Comment in:

Atherosclerosis. 2007 Apr;191(2):460-1.

Do allelic variants of the connexin37 1019 gene polymorphism differentially predict for coronary artery disease and myocardial infarction?

Foundation for Medical Research, Division of Cardiology, Department of Internal Medicine, Geneva University Hospitals, 64 Avenue de la Roseraie, 1211 Geneva 4, Switzerland.

A C1019T polymorphism in the human connexin37 (hCx37) gene has been associated with cardiovascular risk, but it remains debatable whether the 1019C or the 1019T allele carries this risk. Here, we investigated whether these allelic variants are differentially predictive of increased risk for coronary artery disease (CAD) and myocardial infarction (MI). A total of 781 Swiss participants, including 597 patients diagnosed with CAD, 50% who reported previous MI, and 184 control subjects were genotyped. Patients in the +CAD group had a higher frequency of the Cx37-1019C allele (70.3% versus 65.0%, p=0.004). Multivariate analysis showed that the hCx37-C1019T polymorphism is an independent predictor of CAD (odds ratio=2.13, confidence interval=1.31-3.46 and p<0.01). Moreover, this polymorphism is not associated with any of the other characteristics examined, including gender, age, body-mass-index, diabetes, total/HDL/LDL-cholesterol, triglycerides, apoA-I, apoB, hypertension and cigarette smoking. In comparison with the -CAD group, we observed an increase of the Cx37-1019C allele in the +MI +CAD subgroup (71.2% versus 65.0%, p=0.002) but not in the -MI +CAD subgroup. Allelic frequency comparisons of these three subgroups predicted that this polymorphism is also an independent risk factor for MI. In conclusion, our results reveal the importance of screening the Cx37-1019C allele for both CAD and MI risk assessments.

PMID: 16677656 [PubMed - indexed for MEDLINE]

Expression and comparison of gap junction protein connexin 37 in granulosa cells aspirates from follicles of poor responder and nonpoor responder patients.

Cerrahpasa Medical Faculty, Department of Obstetrics and Gynecology, IVF-ET Unit, Istanbul University, Istanbul, Turkey.

OBJECTIVE: To localize gap junction protein connexin 37 (Cx37) in granulosa cells obtained from aspiration of follicles, and to compare differences between poor responder and nonpoor responder patients in assisted reproductive technology. DESIGN: Prospective clinical study. SETTING: IVF unit of a university hospital. PATIENT(S): Seventy patients with various causes of infertility, undergoing an IVF treatment. INTERVENTION(S): Controlled ovarian hyperstimulation, serum hormone level measurements, ultrasonography scanning of ovarian follicles, oocyte retrieval after hCG administration and embryo transfer. MAIN OUTCOME MEASURE(S): Outcome of the IVF treatment and expression rate of Cx37 in granulosa cells. RESULT(S): Connexin 37 was expressed in the granulosa cells of all the patients. Connexin 37 rate in granulosa cells in the poor responder group was 81.32 +/- 35.86% (distribution: 2.95%-99.9%), while it was 88.98 +/- 23.73% (distribution: 6.30%-100.00%) in the nonpoor responder group. Connexin 37 rates between the two groups were not significantly different. CONCLUSION(S): Connexin 37 is expressed in the granulosa layer of follicles in the human ovary, and expression of Cx37 in granulosa cells was not different between poor responder and nonpoor responder patients.

PMID: 17531234 [PubMed - indexed for MEDLINE]

Association between C1019T polymorphism of connexin37 and acute myocardial infarction: a study in patients from Sicily.

Gruppo di Studio sull'Immunosenescenza, Dipartimento di Biopatologia e Metodologie Biomediche, Università di Palermo, Corso Tukory 211, 90134 Palermo, Italy.

