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Felix Claverie-martin - One of the best experts on this subject based on the ideXlab platform.
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Novel compound heterozygous mutations of CLDN16 in a patient with familial hypomagnesemia with hypercalciuria and nephrocalcinosis
Molecular genetics & genomic medicine, 2020Co-Authors: Alejandro García-castaño, Ana Perdomo-ramirez, Gema Ariceta, Elena Ramos-trujillo, Mònica Vall-palomar, Leire Madariaga, Felix Claverie-martinAbstract:Background Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is an autosomal recessive tubulopathy characterized by excessive urinary wasting of magnesium and calcium, bilateral nephrocalcinosis, and progressive chronic renal failure in childhood or adolescence. FHHNC is caused by mutations in CLDN16 and CLDN19, which encode the tight-junction proteins claudin-16 and claudin-19, respectively. Most of these mutations are missense mutations and large deletions are rare. Methods We examined the clinical and biochemical features of a Spanish boy with early onset of FHHNC symptoms. Exons and flanking intronic segments of CLDN16 and CLDN19 were analyzed by direct sequencing. We developed a new assay based on Quantitative Multiplex PCR of Short Fluorescent Fragments (QMPSF) to investigate large CLDN16 deletions. Results Genetic analysis revealed two novel compound heterozygous mutations of CLDN16, comprising a missense mutation, c.277G>A; p.(Ala93Thr), in one allele, and a gross deletion that lacked exons 4 and 5,c.(840+25_?)del, in the other allele. The patient inherited these variants from his mother and father, respectively. Conclusions Using direct sequencing and our QMPSF assay, we identified the genetic cause of FHHNC in our patient. This QMPSF assay should facilitate the genetic diagnosis of FHHNC. Our study provided additional data on the genotypic spectrum of the CLDN16 gene.
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Exonic CLDN16 mutations associated with familial hypomagnesemia with hypercalciuria and nephrocalcinosis can induce deleterious mRNA alterations
BMC Medical Genetics, 2019Co-Authors: Ana Perdomo-ramirez, Elena Ramos-trujillo, Marian De Armas-ortiz, Lorena Suarez-artiles, Felix Claverie-martinAbstract:Background Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis type 1 is an autosomal recessive disease characterized by excessive renal magnesium and calcium excretion, bilateral nephrocalcinosis, and progressive chronic renal failure. This rare disease is caused by mutations in CLDN16 that encodes claudin-16, a tight-junction protein involved in paracellular reabsorption of magnesium and calcium in the renal tubule. Most of these variants are located in exons and have been classified as missense mutations. The functional consequences of some of these claudin-16 mutant proteins have been analysed after heterologous expression showing indeed a significant loss of function compared to the wild-type claudin-16. We hypothesize that a number of CLDN16 exonic mutations can be responsible for the disease phenotype by disrupting the pre-mRNA splicing process. Methods We selected 12 previously described presumed CLDN16 missense mutations and analysed their potential effect on pre-mRNA splicing using a minigene assay. Results Our results indicate that five of these mutations induce significant splicing alterations. Mutations c.453G > T and c.446G > T seem to inactivate exonic splicing enhancers and promote the use of an internal cryptic acceptor splice site resulting in inclusion of a truncated exon 3 in the mature mRNA. Mutation c.571G > A affects an exonic splicing enhancer resulting in partial skipping of exon 3. Mutations c.593G > C and c.593G > A disturb the acceptor splice site of intron 3 and cause complete exon 4 skipping. Conclusions To our knowledge, this is the first report of CLDN16 exonic mutations producing alterations in splicing. We suggest that in the absence of patients RNA samples, splicing functional assays with minigenes could be valuable for evaluating the effect of exonic CLDN16 mutations on pre-mRNA splicing.
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Exonic CLDN16 mutations associated with familial hypomagnesemia with hypercalciuria and nephrocalcinosis can induce deleterious mRNA alterations.
BMC medical genetics, 2019Co-Authors: Ana Perdomo-ramirez, Elena Ramos-trujillo, Marian De Armas-ortiz, Lorena Suarez-artiles, Felix Claverie-martinAbstract:Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis type 1 is an autosomal recessive disease characterized by excessive renal magnesium and calcium excretion, bilateral nephrocalcinosis, and progressive chronic renal failure. This rare disease is caused by mutations in CLDN16 that encodes claudin-16, a tight-junction protein involved in paracellular reabsorption of magnesium and calcium in the renal tubule. Most of these variants are located in exons and have been classified as missense mutations. The functional consequences of some of these claudin-16 mutant proteins have been analysed after heterologous expression showing indeed a significant loss of function compared to the wild-type claudin-16. We hypothesize that a number of CLDN16 exonic mutations can be responsible for the disease phenotype by disrupting the pre-mRNA splicing process. We selected 12 previously described presumed CLDN16 missense mutations and analysed their potential effect on pre-mRNA splicing using a minigene assay. Our results indicate that five of these mutations induce significant splicing alterations. Mutations c.453G > T and c.446G > T seem to inactivate exonic splicing enhancers and promote the use of an internal cryptic acceptor splice site resulting in inclusion of a truncated exon 3 in the mature mRNA. Mutation c.571G > A affects an exonic splicing enhancer resulting in partial skipping of exon 3. Mutations c.593G > C and c.593G > A disturb the acceptor splice site of intron 3 and cause complete exon 4 skipping. To our knowledge, this is the first report of CLDN16 exonic mutations producing alterations in splicing. We suggest that in the absence of patients RNA samples, splicing functional assays with minigenes could be valuable for evaluating the effect of exonic CLDN16 mutations on pre-mRNA splicing.
