Biomedical subjects

Mark Kibschull

Publications and source records attributed to Mark Kibschull.

8 recordsLinked to original sources

PubMed2006

Expression pattern and functional characterization of connexin29 in transgenic mice.

Using newly generated transgenic mice in which the coding region of the connexin29 (Cx29) gene was replaced by the lacZ reporter gene, we confirmed previous immunochemical results that Cx29 is expressed in Schwann cells, oligodendrocytes and Bergmann glia cells. In addition, we detected lacZ/Cx29 in Schwann cells of the sciatic nerve and in particular of the spiral ganglion in the inner ear, as well as at low abundance in the stria vascularis. Furthermore, we found lacZ/Cx29 expression in nonmyelinating Schwann cells of the adrenal gland, in chondrocytes of intervertebral discs and the epiphysis of developing bones. Electron microscopic analyses of myelin sheaths in the central and peripheral nervous system of Cx29-deficient mice detected no abnormalities. The nerve conduction in the sciatic nerve of adult Cx29-deficient mice and the auditory brain stem response as well as visually evoked potentials in 4- to 10-week-old Cx29-deficient mice were not different from wild-type littermate controls. Thus, in contrast to connexin32 and connexin47, which are also expressed in myelinating cells, Cx29 does not contribute to the function of myelin in adult mice.

Adrenal Medulla↗

PubMed2006

Connexin31 cannot functionally replace connexin43 during cardiac morphogenesis in mice.

In the gastrulating mouse embryo, the gap junction protein connexin43 is expressed exclusively in cells derived from the inner cell mass, whereas connexin31 is expressed in cells of the trophoblast lineage. Since connexin43 and connexin31 do not form heterotypic gap junction channels in exogenous expression systems, such as HeLa cells and Xenopus oocytes, previous studies have suggested that the incompatibility of these two connexins could contribute to the separation of connexin43-expressing and connexin31-expressing compartments between embryo and extraembryonic tissues at gastrulation, respectively. Thus, we have generated connexin43 knock-in connexin31 mice, in which the coding region of the connexin43 gene was replaced by that of connexin31. Interbreeding of heterozygous connexin43 knock-in connexin31 mice resulted in homozygous connexin43 knock-in connexin31 mice, but none of them survived to adulthood. As these mice were born at the expected Mendelian frequency, we conclude that the reported incompatibility of connexin43 and connexin31 to form heterotypic gap junction channels does not interfere with normal embryonic development. Neonatal homozygous connexin43 knock-in connexin31 hearts showed malformation in the subpulmonary outlet of the right ventricle, similar to general connexin43-deficient mice. Electrocardiograms of neonatal hearts in homozygous connexin43 knock-in connexin31 mice revealed significantly low voltage of the QRS complex. This is in contrast to previous results from our laboratory which showed that replacement of connexin43 by connexin40 resulted in morphologically and functionally normal hearts. We conclude that connexin31 cannot functionally replace connexin43 during cardiac morphogenesis.

Animals↗

PubMed2006

Connexins and trophoblast cell lineage development.

The mouse is a valuable model for studying basic mechanisms of gene regulation in trophoblast cell lineage differentiation. Elements of placental development are conserved across species, including trophoblast proliferation, differentiation, migration, and vessel invasion. Among the regulatory processes, direct intercellular communication between trophoblast cells via gap junction channels seems to play a crucial role in placental development and physiology. Here we describe in detail the generation of trophoblast stem (TS) cell lines from connexin-deficient mice. The design of differentiation and proliferation assays are specified including marker gene sets which are important for analyzing and comparing the differentiation capacity of the connexin-deficient TS cell lines. Furthermore, we show that TS cells are capable of forming tumors after subcutaneous injection into nude mice, providing the opportunity to investigate trophoblast invasion into host vessels in vivo.

Animals↗

PubMed2005

Cx31 and Cx43 double-deficient mice reveal independent functions in murine placental and skin development.

The overlapping expression of gap junctional connexins in tissues has indicated that the channels may compensate for each other. During development, Cx31 and Cx43 are coexpressed in preimplantation embryos, in the spongiotrophoblast of the placenta and in the epidermis. This study shows that Cx31/Cx43 double-deficient mice exhibit the known phenotypes of the single-knockout strains but no combined effects. Thus, Cx43, coexpressed with Cx31 at midgestation in the spongiotrophoblast of the placenta, cannot be responsible for a partial rescue of the lethal Cx31 knockout phenotype, as assumed before (Plum et al. [2001] Dev Biol 231:334-337). It follows that both connexins have unique functions in placental development. Despite an altered expression of other epidermal connexin mRNAs, epidermal differentiation and physiology was unaltered by the absence of Cx31 and Cx43. Therefore, in epidermal and preimplantation development, gap junctional communication can probably be compensated by other isoforms coexpressed with Cx31 and Cx43.

Animals↗

PubMed2004

Connexin31-deficient trophoblast stem cells: a model to analyze the role of gap junction communication in mouse placental development.