During atherogenesis, a critical role is played by intercellular communication via gap junctions, cell membrane channels linking the cytoplasmic compartments of adjacent cells. The component protein subunits of these channels, called connexin (Cx), belong to a multigene family. Cx37 is involved in growth, regeneration after injury and ageing of the endothelial cells, suggesting its role in atherosclerosis. The C1019 single nucleotide polymorphism (SNP) of Cx37 gene was associated with thickening of the carotid intima in Swedish men and was also associated with coronary artery disease in a Taiwanese population. On the other hand, in two more recent studies performed in male Japanese population, T1019 Cx37 SNP has shown to be a risk factor for acute myocardial infarction (AMI). In the light of these discrepant results, we have studied the frequency of this SNP in a very homogeneous cohort of young male people affected by AMI. We analysed 97 male Sicilian patients (mean age 40, age range 20-46) and 196 healthy male controls (mean age 39, age range 20-55) for C1019T of the Cx37. The 1019T SNP was significantly increased in the patients compared to the controls (43.8% vs. 34.4%; p=0.03 by chi2 test with Yates' correction; odds ratio (OR) 1.5, (1.0-2.1) 95% confidence interval (CI)). The present case control study performed in a homogeneous Caucasoid population confirms the Japanese results that T SNP of Cx37 gene is involved in AMI phenotype, demonstrating the consistency of the association across past studies and across different populations. The differences between patients and controls are significant but relatively small with an odd ratio risk of 1.5. However, as AMI is a multifactorial disease, any single mutation will only provide a small or modest contribution to risk, also depending on interaction with other genes and/or a particular environment.

PMID: 15982495 [PubMed - indexed for MEDLINE]

Human hemangiosarcomas have a common polymorphism but no mutations in the connexin37 gene.

Unit of Multistage Carcinogenesis, International Agency for Research on Cancer, Lyon, France.

Gap junctional intercellular communication is often impaired in cancers, and the genes which encode the connexin gap junction proteins are considered to be tumor-suppressor genes. In this study, we analyzed the presence of mutations in the connexin 37 (Cx37) gene in 22 human hepatic angiosarcomas, 6 and 4 of which were associated with exposure to vinyl chloride and Thorotrast, respectively. The other 12 samples were from patients with no history of exposure to these 2 agents. In 9 samples, a proline (ACC) to serine (ACT) amino acid change in codon 319 was detected. However, DNA from non-tumorigenic tissue of the same patients also showed this amino acid change, suggesting that this is a polymorphism rather than a mutation. Subsequent analysis of 84 DNA samples from normal donors revealed the frequencies of Pro/Pro, Pro/Ser and Ser/Ser alleles to be 65.5%, 23.8% and 10.7%, respectively, while among the group of angiosarcoma patients the corresponding figures were 59.1%, 31.8% and 9. 1%, respectively. Thus, there was no correlation between the polymorphism at codon 319 and hepatic angiosarcoma occurrence. However, among the 6 cases of vinyl chloride-associated angiosarcoma, the percentages of the polymorphic alleles were 33.3%, 66.7% and 0%, respectively. While the number of samples was too small to allow us to conclude that the Ser319 allele in Cx37 predisposes to this rare type of human cancer, it may be noted that codon 319 is located at the cytoplasmic tail of Cx37, where most regulatory sequences reside, and that it could be a site of phosphorylation for some protein kinases, which may in turn affect the function of Cx37, including intercellular communication.

PMID: 10728596 [PubMed - indexed for MEDLINE]

Significance of mRNA levels of connexin37, connexin43, and connexin45 in luteinized granulosa cells of controlled hyperstimulated follicles.

Department of Obstetrics and Gynecology, Kaohsiung Chang-Gung Memorial Hospital, Kaohsiung County, Taiwan.

OBJECTIVE: To evaluate the mRNA levels of connexins in different sizes of luteinized follicles. DESIGN: Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to determine the connexin mRNA levels in the granulosa cells of 91 luteinized follicles. SETTING: Academic tertiary care medical center and research unit of university. PATIENT(S): Ninety-one female patients on controlled ovarian hyperstimulation (COH). INTERVENTION(S): Sonoguided aspiration to collect the oocytes and the granulosa cells simultaneously. MAIN OUTCOME MEASURE(S): The RT-PCR data are normalized by comparing the intensity of the connexins to the intensity of internal controls (beta-actin). The follicles are grouped according to the size and the mRNA levels of the connexins. The correlations among the size of the follicles, the outcome of oocytes, and the mRNA levels of the connexins are compared by Fisher's exact test and Mann-Whitney test. RESULT(S): The mRNA levels of the connexins are low in the follicles equal or larger than 5.5 mL. High cx43 levels are linked to good prognosis of oocytes. CONCLUSION(S): The luteinized granulosa cells from the large follicles are relatively quiescent in the connexin mRNA expression. In addition to the volume, the mRNA levels of cx43 may serve as a marker to predict the outcome of oocytes.