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Additional file 2: of Exonic CLDN16 mutations associated with familial hypomagnesemia with hypercalciuria and nephrocalcinosis can induce deleterious mRNA alterations
2019Co-Authors: Ana Perdomo-ramirez, Elena Ramos-trujillo, Marian De Armas-ortiz, Lorena Suarez-artiles, Felix Claverie-martinAbstract:Table S2. Bioinformatics predictions of splicing defects for CLDN16 exonic mutations and comparison with experimental results. (PDF 94 kb
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Characterization of two novel mutations in the claudin-16 and claudin-19 genes that cause familial hypomagnesemia with hypercalciuria and nephrocalcinosis.
Gene, 2018Co-Authors: Ana Perdomo-ramirez, Mireia Aguirre, Tinatin Davitaia, Gema Ariceta, Elena Ramos-trujillo, Felix Claverie-martinAbstract:Abstract Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is an autosomal-recessive renal tubular disorder characterized by excessive urinary losses of magnesium and calcium, bilateral nephrocalcinosis and progressive chronic renal failure in childhood or adolescence. The disease is caused by mutations in the tight-junction proteins claudin-16 and claudin-19 that are encoded by the CLDN16 and CLDN19 genes, respectively. Patients with CLDN19 mutations also are affected with severe ocular abnormalities. The aim of our study was to identify and characterize the molecular defects causing this disease in a Georgian girl and two Spanish siblings. Clinical and biochemical parameters were studied. The CLDN16 and CLDN19 genes were analyzed by DNA sequencing. The functional consequences of the identified mutations on pre-mRNA splicing were investigated using a minigene assay. Sequence analysis revealed that the patient from Georgia was homozygous for a novel mutation, c.602G > A; p.(G201E), in exon 4 of the CLDN16 gene. The two Spanish siblings were homozygous for a new CLDN19 mutation, c.388G > T; p.(G130C), located in exon 2, and both parents were heterozygous carriers of the mutation. Bioinformatics analysis predicted that the amino acid substitutions generated by these mutations were pathogenic. Functional studies showed that mutation c.388G > T also results in partial skipping of CLDN19 exon 2, which would imply significant alterations in the claudin-19 protein structure. Conversely, CLDN16 mutation c.602G > A had no effect on pre-mRNA splicing. Our study expands the genotypic classification of this rare disease and provides the first report of a CLDN19 mutation affecting splicing.
Jianghui Hou - One of the best experts on this subject based on the ideXlab platform.
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Mosaic expression of claudins in thick ascending limbs of Henle results in spatial separation of paracellular Na+ and Mg2+ transport.
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Susanne Milatz, Jianghui Hou, Dominik N. Müller, Vera Christine Wulfmeyer, Hoora Drewell, Kerim Mutig, Tilman Breiderhoff, Michael FrommAbstract:The thick ascending limb (TAL) of Henle's loop drives paracellular Na+, Ca2+, and Mg2+ reabsorption via the tight junction (TJ). The TJ is composed of claudins that consist of four transmembrane segments, two extracellular segments (ECS1 and -2), and one intracellular loop. Claudins interact within the same (cis) and opposing (trans) plasma membranes. The claudins Cldn10b, -16, and -19 facilitate cation reabsorption in the TAL, and their absence leads to a severe disturbance of renal ion homeostasis. We combined electrophysiological measurements on microperfused mouse TAL segments with subsequent analysis of claudin expression by immunostaining and confocal microscopy. Claudin interaction properties were examined using heterologous expression in the TJ-free cell line HEK 293, live-cell imaging, and Forster/FRET. To reveal determinants of interaction properties, a set of TAL claudin protein chimeras was created and analyzed. Our main findings are that (i) TAL TJs show a mosaic expression pattern of either cldn10b or cldn3/CLDN16/cldn19 in a complex; (ii) TJs dominated by cldn10b prefer Na+ over Mg2+, whereas TJs dominated by CLDN16 favor Mg2+ over Na+; (iii) cldn10b does not interact with other TAL claudins, whereas cldn3 and CLDN16 can interact with cldn19 to form joint strands; and (iv) further claudin segments in addition to ECS2 are crucial for trans interaction. We suggest the existence of at least two spatially distinct types of paracellular channels in TAL: a cldn10b-based channel for monovalent cations such as Na+ and a spatially distinct site for reabsorption of divalent cations such as Ca2+ and Mg2.
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Claudin-7, -16, and -19 during mouse kidney development.