The connexin (Cx) expression during placental development in rodents is subject to exacting spatiotemporal regulation. Following implantation, Cx31 characterizes the early trophoblast cell lineage and is expressed by the spongiotrophoblast during placental development until birth. Inactivation of the Cx31 gene results in a transient placental dysmorphogenesis with an imbalance in the trophoblast cell lineage differentiation in favor to giant cells [Dev. Biol. 231 (2001) 334]. In this study, we show that trophoblast stem (TS) cells exhibit the same connexin expression found in trophoblast cell lineage differentiation. Undifferentiated TS cells exclusively express Cx31 protein and Cx31.1 transcripts. Upon differentiation of TS cells, placental-specific Cx26 and Cx43 are induced. Cx31 knockout TS cells revealed an accelerated differentiation process to giant cells compared to controls, indicated by an overall shift in expression of connexins and marker genes such as Mash2, Pl-1, and Tpbpa. Moreover, proliferation was significantly reduced in Cx31 knockout TS cells upon differentiation. Both wild type and Cx31 knockout TS cells are able to invade and erode host vessels when injected into nude mice. We conclude that during trophoblast cell lineage differentiation, the Cx31 gap junction channel is involved in maintaining the proliferative diploid trophoblast cell population.

Animals↗

PubMed2004

Connexin43 interacts with NOV: a possible mechanism for negative regulation of cell growth in choriocarcinoma cells.

The gap junction protein connexin43 (Cx43) is thought to be involved in growth control in several tissues. Using the doxycycline inducible tet-on system, we generated human malignant trophoblast Jeg3 cells transfected with either Cx40, Cx43, or C-terminal truncated Cx43 (trCx43). Cx43, but not Cx40 or trCx43, displayed a reduced cell growth of Jeg3 cells in vitro and tumor growth in nude mice, suggesting a role of the C terminus of Cx43 in growth regulation. Using gene array analysis, the growth regulator NOV (CCN3), a member of the CCN gene family, was found to be up-regulated only in the Cx43-transfected cells. Validation by reverse transcriptase-PCR confirmed an up-regulation of the NOV transcript exclusively upon Cx43 induction. In contrast to Cx40 or trCx43, induction of Cx43 led to a switch in localization of NOV from the nucleus to the cell membrane, where it is colocalized with Cx43. Coimmunoprecipitation showed a binding of NOV to the C terminus of Cx43 in vitro as well as in transfected cells. Jeg3 cells transfected only with NOV revealed that NOV itself acts as a growth regulator. We suggest that Cx43 is able to regulate cell growth via an up-regulation of NOV transcription, a change in localization of the NOV protein and a binding of NOV to the C terminus of Cx43.

Animals↗

PubMed2004

Expression of connexins in human preimplantation embryos in vitro.

Intercellular communication via gap junctions is required to coordinate developmental processes in the mammalian embryo. We have investigated if the connexin (Cx) isoforms known to form gap junctions in rodent preimplantation embryos are also expressed in human embryos, with the aim of identifying species differences in communication patterns in early development. Using a combination of polyA PCR and immunocytochemistry we have assessed the expression of Cx26, Cx31, Cx32, Cx40, Cx43 and Cx45 which are thought to be important in early rodent embryos. The results demonstrate that Cx31 and Cx43 are the main connexin isoforms expressed in human preimplantation embryos and that these isoforms are co-expressed in the blastocyst. Cx45 protein is expressed in the blastocyst but the protein may be translated from a generally low level of transcripts: which could only be detected in the PN to 4-cell embryos. Interestingly, Cx40, which is expressed by the extravillous trophoblast in the early human placenta, was not found to be expressed in the blastocyst trophectoderm from which this tissue develops. All of the connexin isoforms in human preimplantation embryos are also found in rodents pointing to a common regulation of these connexins in development of rodent and human early embryos and perhaps other species.

Blastocyst↗

PubMed2003

Apoptosis in uterine epithelium and decidua in response to implantation: evidence for two different pathways.

During the initial steps of implantation, the mouse uterine epithelium of the implantation chamber undergoes apoptosis in response to the interacting blastocyst. With progressing implantation, regression of the decidual cells allows a restricted and coordinated invasion of trophoblast cells into the maternal compartment. In order to investigate pathways of apoptosis in mouse uterine epithelium and decidua during early pregnancy (day 4.5-7.0 post coitum), we have investigated different proteins such as TNFalpha, TNF receptor1, Fas ligand, Fas receptor1, Bax and Bcl2 as well as caspase-9 and caspase-3 using immunohistochemistry. To detect cells undergoing apoptosis the Tunel assay was performed. Immunoreactivity for TNFalpha as well as for TNF receptor1 was observed exclusively in the epithelium of the implantation chamber and the adjacent luminal epithelium from day 4.5 post coitum onwards. In the developing decidua the Fas ligand, but not the Fas receptor, was expressed. Bax and Bcl2 revealed a complementary expression pattern with Bax in the primary and Bcl2 in the adjacent decidual zone. Strong immunolabelling for the initiator caspase-9 was restricted to the decidual compartment, whereas caspase-3 expression characterized the apoptotic uterine epithelium. Only some caspase-3 positive decidual cells were found around the embryo which correlated to the pattern of Tunel staining. Taken together, the apoptotic degeneration of the uterine epithelium seems to be mediated by TNF receptor1 followed by caspase-3, whereas the very moderate regression of the decidua did not show the investigated death receptor, but Bax and Blc2 instead and in addition caspase-9, which indicates a different regulation for epithelial versus decidual apoptosis.

Animals↗