• Reproductive and Developmental Biology
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• v.28 no.3
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• pp.147-153
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• 2004

The oocyte and its surrounding granulosa cells co-exist in a closed compartment called a follicle, although they receive many signals from other parts of the body. It is well established that the intercellular communications between the oocyte and granulosa cells are required for normal oocyte development and ovulation during folliculogenesis. Gap junctions are intercellular channels allowing the direct transmission of ions and small molecules between coupled cells. Several lines of studies have shown that multiple connexins (Cx, subunits of gap junction) are expressed in mammalian ovarian follicles. Among them, two major connexins Cx37 and Cx43 are expressed in different manner. While the gap junction channels formed by Cx37 are localized between the oocyte and encompassing granulosa cells, the intercellular channels by Cx43 are located between granulosa cells. In this review, I will summarize the general properties of gap junction channels and discuss their possible formation (or compatibility) of intercellular channels formed by the oocyte and granulosa cells.

• Journal of Animal Science and Technology
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• v.55 no.6
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• pp.521-530
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• 2013

Direct cell-cell communication via the transfer of small molecules between neighboring cells in tissue is accomplished by gap junctions composed of various connexins (Cxs). Proper postnatal development of the epididymis is important for acquisition of male reproduction. The epididymal epithelium is composed of several cell types, and some of these cells are connected by gap junctions. The present study was conducted to determine the presence of Cx transcripts in the corpus and cauda epididymis. In addition, transcriptional changes of Cxs expressed during different postnatal stages were examined by real-time PCR analysis. In both epididymal regions, the same nine Cx transcripts of thirteen Cxs tested were detected. In the corpus epididymis, the highest levels of Cxs31.1 and 37 transcripts were observed at 45 days of age, and amounts of Cxs26, 30.3, and 32 transcripts increased with age and subsequently decreased in the elderly. Expression of Cx31 was greatly increased in the adult and elder stages, while Cxs40, 43, and 45 were abundant in the early postnatal stages. In the cauda epididymis, expression of Cxs26, 30.3, 31.1, 37, and 40 reached the highest levels at 5 months of age. The levels of Cxs31 and 32 mRNAs fluctuated throughout the postnatal period. The amounts of Cxs43 and 45 transcripts were more abundant during the late neonatal and prepubertal ages than later ages. These findings suggest that regional specification of the epididymis is partly regulated by differential expression of Cx genes during the postnatal developmental period.

• Journal of Animal Science and Technology
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• v.49 no.1
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• pp.15-24
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• 2007

The purpose of this study was to evaluate the presence and differential expression of connexin isoforms in the efferent ductules (ED) of male rat reproductive tract during postnatal development. Total RNA was isolated from the ED collected from rats at 1 week, 2 weeks, 1 month, 3 months, and 6 months of ages. Expression of six connexin mRNAs of 14 isoforms tested was detected by semi-quantitative RT-PCR. Fluctuation of mRNA levels of connexins 26 and 30 was found according to ages. A significant decrease of connexin 31.1 mRNA level was observed in the ED at 1 month of age. The highest levels of connexin 37 and 45 mRNAs were detected in the ED of early developmental period, while the expression of connexin 43 was the lowest at 1 week of age. The present study demonstrates differential regulation on expression of connexin isoforms in the rat ED in age-dependent manner.

• Korean Journal of Veterinary Research
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• v.43 no.4
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• pp.649-656
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• 2003

