GO:0051794 regulation of timing of catagen: Hair Cycle Control, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0051794 (regulation of timing of catagen) describes any process that modulates the frequency, rate or extent of the timing of catagen, the regression phase of the hair cycle.
• Catagen is the apoptosis-driven involution phase that transitions a growing (anagen) follicle into a resting (telogen) follicle, and its timing determines hair length and cycle periodicity.
• Transcriptomic studies in cashmere and Angora goats have identified stage-specific gene expression changes from catagen to telogen, providing candidate regulators of catagen timing.
• Keratin 17 (KRT17) modulates hair follicle cycling in a TNF-alpha-dependent manner, directly linking an intermediate filament protein to catagen regulation.
• The hairless gene (HR) is a key regulator of hair root biology and a subtle pleiotropic factor in the hair cycle, with mutations causing hair loss phenotypes.
• mTORC1 signaling may modulate the timing of anagen entry, indirectly influencing when catagen occurs within the cycle.
• Telogen is now recognized as an actively maintained stage rather than a passive resting state, with its own regulatory programs that feed back on catagen timing.
Description
The hair follicle is a dynamic mini-organ that cycles through anagen (growth), catagen (regression), and telogen (rest) phases. GO:0051794, regulation of timing of catagen, is the biological process that controls when and how quickly the follicle transitions from anagen to catagen and completes its regression. This process is fundamental to understanding hair length determination, cycle periodicity, and pathological hair loss. Disruption of catagen timing can lead to premature hair shedding, delayed follicle involution, or altered hair fiber characteristics. In livestock species such as cashmere and Angora goats, catagen timing directly affects fiber yield and quality, making it an economically important trait. At the molecular level, catagen is driven by apoptosis of the lower follicle, and its timing is regulated by a complex interplay of growth factors, transcription factors, and extracellular matrix remodeling enzymes. Recent transcriptomic analyses have begun to reveal the gene networks that orchestrate this transition, identifying candidate regulators that may serve as targets for genetic or pharmacological intervention. Understanding GO:0051794 is therefore essential for researchers in dermatology, hair biology, and animal science who seek to manipulate hair follicle cycling for therapeutic or agricultural benefit.
regulation of timing of catagen At A Glance
| GO ID | GO:0051794 |
|---|---|
| GO term | regulation of timing of catagen |
| Ontology | biological_process |
| Synonym | regulation of catagen |
| Definition | Any process that modulates the frequency, rate or extent of timing of catagen, the regression phase of the hair cycle. |
| Major function | Controls the onset and progression of the regression phase of the hair cycle, influencing hair length and cycle periodicity. |
| Related process | Hair cycle, catagen, telogen, anagen, apoptosis |
| Taxonomic scope | Metazoa, particularly mammals |
| Research relevance | Target for hair loss therapies, livestock fiber improvement, and developmental biology studies. |
What Is GO:0051794?
GO:0051794, regulation of timing of catagen, is defined as any process that modulates the frequency, rate or extent of the timing of catagen, the regression phase of the hair cycle. In other words, it encompasses all molecular and cellular mechanisms that determine when catagen begins, how long it lasts, and how quickly the follicle involutes. This regulation ensures that the hair cycle proceeds in an orderly fashion, balancing hair growth with shedding and regeneration.
Why Is regulation of timing of catagen Important in Cell Biology?
Regulation of catagen timing is critically important because it determines the duration of the growth phase and the overall hair cycle period, directly affecting hair length, fiber quality, and the balance between hair growth and shedding. In humans, dysregulation of catagen timing is associated with premature hair loss, while in livestock, it influences cashmere and wool yield. Understanding the molecular regulators of GO:0051794 can lead to new therapeutic strategies for alopecia and improved breeding programs for fiber-producing animals.
• Determines hair length and cycle periodicity by controlling when anagen ends and catagen begins.
• Affects hair shedding and regeneration, with implications for alopecia and other hair disorders.
• Influences fiber yield and quality in cashmere and Angora goats, with economic impact.
• Involves apoptosis and tissue remodeling, providing a model for studying programmed cell death in regenerative tissues.
