiosis, K8 and K12 were substantially deacetylated without any differences between in vivo and in vitro conditions, while K16 displayed a strong acetylation in oocytes matured in vivo, and in contrast, it was markedly deacetylated following IVM. Although the functional meaning of residue-specific acetylation during oocyte differentiation and meiotic resumption needs further investigation, our results support the hypothesis that IVM conditions can adversely affect oocyte ability to regulate the epigenetic reprogramming, critical for successful meiosis and subsequent embryonic development.

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The equine oocyte: Factors affecting meiotic and developmental competence

Cited by 56 publications

References 92 publications

Follicle environment and quality of in vitro matured oocytes

Follicle environment and quality of in vitro matured oocytes

Cell lineage allocation in equine blastocysts produced in vitro under varying glucose concentrations

Changes in histone H4 acetylation during in vivo versus in vitro maturation of equine oocytes

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