title: A rare homozygous MFSD8 single-base-pair deletion and frameshift in the whole genome sequence of a Chinese Crested dog with neuronal ceroid lipofuscinosis.
abstract: BACKGROUND
  The neuronal ceroid lipofuscinoses are heritable lysosomal storage diseases characterized by progressive neurological impairment and the accumulation of autofluorescent storage granules in neurons and other cell types. Various forms of human neuronal ceroid lipofuscinosis have been attributed to mutations in at least 13 different genes. So far, mutations in the canine orthologs of 7 of these genes have been identified in DNA from dogs with neuronal ceroid lipofuscinosis. The identification of new causal mutations could lead to the establishment of canine models to investigate the pathogenesis of the corresponding human neuronal ceroid lipofuscinoses and to evaluate and optimize therapeutic interventions for these fatal human diseases.
  
  
  METHODS
  We obtained blood and formalin-fixed paraffin-embedded brain sections from a rescue dog that was reported to be a young adult Chinese Crested. The dog was euthanized at approximately 19 months of age as a consequence of progressive neurological decline that included blindness, anxiety, and cognitive impairment. A diagnosis of neuronal ceroid lipofuscinosis was made based on neurological signs, magnetic resonance imaging of the brain, and fluorescence microscopic and electron microscopic examination of brain sections. We isolated DNA from the blood and used it to generate a whole genome sequence with 33-fold average coverage. Among the 7.2 million potential sequence variants revealed by aligning the sequence reads to the canine genome reference sequence was a homozygous single base pair deletion in the canine ortholog of one of 13 known human NCL genes: MFSD8:c.843delT. MFSD8:c.843delT is predicted to cause a frame shift and premature stop codon resulting in a truncated protein, MFSD8:p.F282Lfs13*, missing its 239 C-terminal amino acids. The MFSD8:c.843delT allele is absent from the whole genome sequences of 101 healthy canids or dogs with other diseases. The genotyping of archived DNA from 1478 Chinese Cresteds did not identify any additional MFSD8:c.843delT homozygotes and found only one heterozygote.
  
  
  CONCLUSIONS
  We conclude that the neurodegenerative disease of the Chinese Crested rescue dog was neuronal ceroid lipofuscinosis and that homozygosity for the MFSD8:c.843delT sequence variant was very likely to be the molecular-genetic cause of the disease.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA. guoj@missouri.edu.
authors.forename: Juyuan
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA. obriend@missouri.edu.
authors.forename: Dennis P
authors.initials: DP
authors.lastname: O'Brien
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA. mutangadurat@missouri.edu.
authors.forename: Tendai
authors.initials: T
authors.lastname: Mhlanga-Mutangadura
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA. njolby@ncsu.edu.
authors.forename: Natasha J
authors.initials: NJ
authors.lastname: Olby
authors.affiliation: Division of Animal Science, College of Agriculture, Food and Natural Resources, University of Missouri, Columbia, MO, USA. taylorjerr@missouri.edu.
authors.forename: Jeremy F
authors.initials: JF
authors.lastname: Taylor
authors.affiliation: Division of Animal Science, College of Agriculture, Food and Natural Resources, University of Missouri, Columbia, MO, USA. schnabelr@missouri.edu.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Schnabel
authors.affiliation: Mason Eye Institute, School of Medicine, University of Missouri, Columbia, MO, USA. katzm@health.missouri.edu.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Katz
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA. johnsongs@missouri.edu.
authors.forename: Gary S
authors.initials: GS
authors.lastname: Johnson
mesh_terms: D000818:Animals; D002531:Cerebellum / Q000473:pathology; D004283:Dog Diseases / Q000235:genetics* / Q000473:pathology; D004285:Dogs / Q000235:genetics; D016368:Frameshift Mutation / Q000235:genetics*; D017353:Gene Deletion; D016678:Genome / Q000235:genetics; D006720:Homozygote; D008279:Magnetic Resonance Imaging / Q000662:veterinary; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics*; D059906:Neuroimaging / Q000662:veterinary; D009472:Neuronal Ceroid-Lipofuscinoses / Q000235:genetics / Q000662:veterinary*
chemical_list: D026901:Membrane Transport Proteins