title: Mice homozygous for c.451C>T mutation in Cln1 gene recapitulate INCL phenotype.
abstract: OBJECTIVE
  Nonsense mutations account for 5-70% of all genetic disorders. In the United States, nonsense mutations in the CLN1/PPT1 gene underlie >40% of the patients with infantile neuronal ceroid lipofuscinosis (INCL), a devastating neurodegenerative lysosomal storage disease. We sought to generate a reliable mouse model of INCL carrying the most common Ppt1 nonsense mutation (c.451C>T) found in the United States patient population to provide a platform for evaluating nonsense suppressors in vivo.
  
  
  METHODS
  We knocked-in c.451C>T nonsense mutation in the Ppt1 gene in C57 embryonic stem (ES) cells using a targeting vector in which LoxP flanked the Neo cassette, which was removed from targeted ES cells by electroporating Cre. Two independently targeted ES clones were injected into blastocysts to generate syngenic C57 knock-in mice, obviating the necessity for extensive backcrossing.
  
  
  RESULTS
  Generation of Ppt1-KI mice was confirmed by DNA sequencing, which showed the presence of c.451C>T mutation in the Ppt1 gene. These mice are viable and fertile, although they developed spasticity (a "clasping" phenotype) at a median age of 6 months. Autofluorescent storage materials accumulated throughout the brain regions and in visceral organs. Electron microscopic analysis of the brain and the spleen showed granular osmiophilic deposits. Increased neuronal apoptosis was particularly evident in cerebral cortex and abnormal histopathological and electroretinographic (ERG) analyses attested striking retinal degeneration. Progressive deterioration of motor coordination and behavioral parameters continued until eventual death.
  
  
  CONCLUSIONS
  Our findings show that Ppt1-KI mice reliably recapitulate INCL phenotype providing a platform for testing the efficacy of existing and novel nonsense suppressors in vivo.
authors.affiliation: Program on Developmental Endocrinology and Genetics, Section on Developmental Genetics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development Bethesda, Maryland.
authors.forename: Ashleigh
authors.initials: A
authors.lastname: Bouchelion
authors.affiliation: Program on Developmental Endocrinology and Genetics, Section on Developmental Genetics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development Bethesda, Maryland.
authors.forename: Zhongjian
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Visual Function Core (HNW2-L), National Eye Institute, National Institutes of Health Bethesda, Maryland, 20892-1830.
authors.forename: Yichao
authors.initials: Y
authors.lastname: Li
authors.affiliation: Visual Function Core (HNW2-L), National Eye Institute, National Institutes of Health Bethesda, Maryland, 20892-1830.
authors.forename: Haohua
authors.initials: H
authors.lastname: Qian
authors.affiliation: Program on Developmental Endocrinology and Genetics, Section on Developmental Genetics, Eunice Kennedy-Shriver National Institute of Child Health and Human Development Bethesda, Maryland.
authors.forename: Anil B
authors.initials: AB
authors.lastname: Mukherjee