Tissue barriers, 2014Co-Authors: Halim Khairallah, Yan-hua Chen, Jasmine El Andalousi, Annie Simard, Nicholas Haddad, Jianghui Hou, Aimee K. Ryan, Indra R. GuptaAbstract:Members of the claudin family of tight junction proteins are critical for establishing epithelial barriers and for the regulation of paracellular transport. To understand their roles during kidney development, we first performed RT-PCR analyses and determined that 23 claudin family members were expressed in embryonic day (E) 13.5 mouse kidneys. Based on their developmental expression and phenotypes in mouse models, we hypothesized that 3 claudin members could affect nephron formation during kidney development. Using whole mount in situ hybridization and immunohistochemistry, we demonstrated that Claudin-7 (Cldn7) was expressed in the nephric duct, the emerging ureteric bud, and in tubules derived from ureteric bud branching morphogenesis. In contrast, Claudin-16 (CLDN16) and Claudin-19 (Cldn19) were expressed at later stages of kidney development in immature renal tubules that become the Loop of Henle. To determine if a loss of these claudins would perturb kidney development, we examined newborn kidneys from mutant mouse models lacking Cldn7 or CLDN16. In both models, we noted no evidence for any congenital renal malformation and quantification of nephron number did not reveal a decrease in nephron number when compared to wildtype littermates. In summary, Cldn7, CLDN16, and Cldn19 are expressed in different epithelial lineages during kidney development. Mice lacking Cldn7 or CLDN16 do not have defects in de novo nephron formation, and this suggests that these claudins primarily function to regulate paracellular transport in the mature nephron.
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Claudins and Renal Magnesium Handling
Current Topics in Membranes, 2010Co-Authors: Jianghui Hou, Martin KonradAbstract:Publisher Summary Claudins are tight junction (TJ) integral membrane proteins that are key regulators of the paracellular pathway. Defects in claudin-16 (CLDN16) and claudin-19 (CLDN19) function result in the inherited human renal disorder familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC). Significant advances have been made toward understanding the mechanisms underlying the roles of these claudins in mediating paracellular ion reabsorption in the kidney. This chapter reviews the biosynthesis, trafficking, and interaction of CLDN16 and CLDN19 molecules; the biophysical properties of CLDN16 and CLDN19 channels; and the pathogenic mechanisms for the role of mutant forms of CLDN16 and CLDN19 in the development of FHHNC. FHHNC is a genetically heterogeneous disorder. Mutations in TJ gene encoding CLDN19 are also linked to this disease. The renal tubular phenotypes are indistinguishable of patients with mutations in CLDN16 from those with CLDN19. CLDN19 mutations are invariably associated with severe ocular abnormalities. This association has been named FHHNC with severe ocular involvement.
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Claudin-16 and claudin-19 interaction is required for their assembly into tight junctions and for renal reabsorption of magnesium
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Jianghui Hou, Aparna Renigunta, Antonio S. Gomes, Mingli Hou, David L. Paul, Siegfried Waldegger, Daniel A. GoodenoughAbstract:Claudins are tight junction integral membrane proteins that are key regulators of the paracellular pathway. Defects in claudin-16 (CLDN16) and CLDN19 function result in the inherited human renal disorder familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC). Previous studies showed that siRNA knockdown of CLDN16 in mice results in a mouse model for FHHNC. Here, we show that CLDN19-siRNA mice also developed the FHHNC symptoms of chronic renal wasting of magnesium and calcium together with defective renal salt handling. siRNA knockdown of CLDN19 caused a loss of CLDN16 from tight junctions in the thick ascending limb (TAL) without a decrease in CLDN16 expression level, whereas siRNA knockdown of CLDN16 produced a similar effect on CLDN19. In both mouse lines, CLDN10, CLDN18, occludin, and ZO-1, normal constituents of TAL tight junctions, remained correctly localized. CLDN16- and CLDN19-depleted tight junctions had normal barrier function but defective ion selectivity. These data, together with yeast two-hybrid binding studies, indicate that a heteromeric CLDN16 and CLDN19 interaction was required for assembling them into the tight junction structure and generating cation-selective paracellular channels.
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Insights into driving forces and paracellular permeability from claudin-16 knockdown mouse.
Annals of the New York Academy of Sciences, 2009Co-Authors: Qixian Shan, Nina Himmerkus, Jianghui Hou, Daniel A. Goodenough, Markus BleichAbstract:Tight junction (TJ) properties are determined by membrane protein complexes of neighboring cells that form both a barrier and a selective pathway for paracellular substrate transport. Our previous work supports the view that paracellular permeability changes in the thick ascending limb (TAL) may underlie the mechanism for familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), a rare autosomal recessive disease linked to mutations in claudin-16 (CLDN16) and claudin-19 (CLDN19). CLDN16 knockdown (KD) mice are lacking CLDN16 expression by transgenic RNA interference. We observed that the transport defect for Mg2+ and Ca2+ in this animal model is caused by a loss of paracellular cation selectivity. The permeability ratio for Na+ over Cl- in KD mice was lower by a factor of two without a change in paracellular conductance, compared to wild type (WT). This resulted in a collapse of the transepithelial voltage, which is the driving force for Mg2+ and Ca2+ absorption in TAL. Since CLDN16 KD mice revealed lower blood pressure and an increased aldosterone plasma concentration, we hypothesize that the reduction in paracellular selectivity could allow backflow of Na+ and Cl- into the lumen of the TAL, thus enhancing the distal NaCl load and challenging the organism with a latent NaCl loss.
