Recently, the research team led by Professor Chenghong Yin at Beijing Obstetrics and Gynecology Hospital, Capital Medical University, published a paper titled “CDH4/UBA1/RBMX axis promotes polycystic ovary syndrome progression through YAP1 activation” in the CAS Q1 journal Cellular & Molecular Biology Letters. This study confirms that abnormal proliferation of ovarian granulosa cells promotes ovarian dysfunction in polycystic ovary syndrome (PCOS) and reveals for the first time the molecular mechanism by which the CDH4/UBA1/RBMX axis regulates abnormal granulosa cell proliferation.

In PCOS patients, reduced apoptosis and abnormal proliferation of ovarian granulosa cells are core causes of ovulatory dysfunction and infertility. CDH4 acts as a “molecular switch” that is abnormally highly expressed in the ovarian granulosa cells of PCOS patients. By manipulating a novel UBA1-RBMX-YAP1 signaling axis, it not only exacerbates ovarian inflammation but also blocks normal apoptosis of granulosa cells, providing a highly promising new therapeutic target for PCOS.

CDH4 is abnormally elevated in the ovaries of PCOS patients and is closely associated with the Hippo pathway

The research team first analyzed public database sequencing data of ovarian granulosa cells from PCOS patients (GSE168404 and PMID29344314) and found that CDH4 (cadherin 4) expression was significantly higher in PCOS patients than in normal women. Further bioinformatics analysis revealed a close correlation between CDH4 and multiple core components of the Hippo signaling pathway (Figure 1A-C).

In vitro experiments confirmed that after stimulating the human granulosa cell line KGN with dehydroepiandrosterone (DHEA) to simulate the PCOS environment, both mRNA and protein levels of CDH4 increased with increasing stimulation concentration and time (Figure 1F-H). This provided the first clue to the involvement of CDH4 in PCOS pathogenesis.

Animal model confirms that CDH4 knockout significantly improves reproductive and metabolic abnormalities in PCOS

To clarify the function of CDH4, the research team constructed two different PCOS mouse models and used CDH4 knockout mice.

In the DHEA-induced PCOS model, compared with wild-type PCOS mice, CDH4 knockout mice (KO+DHEA) showed significantly reduced serum testosterone levels and markedly decreased inflammatory cytokines IL-6 and TNF-α (Figure 2C-E).

Ovarian histomorphology revealed that in CDH4-deficient mice, the number of abnormally developed cystic follicles decreased, and normal follicular structure was partially restored (Figure 2F).

At the molecular level, the elevated levels of YAP1 (a key effector of the Hippo pathway), the proliferation marker PCNA, and the anti-apoptotic protein Bcl-2 in the ovaries of PCOS mice were all significantly reduced after CDH4 knockout, while the level of the pro-apoptotic cleaved Caspase-3 increased (Figure 2J).

In the letrozole combined with high-fat diet-induced PCOS model with insulin resistance, CDH4 knockout also brought significant benefits. These mice not only showed less weight gain and lower serum testosterone and inflammatory cytokine levels (Figure 3B-E), but also exhibited marked improvement in insulin resistance, as evidenced by a reduced area under the glucose curve in the oral glucose tolerance test and lower serum insulin levels (Figure 3F-H).

Ovarian morphology and molecular changes were consistent with the DHEA model, indicating that CDH4 deficiency partially reversed PCOS-related ovarian abnormalities and the elevations of YAP1 and Bcl-2 (Figure 3I-L).

Taken together, the results from both animal models clearly demonstrate that CDH4 is a key driver of PCOS pathology, and its deficiency effectively ameliorates ovulatory, metabolic, and inflammatory symptoms of PCOS.

Cellular mechanism: CDH4 affects granulosa cell function by regulating YAP1

In cultured human granulosa cell line KGN, the study further elucidated the function of CDH4. By constructing KGN cells with stable CDH4 knockdown, the researchers found that:

Knockdown of CDH4 significantly inhibited cell proliferation (Figure 4C-D).

In a DHEA-stimulated PCOS-like cell model, knockdown of CDH4 reversed PCOS-related pathological changes, manifested by downregulated YAP1 expression, increased cleaved Caspase-3 (increased apoptosis), decreased Bcl-2, IL-6, and TNF-α levels, along with decreased mitochondrial membrane potential and increased apoptosis (Figure 4E-G).

Most critically, the study established a regulatory relationship between CDH4 and YAP1. Results showed that CDH4 knockdown reduced YAP1 mRNA and protein levels (including total and phosphorylated protein) (Figure 5A-B), whereas CDH4 overexpression upregulated YAP1 expression (Figure 5C-D).

Functionally, treatment of PCOS-like cells with the YAP1 inhibitor verteporfin similarly reduced inflammatory cytokine levels and impaired mitochondrial function (Figure 5G-H), consistent with the effect of CDH4 knockdown. This indicates that CDH4 exerts its pathogenic role by positively regulating YAP1.

Core mechanism revealed: The CDH4/UBA1/RBMX axis regulates YAP1 through ubiquitin-mediated degradation

Then, how does CDH4, a membrane-bound cadherin, regulate the downstream transcription factor YAP1? Using co-immunoprecipitation combined with mass spectrometry, the researchers identified a key intermediary bridge—RBMX (RNA-binding motif protein X-linked).

