Prior to release from the ovary oocytes (eggs, ova) are arrested at an early stage of the first meiotic division as a primary oocyte (primordial follicle). Following puberty, during each menstrual cycle, pituitary gonadotrophin stimulates completion of meiosis 1 the day before ovulation. Early oocytes are also classified as immature (germinal vesicle (GV) or metaphase I (MI) stage). The breakdown of the germinal vesicle indicates a resumption of meiosis and the extrusion of the first polar body (1 PB) indicates completion of the first meiotic division in human oocytes.
- In an adult human female the development of a primordial follicle containing an oocyte to a preovulatory follicle takes in excess of 120 days.
- Genital Links: Introduction | Lecture - Medicine | Lecture - Science | Online Practical | Primordial Germ Cell | Meiosis | Female | Ovary | Oocyte | Uterus | Vagina | Male | Testis | Spermatozoa | Prostate | Genital Movies | Abnormalities | Assisted Reproductive Technology | Puberty | Category:Genital
Some Recent Findings
|More recent papers|
References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.
Amanda Charlesworth, Hedda A Meijer, Cornelia H de Moor Specificity factors in cytoplasmic polyadenylation. Wiley Interdiscip Rev RNA: 2013, 4(4);437-61 PMID:23776146 Bo Zhao, Yi-Xian Cun, Xie-Chao He, Ping Zheng [Maternal-effect Floped gene is essential for the derivation of embryonic stem cells in mice]. Zool. Res.: 2013, 34(3);E82-6 PMID:23776005 Alicia R Timme-Laragy, Jared V Goldstone, Barry R Imhoff, John J Stegeman, Mark E Hahn, Jason M Hansen Glutathione redox dynamics and expression of glutathione-related genes in the developing embryo. Free Radic. Biol. Med.: 2013; PMID:23770340 Jordi Roca, Maria J Martinez-Alborcia, Maria A Gil, Inmaculada Parrilla, Emilio A Martinez Dead spermatozoa in raw semen samples impair in vitro fertilization outcomes of frozen-thawed spermatozoa. Fertil. Steril.: 2013; PMID:23768987 Daniela Paes Almeida Ferreira Braga, Amanda S Setti, Rita de Cássia S Figueira, Rogério Bonassi Machado, Assumpto Iaconelli, Edson Borges Influence of oocyte dysmorphisms on blastocyst formation and quality. Fertil. Steril.: 2013; PMID:23768986
A human infant ovary histology, showing the large number of oocytes occupying the ovary cortical region. Compare this with a mature ovary and note the absence of any follicle development in the infant. These early oocytes remain at the diplotene stage of the meiosis I during development from fetal life and postnatal childhood, until puberty when the lutenizing hormone (LH) surges stimulate the resumption of meiosis.
The graph below shows the changes in human germ cell numbers in the ovary with age, peaking at about 7 million (occuring in early fetal development) and then decreasing by apopotic cell death. At puberty there remain only about 400,000 and only about 10% of these will be released through reproductive life. (More? Menstrual Cycle)
Human ovary non-growing follicle model
In females, the total number of eggs ever to be produced are present in the newborn female initially arrested at the diplotene stage of the meiosis I from fetal life through childhood until puberty, when the lutenizing hormone (LH) surges stimulate the resumption of meiosis.
- All eggs are arrested at an early stage (prophase I) of the first meiotic division as a primary oocyte (primordial follicle). Following purberty, during each menstrual cycle, pituitary gonadotrophin stimulates completion of meiosis 1 the day before ovulation.
- In meiosis 1, a diploid cell becomes 2 haploid (23 chromosomes) daughter cells, each chromosome has two chromatids. One cell becomes the secondary oocyte the other cell forms the first polar body.
- The secondary oocyte then commences meiosis 2 which arrests at metaphase and will not continue without fertilization.
- At fertilization meiosis 2 completes, forming a second polar body. Note that the first polar body may also undergo this process forming a third polar body.
- Links: Cell Division - Meiosis
The breakdown of the germinal vesicle indicates a resumption of meiosis and the extrusion of the first polar body (1 PB) indicates completion of the first meiotic division in human oocytes. The polar body is a small cytoplasmic exclusion body formed to enclose the excess DNA formed during the oocyte (egg) meiosis and following sperm fertilization. There are 2-3 polar bodies derived from the oocyte present in the zygote, the number is dependent upon whether polar body 1 (the first polar body formed during meiosis 1) divides during meiosis 2. This exclusion body contains the excess DNA from the reductive division (the second and third polar bodies are formed from meiosis 2 at fertilization). These polar bodies do not contribute to the future genetic complement of the zygote, embryo or fetus.
Recent research in some species suggest that the space formed by the peripheral polar body (between the oocyte and the zona pellucia) can influence the site of spermatozoa fertilization.
Polar Body Extrusion Model
The following cartoon model from mouse oocyte study of polar body extrusion, involving cortical cap protrusion and spindle midzone-induced membrane furrowing.
Assisted reproductive techniques involving intracytoplasmic sperm injection (ICSI) have looked at the "quality" of the polar body and found that the morphology is related to mature oocyte viability and has the potential to predict oocyte fertilization rates and pregnancy achievement.
- Links: Meiosis
Oocyte calcium ion (Ca2+) release occurs after spermatozoa fusion and is part of the reactivation of meiosis (arrested at metaphase II) and the primary block to polyspermy. Earlier in oocyte meiosis, between prophase I (germinal vesicle stage) and MII, this release mechanism is developed within the cell.
