GO:0007144 female meiosis I: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0007144 (female meiosis I) is the first meiotic division in the female germline, producing two haploid secondary oocytes from one primary oocyte.
• Errors in female meiosis I are the leading cause of aneuploidy in human oocytes, and maternal age is the strongest risk factor.
• Key regulators include MEIOSIN, which triggers the mitosis-to-meiosis switch, and SIRT7, which promotes chromosome synapsis during prophase I.
• The spindle assembly checkpoint protein CDC20 is essential for meiosis I progression and female fertility in mice.
• RNA-binding proteins such as hnRNPC and HuR regulate alternative splicing required for meiosis, linking RNA processing to meiotic progression.
• Drosophila melanogaster is a powerful model for dissecting female meiosis I mechanisms, including synapsis, recombination, and segregation.
Description
Female meiosis I (GO:0007144) is the specialized cell cycle process in which the first meiotic division occurs in the female germline. Unlike mitosis, meiosis I involves a single round of DNA replication followed by two successive divisions, with meiosis I separating homologous chromosomes and meiosis II separating sister chromatids. This process is fundamental to sexual reproduction, as it generates haploid oocytes while introducing genetic diversity through recombination. In humans, female meiosis I is particularly error-prone, and mistakes during this division are the leading cause of aneuploidy in oocytes, which increases with maternal age and contributes to infertility, miscarriage, and developmental disorders such as Down syndrome. Understanding the molecular mechanisms of female meiosis I is therefore critical for reproductive biology and medicine. Research in model organisms, especially Drosophila melanogaster, has revealed conserved principles of synapsis, recombination, and chromosome segregation that operate during female meiosis I. Recent studies have identified key regulators such as MEIOSIN, which directs the switch from mitosis to meiosis in germ cells, and SIRT7, which promotes chromosome synapsis during prophase I. Additionally, RNA-binding proteins like hnRNPC and HuR have been shown to regulate alternative splicing essential for meiosis, highlighting the importance of post-transcriptional control. These findings underscore the complexity of female meiosis I and the need for continued research to uncover its regulatory networks and links to human disease.
female meiosis I At A Glance
| GO ID | GO:0007144 |
|---|---|
| GO term | female meiosis I |
| Ontology | biological_process |
| Synonym | female meiosis I nuclear division |
| Major function | First meiotic division in the female germline, reducing chromosome number and generating haploid oocytes |
| Related process | Meiosis I, oogenesis, homologous chromosome segregation |
| Key regulators | MEIOSIN, SIRT7, CDC20, hnRNPC, HuR |
| Model organisms | Mus musculus, Drosophila melanogaster, Homo sapiens |
What Is GO:0007144?
GO:0007144 (female meiosis I) is defined as the cell cycle process in which the first meiotic division occurs in the female germline. It encompasses the specialized nuclear division that reduces the chromosome number by half, producing two haploid secondary oocytes from a single diploid primary oocyte, and is also known as female meiosis I nuclear division.
Why Is female meiosis I Important in Cell Biology?
Female meiosis I is essential for sexual reproduction and genetic diversity, but its error-prone nature in humans makes it a central focus of reproductive biology and medicine. Aneuploidy arising from female meiosis I errors is the leading cause of miscarriage, infertility, and congenital disorders such as Down syndrome, and its incidence increases dramatically with maternal age. Understanding the molecular mechanisms of female meiosis I can inform diagnostic and therapeutic strategies for reproductive disorders and improve assisted reproductive technologies.
• Female meiosis I errors are the primary cause of aneuploidy in human oocytes, leading to miscarriage and developmental disorders.
• Maternal age is the strongest risk factor for female meiosis I errors, with a sharp increase in aneuploidy after age 35.
• MEIOSIN acts as a master regulator that switches germ cells from mitosis to meiosis, and its dysfunction can impair female meiosis I.
• SIRT7 promotes chromosome synapsis during prophase I, and its loss leads to meiotic defects.
• CDC20 is critical for meiosis I progression and female fertility in mice, linking spindle assembly checkpoint to oocyte quality.
• RNA-binding proteins hnRNPC and HuR regulate alternative splicing essential for meiosis, revealing post-transcriptional control of female meiosis I.
• Drosophila melanogaster provides a powerful genetic model to study conserved mechanisms of female meiosis I.
• Germline stem cells in humans give rise to oocytes, and understanding their regulation is key to reproductive longevity.
• Defects in female meiosis I are associated with premature ovarian insufficiency and infertility.
• Research on female meiosis I informs the development of contraceptives and fertility treatments.
What Happens During female meiosis I?
Prophase I and Synapsis
In simple terms: In prophase I, homologous chromosomes pair up and exchange genetic material, a process that is tightly regulated.
