GO:0042698 ovulation cycle: Reproductive Cycle Regulation, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0042698 (ovulation cycle) describes the recurring sexual cycle in females, often with regular physiologic changes in the endometrium during reproductive years.
• The ovulation cycle encompasses follicular development, ovulation, luteal function, and menstrual or estrous bleeding, and is regulated by hypothalamic-pituitary-ovarian hormones.
• Ovulation side and cycle characteristics vary among normally fertile women, with right-sided ovulation more frequent in some studies.
• Salivary cortisol awakening response can vary with menstrual cycle phase and ovulation, linking stress axis to reproductive cycling.
• Ovulation can be induced or triggered in assisted reproduction, for example with hCG in natural frozen-thawed embryo transfer cycles.
• Comparative studies in medaka fish, cats, and jennies reveal conserved and species-specific features of ovulation cycles.
Description
The ovulation cycle (GO:0042698) is the recurring sexual cycle in females, characterized by physiologic changes in the endometrium that recur at regular intervals during reproductive years. This biological process is fundamental to female fertility and encompasses a coordinated series of hormonal and ovarian events that culminate in the release of a mature oocyte. Understanding the ovulation cycle is essential for reproductive biology, clinical infertility management, and comparative physiology across species. In humans, the menstrual cycle is the most familiar example, but ovulation cycles also occur in other mammals and even in some fish, such as the medaka, where ovulation follows a light-dependent daily cycle. The cycle is not merely a local ovarian phenomenon; it integrates hypothalamic, pituitary, and ovarian signals, and it can be influenced by stress, as shown by the relationship between menstrual cycle phase and the salivary cortisol awakening response. Clinically, ovulation cycle characteristics such as ovulation side and cycle regularity have been studied in normally fertile women, revealing that right-sided ovulation is more common and that cycle length and ovulation side may vary. In assisted reproduction, understanding the natural cycle is critical for timing embryo transfer, and spontaneous ovulation versus hCG triggering has been compared in frozen-thawed embryo transfer cycles. Comparative studies in domestic species, including the queen cat and the Catalonian jenny, provide additional insights into estrous cycle characteristics and ovulation prediction. Thus, GO:0042698 represents a central process in reproductive physiology with broad implications for fertility, stress physiology, and veterinary medicine.
ovulation cycle At A Glance
| GO ID | GO:0042698 |
|---|---|
| GO term | ovulation cycle |
| Ontology | biological_process |
| Synonym | None listed |
| Definition | The type of sexual cycle seen in females, often with physiologic changes in the endometrium that recur at regular intervals during the reproductive years. |
| Major function | Coordination of cyclic ovarian and endometrial changes leading to ovulation and preparation for pregnancy. |
| Related processes | Follicular development, ovulation, luteal phase, menstruation or estrus. |
| Key regulators | Hypothalamic-pituitary-ovarian axis, gonadotropins, steroid hormones. |
| Taxonomic scope | Female animals, including humans, other mammals, and some fish. |
What Is GO:0042698?
According to the Gene Ontology, GO:0042698 (ovulation cycle) is defined as the type of sexual cycle seen in females, often with physiologic changes in the endometrium that recur at regular intervals during the reproductive years. In other words, it is the recurring, hormonally driven cycle that prepares the female reproductive tract for potential pregnancy and includes ovulation, the release of a mature egg from the ovary. This term captures the cyclical nature of female reproductive physiology, including the endometrial changes that occur in menstruating species. It is a biological process that spans multiple organ systems and is regulated by complex neuroendocrine feedback loops.
Why Is ovulation cycle Important in Cell Biology?
The ovulation cycle is important because it is the foundation of female fertility and reproductive health. Disruptions in this cycle can lead to infertility, menstrual disorders, and other reproductive pathologies. Understanding the ovulation cycle also has implications for stress physiology, as the salivary cortisol awakening response varies with menstrual cycle phase and ovulation. In clinical practice, knowledge of ovulation cycle characteristics helps in diagnosing ovulatory disorders and in optimizing assisted reproductive technologies, such as timing frozen-thawed embryo transfer. Comparative studies across species, including the medaka fish, cat, and jenny, reveal conserved mechanisms and species-specific adaptations that inform evolutionary and veterinary reproductive biology. Moreover, the ovulation cycle serves as a model for studying hormonal regulation and cyclic tissue remodeling, which are relevant to broader fields such as endocrinology and cancer biology.
• Essential for female fertility and successful reproduction.
• Disruptions can cause infertility, irregular menstruation, and endocrine disorders.
