Exocrine pancreatic disorders in transsgenic mice expressing human keratin 8

Casanova, Mercedes; Bravo, Ana; Ramı́rez, Ángel; Escobar, Gustavo; Were, Felipe; Merlino, Glenn; Vidal, Miguel; Jorcano, José L.

doi:10.1172/jci5343

Cited by 73 publications

(75 citation statements)

References 44 publications

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“…2,3,[28][29][30][31][32][33] In agreement with the general view of IF functions, the results from studies on transgenic mutant and K8-and K18-deficient mouse models have emphasized the role of these keratins in maintaining the integrity of cells and tissues. 13,17,34,35 In the present study, we provide evidence that K8 and K18 also play an important role in the development and organization of liver and pancreas structure. When keratins are absent or their assembly is disturbed, we observed in both liver and pancreas architectural and organizational defects that were reflected as lesion areas with multinuclear giant cells and absence of normal liver parenchymal structure.…”

Section: Discussionsupporting

confidence: 59%

“…14,15 Several transgenic mouse lines targeting epithelial keratins have been generated to study the requirement of keratins for the formation and function of simple epithelia. 12,[16][17][18][19][20][21][22] The targeted null mutation of K8 causes mid-gestational lethality with bleeding into the embryonic liver. 19 The lethality does not have a complete penetrance, because approximately half of the homozygous K8 null embryos escape lethality in mice with the FVB/n genetic background.…”

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confidence: 99%

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Disturbances in hepatic cell-cycle regulation in mice with assembly-deficient keratins 8/18

et al. 2001

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Simple epithelial tissues such as liver and pancreas express keratins 8 (K8) and 18 (K18) as their major intermediate filament proteins. K8 and K18 null mice and transgenic mice that express mutant K18 (K18C) manifest several hepatocyte abnormalities and demonstrate that K8/18 are important in maintaining liver tissue and cell integrity, although other potential functions remain uncharacterized. Here, we report an additional abnormal liver phenotype, which is similar in K8 null, K18 null, and K18C mouse models. Liver histologic examination showed large polynuclear areas that lacked cell membranes, desmosomal structures, and filamentous actin. Similar, but less prominent, areas were observed in the pancreas. The parenchyma outside the polynuclear areas displayed irregular sinusoidal structures and markedly enlarged nuclei. Most K8 null hepatocytes were positive for the proliferating cell nuclear antigen (PCNA) with a doubled DNA content in comparison with the predominantly PCNA-negative wild-type hepatocytes. The distribution of the 14-3-3 protein was also altered in K8 null mice. Taken together, our results indicate that absence of keratin filaments causes disturbances in cellcycle regulation, driving cells into the S-G2 phase and causing aberrant cytokinesis. These effects could stem from disturbed functions of K8/18-dependent cell-cycle regulators, such as the signaling integrator, 14-3-3. (HEPATOLOGY 2001; 34:1174-1183

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Section: Discussionsupporting

confidence: 59%

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confidence: 99%

Disturbances in hepatic cell-cycle regulation in mice with assembly-deficient keratins 8/18

et al. 2001

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“…To explore the possibility that the defect in F-actin and ezrin observed above may be due to IF-dependent localization of ezrin and F-actin, we analyzed the phenotype of transgenic mice that overexpress a tandem of at least 17 copies of the human K8 (hK8) gene under its natural promoter (Casanova et al, 1995(Casanova et al, , 1999. The rationale for this approach is that if IFs serve as a scaffold for ezrin or F-actin, overexpression and mislocalization of IFs is expected to cause a redistribution of these proteins.…”

Section: Overexpression Of K8 Results In Ezrin Redistribution To a Sumentioning

confidence: 99%

“…Transgenic mice overexpressing human K8 (HK8) and their pancreatic phenotype have been described previously (Casanova et al, 1995(Casanova et al, , 1999. In this work, samples from hemizygous HK8-4 (severe phenotype) and HK8-8 (milder phenotype) mice were used for frozen sections and immunofluorescence, or extraction-immunoblot.…”

Section: Transgenic Mice and Electron Microscopy (Em)mentioning

confidence: 99%

Intermediate Filaments Interact with Dormant Ezrin in Intestinal Epithelial Cells

