Development, Vol 105, Issue 2 317-322, Copyright © 1989 by Company of Biologists

JOURNAL ARTICLES

Involvement of oocyte-coded message in cell differentiation control of early human embryos

J Tesarik
Centre for Reproductive Medicine, Purkyne University Medical Faculty, Brno, Czechoslovakia.

Considerable evidence indicates that the first phenotypical diversification of embryonic cells during mammalian preimplantation development is achieved in two successive steps: (i) generation of cell asymmetry and (ii) unequal cell division. This paper shows that ultrastructural signs of blastomere surface regionalization in human preimplantation embryos are evident as early as the 2-cell stage when modifications of the plasma membrane (loss of microvilli and endocytotic activity, formation of cell junctions) are induced in places of blastomere contact. The capacity of the plasma membrane to undergo these cell-contact-dependent changes precedes any detectable activity of the embryonic genome. The area of the modified plasma membrane shows a continuous increase during the first three cleavage stages. The progression of these membrane modifications is the same in embryos that have properly enhanced their transcriptional activity at the 8-cell stage and in those that have not. In spite of the failure of this early-cleavage-progressed-cleavage transition of gene activity, the formation of zonula adherens and gap junctions goes on apparently normally in the respective embryos and morphologically distinct inner cell mass and trophectoderm cell lineages are subsequently segregated in 16-cell morulae. However, tight junctions do not develop under these conditions. The occurrence of the progressed-cleavage pattern of gene activity in the majority of embryonic cells is a necessary prerequisite for the appearance of the blastocyst cavity. Thus, oocyte-coded message is apparently involved in the control of relatively late stages of human preimplantation development including the differentiation of the first two embryonic tissues, but the embryonic genome is required for the full achievement of this early differentiative event.

This article has been cited by other articles:

				R.D. Schramm, A. M. Paprocki, and C. A. VandeVoort Causes of developmental failure of in-vitro matured rhesus monkey oocytes: impairments in embryonic genome activation Hum. Reprod., April 1, 2003; 18(4): 826 - 833. [Abstract] [Full Text] [PDF]

				W. Harrouk, B. Robaire, and B. F. Hales Paternal Exposure to Cyclophosphamide Alters Cell-Cell Contacts and Activation of Embryonic Transcription in the Preimplantation Rat Embryo Biol Reprod, July 1, 2000; 63(1): 74 - 81. [Abstract] [Full Text]

				R.D. Schramm and B.D. Bavister A macaque model for studying mechanisms controlling oocyte development and maturation in human and non-human primates Hum. Reprod., October 1, 1999; 14(10): 2544 - 2555. [Abstract] [Full Text] [PDF]

				R. D. Schramm and B. D. Bavister Onset of Nucleolar and Extranucleolar Transcription and Expression of Fibrillarin in Macaque Embryos Developing In Vitro Biol Reprod, March 1, 1999; 60(3): 721 - 728. [Abstract] [Full Text]

				C. Chia, R. Winston, and A. Handyside EGF, TGF-alpha and EGFR expression in human preimplantation embryos Development, January 2, 1995; 121(2): 299 - 307. [Abstract] [PDF]