Oocyte cytoplasmic changes include:
- endoplasmatic reticulum reorganization.
- IP3 receptor increase in both number and sensitivity.
- increase in calcium ion concentration.
The release of cortical granules by exocytosis, the "cortical reaction", occurs following spermatozoa fertilisation and is the main block to polyspermy by modifying the zone pellucida. These granules develop from the golgi apparatus initially forming smaller vesicles that coalesce to form mature membrane bound cortical granules (0.2 to 0.6 microns in diameter) located in the cortex of unfertilized oocytes. In mammals, cortical granule production in the developing follicular oocyte is an ongoing and continuous process, with newly synthesized granules translocating to the cortex until the time of ovulation.
- vary in time of initial development between species.
- primordial follicle stage - rat and mouse.
- primary follicle stage - human, monkey, hamsters, and rabbit.
- vary in type formed in the same species.
- migration requires the microfilaments of the cell cytoskeleton.
- are evenly distributed in the cortex of unfertilised oocytes.
- contain carbohydrates, proteinases, ovoperoxidase, calreticulin, N-acetylglucosaminidase
Oocyte-Follicle Cell Interaction
The oocyte and the surrounding granulosa cells have a complex paracrine interactions during follicle growth and development. Oocyte maturation has been shown to depend on secretory products of both the granulosa and cumulus cells.
- promotes granulosa cell proliferation in preantral and antral follicles (GDF-9, BMP15)
- cumulus expansion and granulosa cell differentiation are dependent upon oocyte-derived factors
- BMP15 inhibits FSH-stimulated progesterone production
Oocyte Different Species
Oocyte Protein Expression
The table above shows the pattern of protein expression (as percentages of total) in the mouse germinal vesicle and MII oocyte according to 14 molecular function categories.
- Links: Germinal vesicle oocyte protein expression | MII oocyte protein expression | Zygote Protein Expression | Mouse Development | Oocyte Development | Zygote
Oocyte Telomerase Reverse Transcriptase
There is a redistribution of the enzyme that regulates telomere length during oocyte development. The following oocyte images are from a recent study of sheep in vitro follicle development.
|early antral||preovulatory follicle|
- TERT - Red (Cy3-conjugated secondary antibody) (telomerase reverse transcriptase, TERT)
- DNA - Green (SYBR Green 14/I)
- Sheep Oocyte TERT: preantral | early antral | early antral | preovulatory follicle | Oocyte Development | Sheep Development
Meiotic non-disjunction resulting in aneuploidy, most are embryonic lethal and not seen. The potential for genetic abnormalities increase with maternal age.
- Autosomal chromosome aneuploidy
- Sex chromosome aneuploidy
- monosomy X - Turner's Syndrome
- trisomy X - Triple-X syndrome
- 47 XXY - Klinefelter's Syndrome
- ↑ Yvonne A R White, Dori C Woods, Yasushi Takai, Osamu Ishihara, Hiroyuki Seki, Jonathan L Tilly Oocyte formation by mitotically active germ cells purified from ovaries of reproductive-age women. Nat. Med.: 2012, 18(3);413-21 PMID:22366948
- ↑ W Hamish B Wallace, Thomas W Kelsey Human ovarian reserve from conception to the menopause. PLoS ONE: 2010, 5(1);e8772 PMID:20111701
- ↑ Qiong Wang, Catherine Racowsky, Manqi Deng Mechanism of the chromosome-induced polar body extrusion in mouse eggs. Cell Div: 2011, 6();17 PMID:21867530 | PMC3179692 | Cell Div.
- ↑ T Ebner, C Yaman, M Moser, M Sommergruber, O Feichtinger, G Tews Prognostic value of first polar body morphology on fertilization rate and embryo quality in intracytoplasmic sperm injection. Hum. Reprod.: 2000, 15(2);427-30 PMID:10655316
- ↑ Johnny S Younis, Orit Radin, Ido Izhaki, Moshe Ben-Ami Does first polar body morphology predict oocyte performance during ICSI treatment? J. Assist. Reprod. Genet.: , 26(11-12);561-7 PMID:19960239 | PMC2799563
- ↑ Shufang Wang, Zhaohui Kou, Zhiyi Jing, Yu Zhang, Xinzheng Guo, Mengqiu Dong, Ian Wilmut, Shaorong Gao Proteome of mouse oocytes at different developmental stages. Proc. Natl. Acad. Sci. U.S.A.: 2010, 107(41);17639-44 PMID:20876089 | PNAS
- ↑ Barbara Barboni, Valentina Russo, Sandra Cecconi, Valentina Curini, Alessia Colosimo, Maria Luigia A Garofalo, Giulia Capacchietti, Oriana Di Giacinto, Mauro Mattioli In vitro grown sheep preantral follicles yield oocytes with normal nuclear-epigenetic maturation. PLoS ONE: 2011, 6(11);e27550 PMID:22132111 | PLoS One.
Rong Li, David F Albertini The road to maturation: somatic cell interaction and self-organization of the mammalian oocyte. Nat. Rev. Mol. Cell Biol.: 2013, 14(3);141-52 PMID:23429793
Min Liu The biology and dynamics of mammalian cortical granules. Reprod. Biol. Endocrinol.: 2011, 9();149 PMID:22088197
- oolemma - (zona pellucida, vitelline membrane)
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Cite this page:
Hill, M.A. (2013) Oocyte Development. Retrieved June 19, 2013, from http://php.med.unsw.edu.au/embryology/index.php?title=Oocyte_Development
- Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G