Wald

Oriolo

Casanova

et al. 2005

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Ezrin connects the apical F-actin scaffold to membrane proteins in the apical brush border of intestinal epithelial cells. Yet, the mechanisms that recruit ezrin to the apical domain remain obscure. Using stable CACO-2 transfectants expressing keratin 8 (K8) antisense RNA under a tetracycline-responsive element, we showed that the actin-ezrin scaffold cannot assemble in the absence of intermediate filaments (IFs). Overexpression of ezrin partially rescued this phenotype. Overexpression of K8 in mice also disrupted the assembly of the brush border, but ezrin distributed away from the apical membrane in spots along supernumerary IFs. In cytochalasin D-treated cells ezrin localized to a subapical compartment and coimmunoprecipitated with IFs. Overexpression of ezrin in undifferentiated cells showed a Triton-insoluble ezrin compartment negative for phospho-T567 (dormant) ezrin visualized as spots along IFs. Pulse-chase analysis showed that Triton-insoluble, newly synthesized ezrin transiently coimmunoprecipitates with IFs during the first 30 min of the chase. Dormant, but not active (p-T567), ezrin bound in vitro to isolated denatured keratins in Far-Western analysis and to native IFs in pull-down assays. We conclude that a transient association to IFs is an early step in the polarized assembly of apical ezrin in intestinal epithelial cells. INTRODUCTIONEzrin, a member of the ezrin-radixin-moesin (ERM) family, is a conspicuous component of the apical F-actin-based scaffold in simple epithelial cells. It connects NHERF/EBP-50 (which in turn binds important membrane proteins such as CFTR and NHE-3) to F-actin and also enables protein kinase A-mediated regulation of apical channels (Kurashima et al., 1999;Louvet-Vallée, 2000;Weinman et al., 2000Weinman et al., , 2001. Because ezrin is the earliest protein of this complex scaffold to be recruited, it has long been considered as an organizer of the brush border (Bretscher et al., 1997). In support of that view, ezrin knockout mice show a distinctive brush-border phenotype with much shorter microvilli that resemble undifferentiated stages (Saotome et al., 2004). Furthermore, expression of ezrin in fibroblasts is sufficient to organize microvilli (Shaw et al., 1998). After translation, ezrin initially adopts a "dormant" configuration, in which the C-and N-terminal domains bind to each other. On phosphorylation in T567, it changes to an open "active" configuration, freeing the C-terminal domain (C-ERMAND) to bind F-actin and the N-terminal domain (N-ERMAND) to bind NHERF or transmembrane proteins (Bretscher et al., 2000). Although the mechanism of activation and assembly of ezrin has been studied in great detail by several groups, the mechanisms that ensure that ezrin assembly occur mostly under the apical membrane of simple epithelial cells remain obscure. Fievet et al. (2004) have shown that binding to phosphatidylinositol 4,5-diphosphate (PIP 2 ) is a prerequisite for activation. However, PIP 2 is not known to be apically polarized in epithelial cells, rather it is basol...

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“…Some reports have suggested a possible transcriptional regulation of several Keratin genes for epithelial cell proliferation and/or differentiation. 43,44 Some types of Keratins can regulate cell growth through several signaling pathways. 45 Whether an alteration of Keratin gene expression, such as the case of K8, thus consequently affects on urethra differentiation, requires further analyses.…”

Section: Discussionmentioning

confidence: 99%

Abnormal urethra formation in mouse models of Split-hand/split-foot malformation type 1 and type 4

et al. 2007

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Urogenital birth defects are one of the common phenotypes observed in hereditary human disorders. In particular, limb malformations are often associated with urogenital developmental abnormalities, as the case for Hand -foot -genital syndrome displaying similar hypoplasia/agenesis of limbs and external genitalia. Split-hand/split-foot malformation (SHFM) is a syndromic limb disorder affecting the central rays of the autopod with median clefts of the hands and feet, missing central fingers and often fusion of the remaining ones. SHFM type 1 (SHFM1) is linked to genomic deletions or rearrangements, which includes the distal-less-related homeogenes DLX5 and DLX6 as well as DSS1. SHFM type 4 (SHFM4) is associated with mutations in p63, which encodes a p53-related transcription factor. To understand that SHFM is associated with urogenital birth defects, we performed gene expression analysis and gene knockout mouse model analyses. We show here that Dlx5, Dlx6, p63 and Bmp7, one of the p63 downstream candidate genes, are all expressed in the developing urethral plate (UP) and that targeted inactivation of these genes in the mouse results in UP defects leading to abnormal urethra formation. These results suggested that different set of transcription factors and growth factor genes play similar developmental functions during embryonic urethra formation. Human SHFM syndromes display multiple phenotypes with variations in addition to split hand foot limb phenotype. These results suggest that different genes associated with human SHFM could also be involved in the aetiogenesis of hypospadias pointing toward a common molecular origin of these congenital malformations.

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Exocrine pancreatic disorders in transsgenic mice expressing human keratin 8

Cited by 73 publications

References 44 publications

Disturbances in hepatic cell-cycle regulation in mice with assembly-deficient keratins 8/18

Disturbances in hepatic cell-cycle regulation in mice with assembly-deficient keratins 8/18

Intermediate Filaments Interact with Dormant Ezrin in Intestinal Epithelial Cells

Abnormal urethra formation in mouse models of Split-hand/split-foot malformation type 1 and type 4

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