• Provides a model for studying cyclic hormonal regulation and tissue remodeling.
• Influences stress axis activity, as shown by cortisol awakening response changes across the menstrual cycle.
• Critical for timing assisted reproductive procedures like frozen-thawed embryo transfer.
• Comparative studies in medaka, cats, and jennies reveal conserved and divergent mechanisms.
• Ovulation side and cycle characteristics have been documented in normally fertile women, informing clinical expectations.
• Menstrual cycle changes with age, as highlighted in studies of the menstrual cycle's SWAN song.
• Ovulation induction protocols, such as stair-step clomiphene citrate, rely on understanding cycle dynamics.
• Veterinary reproduction management depends on accurate prediction of ovulation in species like the jenny.
What Happens During ovulation cycle?
Follicular Phase and Follicular Development
In simple terms: The cycle starts with the growth of eggs in the ovary, preparing one to be released.
The follicular phase begins with the recruitment of a cohort of ovarian follicles, one of which becomes dominant. Under the influence of follicle-stimulating hormone (FSH), the dominant follicle grows and produces estradiol, which thickens the endometrium. This phase varies in length among individuals and species. In normally fertile women, cycle characteristics such as ovulation side have been studied, showing that right-sided ovulation is more frequent. In the queen cat, estrous cycle characteristics and ovulation prediction have been described, highlighting species differences. In the medaka fish, ovulation occurs in a light-dependent daily cycle, demonstrating environmental regulation of follicular maturation.
Ovulation
In simple terms: The mature egg is released from the ovary.
Ovulation is the rupture of the dominant follicle and release of the oocyte. It is triggered by a surge in luteinizing hormone (LH), which is induced by peak estradiol levels. The side of ovulation can vary between cycles; in normally fertile women, right-sided ovulation is more common, but the side can alternate. In assisted reproduction, ovulation can be triggered artificially with human chorionic gonadotropin (hCG) in natural cycle frozen-thawed embryo transfer, as compared with spontaneous ovulation. In the medaka fish, ovulation is tightly regulated by the daily light cycle, showing that environmental cues can entrain ovulation timing.
Luteal Phase and Corpus Luteum Formation
In simple terms: After the egg is released, the remaining follicle becomes a gland that produces hormones to support a possible pregnancy.
After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. Progesterone prepares the endometrium for implantation and maintains early pregnancy if fertilization occurs. If pregnancy does not occur, the corpus luteum regresses, leading to a drop in progesterone and shedding of the endometrium (menstruation in humans) or a return to estrus in other species. The luteal phase is relatively constant in length within a species. In the context of assisted reproduction, the natural cycle for frozen-thawed embryo transfer relies on the corpus luteum from spontaneous ovulation or is supported by exogenous hormones when ovulation is triggered.
Menstruation or Estrus
In simple terms: If pregnancy does not happen, the uterine lining is shed or the animal returns to heat.
In menstruating species, including humans, the fall of progesterone causes shedding of the endometrial lining, resulting in menstruation. In non-menstruating mammals, such as cats and jennies, the cycle returns to estrus without significant bleeding. The menstrual cycle's changes with age, including the transition to menopause, have been described as the 'SWAN song'. In the queen cat, the estrous cycle is characterized by specific behavioral and physiological signs, and ovulation prediction is important for breeding management. In the Catalonian jenny, estrous cycle characteristics and prediction of ovulation have been studied to optimize reproductive efficiency.
Hormonal Regulation and Feedback
In simple terms: Hormones from the brain and ovary talk to each other to keep the cycle running.
The ovulation cycle is regulated by the hypothalamic-pituitary-ovarian axis. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the pituitary to release FSH and LH. These gonadotropins act on the ovary to promote follicular growth, estradiol production, and ovulation. Estradiol and progesterone feedback to the hypothalamus and pituitary to modulate gonadotropin secretion. Stress can influence this axis; the salivary cortisol awakening response varies with menstrual cycle phase and ovulation, indicating cross-talk between the stress and reproductive systems. In clinical settings, ovulation induction with agents like clomiphene citrate can alter cycle characteristics, as shown in stair-step protocols.
