title: Nebulette knockout mice have normal cardiac function, but show Z-line widening and up-regulation of cardiac stress markers.
abstract: OBJECTIVE
  Nebulette is a 109 kDa modular protein localized in the sarcomeric Z-line of the heart. In vitro studies have suggested a role of nebulette in stabilizing the thin filament, and missense mutations in the nebulette gene were recently shown to be causative for dilated cardiomyopathy and endocardial fibroelastosis in human and mice. However, the role of nebulette in vivo has remained elusive. To provide insights into the function of nebulette in vivo, we generated and studied nebulette-deficient (nebl(-) (/-)) mice.
  
  
  RESULTS
  Nebl(-) (/-) mice were generated by replacement of exon 1 by Cre under the control of the endogenous nebulette promoter, allowing for lineage analysis using the ROSA26 Cre reporter strain. This revealed specific expression of nebulette in the heart, consistent with in situ hybridization results. Nebl(-) (/-) mice exhibited normal cardiac function both under basal conditions and in response to transaortic constriction as assessed by echocardiography and haemodynamic analyses. Furthermore, histological, IF, and western blot analysis showed no cardiac abnormalities in nebl(-) (/-) mice up to 8 months of age. In contrast, transmission electron microscopy showed Z-line widening starting from 5 months of age, suggesting that nebulette is important for the integrity of the Z-line. Furthermore, up-regulation of cardiac stress responsive genes suggests the presence of chronic cardiac stress in nebl(-) (/-) mice.
  
  
  CONCLUSIONS
  Nebulette is dispensable for normal cardiac function, although Z-line widening and up-regulation of cardiac stress markers were found in nebl(-) (/-) heart. These results suggest that the nebulette disease causing mutations have dominant gain-of-function effects.
authors.affiliation: Humanitas Clinical and Research Center, Via Manzoni 113, 20089 Rozzano, Milan, Italy University of Milano-Bicocca, Milan, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Mastrototaro
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Xingqun
authors.initials: X
authors.lastname: Liang
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.affiliation: Humanitas Clinical and Research Center, Via Manzoni 113, 20089 Rozzano, Milan, Italy Institute of Genetic and Biomedical Research, UOS Milan, National Research Council, Milan, Italy.
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Carullo
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Piroddi
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Tesi
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Yusu
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Dalton
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Kirk L
authors.initials: KL
authors.lastname: Peterson
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Corrado
authors.initials: C
authors.lastname: Poggesi
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA.
authors.forename: Farah
authors.initials: F
authors.lastname: Sheikh
authors.affiliation: Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA juchen@ucsd.edu marie-louise.bang@cnr.it.
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
authors.affiliation: Humanitas Clinical and Research Center, Via Manzoni 113, 20089 Rozzano, Milan, Italy Institute of Genetic and Biomedical Research, UOS Milan, National Research Council, Milan, Italy juchen@ucsd.edu marie-louise.bang@cnr.it.
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Bang
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000172:deficiency / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D060588:LIM Domain Proteins / Q000172:deficiency / Q000378:metabolism*; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D012518:Sarcomeres / Q000502:physiology*; D013312:Stress, Physiological; D015854:Up-Regulation
chemical_list: D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D060588:LIM Domain Proteins; D009124:Muscle Proteins; C486891:Nebl protein, mouse
keywords: Dilated cardiomyopathy; Heart; Knockout mice; Sarcomere; Z-line