Prophase I is the longest and most complex stage of female meiosis I, during which homologous chromosomes pair, synapse, and undergo recombination. Synapsis is mediated by the synaptonemal complex, and SIRT7 has been shown to promote chromosome synapsis during prophase I in female meiosis. In Drosophila, synapsis and recombination are essential for proper chromosome segregation, and mutations in synaptonemal complex components lead to meiotic errors. The RNA-binding protein hnRNPC, together with HuR, regulates alternative splicing of genes involved in synapsis and meiosis, and its depletion impairs meiotic progression.
Meiotic Recombination
In simple terms: Recombination shuffles genetic material between homologous chromosomes, creating genetic diversity.
Meiotic recombination during female meiosis I generates crossovers that physically link homologous chromosomes and ensure their proper segregation. In Drosophila, recombination is required for accurate chromosome segregation, and defects in crossover formation lead to nondisjunction and aneuploidy. The process is regulated by numerous proteins, including those involved in DNA double-strand break repair and crossover resolution. Maternal age affects recombination patterns and increases the risk of aneuploidy in human oocytes.
Spindle Assembly and Chromosome Segregation
In simple terms: The spindle machinery separates homologous chromosomes into two new cells.
During female meiosis I, the spindle apparatus captures homologous chromosomes and segregates them to opposite poles. The spindle assembly checkpoint ensures proper attachment and delays anaphase until all chromosomes are correctly aligned. CDC20, a key regulator of the spindle assembly checkpoint, is critical for meiosis I progression and female fertility in mice; its depletion causes meiotic arrest and infertility. Errors in spindle assembly and chromosome segregation are a major source of aneuploidy in human oocytes, particularly with advanced maternal age.
Meiosis I Completion and Cytokinesis
In simple terms: The first meiotic division ends with the formation of two haploid cells, one of which becomes the secondary oocyte.
At the end of female meiosis I, homologous chromosomes are separated into two daughter cells, with one receiving the majority of cytoplasm to become the secondary oocyte and the other forming the first polar body. This asymmetric division is essential for preserving nutrients for the future embryo. The completion of meiosis I is regulated by the spindle assembly checkpoint and proteolytic degradation of cyclin B and securin. Defects in this final step can lead to premature separation of sister chromatids and aneuploidy.
Key Genes Involved in GO:0007144 female meiosis I
The following genes and proteins are key regulators of female meiosis I, as supported by published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MEIOSIN | Directs the switch from mitosis to meiosis in germ cells | Essential for initiating female meiosis I; knockout causes meiotic failure |
| SIRT7 | Promotes chromosome synapsis during prophase I | Loss leads to defective synapsis and meiotic arrest |
| CDC20 | Regulates spindle assembly checkpoint and meiosis I progression | Critical for female fertility; knockout causes meiotic arrest |
| hnRNPC | Regulates alternative splicing in an m6A-dependent manner | Essential for meiosis; depletion impairs splicing and meiotic progression |
| HuR | RNA-binding protein that partners with hnRNPC | Regulates alternative splicing required for meiosis |
| SYCP1 | Component of the synaptonemal complex | Required for synapsis and recombination during prophase I |
| SYCP3 | Component of the synaptonemal complex | Essential for synapsis and chromosome segregation |
| DMC1 | Meiotic recombinase | Required for double-strand break repair and crossover formation |
| RAD51 | Recombinase involved in DNA repair | Functions in meiotic recombination |
| MLH1 | Mismatch repair protein involved in crossover formation | Marks crossover sites during meiosis |
| BUB1 | Spindle assembly checkpoint kinase | Monitors chromosome attachment during meiosis I |
| MAD2 | Spindle assembly checkpoint protein | Ensures proper chromosome segregation |
| SEPARASE | Cleaves cohesin to separate chromosomes | Required for anaphase I progression |
| SECURIN | Inhibits separase until anaphase | Regulates timing of chromosome segregation |
| CYCLIN B | Regulates CDK1 activity | Controls meiotic progression and exit |
| CDK1 | Cyclin-dependent kinase | Drives meiotic cell cycle transitions |
| MOS | MAPK pathway activator | Regulates meiotic arrest and maturation |
How Is female meiosis I Regulated?