Key Genes Involved in GO:0042698 ovulation cycle
The ovulation cycle is governed by a network of genes and proteins that regulate hormone signaling, follicular development, and ovulation; the following table highlights key players with relevance to research.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GNRH1 | Encodes gonadotropin-releasing hormone, master regulator of pituitary gonadotropin release. | Target for studying hypothalamic control of ovulation cycle. |
| FSHB | Beta subunit of follicle-stimulating hormone, essential for follicular growth. | Knockout models show arrested follicular development. |
| LHB | Beta subunit of luteinizing hormone, triggers ovulation. | Mutations linked to ovulatory dysfunction. |
| ESR1 | Estrogen receptor alpha, mediates estradiol feedback. | Knockout mice exhibit anovulation and cystic follicles. |
| ESR2 | Estrogen receptor beta, modulates ovarian function. | Polymorphisms associated with ovulation disorders. |
| PGR | Progesterone receptor, mediates progesterone effects on endometrium. | Knockout mice fail to ovulate and have endometrial defects. |
| CYP19A1 | Aromatase, converts androgens to estrogens. | Critical for estradiol production and follicular development. |
| CYP17A1 | 17α-hydroxylase, involved in steroidogenesis. | Mutations cause disorders of sex development and ovulation issues. |
| STAR | Steroidogenic acute regulatory protein, transports cholesterol for steroidogenesis. | Knockout mice have impaired steroidogenesis and ovulation. |
| INHA | Inhibin alpha subunit, regulates FSH secretion. | Knockout mice develop ovarian tumors and abnormal cycles. |
| INHBA | Inhibin beta A subunit, forms activin and inhibin. | Involved in follicular development and ovulation. |
| BMP15 | Oocyte-derived growth factor, promotes follicular growth. | Mutations cause premature ovarian failure in humans. |
| GDF9 | Oocyte-derived growth factor, essential for folliculogenesis. | Knockout mice are infertile with arrested follicular development. |
| AMH | Anti-Müllerian hormone, regulates follicle recruitment. | Marker of ovarian reserve and predictor of ovulation response. |
| LHCGR | Luteinizing hormone/choriogonadotropin receptor, mediates LH action. | Mutations cause Leydig cell hypoplasia and ovulatory defects. |
| FSHR | Follicle-stimulating hormone receptor, mediates FSH action. | Mutations cause ovarian dysgenesis and infertility. |
| KISS1 | Kisspeptin, regulates GnRH secretion. | Critical for puberty onset and ovulatory cycle. |
| KISS1R | Kisspeptin receptor, mediates kisspeptin effects. | Mutations cause hypogonadotropic hypogonadism. |
How Is ovulation cycle Regulated?
The ovulation cycle is regulated by a complex interplay of hormonal signals, primarily through the hypothalamic-pituitary-ovarian axis. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. These hormones act on the ovary to promote follicular development, estradiol production, and ovulation. Estradiol and progesterone provide feedback regulation at the hypothalamus and pituitary. Additionally, stress-related pathways can influence the cycle; the salivary cortisol awakening response varies with menstrual cycle phase and ovulation, suggesting that the hypothalamic-pituitary-adrenal axis interacts with the reproductive axis. In assisted reproduction, ovulation can be triggered exogenously with hCG, bypassing the natural LH surge. Ovulation induction agents like clomiphene citrate modulate estrogen feedback to stimulate gonadotropin release, as studied in stair-step protocols.
ovulation cycle and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ESR1 | Estrogen resistance, ovulatory dysfunction | Knockout mouse, point mutation knock-in |
| PGR | Luteal phase defect, infertility | Conditional knockout mouse |
| BMP15 | Premature ovarian failure | Knock-in mouse with human mutation |
| FSHR | Ovarian dysgenesis, hypergonadotropic hypogonadism | Knockout mouse, patient-derived iPSCs |
| KISS1R | Hypogonadotropic hypogonadism | Knockout mouse, overexpression models |
Ovulatory Disorders and Infertility
Disruptions in the ovulation cycle can lead to ovulatory disorders, which are a major cause of female infertility. Conditions such as polycystic ovary syndrome (PCOS) and hypothalamic amenorrhea involve abnormal regulation of the hypothalamic-pituitary-ovarian axis. Research on ovulation cycle characteristics in normally fertile women provides a baseline for identifying deviations. In clinical practice, ovulation induction with agents like clomiphene citrate is used to restore ovulation, and stair-step protocols have been studied to optimize outcomes. Understanding the natural cycle is also crucial for assisted reproduction, such as frozen-thawed embryo transfer, where spontaneous ovulation versus hCG triggering can affect outcomes.
Menstrual Cycle and Aging
The ovulation cycle changes across the reproductive lifespan, with the transition to menopause marked by altered cycle regularity and hormonal profiles. The menstrual cycle's 'SWAN song' refers to the changes observed in the Study of Women's Health Across the Nation, highlighting the importance of understanding cycle dynamics in aging women. These changes have implications for fertility, bone health, and cardiovascular risk. Research into the ovulation cycle can inform interventions for age-related reproductive decline.
