title: Loss of function of C9orf72 causes motor deficits in a zebrafish model of amyotrophic lateral sclerosis.
abstract: OBJECTIVE
  To define the role that repeat expansions of a GGGGCC hexanucleotide sequence of the C9orf72 gene play in the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). A genetic model for ALS was developed to determine whether loss of function of the zebrafish orthologue of C9orf72 (zC9orf72) leads to abnormalities in neuronal development.
  
  
  METHODS
  C9orf72 mRNA levels were quantified in brain and lymphoblasts derived from FTLD and ALS/FTLD patients and in zebrafish. Knockdown of the zC9orf72 was performed using 2 specific antisense morpholino oligonucleotides to block transcription. Quantifications of spontaneous swimming and tactile escape response, as well as measurements of axonal projections from the spinal cord, were performed.
  
  
  RESULTS
  Significantly decreased expression of C9orf72 transcripts in brain and lymphoblasts was found in sporadic FTLD and ALS/FTLD patients with normal-size or expanded hexanucleotide repeats. The zC9orf72 is selectively expressed in the developing nervous system at developmental stages. Loss of function of the zC9orf72 transcripts causes both behavioral and cellular deficits related to locomotion without major morphological abnormalities. These deficits were rescued upon overexpression of human C9orf72 mRNA transcripts.
  
  
  CONCLUSIONS
  Our results indicate C9orf72 haploinsufficiency could be a contributing factor in the spectrum of ALS/FTLD neurodegenerative disorders. Loss of function of the zebrafish orthologue of zC9orf72 expression in zebrafish is associated with axonal degeneration of motor neurons that can be rescued by expressing human C9orf72 mRNA, highlighting the specificity of the induced phenotype. These results reveal a pathogenic consequence of decreased C9orf72 levels, supporting a loss of function mechanism of disease.
authors.affiliation: Research Center of the Institute for Brain and Spinal Cord CRICM, National Institute of Health and Medical Research - Inserm UMR_S975, National Center for Scientific Reseach CNRS UMR_7225, Pierre and Marie Curie University UPMC Paris 6, F-75013, Paris, France.
authors.forename: Sorana
authors.initials: S
authors.lastname: Ciura
authors.forename: Serena
authors.initials: S
authors.lastname: Lattante
authors.forename: Isabelle
authors.initials: I
authors.lastname: Le Ber
authors.forename: Morwena
authors.initials: M
authors.lastname: Latouche
authors.forename: Hervé
authors.initials: H
authors.lastname: Tostivint
authors.forename: Alexis
authors.initials: A
authors.lastname: Brice
authors.forename: Edor
authors.initials: E
authors.lastname: Kabashi
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000473:pathology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D000073885:C9orf72 Protein; D004195:Disease Models, Animal; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics* / Q000473:pathology; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism / Q000473:pathology; D009043:Motor Activity / Q000235:genetics*; D011506:Proteins / Q000235:genetics*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000172:deficiency / Q000235:genetics*
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins; D029961:Zebrafish Proteins