PMID: 14667880 [PubMed - indexed for MEDLINE]

Genotypes associated with myocardial infarction risk are more common in African Americans than in European Americans.

Washington University School of Medicine, Department of Medicine, St. Louis, Missouri 63110-1093, USA.

OBJECTIVES: This study was designed to describe the frequencies of multiple myocardial infarction (MI) risk-associated genotypes among different racial groups. BACKGROUND: Racial disparities in the prevalence of cardiovascular disease (CVD) are well known. Recent large Japanese case-control studies identified connexin-37 (GJA-4), plasminogen activator inhibitor-1 (PAI-1), and stromelysin-1 (MMP-3) polymorphisms as risk factors for MI, but the prevalence of these genotypes among different racial groups in the U.S. needs to be determined. METHODS: Genomic deoxyribonucleic acid from 95 healthy African Americans (AA) and 95 healthy European Americans (EA) was used for genotyping. Deoxyribonucleic acid containing the region of interest was amplified using the polymerase chain reaction, followed by genotyping using pyrosequencing. RESULTS: All three MI-risk genotypes were observed in both populations and were in Hardy-Weinberg equilibrium. The frequencies of two of the three "risk-associated" genotypes were significantly higher in the AA population: GJA4 C1019T T/T: AA, 20%, EA, 7% (p = 0.053); MMP3 -1171delA A/A: AA, 78%, EA, 24% (p < 0.001); PAI-1 -668delG G/G: AA, 55%, EA, 16% (p < 0.001). The likelihood of two or more high-risk genotypes was 3.3% among EA subjects and 51% in the AA group (p < 0.001). We found that 9.1% of AA had all three high-risk genotypes, compared with 0% among the EA group (p = 0.0097). CONCLUSIONS: We found higher frequencies of disease-associated genotypes in AA than in EA. Our results also show that more AA than EA carry multiple risk-associated genotypes. Future studies need to assess whether such genetic profiles predict adverse outcomes in U.S. populations and contribute to racial disparities in CVD burden.

PMID: 15234427 [PubMed - indexed for MEDLINE]

Polyvalent cations constitute the voltage gating particle in human connexin37 hemichannels.

Department of Neurobiology, Pharmacology, and Physiology, The University of Chicago, IL 60637, USA. mpuljung@uchicago.edu

Connexins oligomerize to form intercellular channels that gate in response to voltage and chemical agents such as divalent cations. Historically, these are believed to be two independent processes. Here, data for human connexin37 (hCx37) hemichannels indicate that voltage gating can be explained as block/unblock without the necessity for an independent voltage gate. hCx37 hemichannels closed at negative potentials and opened in a time-dependent fashion at positive potentials. In the absence of polyvalent cations, however, the channels were open at relatively negative potentials, passing current linearly with respect to voltage. Current at negative potentials could be inhibited in a concentration-dependent manner by the addition of polyvalent cations to the bathing solution. Inhibition could be explained as voltage-dependent block of hCx37, with the field acting directly on polyvalent cations, driving them through the pore to an intracellular site. At positive potentials, in the presence of polyvalent cations, the field favored polyvalent efflux from the intracellular blocking site, allowing current flow. The rate of appearance of current depended on the species and valence of the polyvalent cation in the bathing solution. The rate of current decay upon repolarization depended on the concentration of polyvalent cations in the bathing solution, consistent with deactivation by polyvalent block, and was rapid (time constants of tens of milliseconds), implying a high local concentration of polyvalents in or near the channel pore. Sustained depolarization slowed deactivation in a flux-dependent, voltage- and time-independent fashion. The model for hCx37 voltage gating as polyvalent block/unblock can be expanded to account for observations in the literature regarding hCx37 gap junction channel behavior.

PMID: 15504903 [PubMed - indexed for MEDLINE]

PMCID: PMC2234009

Nitric oxide specifically reduces the permeability of Cx37-containing gap junctions to small molecules.