Stress and Reproductive Axis
Stress can impact the ovulation cycle through the hypothalamic-pituitary-adrenal axis. The salivary cortisol awakening response has been shown to vary with menstrual cycle phase and ovulation, indicating a bidirectional relationship between stress and reproductive function. Chronic stress may contribute to ovulatory dysfunction, and understanding these interactions can guide therapeutic strategies for stress-related infertility.
Comparative and Veterinary Reproductive Disorders
Ovulation cycle abnormalities also affect domestic animals, impacting breeding programs. In the queen cat, understanding estrous cycle characteristics and ovulation prediction is important for managing reproductive disorders and optimizing breeding. In the Catalonian jenny, prediction of ovulation helps in artificial insemination timing. In the medaka fish, the light-dependent daily ovulation cycle provides a model for studying environmental influences on reproduction. These comparative studies can reveal conserved mechanisms and potential therapeutic targets.
From ovulation cycle-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate ovulation timing? | Knockout mouse with estrous cycle monitoring |
| Does a point mutation in gene Y affect fertility? | Point mutation knock-in mouse |
| Can a human variant cause ovulatory disorder? | Knock-in mouse expressing human variant |
| Where is protein Z expressed in the ovary? | Tagged knock-in mouse with fluorescent reporter |
| Does overexpression of gene W cause ovarian hyperstimulation? | Transgenic overexpression mouse |
| What is the role of gene V in follicular development? | Conditional knockout mouse (ovary-specific) |
How to Study the ovulation cycle Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Hormone assays | Concentrations of reproductive hormones | Diagnosing ovulatory disorders, timing ovulation |
| Ultrasound | Follicular size, endometrial thickness, ovulation | Assisted reproduction, veterinary breeding |
| RNA-seq | Gene expression changes across cycle | Identifying regulatory pathways |
| Single-cell RNA-seq | Cell-type-specific expression in ovary | Mapping follicular development |
| Knockout mouse models | Gene function in vivo | Causal testing of candidate genes |
| Knock-in mouse models | Effect of specific mutations | Modeling human variants |
| Salivary cortisol awakening response | Stress axis activity | Studying stress-reproduction interactions |
| Vaginal cytology | Estrous cycle stage | Veterinary reproductive monitoring |
Hormone Profiling
Measuring serum or salivary hormone levels (e.g., estradiol, progesterone, LH, FSH) across the cycle is fundamental to characterizing the ovulation cycle. The salivary cortisol awakening response can be assessed to study stress axis interactions. In clinical research, hormone profiles help determine ovulation timing and diagnose disorders.
Ultrasound Imaging
Transvaginal ultrasound is used to monitor follicular growth, endometrial thickness, and ovulation. It is essential for predicting ovulation in assisted reproduction and veterinary practice. In jennies, ultrasound helps predict ovulation for breeding management.
Genetic and Genomic Approaches
RNA sequencing and single-cell transcriptomics can reveal gene expression changes in the ovary and endometrium across the cycle. Knockout and knock-in mouse models are used to test gene function. Comparative genomics across species like medaka and cat can identify conserved regulatory elements.
Behavioral and Physiological Monitoring
In animal models, behavioral signs of estrus and physiological markers (e.g., vaginal cytology) are used to track the cycle. In the queen cat, estrous behavior and cycle characteristics are monitored for breeding. In medaka, the daily ovulation cycle is observed under controlled light conditions.
How CRISPR Can Be Used to Study GO:0042698 ovulation cycle
Knockout
CRISPR knockout models are used to delete candidate genes involved in the ovulation cycle, such as Esr1 or Pgr, to assess their role in follicular development, ovulation, and fertility. These models help establish causality and reveal compensatory mechanisms. For example, knockout of Esr1 in mice leads to anovulation and cystic follicles, demonstrating its essential role.
Point Mutation
Point mutation knock-in models introduce specific human variants into the mouse genome to study their impact on ovulation cycle. For instance, mutations in BMP15 associated with premature ovarian failure can be modeled to understand their functional consequences. These models are valuable for precision medicine approaches.
Knock-in
Knock-in models can tag endogenous proteins with reporters or epitopes to track expression and localization during the ovulation cycle. This is useful for imaging studies and for understanding protein dynamics in follicular development and ovulation.
Overexpression
Overexpression models, such as transgenic mice with elevated expression of growth factors like GDF9 or BMP15, can reveal effects on follicular recruitment and ovulation rate. These models help identify dosage-sensitive pathways in the ovulation cycle.
