Mucin-like glycoproteins in the equine embryonic capsule.
Abstract: The equine embryonic capsule replaces the zona pellucida and envelopes the conceptus during the second and third weeks of pregnancy. Although this capsule was described more than 100 years ago, its molecular structure has not been characterized. Here we present evidence that the glycoprotein(s) of the equine capsule resembles those of the mucin glycoprotein family. The resistance of the capsule to chemical and enzymatic solubilization was confirmed, and, as in mucins, protein constituted only 35-40% of its total dry mass. Determination of the sugar composition of the capsule using colorimetric assays and high-performance anion-exchange chromatography also showed it to have mucin-like characteristics. Gal, GalNAc, sulfated sugars, and sialic acid make up a high proportion of the capsular carbohydrate, while GlcNAc, Glc, and Man are minor components. These findings were verified using lectin histochemical staining of frozen sections of conceptuses. The results of amino acid analysis were also consistent with the proposal that the capsular glycoproteins belong to the mucin family. Removal of the covalently bound carbohydrate by beta-elimination under reducing conditions demonstrated that the capsule is O-glycosylated mainly on threonine residues. Affinity chromatography on jacalin-agarose confirmed that, like mucins, the capsular glycoproteins are heavily O-glycosylated. SDS-PAGE analysis revealed a prominent 21-kDa band, specific to the capsule, in preparations solubilized by trypsin but not by other proteases. Characterization of its constituent glycoprotein(s) should be helpful in elucidating the role of the capsule (and analogous blastocyst coverings in other species) during early pregnancy.
Publication Date: 1993-03-01 PubMed ID: 8471247DOI: 10.1002/mrd.1080340305Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research examines the molecular structure of the equine embryonic capsule which envelopes a horse fetus in the early weeks of pregnancy. It suggests that the glycoproteins of the capsule are similar to those found in the mucin glycoprotein family.
Study Overview
- The equine embryonic capsule is an organ that surrounds the horse conceptus or the embryonic stage of a mammal. Its structure was studied in this research which revealed it resembles the mucin glycoprotein family in molecular makeup.
- Analyses were performed to determine the resistance of the capsule to solubilization, i.e whether it could be dissolved chemically or enzymatically. As with mucins, the protein of the equine embryonic capsule accounted for just 35-40% of its total dry mass.
- The study also examined the sugar composition of the equine embryonic capsule using colorimetric assays and high-performance anion-exchange chromatography. The results suggested its likeness to mucins.
Findings
- The researchers found that Gal, GalNAc, sulfated sugars, and sialic acid made up a significant part of the capsular carbohydrate, while minor components included GlcNAc, Glc, and Man. This information was verified through lectin histochemical staining of conceptus frozen sections.
- The results also indicated that the glycoproteins in the equine embryonic capsule belong to the mucin family based on amino acid analysis.
- By removing the covalently bound carbohydrate under reducing conditions, it was found that the capsule is O-glycosylated mainly on threonine residues.
- The findings revealed heavy O-glycosylation of the capsular glycoproteins similar to mucins as confirmed by affinity chromatography on jacalin-agarose.
- An SDS-PAGE analysis showed a specific 21-kDa band from the capsule in preparations solubilized by trypsin but not by other proteases.
Conclusion
- The findings shed light on the molecular structure of the equine embryonic capsule, suggesting its similarity to the mucin glycoprotein family. However, further characterization of its glycoproteins is needed to understand the role of the capsule (and similar blastocyst coverings in other species) during early pregnancy.
Cite This Article
APA
Oriol JG, Betteridge KJ, Clarke AJ, Sharom FJ.
(1993).
Mucin-like glycoproteins in the equine embryonic capsule.
Mol Reprod Dev, 34(3), 255-265.
https://doi.org/10.1002/mrd.1080340305 Publication
Researcher Affiliations
- Department of Biomedical Sciences, University of Guelph, Ontario, Canada.
MeSH Terms
- Amino Acids / analysis
- Animals
- Carbohydrates / analysis
- Embryo, Mammalian / anatomy & histology
- Embryo, Mammalian / chemistry
- Female
- Glycoproteins / analysis
- Glycoproteins / chemistry
- Histocytochemistry
- Horses
- Mucins / analysis
- Mucins / chemistry
- Pregnancy
- Proteins / analysis
- Solubility
Citations
This article has been cited 6 times.- Vegas AR, Podico G, Canisso IF, Bollwein H, Fröhlich T, Bauersachs S, Almiñana C. Dynamic regulation of the transcriptome and proteome of the equine embryo during maternal recognition of pregnancy.. FASEB Bioadv 2022 Dec;4(12):775-797.
- Antczak DF, Allen WRT. Placentation in Equids.. Adv Anat Embryol Cell Biol 2021;234:91-128.
- Smits K, Gansemans Y, Tilleman L, Van Nieuwerburgh F, Van De Velde M, Gerits I, Ververs C, Roels K, Govaere J, Peelman L, Deforce D, Van Soom A. Maternal Recognition of Pregnancy in the Horse: Are MicroRNAs the Secret Messengers?. Int J Mol Sci 2020 Jan 9;21(2).
- Tachibana Y, Sakurai T, Bai H, Shiota K, Nambo Y, Nagaoka K, Imakawa K. RNA-seq analysis of equine conceptus transcripts during embryo fixation and capsule disappearance.. PLoS One 2014;9(12):e114414.
- Iqbal K, Chitwood JL, Meyers-Brown GA, Roser JF, Ross PJ. RNA-seq transcriptome profiling of equine inner cell mass and trophectoderm.. Biol Reprod 2014 Mar;90(3):61.
- Crossett B, Allen WR, Stewart F. A 19 kDa protein secreted by the endometrium of the mare is a novel member of the lipocalin family.. Biochem J 1996 Nov 15;320 ( Pt 1)(Pt 1):137-43.
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