Institute of Physiology, Ludwig-Maximilians-University Munich, Schillerstr, Munich, Germany. Petra.Kameritsch@lrz.uni-muenchen.de

Gap junction intercellular communication (GJIC) plays a significant role in the vascular system. Regulation of GJIC is a dynamic process, with alterations in connexin (Cx) protein expression and post-translational modification as contributing mechanisms. We hypothesized that the endothelial autacoid nitric oxide (NO) would reduce dye coupling in human umbilical vein endothelial cells (HUVECs). In our subsequent experiments, we sought to isolate the specific Cx isoform(s) targeted by NO or NO-activated signaling pathways. Since HUVEC cells variably express three Cx (Cx37, Cx40, and Cx43), this latter aim required the use of transfected HeLa cells (HeLaCx37, HeLaCx43), which do not express Cx proteins in their wild type form. Dye coupling was measured by injecting fluorescent dye (e.g., Alexa Fluor 488) into a single cell and determining the number of stained adjacent cells. Application of the NO donor SNAP (2 microM, 20 min) reduced dye coupling in HUVEC by 30%. In HeLa cells, SNAP did not reduce dye transfer of cells expressing Cx43, but decreased the dye transfer from Cx37-expressing cells to Cx43-expressing cells by 76%. The effect of SNAP on dye coupling was not mediated via cGMP. In contrast to its effect on dye coupling, SNAP had no effect on electrical coupling, measured by a double patch clamp in whole cell mode. Our results demonstrate that NO inhibits the intercellular transfer of small molecules by a specific influence on Cx37, suggesting a potential role of NO in controlling certain aspects of vascular GJIC. 2004 Wiley-Liss, Inc.

PMID: 15481066 [PubMed - indexed for MEDLINE]

Connexin37 gene polymorphism and coronary artery disease in Taiwan.

Department of Internal Medicine, Mackay Memorial Hospital, Taipei Medical College, Taipei, Taiwan, ROC.

BACKGROUND: A recent study shows that a C1019T polymorphism of the gene encoding the gap junction protein connexin37 contributes to the genesis of atherosclerotic plaques in human carotid artery. However, whether such a polymorphism can be used as a prognostic marker in atherosclerotic disease of other arterial sites, such as coronary artery disease, is not known. METHODS: We analyzed the allelic status in 177 subjects with coronary artery disease (age, 61+/-11 years; male/female, 120/57) and 102 controls (60+/-11 years; male/female, 70/32). Both groups were matched, before genotype analysis, for a variety of other traditional risk factors, including body mass index, smoking status, levels of blood pressure, sugar, creatinine, and lipid profiles, in addition to age and sex. RESULTS: The T allele was less frequently seen in the control group, compared to the disease group (10.7 vs. 20.1%, TT+TC vs. CC, P<0.01). Subsequent analysis demonstrated that a significant difference existed in the male (9.2 vs. 22.8%, TT+TC vs. CC, P<0.005), but not in the female. Another finding was that the T allele frequency in all participants was less than 15%, markedly lower than that reported in non-Taiwanese. CONCLUSIONS: The observation indicates that the polymorphism in the connexin37 gene potentially plays a role in the manifestation of coronary atherosclerosis in Taiwan.

PMID: 11744143 [PubMed - indexed for MEDLINE]

Modulation of gap junction transcript and protein expression during pregnancy in the rat.

Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.