Satoshi Endo - One of the best experts on this subject based on the ideXlab platform.
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chrysin enhances anticancer drug induced toxicity mediated by the reduction of claudin 1 and 11 expression in a spheroid culture model of lung squamous cell carcinoma cells
Scientific Reports, 2019Co-Authors: Ryohei Maruhashi, Satoshi Endo, Takumi Furuta, Toshiyuki Matsunaga, Hiroaki Eguchi, Risa Akizuki, Shohei Hamada, Kenji Ichihara, Akira IkariAbstract:The aberrant expression of claudins (CLDNs), which are tight junctional proteins, is seen in various solid tumors, but the regulatory mechanisms and their pathophysiological role are not well understood. Both CLDN1 and CLDN11 were highly expressed in human lung squamous cell carcinoma (SCC). Chrysin, found in high concentration in honey and propolis, decreased CLDN1 and CLDN11 expression in RERF-LC-AI cells derived from human lung SCC. The phosphorylation level of Akt was decreased by chrysin, but those of ERK1/2 and c-Jun were not. LY-294002, an inhibitor of phosphatidylinositol 3-kinase, inhibited the phosphorylation of Akt and decreased the expression levels of CLDN1 and CLDN11. The association between phosphoinositide-dependent kinase 1 (PDK1) and Akt was inhibited by chrysin, but the phosphorylation of PDK1 was not. Immunoprecipitation and quartz-crystal microbalance assays revealed that biotinylated-chrysin binds directly to Akt. The knockdown of CLDN1 and CLDN11 using small interfering RNAs increased the transepithelial flux of doxorubicin (DXR), an anthracycline anticancer drug. Similarly, both chrysin and LY-294002 increased DXR flux. Neither CLDN1 knockdown, CLDN11 knockdown, nor chrysin changed the anticancer drug-induced cytotoxicity in a two-dimensional culture model, whereas they enhanced cytotoxicity in a spheroid culture model. Taken together, chrysin may bind to Akt and inhibit its phosphorylation, resulting in the elevation of anticancer drug-induced toxicity mediated by reductions in CLDN1 and CLDN11 expression in RERF-LC-AI cells. We suggest that chrysin may be useful as an adjuvant chemotherapy in lung SCC.
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Rescue of tight junctional localization of a claudin-16 mutant D97S by antimalarial medicine primaquine in Madin-Darby canine kidney cells.
Scientific reports, 2019Co-Authors: Kana Marunaka, Toru Kimura, Hajime Hasegawa, Satoshi Endo, Naoko Fujii, Takumi Furuta, Toshiyuki Matsunaga, Akira IkariAbstract:Magnesium ion (Mg2+) is paracellularly reabsorbed through claudin-16 (CLDN16) in the thick ascending limb (TAL) of Henle’s loop in the kidney. Genetic disorders of CLDN16 cause mislocalization of CLDN16, resulting in hypomagnesemia. There is no effective treatment for hypomagnesemia except for magnesium administration. Here, we searched for a novel drug to restore tight junctional localization of a CLDN16 mutant. A D97S mutant, which has a mutation in the first extracellular loop (ECL) of CLDN16, was mainly colocalized with endosome marker, whereas wild-type (WT) CLDN16 was colocalized with ZO-1, an adaptor protein of tight junctions. The protein stability of the D97S mutant was lower than that of WT. The expression level of the D97S mutant was increased by lactacystin, a proteasomal inhibitor. Endocytosis inhibitors increased the tight junctional localization of the D97S mutant. We found that primaquine, an antimalarial agent, increased the protein stability and cell surface localization of the D97S mutant, but the localization of other mutants, which have mutations in the cytosolic domain or second ECL, was not affected. Transepithelial Mg2+ flux was increased by primaquine in D97S mutant-expressing cells. The expression of chaperon proteins, proteasome activity, and lactate dehydrogenase release were decreased by primaquine, and the proportion of viable cells increased. In contrast, these effects were not observed in WT CLDN16-expressing cells. These results suggested that primaquine increases the tight junctional localization of the D97S mutant, resulting in a reduction in ER stress and cellular injury. Primaquine may become an effective treatment drug for selected patients with mutant CLDN16.
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The RING finger- and PDZ domain-containing protein PDZRN3 controls localization of the Mg2+ regulator claudin-16 in renal tube epithelial cells.