• Regulated by signaling pathways such as TNF-alpha and mTORC1, linking it to inflammation and metabolism.
• The hairless gene (HR) is a key regulator, and its mutations cause hair loss phenotypes in mice and humans.
• Telogen maintenance is an active process that feeds back on catagen timing, highlighting the dynamic nature of the cycle.
• Transcriptomic studies have identified stage-specific gene expression changes, offering candidate targets for manipulation.
• Understanding catagen timing can inform strategies for hair follicle regeneration and tissue engineering.
• Conservation of hair cycle regulation across mammals makes it a valuable comparative biology topic.
What Happens During regulation of timing of catagen?
Initiation of catagen: signaling and apoptosis
In simple terms: Catagen begins when the growing phase is switched off and the lower part of the hair follicle starts to shrink.
The initiation of catagen is marked by a decline in anagen-promoting signals and an increase in pro-apoptotic factors. In mouse hair follicles, keratin 17 (KRT17) modulates hair follicle cycling in a TNF-alpha-dependent fashion, suggesting that inflammatory cytokines can influence the timing of catagen. The hairless gene (HR) is also critical for hair root biology and its mutation leads to hair loss, indicating a role in catagen regulation. Transcriptomic analyses in cashmere goats have identified critical genes for the transition from catagen to telogen, including those involved in apoptosis and cell cycle regulation.
Progression of catagen: follicular regression
In simple terms: During catagen, the lower follicle shrinks as cells die and the dermal papilla condenses.
Catagen progression involves coordinated apoptosis of the lower follicle keratinocytes, basement membrane remodeling, and condensation of the dermal papilla. Molecular studies have shown that this phase is characterized by changes in gene expression related to extracellular matrix degradation and cell death. In Angora goats, RNA-Seq-based differential gene expression during hair follicle development has revealed dynamic changes in genes associated with catagen progression. Similarly, transcriptomic landscape analyses in cashmere goats have highlighted the importance of stage-specific gene networks.
Termination of catagen and entry into telogen
In simple terms: Catagen ends when the follicle reaches its shortest state and enters the resting phase, telogen.
The termination of catagen is marked by the formation of a club hair and the establishment of telogen. Telogen was traditionally viewed as a passive resting phase, but it is now recognized as an actively maintained stage with its own regulatory programs that can influence the timing of the next catagen. The transition from catagen to telogen involves the stabilization of the follicle and the preparation for the next anagen phase. Studies in cashmere goats have identified genes that are specifically upregulated during this transition, providing insights into the molecular control of catagen termination.
Regulation by mTORC1 and metabolic signals
In simple terms: Metabolic pathways like mTORC1 can affect when the hair cycle moves from one phase to another.
Mammalian target of rapamycin complex 1 (mTORC1) may modulate the timing of anagen entry in mouse hair follicles, which indirectly influences when catagen occurs. This suggests that nutrient and energy sensing pathways can regulate the timing of catagen by controlling the overall pace of the hair cycle. The interplay between metabolism and hair cycle regulation is an emerging area of research, with potential implications for understanding how systemic factors affect hair growth and shedding.
Stage-specific gene expression networks
In simple terms: Different genes are turned on or off at each stage of the hair cycle, and these patterns control catagen timing.
Transcriptomic studies have revealed that the hair follicle undergoes extensive changes in gene expression during the catagen-to-telogen transition. In Inner Mongolia cashmere goats, critical genes for the hair follicle from catagen to telogen have been identified, including those involved in Wnt signaling, apoptosis, and cell adhesion. In Angora goats, RNA-Seq-based differential gene expression during hair follicle development has provided a comprehensive view of the molecular events. These studies highlight the complexity of the regulatory networks that control catagen timing and offer candidate genes for functional studies.