The expression of three different gap junction transcripts, alpha 1 (Cx43), beta 1 (Cx32), and beta 2 (Cx26) was examined in several organs during pregnancy in the rat. In all of the organs that were examined--uterus, ovary, heart, and liver--there was a strong correlation between levels of gap junction mRNA and gap junction antigens that were detected at different stages of pregnancy. A striking change in alpha 1 transcript levels (a 5.5-fold increase) was detected in the uterine myometrium on the day before parturition. This elevation of the alpha 1 transcript is thought to be associated with the formation of gap junctions that are required for synchronizing the contractility of the myometrial cells during parturition. 2 d before parturition, there was a detectable elevation of beta 2 transcripts and protein in the endometrial epithelium, which was then followed by a dramatic decrease in beta 2 gap junctional protein on the day before parturition. There was also a substantial elevation of alpha 1 transcripts (a 6.7-fold increase) in the stromal regions of the ovary on the day before parturition that was identical to the temporal pattern of alpha 1 expression in the myometrium. In all three instances--the alpha 1 transcripts in the myometrium, beta 2 transcripts in the endometrium, and alpha 1 transcripts in the ovary--the transcript modulation appeared to be cell specific, because the changes in transcript levels of these three gene products occurred independently of the poly(A) + RNA concentrations at the same pregnancy stages in the respective organs. There were no specific changes detected in gap junction transcript levels in the heart and liver during pregnancy. These observations indicate that a cell-specific modulation of gap junction expression occurs in two regions of the uterus and the ovary during pregnancy. Further, it appears that the same gap junction gene in different organs, such as the alpha 1 gene in the uterine myometrium and the heart, can be differentially regulated.

PMID: 1688855 [PubMed - indexed for MEDLINE]

PMCID: PMC2116004

Flow regulates intercellular communication in HAEC by assembling functional Cx40 and Cx37 gap junctional channels.

Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.

Direct cell-to-cell transfer of ions and small signaling molecules via gap junctions plays a key role in vessel wall homeostasis. Vascular endothelial gap junctional channels are formed by the connexin (Cx) proteins Cx37, Cx40, and Cx43. The mechanisms regulating connexin expression and assembly into functional channels have not been fully identified. We investigated the dynamic regulation of endothelial gap junctional intercellular communication (GJIC) by fluid flow and the participation of each vascular connexin in functional human endothelial gap junctions in vitro. Human aortic endothelial cells (HAEC) were exposed for 5, 16, and 24 h to physiological flows in a parallel-plate flow chamber. Connexin protein expression and localization were evaluated by immunocytochemistry, and functional GJIC was evaluated by dye injection. Connexin-mimetic peptide inhibitors were used to assess the specific connexin composition of functional channels. HAEC monolayers in culture exhibited baseline functional communication at a striking low level despite abundant expression of Cx43 and Cx40 localized at cell-to-cell appositions. Upon exposure to flow, GJIC by dye spread demonstrated a significant time-dependent increase from baseline levels, reaching 7.5-fold in 24 h. Inhibition studies revealed that this response was mediated primarily by Cx40, with lesser contributions of the other two vascular connexins assembled into functional homotypic and/or heterotypic channels. This is the first study to demonstrate that flow simultaneously and differentially regulates expression of the Cx37, Cx40, and Cx43 proteins and their involvement in the augmentation of intercellular communication by dye transfer in human endothelial cells in vitro.

PMID: 16361362 [PubMed - indexed for MEDLINE]

Connexin37 (GJA4) genotype predicts survival after an acute coronary syndrome.

Henry Ford Heart and Vascular Institute and Wayne State University, Detroit, MI, USA.

BACKGROUND: GJA4 1019 C > T, MMP3 -1171delA, and SERPINE1 -668delG genotypes have been associated with the risk of incident myocardial infarction. We tested the hypothesis that these genotypes would predict long-term mortality after an acute coronary syndrome (ACS). METHODS: We assembled a prospective cohort study on 726 patients with ACS admitted between March 2000 and October 2001. Kaplan-Meier estimates and Cox proportional hazards models of 3-year mortality adjusted for age, race, ACS type, prior heart failure, diabetes, and revascularization were used to compare groups. RESULTS: The GJA4 1019 C > T genotype was significantly related to mortality over 3 years (8.3% vs 14%, for the C/C vs T allele carriers; P = .02), with an adjusted hazard ratio of 1.7 (95% confidence interval 1.05-2.8, P = .03). This finding was consistent in both men and women (hazard ratio = 1.9 and 1.7, respectively) with no significant sex interaction (P = .8). The MMP3 -1171delA and SERPINE1 -668delG genotypes were not significantly related to mortality in the overall population (all P > .4). CONCLUSIONS: GJA4 1019 C > T genotype predicted risk of death after an ACS, whereas the MMP3 and SERPINE1 genotypes did not. The GJA4 1019 C > T polymorphism may warrant integration into comprehensive risk stratification algorithms for patients with ACS.