The Journal of biological chemistry, 2017Co-Authors: Kana Marunaka, Naohiko Anzai, Toru Kimura, Hajime Hasegawa, Satoshi Endo, Naoko Fujii, Takumi Furuta, Toshiyuki Matsunaga, Chisa Furukawa, Yasuhiro YamazakiAbstract:Ion exchange in the renal tubules is fundamental to the maintenance of physiological ion levels. Claudin-16 (CLDN16) regulates the paracellular reabsorption of Mg2+ in the thick ascending limb of Henle's loop in the kidney, with dephosphorylation of CLDN16 increasing its intracellular distribution and decreasing paracellular Mg2+ permeability. CLDN16 is located in the tight junctions, but the mechanism regulating its localization is unclear. Using yeast two-hybrid systems, we found that CLDN16 binds to PDZRN3, a protein containing both RING-finger and PDZ domains. We also observed that the carboxyl terminus of the cytoplasmic CLDN16 region was required for PDZRN3 binding. PZDRN3 was mainly distributed in the cytosol of rat kidney cells and upon cell treatment with the protein kinase A inhibitor H-89, colocalized with CLDN16. H-89 also increased mono-ubiquitination and the association of CLDN16 with PDZRN3. Mono-ubiquitination levels of a K275A mutant were lower, and its association with PDZRN3 was reduced compared with wild-type (WT) CLDN16 and a K261A mutant, indicating that Lys-275 is the major ubiquitination site. An S217A mutant, a dephosphorylated form of CLDN16, localized to the cytosol along with PDZRN3 and the endosomal marker Rab7. PDZRN3 siRNA increased cell-surface localization of WT CLDN16 in H-89-treated cells or containing the S217A mutant and also suppressed CLDN16 endocytosis. Of note, H-89 decreased paracellular Mg2+ flux in WT CLDN16 cells, and PDZRN3 siRNA increased Mg2+ flux in the H-89-treated WT CLDN16 and S217A mutant cells. These results suggest that PDZRN3 mediates endocytosis of dephosphorylated CLDN16 and represents an important component of the CLDN16-trafficking machinery in the kidney.
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Tight Junctional Localization of Claudin-16 is Regulated by Syntaxin 8 in Renal Tubular Epithelial Cells
The Journal of biological chemistry, 2014Co-Authors: Akira Ikari, Yasuhiro Yamazaki, Chie Tonegawa, Ayumi Sanada, Toru Kimura, Hideki Sakai, Hisayoshi Hayashi, Hajime Hasegawa, Masahiko Yamaguchi, Satoshi EndoAbstract:Claudin-16 (CLDN16) regulates the paracellular reabsorption of Mg2+ in the thick ascending limb of Henle's loop. However, the mechanism regulating the tight junctional localization of CLDN16 remains unknown. In yeast two-hybrid systems, we found that CLDN16 bound to syntaxin 8 (STX8), a target soluble N-ethylmaleimide-sensitive factor attachment protein receptor. We have examined the effect of STX8 on the localization and function of CLDN16 using Madin-Darby canine kidney cells expressing FLAG-tagged CLDN16. A pulldown assay showed that the carboxyl cytoplasmic region of human CLDN16 bound to STX8. CLDN16 was localized in the thick ascending limb, whereas STX8 was widely distributed throughout the rat kidney. An association between CLDN16 and STX8 was observed in rat renal homogenates and Madin-Darby canine kidney cells. STX8 siRNA decreased the cell surface localization of CLDN16 and transepithelial electrical resistance and permeability to Mg2+ but increased the co-localization of CLDN16 with early endosome and lysosome markers. Dephosphorylation of CLDN16 by protein kinase A inhibitors and S217A mutant, a dephosphorylated form, decreased the association with STX8 and the cell surface localization of CLDN16. Recycling assays indicated that STX8 siRNA decreased the trafficking of CLDN16 to the plasma membrane without affecting endocytosis. Dominant negative Rab11 and recycling inhibitor primaquine decreased the cell surface localization of CLDN16, which was similar to that in STX8 siRNA-transfected cells. These results suggest that STX8 mediates the recycling of CLDN16 and constitutes an important component of the CLDN16 trafficking machinery in the kidney.
Kursad Turksen - One of the best experts on this subject based on the ideXlab platform.