How EDITGENE Supports ovulation cycle Research
Researchers studying ovulation cycle-related genes often need to determine whether a candidate gene is causally involved in follicular development, ovulation, or luteal function. EDITGENE provides comprehensive CRISPR gene editing services to create knockout, point mutation, knock-in, and overexpression cell models, as well as CRISPR library screening and bioinformatics support, enabling rigorous functional studies of ovulation cycle biology.
Contact EDITGENE today to design your custom CRISPR model for ovulation cycle research.
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Frequently Asked Questions About ovulation cycle
What is the ovulation cycle (GO:0042698)?
The ovulation cycle is the type of sexual cycle seen in females, often with physiologic changes in the endometrium that recur at regular intervals during reproductive years. It includes follicular development, ovulation, and luteal function.
What genes are involved in the ovulation cycle?
Key genes include GNRH1, FSHB, LHB, ESR1, ESR2, PGR, CYP19A1, BMP15, GDF9, and KISS1, among others. These regulate hormone signaling, follicular growth, and ovulation.
How is ovulation triggered?
Ovulation is triggered by a surge in luteinizing hormone (LH), which can be mimicked by hCG in assisted reproduction.
Can stress affect the ovulation cycle?
Yes, the salivary cortisol awakening response varies with menstrual cycle phase and ovulation, indicating stress axis involvement.
What is the difference between spontaneous and triggered ovulation in frozen embryo transfer?
Spontaneous ovulation occurs naturally, while triggered ovulation uses hCG to induce ovulation; both are used in natural cycle frozen-thawed embryo transfer.
How do researchers study the ovulation cycle in animal models?
They use hormone profiling, ultrasound, and genetic models. In medaka, the light-dependent daily ovulation cycle is studied; in cats and jennies, estrous cycle characteristics and ovulation prediction are monitored.
What is the side of ovulation and does it matter?
In normally fertile women, right-sided ovulation is more frequent, but the side can vary; it may have implications for fertility.
How does clomiphene citrate affect the ovulation cycle?
Clomiphene citrate is used for ovulation induction; stair-step protocols can affect ovulation rate and cycle characteristics.
What is the menstrual cycle's SWAN song?
It refers to the changes in the menstrual cycle observed in the Study of Women's Health Across the Nation, particularly during the menopausal transition.
What model organisms are used to study the ovulation cycle?
Common models include mice, rats, medaka fish, cats, and jennies, each offering unique insights into reproductive biology.
Conclusion
The ovulation cycle (GO:0042698) is a fundamental biological process that underpins female fertility and reproductive health. It involves intricate hormonal regulation and cyclic changes in the ovary and endometrium. Research across species, from humans to fish, continues to reveal conserved and divergent mechanisms. Understanding this cycle is crucial for diagnosing and treating ovulatory disorders, optimizing assisted reproduction, and appreciating the impact of stress and aging on reproductive function. With advances in CRISPR gene editing and genomic technologies, researchers are now better equipped to dissect the genetic basis of the ovulation cycle and translate findings into clinical applications.
References
- 1. Haase L et al.. 2024. Effects of menstrual cycle phase and ovulation on the salivary cortisol awakening response.. Psychoneuroendocrinology 160:106669 PMID: 37988874
- 2. Iwamatsu T et al.. 2022. The light-dependent daily cycle of ovulation in the oviparous medaka fish, Oryzias latipes (Atherinomorpha: Beloniformes: Adrianichthyidae) artificially pregnant with developing embryos.. J Exp Zool A Ecol Integr Physiol 337(6):687-693 PMID: 35438259
- 3. Budinetz TH et al.. 2015. Ovulation rate and cycle characteristics in a subsequent clomiphene citrate cycle after stair-step protocol.. Fertil Steril 103(3):675-9 PMID: 25577463
- 4. Johnson AK. 2022. Normal feline reproduction: The queen.. J Feline Med Surg 24(3):204-211 PMID: 35209768
- 5. Ecochard R et al.. 2000. Side of ovulation and cycle characteristics in normally fertile women.. Hum Reprod 15(4):752-5 PMID: 10739814
- 6. Huberlant S et al.. 2018. [Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG].. Gynecol Obstet Fertil Senol 46(5):466-473 PMID: 29656071
- 7. Taberner E et al.. 2008. Oestrus cycle characteristics and prediction of ovulation in Catalonian jennies.. Theriogenology 70(9):1489-97 PMID: 18678401
- 8. Taylor HS. 2015. The menstrual cycle's SWAN song.. Menopause 22(3):256-7 PMID: 25692876