PMID: 17719307 [PubMed - indexed for MEDLINE]

Endothelial connexin 37, connexin 40, and connexin 43 respond uniquely to substrate and shear stress.

Georgia Tech/Emory Center for the Engineering of Living Tissues, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA.

Endothelial connexins have been linked to atherosclerosis and hypertension; however, little is know about their sensitivity to stimuli and individual functions. This study investigates the responses of endothelial connexin 37, connexin 40, and connexin 43 (Cx37, Cx40, and Cx43) to shear stress and substrate. Human endothelial cells were seeded on adsorbed collagen or a collagen gel containing smooth muscle cells and exposed to static or laminar shear stress. Connexin mRNA, protein, and gap junction communication were examined. Endothelial monolayers were treated with connexin-specific short interfering RNA (siRNA) and evaluated for communication, proliferation, and morphology under static and shear stress. Results show differential responses of Cx37, Cx40, and Cx43 to substrate and shear stress with reduced communication after shear exposure. RNA interference of individual connexins resulted in expression change of nontarget connexins, which suggests linked expression. Gap junction communication under static conditions is reduced following Cx43 siRNA treatment. Endothelial cells are more elongated with RNA interference (RNAi) targeting Cx40. In conclusion, endothelial connexins demonstrated novel sensitivity to mechanical environment and substrate. Individual isotypes show differential responses and RNAi knockdown provides new insight into connexin function and potential roles in the vasculature.

PMID: 17922338 [PubMed - indexed for MEDLINE]

Comment in:

Am J Med. 2009 Feb;122(2):e9.

Sex differences in environmental and genetic factors for hypertension.

Department of Cardiology, Institute of Cardiovascular Diseases, First Affiliated Hospital, Guangxi Medical University, Nanning, Guangxi, P. R. China. yinruixing@yahoo.com.cn

BACKGROUND: Sex differences are observed in many aspects of mammalian cardiovascular function and pathology. Hypertension is more common in men than in women of the same age. Although the effects of gonadal hormones on blood pressure are considered contributing factors, the reasons for sex differences in hypertension are still not fully understood. The present study was undertaken to compare the differences in several environmental and genetic factors between men and women in the Hei Yi Zhuang, an isolated subgroup of the Zhuang minority in China. METHODS: Information on demography, diet, and lifestyle was collected in 835 women and 834 men aged 15 to 84 years. Genotyping of angiotensin-converting enzyme, adrenergic receptor beta(3), aldehyde dehydrogenase 2, calpastatin, connexin 37, hepatic lipase, lipoprotein lipase, peroxisome proliferator-activated receptor gamma, thyrotropin-releasing hormone receptor, and von Willebrand factor also was performed in these subjects. RESULTS: The levels of systolic and diastolic blood pressure, and the prevalence, awareness, and treatment of hypertension were lower in women than in men (P < .05). Hypertension was positively associated with age, physical activity, alcohol consumption, body mass index, waist circumference, hyperlipidemia, total energy, total fat, sodium intake, and sodium/potassium ratio, and negatively associated with education level, total dietary fiber, potassium intake, angiotensin-converting enzyme, aldehyde dehydrogenase 2, and hepatic lipase genotypes in men (P < .05). Hypertension was positively associated with age, hyperlipidemia, total energy, total fat, sodium intake, sodium/potassium ratio, calpastatin, and von Willebrand factor genotypes, and negatively associated with education level, total dietary fiber, potassium, calcium intake, lipoprotein lipase, and thyrotropin-releasing hormone receptor genotypes in women (P < .05). CONCLUSION: Sex differences in the prevalence of hypertension in the Hei Yi Zhuang population may be mainly attributed to the differences in dietary habits, lifestyle choices, sodium and potassium intakes, physical activity level, and some genetic polymorphisms.

PMID: 18724972 [PubMed - indexed for MEDLINE]

Molecular cloning and functional expression of human connexin37, an endothelial cell gap junction protein.

Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.

