GO:0022405 hair cycle process: Growth Cycle Regulation, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0022405 hair cycle process describes the cyclical phases of hair growth (anagen), regression (catagen), quiescence (telogen), and shedding (exogen).
• The hair follicle is a dynamic miniorgan that undergoes repeated cycles of regeneration and regression throughout life.
• Key signaling pathways including Wnt/β-catenin, BMP, Shh, and Notch coordinate the transitions between hair cycle phases.
• Dermal exosomes containing miR-218-5p promote hair regeneration by regulating β-catenin signaling.
• Single-cell transcriptomic reconstruction has revealed temporal dynamics of human skin tissue remodeling during the hair cycle.
• Dysregulation of the hair cycle is associated with alopecia, acne vulgaris, and hair graying.
Description
The hair cycle process (GO:0022405) is a fundamental biological process that governs the cyclical phases of hair growth, regression, quiescence, and shedding in multicellular organisms. This process is essential for maintaining the hair follicle, a dynamic miniorgan that undergoes repeated cycles of regeneration and regression throughout the lifetime of an organism. Understanding the molecular and cellular mechanisms underlying the hair cycle is critical for researchers studying skin biology, stem cell biology, and regenerative medicine. The hair cycle consists of four main phases: anagen (growth), catagen (regression), telogen (quiescence), and exogen (shedding). Each phase is characterized by distinct morphological and molecular changes that are tightly regulated by signaling pathways and transcriptional networks. Recent advances in single-cell transcriptomics have provided unprecedented insights into the temporal dynamics of human skin tissue remodeling during the hair cycle. This article provides a comprehensive overview of the hair cycle process, including its definition, molecular mechanisms, key genes, disease associations, and research methods, based on authoritative QuickGO data and verified PubMed literature.
hair cycle process At A Glance
| GO ID | GO:0022405 |
|---|---|
| GO term | hair cycle process |
| Ontology | biological_process |
| Synonym | none |
| Major function | Cyclical phases of hair growth, regression, quiescence, and shedding |
| Key phases | Anagen (growth), catagen (regression), telogen (quiescence), exogen (shedding) |
| Key signaling pathways | Wnt/β-catenin, BMP, Shh, Notch |
| Associated diseases | Alopecia, acne vulgaris, hair graying |
| Research methods | Single-cell transcriptomics, lineage tracing, conditional knockout |
What Is GO:0022405?
GO:0022405 hair cycle process is defined as a multicellular organismal process involved in the cyclical phases of growth (anagen), regression (catagen), quiescence (telogen), and shedding (exogen) in the life of a hair. A hair is one of the collection or mass of filaments growing from the skin of an animal, forming a covering for a part of the head or for any part or the whole of the body. This process encompasses the complete cycle of hair follicle regeneration and regression, which is essential for normal skin function and hair maintenance.
Why Is hair cycle process Important in Cell Biology?
The hair cycle process is critically important because it represents a paradigm for understanding how adult stem cells are activated, maintained, and regulated in a cyclical manner. Dysregulation of this process leads to common human disorders including alopecia, acne vulgaris, and hair graying, affecting millions of individuals worldwide. Furthermore, the hair follicle serves as an accessible model system for studying stem cell biology, tissue regeneration, and cell-cell interactions. Understanding the molecular mechanisms of the hair cycle has direct implications for developing therapeutic strategies for hair loss and skin disorders.
• Provides a model for studying adult stem cell activation and quiescence.
• Dysregulation causes alopecia, a common disorder affecting millions.
• Hair cycle abnormalities are linked to acne vulgaris pathogenesis.
• Hair graying is associated with defective melanocyte stem cell maintenance during the hair cycle.
• Single-cell transcriptomics has revealed temporal dynamics of human hair cycle.
• Dermal exosomes regulate hair regeneration via β-catenin signaling.
• Skin pigmentation and hair cycle are interconnected through stem cell regulation.
• Hair follicle cycling is a model for tissue remodeling and regeneration.
• Understanding hair cycle phases aids in developing treatments for hair loss.
• The hair cycle is regulated by conserved signaling pathways including Wnt, BMP, and Shh.
What Happens During hair cycle process?
Anagen Phase (Growth)
In simple terms: Anagen is the active growth phase when hair follicles rapidly produce hair shafts.
Anagen is the growth phase of the hair cycle, during which hair follicle stem cells are activated and rapidly proliferate to generate the hair shaft. This phase is characterized by robust Wnt/β-catenin signaling, which is essential for stem cell activation and hair follicle regeneration. The duration of anagen determines the length of the hair, and it can last for years on the scalp. During anagen, the hair follicle extends deep into the dermis, and dermal papilla cells interact with epithelial cells to sustain growth.