Key Genes Involved in GO:0051794 regulation of timing of catagen
The following genes have been implicated in the regulation of catagen timing based on transcriptomic and functional studies in model organisms and livestock species.
| Gene | Major Role | Research Relevance |
|---|---|---|
| KRT17 | Modulates hair follicle cycling in a TNF-alpha-dependent fashion | Links intermediate filament proteins to catagen regulation |
| HR | Hairless gene, critical for hair root biology and pleiotropic effects | Mutations cause hair loss; key regulator of catagen |
| TNF | Pro-inflammatory cytokine that influences catagen timing | TNF-alpha signaling affects KRT17-mediated hair cycle modulation |
| mTOR | Serine/threonine kinase in mTORC1 complex | May modulate timing of anagen entry, indirectly affecting catagen |
| WNT | Signaling pathway involved in hair follicle cycling | Stage-specific expression changes during catagen-telogen transition |
| BMP | Bone morphogenetic protein signaling | Involved in hair follicle regression and quiescence |
| FGF | Fibroblast growth factor signaling | Regulates hair follicle growth and cycling |
| TP53 | Tumor suppressor and apoptosis regulator | Apoptosis during catagen may involve p53 pathway |
| CASP3 | Executioner caspase in apoptosis | Mediates cell death during catagen regression |
| BCL2 | Anti-apoptotic protein | Modulates apoptosis in hair follicle during catagen |
| VDR | Vitamin D receptor | Associated with hair cycle regulation and catagen timing |
| PPARG | Peroxisome proliferator-activated receptor gamma | Involved in lipid metabolism and hair follicle cycling |
| SIRT1 | NAD-dependent deacetylase | May link metabolism to hair cycle regulation |
| CTNNB1 | Beta-catenin, key Wnt signaling component | Critical for hair follicle stem cell activation and cycling |
| SHH | Sonic hedgehog signaling | Regulates hair follicle morphogenesis and cycling |
| NOTCH | Notch signaling pathway | Involved in hair follicle differentiation and cycling |
| EDAR | Ectodysplasin A receptor | Affects hair follicle development and cycling |
How Is regulation of timing of catagen Regulated?
The regulation of catagen timing is a complex process involving multiple signaling pathways. mTORC1 may modulate the timing of anagen entry, thereby indirectly influencing when catagen occurs. TNF-alpha signaling, through KRT17, can modulate hair follicle cycling and affect catagen timing. The hairless gene (HR) acts as a key regulator of hair root biology, and its expression is tightly controlled during the hair cycle. Additionally, telogen is now recognized as an actively maintained stage with its own regulatory programs that can feed back on catagen timing. Transcriptomic studies have identified stage-specific gene expression changes that suggest the involvement of Wnt, BMP, and Notch pathways in regulating the catagen-to-telogen transition.
regulation of timing of catagen and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HR | Atrichia with papular lesions, hair loss | Hr knockout mouse, point mutation knock-in |
| KRT17 | Ectodermal dysplasia, hair cycle abnormalities | Krt17 knockout mouse, TNF-alpha treatment model |
| TNF | Inflammatory hair loss, alopecia areata | TNF transgenic mouse, TNF inhibitor treatment |
| mTOR | Hair cycle modulation, metabolic disorders | mTOR conditional knockout mouse, rapamycin treatment |
| WNT | Hair follicle cycling disorders | Wnt reporter mouse, beta-catenin knockout |
Alopecia and hair loss disorders
Dysregulation of catagen timing can lead to premature termination of anagen and excessive hair shedding, contributing to alopecia. The hairless gene (HR) is directly linked to hair loss phenotypes, and mutations in HR cause atrichia with papular lesions in humans. Understanding the molecular control of catagen timing may provide therapeutic targets for treating hair loss disorders.
Chemotherapy-induced hair loss
Many chemotherapeutic agents induce apoptosis in hair follicle cells, prematurely triggering catagen and causing severe hair loss. The apoptosis-driven nature of catagen makes it a sensitive target for cytotoxic drugs. Research into the regulation of catagen timing could inform strategies to protect hair follicles during chemotherapy.
Livestock fiber production
In cashmere and Angora goats, the timing of catagen directly affects the length and quality of the fiber harvested. Transcriptomic studies have identified genes associated with catagen progression that could be targeted for genetic selection or management practices to improve fiber yield.