Gap junctions allow direct intercellular coupling between many cells including those in the blood vessel wall. They are formed by a group of related proteins called connexins, containing conserved transmembrane and extracellular domains, but unique cytoplasmic regions that may confer connexin-specific physiological properties. We used polymerase chain reaction amplification and cDNA library screening to clone DNA encoding a human gap junction protein, connexin37 (Cx37). The derived human Cx37 polypeptide contains 333 amino acids, with a predicted molecular mass of 37,238 D. RNA blots demonstrate that Cx37 is expressed in multiple organs and tissues (including heart, uterus, ovary, and blood vessel endothelium) and in primary cultures of vascular endothelial cells. Cx37 mRNA is coexpressed with connexin43 at similar levels in some endothelial cells, but at much lower levels in others. To demonstrate that Cx37 could form functional channels, we stably transfected communication-deficient Neuro2A cells with the Cx37 cDNA. The induced intercellular channels were studied by the double whole cell patch clamp technique. These channels were reversibly inhibited by the uncoupling agent, heptanol (2 mM). The expressed Cx37 channels exhibited multiple conductance levels and showed a pronounced voltage dependence. These electrophysiological characteristics are similar to, but distinct from, those of previously characterized connexins.

PMID: 7680674 [PubMed - indexed for MEDLINE]

PMCID: PMC288052

Four novel members of the connexin family of gap junction proteins. Molecular cloning, expression, and chromosome mapping.

Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts 02115.

We have used low stringency hybridization and polymerase chain reaction (PCR) amplification with degenerate oligonucleotides to identify four new members of the rat connexin gene family. On the basis of their predicted molecular mass, these proteins have been designated connexin (Cx) 40 (Cx40), Cx37, Cx33, and Cx31.1. The new connexins exhibit all of the conserved structural features of the connexin family, including highly similar extracellular and transmembrane domains but divergent major cytoplasmic domains. On the basis of primary sequence similarity, the connexin family may be divided into two classes. Cx40, Cx37, and Cx33 are similar to the previously characterized Cx43 and Cx46. Cx31.1 is similar to Cx26, Cx31, and Cx32. Cx37 and Cx40 mRNAs are expressed in a wide variety of adult organs and tissues, with particular abundance in lung. However, their relative levels are different in many organs and thus their distribution is not completely coincident. Cx33 and Cx31.1 genes exhibit a much more restricted pattern of expression; mRNAs are detected only in testes and skin, respectively. Chromosomal mapping studies indicate that Cx26 and Cx46 are tightly linked on chromosome 14, and Cx37 and Cx31.1 are linked on chromosome 4, while the rest of the connexin genes are dispersed.

PMID: 1370487 [PubMed - indexed for MEDLINE]

Female infertility in mice lacking connexin 37.

Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

The signals regulating ovarian follicle development and the mechanisms by which they are communicated are largely undefined. At birth, the ovary contains primordial follicles consisting of meiotically arrested oocytes surrounded by a single layer of supporting (granulosa) cells. Periodically, subsets of primordial follicles undergo further development during which the oocyte increases in size and the granulosa cells proliferate, stratify and develop a fluid-filled antrum. After ovulation, oocytes resume meiosis and granulosa cells retained in the follicle differentiate into steroidogenic cells, forming the corpus luteum. It has been proposed that intercellular signalling through gap junction channels may influence aspects of follicular development. Gap junctions are aggregations of intercellular channels composed of connexins, a family of at least 13 related proteins that directly connect adjacent cells allowing the diffusional movement of ions, metabolites, and other potential signalling molecules. Here we show that connexin 37 is present in gap junctions between oocyte and granulosa cells and that connexin 37-deficient mice lack mature (Graafian) follicles, fail to ovulate and develop numerous inappropriate corpora lutea. In addition, oocyte development arrests before meiotic competence is achieved. Thus, cell-cell signalling through intercellular channels critically regulates the highly coordinated set of cellular interactions required for successful oogenesis and ovulation.

PMID: 9020357 [PubMed - indexed for MEDLINE]

Tumour necrosis factor alpha alters the expression of connexin43, connexin40, and connexin37 in human umbilical vein endothelial cells.

