Antibodies in the field of histopathology, very little information regarding the functional role of K7 in vivo exists the lack of suitable mouse models combined with the fact that, to date, there have been no human diseases associated with mutations in the K7 gene, have all limited understanding of K7 function. Title Loaded From File Unlike the epidermal keratins, whose functions are well defined due to their association with a large number of inherited skin disorders [4], the functions of the simple epithelial keratins ie. K7, K8, K18, K19, K20 and K23 have been more difficult to define [5]. Genetically engineered mice, either developed through gene targeting or overexpression of mutant keratin genes, have proved to be a useful tool in helping to understand the functions of the simple keratins and the careful characterisation of these different mouse models have helped in identifying human diseases not previously associated with keratin gene mutations [6]. For example, the phenotypic characterisation of various K8 andK18 knockout and transgenic mouse lines has been important in helping to demonstrate an association between predisposing KRT8 and KRT18 gene mutations in humans with various types of liver disease [7]. Pathogenic missense mutations in both of these genes have now been identified in patients with cryptogenic and non-cryptogenic cirrhosis, primary Title Loaded From File biliary cirrhosis and viral hepatitis [8]. The genes for the simple keratins K8, K18 and K19 have each been knocked out in mice and despite the fact that these keratins share overlapping patterns of expression, especially K8 and K18, the resulting phenotypes are quite different. The most severe phenotype is displayed by K8 knockout mice, which have a straindependent phenotype ranging from a highly penetrant midgestational lethality of K8 null embryos on the C57Bl6 genetic background [9] to colorectal inflammation and hyperplasia on a surviving FVB/N genetic background [10]. In contrast, K18 knockout mice have a relatively mild age-related phenotype which is restricted to the liver and consists of the accumulation of K8positive aggregates in hepatocytes [11]. Knockout of K19 does not lead to any obvious phenotype in mice [12], which is probably due to compensation by K18, but breeding of K19 knockout mice with either K8 or K18 null mice produces K8/K19 and K18/K19 double knockout embryos which die in utero [12,13]. The failure of these double keratin-deficient embryos to survive has been attributed to fragility of trophoblast giant cells in the developingK7 Knockout Miceplacenta caused by the lack of an intact keratin cytoskeleton [13]. Therefore in the placenta at least, simple keratins provide an essential structural role in maintaining the integrity of the trophoblast layer, much akin to the role played by the epidermally-expressed keratins which give structural support to the skin and its appendages. In an attempt to understand better K7 function in vivo, as well as to increase the overall number of keratin knockout mice that are available for study, we used our previous experience with the mouse Krt7 gene [2] to introduce a null mutation into mouse embryonic stem cells by gene targeting. By generating K7 deficient mice, the consequences of the absence of K7 on the development and differentiation of simple epithelia can be studied, the outcome of which might be useful in discovering hitherto unknown human disorders associated with KRT7 gene mutations.separated on 1 (w/v) agarose gels. DNA gels were t.Antibodies in the field of histopathology, very little information regarding the functional role of K7 in vivo exists the lack of suitable mouse models combined with the fact that, to date, there have been no human diseases associated with mutations in the K7 gene, have all limited understanding of K7 function. Unlike the epidermal keratins, whose functions are well defined due to their association with a large number of inherited skin disorders [4], the functions of the simple epithelial keratins ie. K7, K8, K18, K19, K20 and K23 have been more difficult to define [5]. Genetically engineered mice, either developed through gene targeting or overexpression of mutant keratin genes, have proved to be a useful tool in helping to understand the functions of the simple keratins and the careful characterisation of these different mouse models have helped in identifying human diseases not previously associated with keratin gene mutations [6]. For example, the phenotypic characterisation of various K8 andK18 knockout and transgenic mouse lines has been important in helping to demonstrate an association between predisposing KRT8 and KRT18 gene mutations in humans with various types of liver disease [7]. Pathogenic missense mutations in both of these genes have now been identified in patients with cryptogenic and non-cryptogenic cirrhosis, primary biliary cirrhosis and viral hepatitis [8]. The genes for the simple keratins K8, K18 and K19 have each been knocked out in mice and despite the fact that these keratins share overlapping patterns of expression, especially K8 and K18, the resulting phenotypes are quite different. The most severe phenotype is displayed by K8 knockout mice, which have a straindependent phenotype ranging from a highly penetrant midgestational lethality of K8 null embryos on the C57Bl6 genetic background [9] to colorectal inflammation and hyperplasia on a surviving FVB/N genetic background [10]. In contrast, K18 knockout mice have a relatively mild age-related phenotype which is restricted to the liver and consists of the accumulation of K8positive aggregates in hepatocytes [11]. Knockout of K19 does not lead to any obvious phenotype in mice [12], which is probably due to compensation by K18, but breeding of K19 knockout mice with either K8 or K18 null mice produces K8/K19 and K18/K19 double knockout embryos which die in utero [12,13]. The failure of these double keratin-deficient embryos to survive has been attributed to fragility of trophoblast giant cells in the developingK7 Knockout Miceplacenta caused by the lack of an intact keratin cytoskeleton [13]. Therefore in the placenta at least, simple keratins provide an essential structural role in maintaining the integrity of the trophoblast layer, much akin to the role played by the epidermally-expressed keratins which give structural support to the skin and its appendages. In an attempt to understand better K7 function in vivo, as well as to increase the overall number of keratin knockout mice that are available for study, we used our previous experience with the mouse Krt7 gene [2] to introduce a null mutation into mouse embryonic stem cells by gene targeting. By generating K7 deficient mice, the consequences of the absence of K7 on the development and differentiation of simple epithelia can be studied, the outcome of which might be useful in discovering hitherto unknown human disorders associated with KRT7 gene mutations.separated on 1 (w/v) agarose gels. DNA gels were t.
