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Scientific reports2025; 15(1); 6824; doi: 10.1038/s41598-025-90833-3

Comparison of pregnant mare serum gonadotropin products with surprising differences in protein content.

Abstract: Equine chorionic gonadotropin (eCG) is a widely used hormone that synchronizes the female cycle and induces estrus in livestock. eCG is a heterodimeric glycoprotein composed of non-covalently linked α- and β-chains whose glycosylation profiles determine the in vivo activity of the hormone. The commercially available eCG products are crudely purified from the serum of pregnant mares, hence called pregnant mare serum gonadotropin (PMSG). Appropriate glycosylation of the protein is crucial for the correct binding to the receptor, receptor activation, and its half-life. The exact protein composition of the various commercial PMSG products and their specific glycosylation pattern have not been characterized so far. Therefore, we used proteomic approaches to analyse and compare four commercial PMSG products. Here we show that the examined PMSGs share a surprisingly low level of commonalities (5.5%) in protein composition among the four tested products, with serum proteins as the primary variable. Analysing the site-specific N-glycosylation, we confirmed the presence of O-acetylation of sialic acids at the structure of the glycans of eCG, which we could not find in significant amounts on human CG, suggesting that this modification is species-specific. It remains to be tested whether the O-acetylation plays an important role in the function of PMSG. However, this modification shall be considered while recombinant eCG are produced.
© 2025. The Author(s).
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Publication Date: 2025-02-25 PubMed ID: 40000800PubMed Central: PMC11861321DOI: 10.1038/s41598-025-90833-3Google Scholar: Lookup
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Summary

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This study investigates the protein composition and specific glycosylation patterns of commercial pregnant mare serum gonadotropin (PMSG), a hormone used in livestock management. The researchers found surprising differences among the products and found that a specific modification of the hormone, which could be critical to its function, is specific to the species.

Study Background and Objectives

  • Equine chorionic gonadotropin (eCG), also known as pregnant mare serum gonadotropin (PMSG), is a hormone widely used in the livestock industry to synchronize female cycles and induce estrus.
  • The activity of eCG is determined by its glycosylation profile, which refers to the addition of sugar molecules to the protein. This process is crucial for the hormone to bind to its receptors, activate them, and determine its half-life (the time it stays active in the body).
  • Commercially, eCG is extracted from the serum of pregnant mares, but the exact protein composition and its specific glycosylation pattern have not been fully characterized, hence the intent of this study.

Materials and Methods

  • The researchers used proteomic approaches, techniques that allow the study of complete sets of proteins, to analyze and compare four different commercial PMSG products.

Key Findings

  • The primary finding is the significant variation in protein content across the four PMSG products studied. Only 5.5% of the protein composition was common among the four products, with serum proteins being the main variable component.
  • The study also delved into the site-specific N-glycosylation, particularly the existence of O-acetylation of sialic acids in the structure of eCG glycans. This modification was not found in significant amounts in human CG, which suggests that it is specific to the equine species.
  • The authors noted that the role of O-acetylation in the function of PMSG remains to be tested. However, they highlight that this modification should be taken into account when producing recombinant eCG—a genetically engineered version of this hormone.

Implications and Future Directions

  • The findings could have implications for the livestock industry and biotech companies producing recombinant eCG. Understanding the variation in protein composition could inform adjustments in production processes to ensure effective outcomes when using the hormone in livestock.
  • Future studies are needed to investigate the role and significance of the identified O-acetylation modification on the function and effectiveness of eCG/PMSG.

Cite This Article

APA
Lösle M, Lin CW, Beil-Wagner J, Aebi M, Buch T. (2025). Comparison of pregnant mare serum gonadotropin products with surprising differences in protein content. Sci Rep, 15(1), 6824. https://doi.org/10.1038/s41598-025-90833-3

Publication

Scientific reports
ISSN: 2045-2322
NlmUniqueID: 101563288
Country: England
Language: English
Volume: 15
Issue: 1
Pages: 6824
PII: 6824

Researcher Affiliations

Lösle, Martina
  • Institute of Laboratory Animal Science, University of Zurich, Schlieren, 8952, Switzerland.
Lin, Chia-Wei
  • Functional Genomics Center Zürich, ETH Zürich, Zürich, 8057, Switzerland.
  • Institute of Microbiology, Department of Biology, ETH Zürich, Zürich, 8093, Switzerland.
Beil-Wagner, Jane
  • Institute of Laboratory Animal Science, University of Zurich, Schlieren, 8952, Switzerland.
Aebi, Markus
  • Institute of Microbiology, Department of Biology, ETH Zürich, Zürich, 8093, Switzerland.
Buch, Thorsten
  • Institute of Laboratory Animal Science, University of Zurich, Schlieren, 8952, Switzerland. thorsten.buch@uzh.ch.

MeSH Terms

  • Horses / blood
  • Animals
  • Female
  • Glycosylation
  • Pregnancy
  • Humans
  • Proteomics / methods
  • Chorionic Gonadotropin / metabolism
  • Gonadotropins, Equine
  • Blood Proteins / metabolism
  • Blood Proteins / analysis

Conflict of Interest Statement

Declarations. Competing interests: The authors declare no competing interests.

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