Catagen Phase (Regression)
In simple terms: Catagen is the regression phase when hair growth stops and the follicle shrinks.
Catagen is the regression phase of the hair cycle, marked by apoptosis of hair follicle cells and cessation of hair shaft production. During catagen, the lower portion of the hair follicle undergoes programmed cell death, and the follicle retracts toward the skin surface. This phase is regulated by a decline in growth-promoting signals and an increase in inhibitory signals such as BMP. Catagen lasts for a few weeks and transitions the follicle into telogen.
Telogen Phase (Quiescence)
In simple terms: Telogen is the resting phase when the hair follicle is dormant.
Telogen is the quiescent phase of the hair cycle, during which the hair follicle remains dormant and the hair shaft is retained but not actively growing. Hair follicle stem cells are maintained in a quiescent state, poised for activation in the next anagen phase. Telogen can last for months, and the hair is eventually shed during exogen. The transition from telogen to anagen is a critical step regulated by Wnt signaling and other pathways.
Exogen Phase (Shedding)
In simple terms: Exogen is the shedding phase when the old hair is released from the follicle.
Exogen is the shedding phase of the hair cycle, during which the old hair shaft is released from the follicle. This phase is distinct from telogen and involves the active expulsion of the hair shaft. Exogen allows for the replacement of old hair with new hair in the next cycle. The molecular mechanisms of exogen are less well understood but involve proteolytic degradation of cell adhesion molecules.
Molecular Regulation of Phase Transitions
In simple terms: The switch between hair cycle phases is controlled by signaling molecules.
The transitions between hair cycle phases are tightly regulated by a complex interplay of signaling pathways, including Wnt/β-catenin, BMP, Shh, and Notch. Wnt/β-catenin signaling is a key driver of anagen initiation, while BMP signaling promotes quiescence. Dermal exosomes containing miR-218-5p have been shown to promote hair regeneration by regulating β-catenin signaling. Single-cell transcriptomic studies have revealed temporal dynamics of gene expression during the human hair cycle.
Key Genes Involved in GO:0022405 hair cycle process
The following genes and proteins play critical roles in the regulation and execution of the hair cycle process.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CTNNB1 | Encodes β-catenin, a key mediator of Wnt signaling | Essential for anagen initiation and hair follicle regeneration |
| WNT3A | Wnt family member, activates β-catenin signaling | Promotes hair follicle stem cell activation |
| BMP4 | Bone morphogenetic protein, inhibits hair growth | Regulates telogen maintenance and catagen entry |
| SHH | Sonic hedgehog, regulates follicle morphogenesis | Required for anagen progression and follicle development |
| NOTCH1 | Notch signaling receptor | Controls hair follicle differentiation and cycle progression |
| MIR218 | MicroRNA-218-5p, regulates β-catenin signaling | Promotes hair regeneration via dermal exosomes |
| KRT5 | Keratin 5, structural component of hair follicle | Marker of hair follicle stem cells |
| KRT14 | Keratin 14, basal cell marker | Expressed in hair follicle basal layer |
| CD200 | Stem cell marker | Identifies hair follicle stem cells |
| ITGA6 | Integrin alpha-6, stem cell marker | Enriches for hair follicle stem cells |
| LEF1 | Lymphoid enhancer-binding factor 1, Wnt target | Transcription factor in hair follicle development |
| TCF4 | Transcription factor 4, Wnt signaling | Regulates hair follicle gene expression |
| EDAR | Ectodysplasin A receptor | Controls hair follicle morphogenesis |
| FOXN1 | Forkhead box N1, transcription factor | Regulates hair keratin gene expression |
| HOXC13 | Homeobox C13, transcription factor | Controls hair shaft differentiation |
| MSX2 | Msh homeobox 2, transcription factor | Regulates hair follicle cycling |
| GATA3 | GATA binding protein 3, transcription factor | Involved in hair follicle differentiation |
| SOX9 | SRY-box transcription factor 9 | Marks hair follicle stem cells |
How Is hair cycle process Regulated?
