Changing patterns of gap junctional intercellular communication and connexin distribution in mouse epidermis and hair follicles during embryonic development.
ABSTRACT In the mouse embryo between embryonic days 12 (E12) and 16, regular arrays of epidermal placodes on the mystacial pad develop into whisker follicles. This system was chosen for analysis of gap junctional intercellular communication during differentiation. The patterns of communication were studied by microinjection of the tracers Lucifer yellow-CH (LY-CH) and neurobiotin (NB), while immunofluorescent staining was used to study distribution of connexins 26 and 43. Extensive communication was seen between keratinocytes in developing hair pegs or, in later-stage hair follicles, in the germinative matrix. Coupling between adjacent hair pegs via interfollicular epidermis was not observed. Coupling also became restricted as follicular cells differentiated to form outer root sheath, inner root sheath, and hair shaft. Extensive gap junctional coupling is characteristic of keratinocytes that are rapidly proliferating (as in hair pegs and germinative matrix). Follicular keratinocytes commence differentiation shortly before restriction of gap junctional coupling becomes evident. Dermal mesenchymal cells undergoing different modes of differentiation also exhibit differences in gap junctional coupling, as evidenced by poor transfer of LY-CH between cells in dermal condensations of hair follicles compared with extensive transfer elsewhere in the dermis. LY-CH and NB were not transferred between epidermal or follicular epithelium and mesenchyme, arguing against a direct role for gap junctions permeable to known second messenger molecules or nucleotides in epithelial-mesenchymal interactions in this system. The distribution of connexins 26 and 43 in epidermis and hair follicles changed during differentiation but there was no correlation with changing patterns of dye transfer, indicating an unexpected degree of complexity in the relationship between gap junctional intercellular communication and connexin protein distribution during development.
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ABSTRACT: We have characterized the pattern of connexin expression in embryonic and extraembryonic tissues during early mouse development. In the preimplantation blastocyst, at 3.5 days post coitum (dpc), immunofluorescent signals specific for connexin31 and connexin43 proteins were present in both the inner cell mass and the trophectoderm, as shown by confocal laser scan microscopy. Immediately after implantation at 6.5 dpc, however, we find complete compartmentation of these two connexins: connexin31 mRNA and protein are expressed exclusively in cells derived from the trophectoderm lineage, whereas connexin43 mRNA and protein are detected in cells derived from the inner cell mass. This expression pattern of connexin31 and connexin43 is maintained at 7.5 dpc when the axial polarity of the mouse embryo is established. It correlates with the communication compartments in extraembryonic tissues and the gastrulating mouse embryo, respectively. The communication boundary between those compartments may be due to incompatibility of connexin31 and connexin43 hemichannels, which do not communicate with each other in cell culture.Journal of Cell Science 02/1996; 109 ( Pt 1):191-7. · 5.88 Impact Factor
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ABSTRACT: Expression and the role of E- and P-cadherin in the histogenesis of the surface epidermis and hair follicles were examined using the upper lip skin of the mouse. P-cadherin is expressed exclusively in the proliferating region of these tissues, that is in the germinative layer of the surface epidermis, the outer root sheath and the hair matrix. E-cadherin is coexpressed in these layers but this molecule was also detected in non-proliferating regions such as the intermediate layer of the surface epidermis and the immature regions of the inner root sheath. Neither P- nor E-cadherin was detected in fully keratinized layers such as the horny layer of the surface epidermis, the outermost layer of the outer root sheath and the mature hair fibres. These two cadherins were not detected in dermal cells. We cultured pieces of the upper lip skin in vitro in the absence or presence of a monoclonal antibody to E-cadherin (ECCD-1) or to P-cadherin (PCD-1). In control cultures, skin morphogenesis normally occurred in a pattern whereby the hair follicles grew and dermal cells were condensed to form the dermal sheath. A mixture of ECCD-1 and PCD-1, however, induced abnormal morphogenesis in the skin in several respects. (1) The cuboidal or columnar arrangement of basal epithelial cells was distorted. (2) Hair follicles were deformed. (3) Condensation of dermal cells was suppressed, causing a homogeneous distribution of these cells. These results suggest that cadherins present in epidermal cells are involved not only in maintaining the arrangement of these cells but also in inducing dermal condensation.Development 03/1989; 105(2):271-7. · 6.21 Impact Factor
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ABSTRACT: During the first 3 weeks of postnatal development in the ferret retina, cells in the ganglion cell layer spontaneously generate waves of electrical activity that travel across the retina in the absence of mature photoreceptors (Meister et al., 1991; Wong et al., 1993). Since few chemical synapses are present at the earliest stages when waves are present, we have explored whether gap junctions could act to correlate the activity of cells in the immature ganglion cell layer. Retinal ganglion cells in a living in vitro preparation from postnatal day 1 (P1) to P45 were intracellularly injected with the tracer Neurobiotin and the fluorescent dye Lucifer yellow, molecules that are known to pass through gap junctions. Lucifer yellow consistently filled only the injected cell, whereas Neurobiotin filled not only the injected cell but also passed to a constellation of neighboring cells. Coupling revealed by Neurobiotin is seen as early as P1, but, at this stage, it was not possible to identify the various morphological types of cells that were coupled. Thereafter, alpha ganglion cells showed homologous coupling to other alpha cells and to both conventionally placed and displaced amacrine cells. Likewise, gamma ganglion cells appeared coupled to other gamma cells and to amacrine cells. However, beta ganglion cells never showed tracer coupling in the neonatal or in adult retinas. The percentage of alpha and gamma cells that were coupled to other cells increased progressively with age. By the end of the third postnatal week, the pattern of Neurobiotin coupling in the ferret retina was adult-like, with virtually every injected alpha cell showing tracer coupling. Our observations suggest that intercellular junctions able to pass Neurobiotin are present in the inner plexiform layer during the period when the firing of retinal ganglion cells is highly correlated. Such junctions could contribute to synchronization of the activity of subsets of neighboring ganglion cells during development, but it cannot be the sole mediator of this activity because beta cells, which also participate in the correlated activity, showed no coupling at any stage. In addition, the continued presence of coupling in the adult retina implies that other changes in retinal circuitry are likely to contribute to the disappearance of the waves.Journal of Neuroscience 07/1994; 14(6):3805-15. · 6.91 Impact Factor