Female meiosis I is regulated by a complex network of cell cycle kinases, checkpoint proteins, and post-transcriptional modifiers. The spindle assembly checkpoint, involving CDC20, BUB1, and MAD2, ensures proper chromosome segregation and delays anaphase until all chromosomes are correctly attached. MEIOSIN acts as a master transcriptional regulator that switches germ cells from mitosis to meiosis, and its expression is tightly controlled. SIRT7, a sirtuin family deacetylase, promotes chromosome synapsis during prophase I, and its activity is regulated by NAD+ availability. RNA-binding proteins hnRNPC and HuR regulate alternative splicing of meiotic genes in an m6A-dependent manner, adding a layer of post-transcriptional control. Additionally, maternal age affects the regulation of female meiosis I, with altered expression of checkpoint and recombination proteins contributing to increased aneuploidy.
female meiosis I and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CDC20 | Infertility due to meiotic arrest | Cdc20 knockout mouse oocytes |
| SIRT7 | Meiotic defects and aneuploidy | Sirt7 knockout mouse oocytes |
| MEIOSIN | Germ cell failure and infertility | Meiosin knockout mouse germ cells |
| hnRNPC | Impaired meiosis and splicing defects | hnRNPC knockdown mouse oocytes |
| MAD2 | Aneuploidy and miscarriage | Mad2 knockout mouse oocytes |
Aneuploidy and Down Syndrome
Errors in female meiosis I are the leading cause of aneuploidy in human oocytes, and trisomy 21 (Down syndrome) is most often caused by nondisjunction during maternal meiosis I. The incidence of such errors increases with maternal age, making female meiosis I a critical focus for understanding the origins of chromosomal disorders.
Infertility and Premature Ovarian Insufficiency
Defects in female meiosis I can lead to meiotic arrest, oocyte degeneration, and infertility. Premature ovarian insufficiency, characterized by loss of ovarian function before age 40, is associated with meiotic defects and reduced oocyte quality. Understanding the molecular basis of female meiosis I is essential for developing diagnostic and therapeutic approaches for these conditions.
Reproductive Aging
Maternal age is the strongest risk factor for female meiosis I errors, with a dramatic increase in aneuploidy after age 35. Age-related deterioration of meiotic machinery, including cohesin loss and spindle defects, contributes to reduced oocyte quality and fertility. Research on female meiosis I aims to uncover the molecular mechanisms of reproductive aging and identify potential interventions.
From female meiosis I-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does knockout of Cdc20 cause meiosis I arrest? | Cdc20 knockout mouse oocytes |
| Does SIRT7 point mutation affect synapsis? | Sirt7 point-mutation knock-in mouse |
| Does overexpression of MEIOSIN induce meiosis? | MEIOSIN overexpression in germ cells |
| Does hnRNPC knockdown alter splicing? | hnRNPC knockdown in mouse oocytes |
| Does tagged CDC20 localize to the spindle? | CDC20-GFP knock-in mouse oocytes |
| Does maternal age affect aneuploidy rates? | Aged mouse oocytes |
How to Study the female meiosis I Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Spindle dynamics and chromosome segregation | Visualizing meiosis I progression in oocytes |
| RNA-seq | Gene expression and alternative splicing | Identifying meiotic transcripts and splicing targets |
| Proteomics | Protein abundance and modifications | Quantifying meiotic regulators |
| Phosphoproteomics | Phosphorylation events | Mapping spindle checkpoint signaling |
| Immunofluorescence | Protein localization and chromosome structure | Detecting synaptonemal complex proteins |
| CRISPR knockout | Gene function | Generating knockout oocytes/mice |
| CRISPR knock-in | Tagged protein expression | Localizing CDC20 in live oocytes |
| Single-cell sequencing | Transcriptome of individual oocytes | Studying heterogeneity in meiosis I |
Live-Cell Imaging of Meiosis I
Live-cell imaging using fluorescently tagged proteins (e.g., CDC20-GFP, histone H2B-RFP) allows real-time visualization of spindle assembly, chromosome segregation, and meiotic progression in oocytes. This method is essential for understanding the dynamics of female meiosis I and identifying defects associated with aneuploidy.
Transcriptomics and RNA-Seq
RNA sequencing of oocytes at different stages of female meiosis I reveals dynamic changes in gene expression and alternative splicing. Studies using hnRNPC knockdown have shown that RNA-binding proteins regulate splicing of meiotic genes, and RNA-seq can identify these targets.
Proteomics and Phosphoproteomics
Mass spectrometry-based proteomics can quantify protein abundance and phosphorylation during female meiosis I, identifying key regulators such as CDC20 and BUB1. Phosphoproteomics is particularly useful for studying spindle assembly checkpoint signaling.
Genetic Knockout and Knockdown Models
Knockout mouse models (e.g., Cdc20, Sirt7, Meiosin) are powerful tools to study gene function in female meiosis I. Conditional knockout and RNAi knockdown in oocytes allow stage-specific analysis of meiotic defects.
How CRISPR Can Be Used to Study GO:0007144 female meiosis I
Knockout
CRISPR knockout of genes such as Cdc20, Sirt7, and Meiosin in mouse models has provided critical insights into their essential roles in female meiosis I. For example, Cdc20 knockout causes meiotic arrest and infertility, demonstrating its requirement for meiosis I progression.