Department of Medical Physiology and Sports Medicine, Faculty of Medicine, Utrecht University, The Netherlands. H.V.M.vanRijen@med.ruu.nl

Tumour necrosis factor alpha (TNF-alpha) plays an important role in orchestrating inflammatory responses with the vascular endothelium as main target cell type, and was found to promote migration of endothelial cells, as occurs in wound healing processes. Substantial evidence exists that endothelial cell migration in wound healing is related to changes in cell coupling by means of gap junctions. Gap junctions are agglomerates of cell-to-cell channels that allow direct electrical and metabolic communication between cells. The authors have investigated whether TNF-alpha alters the expression of gap junction proteins (connexins, Cx) between human umbilical vein endothelial cells (HUVEC), thereby changing the extent of intercellular communication, as measured by dye coupling. Under control conditions, Cx43, Cx40, and Cx37 protein and mRNA were present in HUVEC. After exposure to 0.5 nM TNF-alpha for 48 h, however, the authors were no longer able to detect Cx37 and Cx40 protein, whereas Cx43 levels seemed unaltered but showed more perinuclear staining. After 24 and 48 h exposure to TNF-alpha, levels of Cx37 and Cx40 mRNA, were reduced, while the level of Cx43 mRNA remained unaltered, suggesting transcriptional regulation. If TNF-alpha was removed from the medium, Cx37 and Cx40 expression was restored within 24 h. The modulation of connexin expression by TNF-alpha resulted in a decrease in dye coupling of 40%.

PMID: 9617570 [PubMed - indexed for MEDLINE]

Comment in:

Nat Genet. 1998 Dec;20(4):319-20.

Mutations in the human connexin gene GJB3 cause erythrokeratodermia variabilis.

Genetic Studies Section, Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA. Gabriele.Richard@mail.tju.edu

Erythrokeratodermia variabilis (EKV, OMIM 133200) is an autosomal dominant genodermatosis with considerable intra- and interfamilial variability. It has a disfiguring phenotype characterized by the independent occurrence of two morphologic features: transient figurate red patches and localized or generalized hyperkeratosis. Both features can be triggered by external factors such as trauma to the skin. After initial linkage to the RH locus on 1p, EKV was mapped to an interval of 2.6 cM on 1p34-p35, and a candidate gene (GJA4) encoding the gap junction protein alpha-4 (connexin 31, Cx31) was excluded by sequence analysis. Evidence in mouse suggesting that the EKV region harbours a cluster of epidermally expressed connexin genes led us to characterize the human homologues of GJB3 (encoding Cx31) and GJB5 (encoding Cx31.1). GJB3, GJB5 and GJA4 were localized to a 1.1-Mb YAC in the candidate interval. We detected heterozygous missense mutations in GJB3 in four EKV families leading to substitution of a conserved glycine by charged residues (G12R and G12D), or change of a cysteine (C86S). These mutations are predicted to interfere with normal Cx31 structure and function, possibly due to a dominant inhibitory effect. Our results implicate Cx31 in the pathogenesis of EKV, and provide evidence that intercellular communication mediated by Cx31 is crucial for epidermal differentiation and response to external factors.

PMID: 9843209 [PubMed - indexed for MEDLINE]

Connexin37: a potential modifier gene of inflammatory disease.

Department of Pediatrics, Geneva University Hospitals, 1211, Geneva 14, Switzerland.

There is an increasing appreciation of the importance of gap junction proteins (connexins) in modulating the severity of inflammatory diseases. Multiple epidemiological gene association studies have detected a link between a single nucleotide polymorphism in the human connexin37 (Cx37) gene and coronary artery disease or myocardial infarction in various populations. This C1019T polymorphism causes a proline-to-serine substitution (P319S) in the regulatory C terminal tail of Cx37, a protein that is expressed in the vascular endothelium as well as in monocytes and macrophages. Indeed, these three cell types are key players in atherogenesis. In the early phases of atherosclerosis, blood monocytes are recruited to the sites of injury in response to chemotactic factors. Monocytes adhere to the dysfunctional endothelium and transmigrate across endothelial cells to penetrate the arterial intima. In the intima, monocytes proliferate, mature, and accumulate lipids to progress into macrophage foam cells. This review focuses on Cx37 and its impact on the cellular and molecular events underlying tissue function, with particular emphasis of the contribution of the C1019T polymorphism in atherosclerosis. We will also discuss evidence for a potential mechanism by which allelic variants of Cx37 are differentially predictive of increased risk for inflammatory diseases.

PMID: 17318613 [PubMed - indexed for MEDLINE]