title: Familial dilated cardiomyopathy caused by an alpha-tropomyosin mutation: the distinctive natural history of sarcomeric dilated cardiomyopathy.
abstract: OBJECTIVE
  We sought to further define the role of sarcomere mutations in dilated cardiomyopathy (DCM) and associated clinical phenotypes.
  
  
  BACKGROUND
  Mutations in several contractile proteins contribute to DCM, but definitive evidence for the roles of most sarcomere genes remains limited by the lack of robust genetic support.
  
  
  METHODS
  Direct sequencing of 6 sarcomere genes was performed on 334 probands with DCM. A novel D230N missense mutation in the gene encoding alpha-tropomyosin (TPM1) was identified. Functional assessment was performed by the use of an in vitro reconstituted sarcomere complex to evaluate ATPase regulation and Ca(2+) affinity as correlates of contractility.
  
  
  RESULTS
  TPM1 D230N segregated with DCM in 2 large unrelated families. This mutation altered an evolutionarily conserved residue and was absent in >1,000 control chromosomes. In vitro studies demonstrated major inhibitory effects on sarcomere function with reduced Ca(2+) sensitivity, maximum activation, and Ca(2+) affinity compared with wild-type TPM1. Clinical manifestations ranged from decompensated heart failure or sudden death in those presenting early in life to asymptomatic left ventricular dysfunction in those diagnosed during adulthood. Notably, several affected infants had remarkable improvement.
  
  
  CONCLUSIONS
  Genetic segregation in 2 unrelated families and functional analyses conclusively establish a pathogenic role for TPM1 mutations in DCM. In vitro results demonstrate contrasting effects of DCM and hypertrophic cardiomyopathy mutations in TPM1, suggesting that specific functional consequences shape cardiac remodeling. Along with previous reports, our data support a distinctive, age-dependent phenotype with sarcomere-associated DCM where presentation early in life is associated with severe, sometimes lethal, disease. These observations have implications for the management of familial DCM.
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Neal K
authors.initials: NK
authors.lastname: Lakdawala
authors.forename: Lisa
authors.initials: L
authors.lastname: Dellefave
authors.forename: Charles S
authors.initials: CS
authors.lastname: Redwood
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sparks
authors.forename: Allison L
authors.initials: AL
authors.lastname: Cirino
authors.forename: Steve
authors.initials: S
authors.lastname: Depalma
authors.forename: Steven D
authors.initials: SD
authors.lastname: Colan
authors.forename: Birgit
authors.initials: B
authors.lastname: Funke
authors.forename: Rebekah S
authors.initials: RS
authors.lastname: Zimmerman
authors.forename: Paul
authors.initials: P
authors.lastname: Robinson
authors.forename: Hugh
authors.initials: H
authors.lastname: Watkins
authors.forename: Christine E
authors.initials: CE
authors.lastname: Seidman
authors.forename: J G
authors.initials: JG
authors.lastname: Seidman
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: McNally
authors.forename: Carolyn Y
authors.initials: CY
authors.lastname: Ho
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002118:Calcium / Q000378:metabolism; D002311:Cardiomyopathy, Dilated / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009218:Myosins / Q000032:analysis; D010641:Phenotype; D012518:Sarcomeres / Q000235:genetics*; D014335:Tropomyosin / Q000235:genetics; D014336:Troponin / Q000378:metabolism; D020257:Ventricular Remodeling / Q000502:physiology
chemical_list: D014335:Tropomyosin; D014336:Troponin; D009218:Myosins; D002118:Calcium