Point Mutation
CRISPR point mutation can be used to model specific amino acid changes in meiotic genes, such as those affecting SIRT7 catalytic activity or CDC20 phosphorylation sites. These models help dissect the molecular mechanisms of female meiosis I and identify disease-associated variants.
Knock-in
Knock-in of fluorescent tags (e.g., GFP) allows real-time imaging of meiotic proteins in oocytes. Tagged knock-in models for CDC20 and other spindle proteins have been used to study their localization and dynamics during female meiosis I.
Overexpression
Overexpression of meiotic regulators such as MEIOSIN can induce meiosis in germ cells and provide insights into the switch from mitosis to meiosis. Overexpression studies also help identify downstream targets and regulatory networks in female meiosis I.
How EDITGENE Supports female meiosis I Research
Researchers studying female meiosis I-related genes often need to determine whether a candidate gene is causally involved in meiotic progression, chromosome segregation, or aneuploidy. EDITGENE provides comprehensive CRISPR-based services to generate knockout, point-mutation, knock-in, and overexpression cell models, as well as CRISPR library screening and bioinformatics support, enabling precise functional interrogation of genes in female meiosis I.
Contact EDITGENE today to design your custom CRISPR model for female meiosis I research.
Frequently Asked Questions About female meiosis I
What is female meiosis I (GO:0007144)?
Female meiosis I is the first meiotic division in the female germline, producing two haploid secondary oocytes from one primary oocyte.
What genes are involved in female meiosis I?
Key genes include MEIOSIN, SIRT7, CDC20, hnRNPC, HuR, SYCP1, SYCP3, DMC1, and others.
Why is female meiosis I important?
It is essential for sexual reproduction and genetic diversity, and its errors cause aneuploidy, miscarriage, and infertility.
How does maternal age affect female meiosis I?
Maternal age is the strongest risk factor for meiosis I errors, with increased aneuploidy due to cohesin loss and spindle defects.
What is the role of CDC20 in female meiosis I?
CDC20 regulates the spindle assembly checkpoint and is critical for meiosis I progression and female fertility.
What is the role of SIRT7 in female meiosis I?
SIRT7 promotes chromosome synapsis during prophase I, and its loss leads to meiotic defects.
What is the role of MEIOSIN in female meiosis I?
MEIOSIN directs the switch from mitosis to meiosis in germ cells, initiating female meiosis I.
How do hnRNPC and HuR regulate female meiosis I?
They regulate alternative splicing in an m6A-dependent manner, essential for meiotic progression.
What model organisms are used to study female meiosis I?
Drosophila melanogaster and Mus musculus are widely used models.
How can CRISPR help study female meiosis I?
CRISPR knockout, knock-in, point mutation, and overexpression models enable functional dissection of meiotic genes.
Conclusion
Female meiosis I (GO:0007144) is a fundamental biological process that ensures haploid gamete formation and genetic diversity, but its error-prone nature in humans leads to aneuploidy, infertility, and developmental disorders. Research using model organisms and CRISPR-based tools has identified critical regulators such as MEIOSIN, SIRT7, CDC20, and hnRNPC, providing insights into the molecular mechanisms of meiosis I. Continued investigation of female meiosis I will advance our understanding of reproductive aging and inform therapeutic strategies for reproductive disorders.
References
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- 2. Vazquez BN et al.. 2019. SIRT7 promotes chromosome synapsis during prophase I of female meiosis.. Chromosoma 128(3):369-383 PMID: 31256246
- 3. Ishiguro KI et al.. 2020. MEIOSIN Directs the Switch from Mitosis to Meiosis in Mammalian Germ Cells.. Dev Cell 52(4):429-445.e10 PMID: 32032549
- 4. Fellmeth JE et al.. 2022. A Brief History of Drosophila (Female) Meiosis.. Genes (Basel) 13(5) PMID: 35627159
- 5. Xiong X et al.. 2025. hnRNPC Functions with HuR to Regulate Alternative Splicing in an m6A-Dependent Manner and is Essential for Meiosis.. Adv Sci (Weinh) 12(13):e2412196 PMID: 39921484
- 6. Cheng H et al.. 2022. Germline stem cells in human.. Signal Transduct Target Ther 7(1):345 PMID: 36184610
- 7. Hughes SE et al.. 2018. Female Meiosis: Synapsis, Recombination, and Segregation in Drosophila melanogaster.. Genetics 208(3):875-908 PMID: 29487146
- 8. Jin F et al.. 2010. Cdc20 is critical for meiosis I and fertility of female mice.. PLoS Genet 6(9):e1001147 PMID: 20941357