We have a cultured method to grow rat mammary epithelial cells (RMEC) for 1 to 14 days in 1:1 mixture of Dulbecco's Modified Eagle Medium: Nutrient and F-12 (DMEM/F-12) containing 10% fetal bovine serum (FBS), human EGF, insulin, hydrocortisone, human transferrin and $17{\beta}$-estradiol in vitro. We were able to isolate and distinguish two cell types, luminal epithelial cells and myoepithelial cells, from primary clutures of RMEC. Immunocytochemical stains were used to distingusih luminal epithelial cells and myoepithelial cells. Peanut lectin (PNA) was stained in most alveolar epithelail cells and luminal epithelial cells of rats, while Thy-1.1, a maker of potential rat mammary myoepithelial cells, was expressed in myoepithelial cells in the rat. Also, we examined the expression patterns of three types of gap junction proteins, connexin 26 ($C{\times}26$), connexins 32 ($C{\times}32$) and connexin 43 ($C{\times}43$) by immunocytochemistry and western blot analysis. In the cell types, the results show that at the early stage of culture, luminal epithelial cells were increased and these cells were surrounded by myoepithelial cells. At the late stage of culture, luminal epithelial cells were decreased, in contrast myoepithelial cells were increased. In the expression pattern of gap junction, $C{\times}26$ maintained it's expression until day 3, but afterwards gradually decreased in intensity. Expression of $C{\times}32$ remained until day 5, then decreased slightly. $C{\times}43$ gradually increased untill the middle time of culture then decreased in intensity. These results suggest that connexins may be important for the control of growth in rat mammary epithelial cell types.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.10a
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• pp.100-101
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• 2003

Gap junctions are membrane channels that directly connect the cytoplasm of neighboring cells, allowing the exchange of ions and small molecules. Two analogous families of proteins, the connexins and innexins are the channel-forming molecular vertebrates and invertebrates, respectively. Here, we present the molecular cloning and sequences analysis of novel innexiins, Binx2, expressed during Bombyx mori embryonic development. (omitted)

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.1
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• pp.73-79
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• 2015

Connexins (Cx) are membrane proteins and monomers for forming gap junction (GJ) channels. Cx46 and Cx50 are also known to function as conductive hemichannels. As part of an ongoing effort to find GJ-specific blocker(s), endocrine disruptors were used to examine their effect on Cx46 hemichannels expressed in Xenopus oocytes. Voltage-dependent gating of Cx46 hemichannels was characterized by slowly activating outward currents and relatively fast inward tail currents. Bisphenol A (BPA, 10 nM) reduced outward currents of Cx46 hemichannels up to ~18% of control, and its effect was reversible (n=5). 4-tert-Octylphenol (OP, $1{\mu}M$) reversibly reduced outward hemichannel currents up to ~28% (n=4). However, overall shapes of Cx46 hemichannel current traces (outward and inward currents) were not changed by these drugs. These results suggest that BPA and OP are likely to occupy the pore of Cx46 hemichannels and thus obstruct the ionic fluxes. This finding provides that BPA and OP are potential candidates for GJ channel blockers.

• Journal of Genetic Medicine
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• v.15 no.2
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• pp.107-109
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• 2018

X-linked Charcot-Marie-Tooth disease type 1 (CMTX1) is caused by the mutation in GJB1 gene, characterized by the transient central nervous system involvement and long standing peripheral polyneuropathy which does not fulfill the criteria of demyelination or axonopathy. We describe a 37-year-old man with progressive bilateral leg weakness since his early teen. He suffered transient right hemiparesis, followed by quadriparesis at 14 years of age. When we examined him at 37 years of age, he presented a distal muscle weakness on lower extremities with a sensory symptom. The nerve conduction study demonstrated a motor conduction velocity between 26 and 49 m/s. The whole exome sequencing revealed a novel variant c.136 G>A in GJB1. This report will raise awareness in this rare disease, which is frequently misdiagnosed early in its course.

• Genomics & Informatics
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• v.20 no.2
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• pp.24.1-24.8
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• 2022