Experiments confirmed a direct physical interaction between CDH4 and RBMX (Figure 6B-C). Upon CDH4 knockdown, RBMX protein levels increased, but its mRNA levels remained unchanged (Figure 6D, 8A), suggesting that CDH4 may negatively regulate RBMX at the protein level. Further investigation revealed that RBMX itself is a negative regulator of YAP1: RBMX knockdown led to increased YAP1 mRNA stability and consequently upregulated YAP1 protein levels (Figure 6G-J).

Thus, a clear regulatory chain emerged: CDH4 binds to and promotes the degradation of RBMX, thereby relieving RBMX-mediated inhibition of YAP1, leading to elevated YAP1 levels. CDH4 degrades RBMX by recruiting the ubiquitin-activating enzyme UBA1. The study found that CDH4, UBA1, and RBMX form a complex (Figure 8E), and CDH4 promotes ubiquitination of RBMX via UBA1, leading to its proteasomal degradation (Figures 8B-D, 8I-J). Knockdown of UBA1 stabilized RBMX protein.

Finally, a series of “rescue” experiments confirmed the functional integrity of this axis. In CDH4 knockdown cells, further knockdown of RBMX (which restores YAP1 levels) partially reversed the cellular phenotypic changes caused by CDH4 deficiency (Figure 7F-I), such as recovery of mitochondrial membrane potential and restoration of inflammatory cytokine levels. This strongly demonstrates that CDH4 primarily influences YAP1 and its downstream functions by regulating RBMX.

Conclusion

This study reveals for the first time a novel pathogenic pathway in PCOS: CDH4 recruits UBA1 to promote ubiquitin-mediated degradation of RBMX, thereby relieving RBMX-mediated negative regulation of YAP1 mRNA, leading to YAP1 overexpression, which ultimately drives abnormal proliferation of ovarian granulosa cells, inflammatory responses, and dysfunction.

These findings not only deepen our understanding of PCOS pathogenesis but also position CDH4 and its downstream targets UBA1 and YAP1 as highly promising therapeutic targets. In the future, specific intervention strategies targeting this pathway may offer new treatment options for PCOS patients.

Expert Profiles

Professor Chenghong Yin

Beijing Obstetrics and Gynecology Hospital, Capital Medical University

Professor, Chief Physician, Doctoral Supervisor.
Beijing Scholar, recipient of the State Council Government Special Allowance.

Professor Yin has long been dedicated to clinical and basic research in obstetrics, gynecology, and internal medicine, solving a series of key clinical technical problems. He has led projects including the National “Tenth Five-Year” Science and Technology Tackling Program, the “Eleventh Five-Year” Key Technology Support Program, the “Thirteenth Five-Year” National Key R&D Program, sub-projects of the “Fourteenth Five-Year” National Key R&D Program, and the National Natural Science Foundation of China. He has published over 500 papers as first or corresponding author, including more than 220 in SCI-indexed journals. He has served as editor-in-chief, associate editor, or associate translator for 35 monographs and textbooks. He has received more than ten scientific and technological awards, including the Beijing Science and Technology Progress Award, the National Ministry of Education Science and Technology Award, the National Maternal and Child Health Science and Technology Award, and the Chinese Medical Science and Technology Award. He has been selected for numerous talent programs, including National Outstanding Contribution Young and Middle-Aged Expert, Beijing Outstanding Contribution Science, Technology, and Management Talent, and various other prestigious talent projects.

Associate Professor Yingyi Luan
Beijing Obstetrics and Gynecology Hospital, Capital Medical University

Researcher, Associate Professor, Master’s Supervisor, Visiting Scholar at the University of Pittsburgh.
Main research directions: pathogenesis and immune intervention strategies of sepsis and MODS; pathogenesis and intervention strategies of PCOS.
Serves as a member of the Shock Professional Committee of the Chinese Pathophysiology Society, a youth member of the Shock and Sepsis Professional Committee of the Chinese Research Hospital Association, a member of the Reproductive Immunology Professional Committee of the National Health Industry Enterprise Management Association, and a youth editorial board member of the Journal of Translational Internal Medicine.
In 2017, she was selected for the Beijing “Science and Technology Rising Star” talent program. As a core member, she received the First Prize of Military Science and Technology Progress Award (2024). She has led 12 research projects as project leader, including the National Natural Science Foundation of China (3 projects), the Beijing Science and Technology Rising Star Program Cross Cooperation Project, the Beijing Natural Science Foundation General Project, and the China University Industry-University-Research Innovation Fund. She has published over 40 SCI papers as first or corresponding author in journals such as Cellular & Molecular Biology Letters, Phytomedicine, and Burns & Trauma. She has co-edited 3 medical monographs and filed 4 invention patents.

Dr. Ning Xu
Beijing Obstetrics and Gynecology Hospital, Capital Medical University

Main research direction: pathogenesis and intervention strategies of PCOS.
Participated in the application and implementation of projects including the Fourteenth Five-Year National Key R&D Program, the National Natural Science Foundation of China, the Beijing High-level Public Health Technical Talent Program, and the Capital Health Development Research Special Project.
She has published 3 SCI papers as first author in journals such as Cell Death Discovery and iScience.