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Abstract 4200: Transgenic mice overexpressing a Claudin-6 tail deletion mutant are resistant to tumor formation
Tumor Biology, 2010Co-Authors: Kursad Turksen, Azadeh Arabzadeh, Tammy-claire TroyAbstract:Morphological and physiological observations suggest that the tight junction (TJ)-based permeability barrier is modified/disrupted during tumorigenesis. It is now also widely recognized that the Claudin (Cldn) family of four tetraspan transmembrane proteins is crucial for tight junction assembly and permeability barrier function. However, the detailed roles of the Cldn cytoplasmic tail and extracellular loop domains in these processes or their dysfunction in tumorigenesis are not yet understood. We recently demonstrated that the tail domain of Cldn6 is crucial for membrane targeting and epidermal permeability barrier (EPB) formation, by forced expression of a Cldn6 tail deletion mutant (CDelta187) via the involucrin (Inv) promoter in the suprabasal compartment of the mouse epidermis. Even though a functional barrier formed, Inv-CDelta187 mice displayed histological and biochemical abnormalities in the epidermal differentiation program leading to a thickening of the epidermis after 1 week of age that persisted throughout life. Notably, a significant amount of not only Cldn6, but also Cldn10, Cldn11, and Cldn18 remained cytoplasmically localized and the protein-unfolding pathway was activated in transgenic epidermal cells. Using a well-established two-stage chemical carcinogenesis model, we are now investigating the temporal and spatial changes in expression of these and other (Cldn1, Cldn12) Cldns that we have previously demonstrated to be important in epidermal differentiation and tumorigenesis in CDelta187 versus wild type (WT) mice. METHODS: The lower dorsal backskin of mice was treated topically with 7,12-dimethylbenz(a)anthracene (DMBA; 0.25 mg/ml in acetone) and following a 10-day incubation period, 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 25 microg/ml in acetone) was applied three times a week to the same area. Backskin samples were dissected 2, 4, 6, 8 and 12 weeks after the initiation of the experimental protocol and immunohistochemistry was performed on sections using antibodies against the following: Cldn1, Cldn6, Cldn11, Cldn12, Cldn18, Ki67 (proliferation marker) and CD3 (immune infiltration marker). Strikingly, epidermal tumor formation was inhibited in CDelta187 as compared to WT animals. This is the first demonstration that alterations in Cldn structure and homeostasis may play a protective role against DMBA/TPA-induced skin tumors. Further investigation into the molecular mechanisms underlying this protective function is underway. Supported by CIHR Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4200.
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involucrin claudin 6 tail deletion mutant cδ206 transgenic mice a model of delayed epidermal permeability barrier formation and repair
Disease Models & Mechanisms, 2010Co-Authors: Adebola Enikanolaiye, Tammy-claire Troy, Azadeh Arabzadeh, Nathalie Larivière, Elif Atasoy, Kursad TurksenAbstract:Preterm birth is a major global health problem that results in a large number of infant deaths, many of which are attributable to the complications of an immature epidermal permeability barrier (EPB), for which there is currently no effective therapeutic option. The mammalian EPB is formed during development and is essential for survival as it maintains thermoregulation and hydration, and provides a defense against infection. Using transgenic mouse technology, we have demonstrated the importance of claudin (Cldn)-containing tight junctions (TJs) in epidermal differentiation and, in particular, that epidermal suprabasal overexpression of Cldn6 results in an EPB-deficient phenotype that phenocopies the dysfunctional EPB of premature human infants. In this study, we used the same approach to target a Cldn6 tail deletion mutant to the epidermis of mice [involucrin (Inv)-Cldn6-CDelta206 transgenic mice]. The Inv-Cldn6-CDelta206 transgenic mice displayed a developmental delay in EPB formation, as shown by the expression of keratins and Cldns, and by X-Gal penetration assays. Trans-epidermal water loss measurements and immunolocalization studies indicated that the epidermal differentiation program was also perturbed in postnatal Inv-Cldn6-CDelta206 transgenic mice resulting in a delayed maturation. Notably, however, expression/localization of epidermal differentiation and maturation markers, including Cldns, indicated that the transgenic epidermis matured and normalized by postnatal day 10, which is 3 days after the wild-type epidermis. Our results suggest that activation of the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway and Cldn1 phosphorylation are associated with the repair and maturation of the skin barrier processes. These studies provide additional support for the crucial role of Cldns in epidermal differentiation, maturation and the formation of the EPB, and describe a novel animal model for evaluating postnatal epidermal maturation and therapies that may accelerate the process.
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Involucrin–claudin-6 tail deletion mutant (CΔ206) transgenic mice: a model of delayed epidermal permeability barrier formation and repair
Disease models & mechanisms, 2010Co-Authors: Adebola Enikanolaiye, Tammy-claire Troy, Azadeh Arabzadeh, Nathalie Larivière, Elif Atasoy, Kursad TurksenAbstract:Preterm birth is a major global health problem that results in a large number of infant deaths, many of which are attributable to the complications of an immature epidermal permeability barrier (EPB), for which there is currently no effective therapeutic option. The mammalian EPB is formed during development and is essential for survival as it maintains thermoregulation and hydration, and provides a defense against infection. Using transgenic mouse technology, we have demonstrated the importance of claudin (Cldn)-containing tight junctions (TJs) in epidermal differentiation and, in particular, that epidermal suprabasal overexpression of Cldn6 results in an EPB-deficient phenotype that phenocopies the dysfunctional EPB of premature human infants. In this study, we used the same approach to target a Cldn6 tail deletion mutant to the epidermis of mice [involucrin (Inv)-Cldn6-CDelta206 transgenic mice]. The Inv-Cldn6-CDelta206 transgenic mice displayed a developmental delay in EPB formation, as shown by the expression of keratins and Cldns, and by X-Gal penetration assays. Trans-epidermal water loss measurements and immunolocalization studies indicated that the epidermal differentiation program was also perturbed in postnatal Inv-Cldn6-CDelta206 transgenic mice resulting in a delayed maturation. Notably, however, expression/localization of epidermal differentiation and maturation markers, including Cldns, indicated that the transgenic epidermis matured and normalized by postnatal day 10, which is 3 days after the wild-type epidermis. Our results suggest that activation of the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway and Cldn1 phosphorylation are associated with the repair and maturation of the skin barrier processes. These studies provide additional support for the crucial role of Cldns in epidermal differentiation, maturation and the formation of the EPB, and describe a novel animal model for evaluating postnatal epidermal maturation and therapies that may accelerate the process.