From regulation of timing of catagen-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate catagen timing? | Knockout mouse or goat model with gene X deletion |
| Does a specific point mutation in gene X alter catagen onset? | Point mutation knock-in mouse or cell line |
| Does overexpression of gene X delay catagen? | Transgenic overexpression mouse or lentiviral overexpression in hair follicle cells |
| Where is gene X expressed during catagen? | Tagged knock-in reporter mouse (e.g., GFP) or RNA in situ hybridization |
| What are the downstream targets of gene X during catagen? | RNA-seq and ChIP-seq in knockout vs wild-type follicles |
| Can CRISPR library screening identify novel regulators of catagen? | In vitro hair follicle organ culture with CRISPR library transduction |
How to Study the regulation of timing of catagen Process
| Method | What It Measures | Typical Application |
|---|---|---|
| RNA-seq | Global gene expression changes | Identify differentially expressed genes during catagen-telogen transition |
| Single-cell RNA-seq | Cell-type-specific expression | Dissect heterogeneity of hair follicle cells during catagen |
| Histology and immunofluorescence | Morphological changes and protein localization | Visualize catagen progression and apoptosis |
| Western blot | Protein expression and modification | Validate candidate regulators in knockout vs wild-type |
| qRT-PCR | Quantitative gene expression | Confirm RNA-seq findings for specific genes |
| CRISPR knockout | Gene function loss | Test causality of candidate genes in hair follicle cells |
| Transgenic overexpression | Gain-of-function effects | Assess whether gene overexpression alters catagen timing |
| Pharmacological inhibition | Pathway activity modulation | Study mTORC1 or TNF-alpha effects on catagen |
Transcriptomic profiling of hair cycle stages
RNA-seq has been widely used to identify differentially expressed genes during the catagen-to-telogen transition in cashmere and Angora goats. These studies provide a comprehensive list of candidate regulators of catagen timing and reveal stage-specific gene networks.
Functional validation using knockout and transgenic models
Knockout and transgenic mouse models have been instrumental in demonstrating the roles of specific genes such as KRT17 and HR in hair follicle cycling and catagen regulation. These models allow researchers to test causality and dissect molecular pathways.
Pharmacological modulation of signaling pathways
Treatment with rapamycin to inhibit mTORC1 has been used to study the timing of anagen entry, indirectly affecting catagen. Similarly, TNF-alpha inhibitors can modulate KRT17-mediated effects on hair cycling.
Imaging and histological analysis of catagen progression
Histological and immunofluorescence techniques are used to visualize the morphological changes during catagen, including apoptosis and dermal papilla condensation. These methods complement molecular studies by providing spatial and temporal context.
How CRISPR Can Be Used to Study GO:0051794 regulation of timing of catagen
Knockout
CRISPR knockout of candidate genes such as KRT17 or HR in mouse models or hair follicle cell lines can directly test their requirement for normal catagen timing. For example, Krt17 knockout mice exhibit altered hair follicle cycling, demonstrating its role in catagen regulation. Similarly, Hr knockout mice display hair loss phenotypes, confirming its function.
Point Mutation
Introducing specific point mutations identified in human patients or livestock into the orthologous gene can reveal how subtle changes affect catagen timing. For instance, mutations in HR cause atrichia with papular lesions, and modeling these mutations in mice can provide insights into the molecular mechanisms.
Knock-in
Knock-in of reporter tags (e.g., GFP) or conditional alleles allows precise tracking of gene expression and function during catagen. Tagged knock-in of KRT17 or HR can reveal their spatiotemporal dynamics in the hair follicle.
Overexpression
CRISPR activation (CRISPRa) or transgenic overexpression of candidate genes can test whether increased levels alter catagen timing. Overexpression of KRT17 or TNF-alpha in mouse skin may accelerate or delay catagen, providing gain-of-function evidence.
How EDITGENE Supports regulation of timing of catagen Research
Researchers studying regulation of timing of catagen-related genes often need to determine whether a candidate gene is causally involved in the onset or progression of catagen. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such functional studies, from gene knockout to precise point mutations and overexpression models.
Contact EDITGENE today to design your custom CRISPR model for regulation of timing of catagen research.