The hair cycle process is regulated by a complex network of signaling pathways, transcription factors, and epigenetic modifiers. Key regulatory pathways include Wnt/β-catenin, which promotes anagen initiation and hair follicle regeneration; BMP signaling, which maintains telogen quiescence; and Shh signaling, which is required for anagen progression. Dermal exosomes containing miR-218-5p have been shown to regulate β-catenin signaling and promote hair regeneration. Single-cell transcriptomic studies have revealed dynamic changes in gene expression during the human hair cycle, highlighting the temporal regulation of skin tissue remodeling. Additionally, stem cell quiescence and activation are controlled by intrinsic and extrinsic factors, including transcription factors such as FOXN1, HOXC13, and MSX2.
hair cycle process and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CTNNB1 | Alopecia, hair regeneration | Conditional knockout mouse, overexpression |
| BMP4 | Alopecia, telogen maintenance | Transgenic overexpression, knockout |
| MIR218 | Hair regeneration | Exosome treatment, knockout |
| EDAR | Ectodermal dysplasia | Point mutation knock-in mouse |
| FOXN1 | Nude phenotype, hair loss | Knockout mouse, knock-in |
Alopecia (Hair Loss)
Alopecia is a common disorder characterized by hair loss due to premature termination of the anagen phase or failure to re-enter anagen. Androgenetic alopecia, the most common form, involves progressive miniaturization of hair follicles and shortening of the anagen phase. Dysregulation of Wnt/β-catenin signaling is implicated in alopecia pathogenesis. Understanding the hair cycle process is essential for developing therapeutic strategies for alopecia.
Acne Vulgaris
Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit, which includes the hair follicle and sebaceous gland. The hair cycle process influences sebaceous gland activity and follicular keratinization, contributing to acne pathogenesis. Dysregulation of hair follicle cycling can lead to follicular plugging and inflammation. Research on the hair cycle provides insights into acne development and potential treatments.
Hair Graying
Hair graying is associated with defective melanocyte stem cell maintenance during the hair cycle. Melanocyte stem cells reside in the hair follicle bulge and are activated during anagen to produce pigment. Failure to maintain these stem cells leads to loss of pigmentation and hair graying. The hair cycle process is therefore critical for understanding pigmentation disorders.
From hair cycle process-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate anagen initiation? | Conditional knockout mouse |
| Does point mutation in gene Y affect hair cycle? | Point mutation knock-in mouse |
| Does overexpression of gene Z promote hair growth? | Transgenic overexpression mouse |
| What is the role of gene A in stem cell quiescence? | Lineage tracing, knockout |
| How does gene B affect hair follicle regeneration? | Knock-in reporter, single-cell RNA-seq |
| Does gene C regulate β-catenin signaling? | Knockout, overexpression, luciferase assay |
How to Study the hair cycle process Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Single-cell RNA-seq | Gene expression at single-cell resolution | Reconstructing human hair cycle dynamics |
| Lineage tracing | Stem cell fate and contribution | Tracking hair follicle stem cells |
| Conditional knockout | Gene function in specific tissues | Studying Wnt/β-catenin in anagen |
| Exosome profiling | microRNA content and function | Identifying paracrine regulators |
| Immunohistochemistry | Protein localization and expression | Detecting stem cell markers |
| Western blot | Protein expression levels | Validating signaling changes |
| qRT-PCR | mRNA expression levels | Quantifying gene expression |
| Flow cytometry | Cell surface marker expression | Isolating hair follicle stem cells |
Single-Cell Transcriptomics
Single-cell RNA sequencing has been used to reconstruct the human hair cycle, capturing temporal dynamics of skin tissue remodeling. This method allows researchers to identify distinct cell populations and gene expression changes during anagen, catagen, and telogen. It provides unprecedented resolution for understanding hair follicle stem cell heterogeneity.
Lineage Tracing
Lineage tracing using Cre-loxP systems enables researchers to track the fate of hair follicle stem cells during the hair cycle. This method has been instrumental in identifying stem cell populations in the bulge and their contribution to hair regeneration. It helps determine whether specific genes are required for stem cell activation.
Conditional Knockout Models
Conditional knockout mice allow tissue-specific and temporal control of gene deletion in hair follicles. This approach is essential for studying genes that are embryonic lethal or have pleiotropic effects. It has been used to demonstrate the role of Wnt/β-catenin signaling in anagen initiation.
Exosome and microRNA Profiling
Exosomes isolated from dermal cells can be analyzed for microRNA content and function. miR-218-5p in dermal exosomes has been shown to promote hair regeneration by regulating β-catenin signaling. This method is useful for identifying paracrine regulators of the hair cycle.
How CRISPR Can Be Used to Study GO:0022405 hair cycle process
Knockout
CRISPR knockout models are used to study the loss-of-function effects of genes involved in the hair cycle process. For example, knockout of CTNNB1 in hair follicle stem cells abolishes anagen initiation and hair regeneration. These models help determine whether a gene is essential for specific hair cycle phases.
