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Related Concept Videos

Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

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The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent...
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In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
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Hormonal Control of the Ovarian Cycle01:30

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The ovarian cycle is meticulously regulated by the hypothalamic-pituitary-gonadal axis. This cycle orchestrates the release of a mature oocyte, essential for reproduction.
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Epigenetic changes alter the physical structure of the DNA without changing the genetic sequence and often regulate whether genes are turned on or off. This regulation ensures that each cell produces only proteins necessary for its function. For example, proteins that promote bone growth are not produced in muscle cells. Epigenetic mechanisms play an essential role in healthy development. Conversely, precisely regulated epigenetic mechanisms are disrupted in diseases like cancer.
X-chromosome...
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The ovarian cycle regulates endometrial changes throughout a single menstrual cycle via the coordinated action of gonadotrophin-releasing hormone (GnRH) and gonadotrophins.
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The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
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Epigenetic/circadian clocks and PCOS.

Camille Vatier1,2, Sophie Christin-Maitre1,3

  • 1Department of Endocrine and Reproductive Medicine, Center of Endocrine Rare Diseases of Growth and Development (CRESCENDO), FIRENDO, Endo-ERN, Hôpital Saint-Antoine, Assistance-Publique-Hôpitaux de Paris, Sorbonne University, Paris, France.

Human Reproduction (Oxford, England)
|April 11, 2024
PubMed
Summary

Epigenetic changes and circadian clock gene disruptions may contribute to Polycystic Ovary Syndrome (PCOS) development. Understanding these factors could lead to new diagnostic and therapeutic strategies for PCOS.

Keywords:
DNA methylationPCOScircadian clock geneepigenetic changesgenome-wide association studieshyperandrogenismmetabolic syndromepolycystic ovary syndromereproductive-aged women

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Area of Science:

  • Endocrinology and Genetics
  • Reproductive Medicine
  • Epigenetics and Chronobiology

Background:

  • Polycystic Ovary Syndrome (PCOS) affects 6-20% of women and is linked to metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer.
  • Genetic studies explain only about 10% of PCOS heritability, indicating other factors are involved in its etiology.
  • Epigenetic alterations and circadian clock gene modifications are increasingly recognized as potential contributors to PCOS pathogenesis.

Purpose of the Study:

  • To review the role of epigenetic changes and circadian clock gene modifications in the development of Polycystic Ovary Syndrome (PCOS).
  • To explore the potential of epigenetic modifications as diagnostic biomarkers and therapeutic targets for PCOS.

Main Methods:

  • Review of existing literature on epigenetic alterations (DNA methylation, histone modifications, non-coding RNAs) in PCOS and related conditions.
  • Analysis of animal models demonstrating epigenetic programming in PCOS-like phenotypes.
  • Examination of human studies reporting epigenetic changes in various tissues (PBMC, adipose, GC, liver) of women with PCOS.

Main Results:

  • Epigenetic changes, including global hypomethylation and specific gene methylation alterations, are observed in women with PCOS.
  • These epigenetic changes affect genes involved in hormonal regulation, inflammation, and metabolism.
  • Disruptions in circadian clock gene expression are noted in women with PCOS, correlating with sleep disorders.

Conclusions:

  • Epigenetic modifications and circadian rhythm disruptions are potential key players in PCOS pathogenesis.
  • Distinguishing cause from consequence remains a challenge for epigenetic biomarkers.
  • Targeting epigenetic modifications offers potential for precision medicine approaches in PCOS management, pending further research in large cohorts.