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Dermatitis and aging-related barrier dysfunction in transgenic mice overexpressing an epidermal-targeted claudin 6 tail deletion mutant.
PloS one, 2009Co-Authors: Tammy-claire Troy, Azadeh Arabzadeh, Nathalie Larivière, Adebola Enikanolaiye, Kursad TurksenAbstract:The barrier function of the skin protects the mammalian body against infection, dehydration, UV irradiation and temperature fluctuation. Barrier function is reduced with the skin's intrinsic aging process, however the molecular mechanisms involved are unknown. We previously demonstrated that Claudin (Cldn)-containing tight junctions (TJs) are essential in the development of the epidermis and that transgenic mice overexpressing Cldn6 in the suprabasal layers of the epidermis undergo a perturbed terminal differentiation program characterized in part by reduced barrier function. To dissect further the mechanisms by which Cldn6 acts during epithelial differentiation, we overexpressed a Cldn6 cytoplasmic tail deletion mutant in the suprabasal compartment of the transgenic mouse epidermis. Although there were no gross phenotypic abnormalities at birth, subtle epidermal anomalies were present that disappeared by one month of age, indicative of a robust injury response. However, with aging, epidermal changes with eventual chronic dermatitis appeared with a concomitant barrier dysfunction manifested in increased trans-epidermal water loss. Immunohistochemical analysis revealed aberrant suprabasal Cldn localization with marked down-regulation of Cldn1. Both the proliferative and terminal differentiation compartments were perturbed as evidenced by mislocalization of multiple epidermal markers. These results suggest that the normally robust injury response mechanism of the epidermis is lost in the aging Involucrin-Cldn6-CΔ196 transgenic epidermis, and provide a model for evaluation of aging-related skin changes.
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The targeted overexpression of a Claudin mutant in the epidermis of transgenic mice elicits striking epidermal and hair follicle abnormalities
Molecular Biotechnology, 2007Co-Authors: Tammy-claire Troy, Kursad TurksenAbstract:Skin is one of the largest organs of the body, and is formed during development through a highly orchestrated process involving mesenchymal–epithelial interactions, cell commitment, and terminal differentiation. It protects against microorganism invasion and UV irradiation, inhibits water loss, regulates body temperature, and is an important part of the immune system. Using transgenic mouse technology, we have demonstrated that Claudin (Cldn)-containing tight junctions (TJs) are intricately involved in cell signaling during epidermal differentiation and that an epidermal suprabasal overexpression of Cldn6 results in a perturbed epidermal terminal differentiation program with distinct phenotypic abnormalities. To delineate the role of the Cldn cytoplasmic tail domain in epidermal differentiation, we engineered transgenic mice targeting the overexpression of a Cldn6 cytoplasmic tail-truncation mutant in the epidermis. Transgenic mice were characterized by a lethal barrier dysfunction in addition to the existence of hyperproliferative squamous invaginations/cysts replacing hair follicles. Immunohistochemical analysis revealed an epidermal cytoplasmic accumulation of Cldn6, Cldn11, Cldn12, and Cldn18, downregulation of Cldn1 and aberrant expression of various classical markers of epidermal differentiation; namely the basal keratins as well as K1, involucrin, loricrin, and filaggrin. Collectively these studies suggest an important role for Cldns in epidermal/hair follicle differentiation programs likely involving cross talk to signaling pathways (e.g., Notch) directing cell fate selection and differentiation.
Akira Ikari - One of the best experts on this subject based on the ideXlab platform.
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chrysin enhances anticancer drug induced toxicity mediated by the reduction of claudin 1 and 11 expression in a spheroid culture model of lung squamous cell carcinoma cells
Scientific Reports, 2019Co-Authors: Ryohei Maruhashi, Satoshi Endo, Takumi Furuta, Toshiyuki Matsunaga, Hiroaki Eguchi, Risa Akizuki, Shohei Hamada, Kenji Ichihara, Akira IkariAbstract:The aberrant expression of claudins (CLDNs), which are tight junctional proteins, is seen in various solid tumors, but the regulatory mechanisms and their pathophysiological role are not well understood. Both CLDN1 and CLDN11 were highly expressed in human lung squamous cell carcinoma (SCC). Chrysin, found in high concentration in honey and propolis, decreased CLDN1 and CLDN11 expression in RERF-LC-AI cells derived from human lung SCC. The phosphorylation level of Akt was decreased by chrysin, but those of ERK1/2 and c-Jun were not. LY-294002, an inhibitor of phosphatidylinositol 3-kinase, inhibited the phosphorylation of Akt and decreased the expression levels of CLDN1 and CLDN11. The association between phosphoinositide-dependent kinase 1 (PDK1) and Akt was inhibited by chrysin, but the phosphorylation of PDK1 was not. Immunoprecipitation and quartz-crystal microbalance assays revealed that biotinylated-chrysin binds directly to Akt. The knockdown of CLDN1 and CLDN11 using small interfering RNAs increased the transepithelial flux of doxorubicin (DXR), an anthracycline anticancer drug. Similarly, both chrysin and LY-294002 increased DXR flux. Neither CLDN1 knockdown, CLDN11 knockdown, nor chrysin changed the anticancer drug-induced cytotoxicity in a two-dimensional culture model, whereas they enhanced cytotoxicity in a spheroid culture model. Taken together, chrysin may bind to Akt and inhibit its phosphorylation, resulting in the elevation of anticancer drug-induced toxicity mediated by reductions in CLDN1 and CLDN11 expression in RERF-LC-AI cells. We suggest that chrysin may be useful as an adjuvant chemotherapy in lung SCC.