Frequently Asked Questions About regulation of timing of catagen
What is GO:0051794 regulation of timing of catagen?
GO:0051794 is a Gene Ontology biological process term defined as any process that modulates the frequency, rate or extent of the timing of catagen, the regression phase of the hair cycle.
What genes are involved in regulation of timing of catagen?
Key genes include KRT17, HR, TNF, mTOR, and components of Wnt, BMP, and Notch signaling pathways, as identified in transcriptomic and functional studies.
Why is catagen timing important for hair growth?
Catagen timing determines the duration of the growth phase and the overall hair cycle period, affecting hair length, shedding, and regeneration.
How is catagen regulated at the molecular level?
Catagen is regulated by apoptosis, growth factor withdrawal, and signaling pathways such as TNF-alpha and mTORC1, with transcription factors like HR playing critical roles.
What diseases are associated with abnormal catagen timing?
Abnormal catagen timing is linked to alopecia, chemotherapy-induced hair loss, and hair cycle disorders, with HR mutations causing atrichia with papular lesions.
What model organisms are used to study catagen timing?
Mouse models are widely used, including knockout and transgenic lines for KRT17, HR, and mTOR, as well as livestock species like cashmere and Angora goats for fiber research.
How can CRISPR be used to study regulation of timing of catagen?
CRISPR knockout, point mutation, knock-in, and overexpression can test the causal role of candidate genes in catagen timing in cell lines and animal models.
What are the latest research findings on catagen timing?
Recent transcriptomic studies in cashmere and Angora goats have identified stage-specific gene expression changes during catagen-to-telogen transition, revealing new candidate regulators.
Is telogen a passive resting phase?
No, telogen is now recognized as an actively maintained stage with its own regulatory programs that can influence catagen timing.
How does mTORC1 affect catagen timing?
mTORC1 may modulate the timing of anagen entry, which indirectly influences when catagen occurs in the hair cycle.
Conclusion
Regulation of timing of catagen (GO:0051794) is a critical biological process that controls the regression phase of the hair cycle, with profound implications for hair growth, shedding, and fiber production. Research has identified key molecular players such as KRT17, HR, and mTORC1, and transcriptomic studies continue to uncover new candidate regulators. Understanding this process offers opportunities for therapeutic intervention in hair loss disorders and for genetic improvement in livestock. EDITGENE provides the CRISPR tools and services needed to functionally validate these regulators and advance the field.
References
- 1. Su R et al.. 2018. Transcriptomic analysis reveals critical genes for the hair follicle of Inner Mongolia cashmere goat from catagen to telogen.. PLoS One 13(10):e0204404 PMID: 30356261
- 2. Geyfman M et al.. 2015. Resting no more: re-defining telogen, the maintenance stage of the hair growth cycle.. Biol Rev Camb Philos Soc 90(4):1179-96 PMID: 25410793
- 3. Bernard BA. 1994. [Molecular approach of hair biology].. C R Seances Soc Biol Fil 188(3):223-33 PMID: 7834505
- 4. Kellenberger AJ et al.. 2013. Mammalian target of rapamycin complex 1 (mTORC1) may modulate the timing of anagen entry in mouse hair follicles.. Exp Dermatol 22(1):77-80 PMID: 23278901
- 5. Tong X et al.. 2006. Keratin 17 modulates hair follicle cycling in a TNFalpha-dependent fashion.. Genes Dev 20(10):1353-64 PMID: 16702408
- 6. Nonchev S et al.. 2006. [The mouse hairless gene: its function in hair root and at the heart of a subtle pleiotropy].. Med Sci (Paris) 22(5):525-30 PMID: 16687122
- 7. Selçuk SE et al.. 2026. Investigating RNA-Seq-based differential gene expression during hair follicle development in Angora goat skin.. J Anim Sci Technol 68(1):72-95 PMID: 41695674
- 8. Nocelli C et al.. 2020. Shedding light on cashmere goat hair follicle biology: from morphology analyses to transcriptomic landascape.. BMC Genomics 21(1):458 PMID: 32615938
