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Updated: Jun 5, 2026
A New Technique for Quantitative Analysis of Hair Loss in Mice Using Grayscale Analysis
Published on: March 9, 2015
Conditional activin receptor type 1B (Acvr1b) knockout mice reveal hair loss abnormality
Wanglong Qiu1, Xiaojun Li, Hongyan Tang
1Department of Otolaryngology and Head and Neck Surgery, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Abstract:
The in vivo functions of the activin A receptor type 1b (Acvr1b) have been difficult to study because Acvr1b(-/-) mice die during embryogenesis. To investigate the roles of Acvr1b in the epithelial tissues, we created mice with a conditional disruption of Acvr1b (Acvr1b(flox/flox)) and crossed them with K14-Cre mice. Acvr1b(flox/flox); K14-Cre mice displayed various degrees of hairlessness at postnatal day 5, and the phenotype is exacerbated by age. Histological analyses showed that those hair follicles that developed during morphogenesis were later disrupted by delays in hair cycle reentry. Failure in cycling of the hair follicles and regrowth of the hair shaft and the inner root sheath resulted in subsequent severe hair loss. Apart from previous reports of other members of the transforming growth factor-β/activin/bone morphogenic protein pathways, we demonstrate a specialized role for Acvr1b in hair cycling in addition to hair follicle development. Acvr1b(flox/flox); K14-Cre mice also had a thicker epidermis than did wild-type mice, which resulted from persistent proliferation of skin epithelial cells; however, no tumor formation was observed by 18 months of age. Our analysis of this Acvr1b knockout mouse line provides direct genetic evidence that Acvr1b signaling is required for both hair follicle development and cycling.
Insights
Activin A receptor type 1b (Acvr1b) is crucial for hair follicle development and cycling. Conditional Acvr1b disruption in mice leads to hair loss and epidermal thickening, highlighting its role in skin epithelial homeostasis.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- The in vivo functions of activin A receptor type 1b (Acvr1b) are largely unknown due to embryonic lethality in Acvr1b knockout mice.
- Understanding Acvr1b's role in epithelial tissues is essential for insights into developmental processes and potential therapeutic targets.
Purpose of the Study:
- To investigate the specific roles of Acvr1b in hair follicle development and cycling within epithelial tissues.
- To elucidate the function of Acvr1b signaling in skin epithelial cell proliferation and homeostasis.
Main Methods:
- Generation of conditional knockout mice (Acvr1b(flox/flox); K14-Cre) to study Acvr1b function in epithelial tissues.
- Histological analysis of hair follicles and epidermis in knockout mice to assess developmental and cycling defects.
- Phenotypic observation of hairlessness and epidermal changes over time in the generated mouse model.
Main Results:
- Conditional Acvr1b disruption resulted in varying degrees of hairlessness and disrupted hair follicle cycling, including delayed reentry into the hair cycle.
- Failure in hair follicle cycling led to severe hair loss, impacting hair shaft and inner root sheath regrowth.
- Knockout mice exhibited thicker epidermis due to persistent skin epithelial cell proliferation, without observed tumor formation up to 18 months of age.
Conclusions:
- Acvr1b signaling plays a specialized and essential role in both hair follicle development and the cyclical process of hair growth.
- Acvr1b is critical for maintaining skin epithelial homeostasis, regulating cell proliferation and preventing abnormal growth.
- This study provides direct genetic evidence for Acvr1b's requirement in hair follicle morphogenesis and the hair cycle.
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