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Rescue of tight junctional localization of a claudin-16 mutant D97S by antimalarial medicine primaquine in Madin-Darby canine kidney cells.
Scientific reports, 2019Co-Authors: Kana Marunaka, Toru Kimura, Hajime Hasegawa, Satoshi Endo, Naoko Fujii, Takumi Furuta, Toshiyuki Matsunaga, Akira IkariAbstract:Magnesium ion (Mg2+) is paracellularly reabsorbed through claudin-16 (CLDN16) in the thick ascending limb (TAL) of Henle’s loop in the kidney. Genetic disorders of CLDN16 cause mislocalization of CLDN16, resulting in hypomagnesemia. There is no effective treatment for hypomagnesemia except for magnesium administration. Here, we searched for a novel drug to restore tight junctional localization of a CLDN16 mutant. A D97S mutant, which has a mutation in the first extracellular loop (ECL) of CLDN16, was mainly colocalized with endosome marker, whereas wild-type (WT) CLDN16 was colocalized with ZO-1, an adaptor protein of tight junctions. The protein stability of the D97S mutant was lower than that of WT. The expression level of the D97S mutant was increased by lactacystin, a proteasomal inhibitor. Endocytosis inhibitors increased the tight junctional localization of the D97S mutant. We found that primaquine, an antimalarial agent, increased the protein stability and cell surface localization of the D97S mutant, but the localization of other mutants, which have mutations in the cytosolic domain or second ECL, was not affected. Transepithelial Mg2+ flux was increased by primaquine in D97S mutant-expressing cells. The expression of chaperon proteins, proteasome activity, and lactate dehydrogenase release were decreased by primaquine, and the proportion of viable cells increased. In contrast, these effects were not observed in WT CLDN16-expressing cells. These results suggested that primaquine increases the tight junctional localization of the D97S mutant, resulting in a reduction in ER stress and cellular injury. Primaquine may become an effective treatment drug for selected patients with mutant CLDN16.
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Tight Junctional Localization of Claudin-16 is Regulated by Syntaxin 8 in Renal Tubular Epithelial Cells
The Journal of biological chemistry, 2014Co-Authors: Akira Ikari, Yasuhiro Yamazaki, Chie Tonegawa, Ayumi Sanada, Toru Kimura, Hideki Sakai, Hisayoshi Hayashi, Hajime Hasegawa, Masahiko Yamaguchi, Satoshi EndoAbstract:Claudin-16 (CLDN16) regulates the paracellular reabsorption of Mg2+ in the thick ascending limb of Henle's loop. However, the mechanism regulating the tight junctional localization of CLDN16 remains unknown. In yeast two-hybrid systems, we found that CLDN16 bound to syntaxin 8 (STX8), a target soluble N-ethylmaleimide-sensitive factor attachment protein receptor. We have examined the effect of STX8 on the localization and function of CLDN16 using Madin-Darby canine kidney cells expressing FLAG-tagged CLDN16. A pulldown assay showed that the carboxyl cytoplasmic region of human CLDN16 bound to STX8. CLDN16 was localized in the thick ascending limb, whereas STX8 was widely distributed throughout the rat kidney. An association between CLDN16 and STX8 was observed in rat renal homogenates and Madin-Darby canine kidney cells. STX8 siRNA decreased the cell surface localization of CLDN16 and transepithelial electrical resistance and permeability to Mg2+ but increased the co-localization of CLDN16 with early endosome and lysosome markers. Dephosphorylation of CLDN16 by protein kinase A inhibitors and S217A mutant, a dephosphorylated form, decreased the association with STX8 and the cell surface localization of CLDN16. Recycling assays indicated that STX8 siRNA decreased the trafficking of CLDN16 to the plasma membrane without affecting endocytosis. Dominant negative Rab11 and recycling inhibitor primaquine decreased the cell surface localization of CLDN16, which was similar to that in STX8 siRNA-transfected cells. These results suggest that STX8 mediates the recycling of CLDN16 and constitutes an important component of the CLDN16 trafficking machinery in the kidney.