Hypomyelinating leukodystrophy type 2 (HLD2), is an inherited genetic disease of the central nervous system caused by recessive mutations in the gap junction protein gamma 2 (GJC2/GJA12). HLD2 is characterized by nystagmus, developmental delay, motor impairments, ataxia, severe speech problem, and hypomyelination in the brain. The GJC2 sequence encodes connexin 47 protein (Cx47). Connexins are a group of membrane proteins that oligomerize to construct gap junctions protein. In the present study, a novel missense mutation gene c.760G>A (p.Val254Met) was identified in a patient with HLD2 by performing whole exome sequencing. Following the discovery of the new mutation in the proband, we used Sanger sequencing to analyze his affected sibling and parents. Sanger sequencing verified homozygosity of the mutation in the proband and his affected sibling. The autosomal recessive inheritance pattern was confirmed since Sanger sequencing revealed both healthy parents were heterozygous for the mutation. PolyPhen2, SIFT, PROVEAN, and CADD were used to evaluate the function prediction scores of detected mutations. Cx47 is essential for oligodendrocyte function, including adequate myelination and myelin maintenance in humans. Novel mutation p.Val254Met is located in the second extracellular domain of Cx47, both extracellular loops are highly conserved and probably induce intramolecular disulfide interactions. This novel mutation in the Cx47 gene causes oligodendrocyte dysfunction and HLD2 disorder.

• BMB Reports
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• v.36 no.1
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• pp.43-48
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• 2003

Understanding the process of carcinogenesis will involve both the accumulation of many scientific facts derived from molecular, biochemical, cellular, physiological, whole animal experiments and epidemiological studies, as well as from conceptual understanding as to how to order and integrate those facts. From decades of cancer research, a number of the "hallmarks of cancer" have been identified, as well as their attendant concepts, including oncogenes, tumor suppressor genes, cell cycle biochemistry, hypotheses of metastasis, angiogenesis, etc. While all these "hallmarks" are well known, two important concepts, with their associated scientific observations, have been generally ignored by many in the cancer research field. The objective of the short review is to highlight the concept of the role of human adult pluri-potent stem cells as "target cells" for the carcinogenic process and the concept of the role of gap junctional intercellular communication in the multi-stage, multi-mechanism process of carcinogenesis. With these two concepts, an attempt has been made to integrate the other well-known concepts, such as the multi-stage, multi-mechanisn or the "initiation/promotion/progression" hypothesis; the stem cell theory of carcinogenesis; the oncogene/tumor suppression theory and the mutation/epigenetic theories of carcinogenesis. This new "integrative" theory tries to explain the well-known "hallmarks" of cancers, including the observation that cancer cells lack either heterologous or homologous gap junctional intercellular communication whereas normal human adult stem cells do not have expressed or functional gap junctional intercellular communication. On the other hand, their normal differentiated, non-stem cell derivatives do express connexins and express gap junctional intercellular communication during their differentiation. Examination of the roles of chemical tumor promoters, oncogenes, connexin knock-out mice and roles of genetically-engineered tumor and normal cells with connexin and anti-sense connexin genes, respectively, seems to provide evidence which is consistent with the roles of both stem cells and gap junctional communication playing a major role in carcinogenesis. The integrative hypothesis provides new strategies for chemoprevention and chemotherapy which focuses on modulating connexin gene expression or gap junctional intercellular communication in the premalignant and malignant cells, respectively.

• BMB Reports
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• v.46 no.1
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• pp.25-30
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• 2013

Gap junctions and their structural proteins, connexins (Cxs), have been implicated in carcinogenesis. To explore the involvement of Cx32 in gastric carcinogenesis, immunochemical analysis of Cx32 and proliferation marker Ki67 using tissue-microarrayed human gastric cancer and normal tissues was performed. In addition, after Cx32 overexpression in the human gastric cancer cell line AGS, cell proliferation, cell cycle analyses, and $p21^{Cip1}$ and $p27^{Kip1}$ expression levels were examined by bromodeoxyuridine assay, flow cytometry, real-time RT-PCR, and western blotting. Immunohistochemical study noted a strong inverse correlation between Cx32 and Ki67 expression pattern as well as their location. In vitro, overexpression of Cx32 in AGS cells inhibited cell proliferation significantly. $G^1$ arrest, up-regulation of cell cycle-regulatory proteins $p21^{Cip1}$ and $p27^{Kip1}$ was also found at both mRNA and protein levels. Taken together, Cx32 plays some roles in gastric cancer development by inhibiting gastric cancer cell proliferation through cell cycle arrest and cell cycle regulatory proteins.