CONTACT

Prof. Dr. med. Dr. rer. nat.
Hans-Werner Denker
email:
Hans-Werner Denker – University Duisburg-Essen Deutsche Version English Version

Early Embryonic Coats (Zona pellucida, Blastocyst Coverings)

 << Back to the Topics of Research

Overview

The zona pellucida is known as a glycoprotein coat that surrounds the oocyte and early embryo. At fertilization, the sperm needs to penetrate this coat, and the blastocyst must shed it before implantation can be initiated. However, detailed morphological and histochemical studies have revealed that this mechanistic view is much too simplified. The embryonic coat does not remain static during early development but undergoes structural and chemical changes which are more or less easily detectable, depending on the species. To investigate these transformations more in detail could shed new light on certain functional aspects of early embryonic coats that have remained obscure so far.

The rabbit is a species in which these changes are very conspicuous so that it can be used as a suitable model for the more delicate changes occurring in other species: In the rabbit, extracellular material is extruded into the subzonal (perivitelline) space during cleavage stages: the perivitelline space matrix. In addition, we discovered a remarkable transformation that takes place during the preimplantation period: A thick new layer (which we called “neozona”) is formed and replaces the zona pellucida inside two other layers, the mucoprotein coat and an outermost gloiolemma, at blastocyst stages. These findings extend and modify data on the situation in the rabbit that were originally presented by B.G. Boving but which had not yet included an identification of the neozona nor of the perivitelline space matrix. In the horse, a zona replacement traditionally called capsule (which reaches a considerable volume and encases the conceptus for many days; studied in detail by K.J. Betteridge) turned out to be just an equivalent of the neozona which we had identified before in the rabbit.

The transformation of extracellular coats during early embryonic development would deserve to be studied more in detail in the future. As discussed in the publications listed below, knowledge of these physiological coat transformations appears to be relevant for understanding the regulation of fertilization, early morphogenesis and implantation, in many species.

Main findings:

  • Discovery of changes in glycoprotein composition of the coats, e.g. with respect to sialic acid content, during the pre-implantation phases in the rabbit.
  • Discovery of the perivitelline space matrix and the neozona.
  • Functional aspects: Morphogenetic role; mechanics of embryo transport in the maternal genital tract; control of signal exchange and of metabolite transport between embryonic and maternal compartments.
  • Role of sialic acid side-chains of coat glycoproteins for resistance against proteolysis.
  • Importance of coat disintegration by specific proteinases for the initiation of embryo implantation.
    (Publications see Topic of Research Embryo Implantation I: Proteinases)

List of Publications

Note: Opening the pdf-files requires a pdf-reader (e.g. Adobe Reader).

DENKER, H.-W.:
Rise of the rabbit model for implantation research. A commemoration of the scientific work of Bent G. Boving (1920-2019).
Biology of Reproduction 102 (6): 1170-1176 (2020). DOI: 10.1093/biolre/ioaa038
PubMed   BOR   BOR (free access)

LITTWIN, T., DENKER, H.-W.:
Segregation during cleavage in the mammalian embryo? A critical comparison of whole-mount/CLSM and section immunohistochemistry casts doubts on segregation of axis-relevant leptin domains in the rabbit.
Histochemistry and Cell Biology 135: 553-570 (2011).
PubMed   SpringerLink

DENKER, H.-W.:
Structural dynamics and function of early embryonic coats.
Cells Tissues Organs 166: 180-207 (2000). PubMed   pdf-download (1.60 MB)

DENKER, H.-W.:
Structural dynamics and function of embryonic coats. (Abstr.)
(Abstr.) Journal of Reproduction & Fertility, Abstract Series No. 22, 3 (1998)
pdf-download (303 KB)

BIERMANN, L.; GABIUS, H.-J. and DENKER, H.-W.:
Neoglycoprotein-binding sites (endogenous lectins) in the Fallopian tube, uterus and blastocyst of the rabbit during the preimplantation phase and implantation.
Acta Anat. 160, 159-171 (1997). PubMed   pdf-download (24.3 MB)

