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Zygotic expression of the connexin43 gene supplies subunits for gap junction assembly during mouse preimplantation development (1991)

Valdimarsson, Gunnar ; De Sousa, Paul A. ; Beyer, Eric C. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Molecular Reproduction and Development 30 (1991), S. 18-26

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ISSN: 1040-452X

Keywords: Gap junction protein ; Gene expression ; Compaction ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology

Notes: De novo assembly of gap junctions begins during compaction in the eight-cell stage of mouse development, and intercellular coupling mediated by gap junctions appears to be required for maintenance of the compacted state. We have begun to explore the expression of the family of genes encoding the connexins, the proteins that form the gap junction channels. We recently reported that a protein with antigenic and size similarity with connexin32, the rat liver gap junction protein, is inherited as an oogenetic product by the mouse zygote, but its gene appears not to be transcribed prior to implantation (Barron et al., Dev Genet 10:318-323, 1989). Here we report that another member of this gene family, connexin43, is transcribed by the embryonic genome from shortly after the time of genomic activation. As revealed by Northern blotting, connexin43 mRNA is absent from ovulated oocytes, becomes detectable in the 4-cell stage, and accumulates steadily thereafter to reach a maximum in blastocysts. In contrast, no transcripts of connexin26 could be detected in any preimplantation stage. A protein with antigenic and size similarity with connexin43 from rat heart was found by Western blotting to accumulate from the four-cell stage onward. Immunofluorescence analysis with embryo whole mounts was used to demonstrate that this protein is incorporated into punctate interblastomeric foci during compaction, consistent with its assembly into gap junction plaques. We conclude that connexin43 is one member of the connexin gene family whose zygotic expression is critical for preimplantation morphogenesis.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/mrd.1080300103

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Coexpression of gap junction proteins in the cumulus-oocyte complex (1993)

Valdimarsson, Gunnar ; De Sousa, Paul A. ; Kidder, Gerald M.

New York, NY [u.a.] : Wiley-Blackwell

Molecular Reproduction and Development 36 (1993), S. 7-15

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ISSN: 1040-452X

Keywords: Intercellular coupling ; Connexin32 ; Connexin43 ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology

Notes: The connexins constitute a family of proteins that make up the intercellular membrane channels of gap junctions. We had previously reported the presence of two members of this protein family, connexins 32 and 43, in mouse one-cell zygotes (Barron et al., Dev Genet 10:318-323, 1989; Valdimarsson et al., Mol Reprod Dev 30:18-26, 1991), implying that both must be present in the mature oocyte and could be involved in mediating the intercellular coupling that occurs between the oocyte and cumulus granulosa during oogenesis. In the present report we provide evidence for this, based on an analysis of the cumulus-oocyte complex (COC) using reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry with a confocal microscope. Transcripts of both connexin32 (Cx32) and connexin43 (Cx43) were detected by RT-PCR in both components of the COC. Cx32 mRNA in the oocyte declined precipitously following human chorionic gonadotropin (hCG) stimulation of pregnant mare serum gonadotropin (PMSG)-primed ovaries, whereas there was no obvious change in Cx43 mRNA. Peptide-specific antibodies against both connexins provided diffuse cytoplasmic staining of oocytes as well as some punctate staining near the oocyte surface, which could not be unequivocally resolved as cumulus-oocyte gap junctions. However, the two antibodies did provide clear evidence of Cx32 and Cx43 in gap junction-like structures between cumulus cells. We could find no evidence of the incorporation of the oocyte's store of Cx32 into gap junctions during postfertilization development. These findings make it very likely that intercellular coupling within the COC involves at least three types of gap junction channels (32-32, 32-43, 43-43), only one of which (43-43) is retained by the preimplantation embryo. © 1993 Wiley-Liss, Inc.

Additional Material: 4 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/mrd.1080360103

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Connexin32, a gap junction protein, is a persistent oogenetic product through preimplantation development of the mouse (1989)

Barron, Douglas J. ; Valdimarsson, Gunnar ; Paul, David L. ; [et al.]

Chichester [u.a.] : Wiley-Blackwell

Developmental Genetics 10 (1989), S. 318-323

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ISSN: 0192-253X

Keywords: Mouse embryos ; Gap junctions ; Connexin43 ; mRNA ; Life and Medical Sciences ; Genetics

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology

Notes: Gap junctions appear de novo during compaction in the eight-cell stage of mouse development. This is a critical event in the life of the embryo, because gap junctional intercellular communication is an essential requirement for maintaining compaction and, hence, for development of the blastocyst. Recently, a family of genes encoding gap junction proteins (connexins) has been identified and cloned, and we have taken advantage of the availability of antibodies and cDNA probes to investigate the expression of these genes in early development. We found that a protein with antigenic and size similarity to the “liver” gap junction protein, connexin32, is present throughout preimplantation development from the zygote through the late morula. Connexin32 mRNA, however, could not be detected in any preimplantation stage. This, and the presence of connexin32 in zygotes before activation of embryonic transcription, leads us to conclude that this protein is inherited as an oogenetic product that persists well beyond the transition from the oogenetic to embryonic program of gene expression. Furthermore, we found that mRNA for another gap junction protein, connexin43, is fairly abundant in preimplantation embryos. We conclude that it is more likely connexin43, and not connexin32, that is used to assemble new connexons as the level of intercellular coupling increases after compaction.

Additional Material: 4 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/dvg.1020100407

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