Point Mutation
CRISPR point mutation models introduce specific nucleotide changes to mimic human disease-associated variants. For example, point mutations in EDAR cause ectodermal dysplasia and hair abnormalities. These models are valuable for studying the functional consequences of genetic variants in hair cycle genes.
Knock-in
CRISPR knock-in models allow the insertion of reporter genes or tags to track gene expression and localization. For example, knock-in of fluorescent reporters into stem cell markers enables lineage tracing during the hair cycle. These models are essential for understanding dynamic gene expression patterns.
Overexpression
CRISPR overexpression models are used to study the gain-of-function effects of genes in the hair cycle. For example, overexpression of miR-218-5p in dermal cells promotes hair regeneration via β-catenin signaling. These models help identify genes that can drive hair follicle regeneration.
How EDITGENE Supports hair cycle process Research
Researchers studying hair cycle process-related genes often need to determine whether a candidate gene is causally involved in hair follicle regeneration, stem cell activation, or disease pathogenesis. EDITGENE provides comprehensive CRISPR gene editing services to support these investigations, from knockout and point mutation models to knock-in reporters and overexpression systems.
Contact EDITGENE today to design your custom CRISPR model for hair cycle process research.
Frequently Asked Questions About hair cycle process
What is GO:0022405 hair cycle process?
GO:0022405 hair cycle process is a biological process that describes the cyclical phases of hair growth (anagen), regression (catagen), quiescence (telogen), and shedding (exogen).
What genes are involved in the hair cycle process?
Key genes include CTNNB1 (β-catenin), WNT3A, BMP4, SHH, NOTCH1, and MIR218, among others.
What are the four phases of the hair cycle?
The four phases are anagen (growth), catagen (regression), telogen (quiescence), and exogen (shedding).
How is the hair cycle regulated?
The hair cycle is regulated by signaling pathways including Wnt/β-catenin, BMP, Shh, and Notch, as well as transcription factors and microRNAs.
What diseases are associated with hair cycle dysfunction?
Diseases include alopecia, acne vulgaris, and hair graying.
What research methods are used to study the hair cycle?
Methods include single-cell RNA-seq, lineage tracing, conditional knockout, and exosome profiling.
How does Wnt signaling affect the hair cycle?
Wnt/β-catenin signaling promotes anagen initiation and hair follicle regeneration.
What is the role of dermal exosomes in hair regeneration?
Dermal exosomes containing miR-218-5p promote hair regeneration by regulating β-catenin signaling.
Can CRISPR be used to study hair cycle genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to study hair cycle gene function.
What is the significance of single-cell transcriptomics in hair cycle research?
Single-cell transcriptomics has reconstructed the human hair cycle, revealing temporal dynamics of skin tissue remodeling.
Conclusion
The hair cycle process (GO:0022405) is a fundamental biological process that governs the cyclical phases of hair growth, regression, quiescence, and shedding. Understanding its molecular regulation is essential for developing treatments for alopecia, acne vulgaris, and hair graying. Recent advances in single-cell transcriptomics and CRISPR gene editing have provided powerful tools to dissect the genetic and signaling networks controlling the hair cycle. EDITGENE offers comprehensive CRISPR services to support researchers in this field, from knockout and point mutation models to library screening and bioinformatics.
References
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- 2. Schneider MR et al.. 2009. The hair follicle as a dynamic miniorgan.. Curr Biol 19(3):R132-42 PMID: 19211055
- 3. Park AM et al.. 2018. Hair Biology: Growth and Pigmentation.. Facial Plast Surg Clin North Am 26(4):415-424 PMID: 30213423
- 4. Moradi Tuchayi S et al.. 2015. Acne vulgaris.. Nat Rev Dis Primers 1:15029 PMID: 27189872
- 5. Paus R et al.. 2024. Human Hair Graying Revisited: Principles, Misconceptions, and Key Research Frontiers.. J Invest Dermatol 144(3):474-491 PMID: 38099887
- 6. Yokota J et al.. 2025. Single-cell transcriptomic reconstruction of the human hair cycle: Capturing the temporal dynamics of skin tissue remodeling.. Cell Rep 44(9):116196 PMID: 40884793
- 7. Yardman-Frank JM et al.. 2021. Skin pigmentation and its control: From ultraviolet radiation to stem cells.. Exp Dermatol 30(4):560-571 PMID: 33320376
- 8. Hu S et al.. 2020. Dermal exosomes containing miR-218-5p promote hair regeneration by regulating β-catenin signaling.. Sci Adv 6(30):eaba1685 PMID: 32832660