FISCHER, B., MOOTZ, U., DENKER, H.-W., LAMBERTZ, M. and BEIER, H.M.:
The dynamic structure of rabbit blastocyst coverings. III. Transformation of coverings under non-physiological developmental conditions.
Anat. Embryol. 183, 17-27 (1991).
PubMed   SpringerLink

LEISER, R. and DENKER, H.-W.:
The dynamic structure of rabbit blastocyst coverings. II. Ultrastructural evidence for a role of the trophoblast in neozona formation.
Anat. Embryol. 179, 129-134 (1988).
PubMed   SpringerLink

LEISER, R. and DENKER, H.-W.:
Rabbit blastocyst coverings: evidence for a role of the trophoblast in neozona formation.
(Abstr.) 8th European Anatomical Congress, Antwerp, Sept. 1987. Acta anat. 130, 53 (1987)
pdf-download (547 KB)

FISCHER, B., DENKER, H.-W., BEIER, H.M. und GERDES, H.-J.:
Der Umbau der extrazellulären Blastozystenhüllen als ein empfindlicher Indikator für unphysiologische Milieubedingungen in der in-vitro-Kultur.
Verh. Anat. Ges. 77, Anat. Anz. Suppl. 154, 427-429 (1983). pdf-download (987 KB)

DENKER, H.-W.:
Extracellular material at the interface between early mammalian embryos and the uterus: dynamic changes in blastocyst coverings in the preimplantation period.
(Abstr.) Jahrestagung der Deutschen Gesellschaft für Zellbiologie, Hamburg 1983. Europ. J. Cell Biol., Suppl. 2, 8 (1983)
pdf-download (304 KB)

DENKER, H.-W.:
Transformation und physiologische Bedeutung der extrazellulären Keimhüllen bei frühen Säugetierembryonen.
(Abstr.) Tagung der Gesellschaft für Entwicklungsbiologie, Salzburg 1983
pdf-download (646 KB)

FISCHER, B., DENKER, H.-W. and BEIER, H.M.:
Incomplete transformation of rabbit embryo coverings in vitro.
(Abstr.) Annual Conference of the Society for the Study of Fertility, Sutton Bonington, Abstract No. 93, 1982
pdf-download (203 KB)

FISCHER, B., DENKER, H.-W. and BEIER, H.M.:
Zum Hüllenumbau von präimplantatorischen Kaninchenembryonen in vitro.
(Abstr.) In: Physiologie und Pathologie der Fortpflanzung. Verhandlungsbericht, VII. Veterinär-Humanmedizinische Tagung, Giessen 1982 (K. Semm, H. Tillmann, W. Gehring und L. Mettler, eds.) München, pp. 128-130 (Summary in: Zuchthygiene 17, 121, 1982)
pdf-download (1.41 MB)

DENKER, H.-W. and GERDES, H.-J.:
The dynamic structure of rabbit blastocyst coverings. I. Transformation during regular preimplantation development.
Anat. Embryol. 157, 15-34 (1979).
PubMed   SpringerLink

GERDES, H.-J. und DENKER, H.-W.:
Die strukturelle Entwicklung der Keimhüllen des Kaninchens vom Stadium der Blastozystenbildung bis zur Implantation.
Verh. Anat. Ges. 73, Anat. Anz. Suppl. 146, 427-434 (1979). pdf-download (3.29 MB)

DENKER, H.-W.:
Discussion Remark to: C. Thibault: Normal and abnormal fertilization in mammals.
In: Schering Symposium on Intrinsic and Extrinsic Factors in Early Mammalian Development, Venice 1970 (Gerhard Raspé, Ed.). Oxford etc.: Pergamon Press / Vieweg (= Advances in the Biosciences 6, ISBN 008 0175716 and 3 528 076887), 1971, pp. 63-85 (Discussion pp. 81-82).
pdf-download (643 KB)

DENKER, H.-W.:
Topochemie hochmolekularer Kohlenhydratsubstanzen in Frühentwicklung und Implantation des Kaninchens.
II. Beiträge zu entwicklungsphysiologischen Fragestellungen.
Zool. Jb. Physiol. 75, 246-308 (1970). pdf-download (23.1 MB)

 To the top

 << Back to the Topics of Research