title: Limitations in a frataxin knockdown cell model for Friedreich ataxia in a high-throughput drug screen.
abstract: BACKGROUND
  Pharmacological high-throughput screening (HTS) represents a powerful strategy for drug discovery in genetic diseases, particularly when the full spectrum of pathological dysfunctions remains unclear, such as in Friedreich ataxia (FRDA). FRDA, the most common recessive ataxia, results from a generalized deficiency of mitochondrial and cytosolic iron-sulfur cluster (ISC) proteins activity, due to a partial loss of frataxin function, a mitochondrial protein proposed to function as an iron-chaperone for ISC biosynthesis. In the absence of measurable catalytic function for frataxin, a cell-based assay is required for HTS assay.
  
  
  METHODS
  Using a targeted ribozyme strategy in murine fibroblasts, we have developed a cellular model with strongly reduced levels of frataxin. We have used this model to screen the Prestwick Chemical Library, a collection of one thousand off-patent drugs, for potential molecules for FRDA.
  
  
  RESULTS
  The frataxin deficient cell lines exhibit a proliferation defect, associated with an ISC enzyme deficit. Using the growth defect as end-point criteria, we screened the Prestwick Chemical Library. However no molecule presented a significant and reproducible effect on the proliferation rate of frataxin deficient cells. Moreover over numerous passages, the antisense ribozyme fibroblast cell lines revealed an increase in frataxin residual level associated with the normalization of ISC enzyme activities. However, the ribozyme cell lines and FRDA patient cells presented an increase in Mthfd2 transcript, a mitochondrial enzyme that was previously shown to be upregulated at very early stages of the pathogenesis in the cardiac mouse model.
  
  
  CONCLUSIONS
  Although no active hit has been identified, the present study demonstrates the feasibility of using a cell-based approach to HTS for FRDA. Furthermore, it highlights the difficulty in the development of a stable frataxin-deficient cell model, an essential condition for productive HTS in the future.
authors.affiliation: IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), CNRS/INSERM/Université Louis Pasteur, Illkirch cedex, France. nadege.calmels@chru-strasbourg.fr
authors.forename: Nadège
authors.initials: N
authors.lastname: Calmels
authors.forename: Hervé
authors.initials: H
authors.lastname: Seznec
authors.forename: Pascal
authors.initials: P
authors.lastname: Villa
authors.forename: Laurence
authors.initials: L
authors.lastname: Reutenauer
authors.forename: Marcel
authors.initials: M
authors.lastname: Hibert
authors.forename: Jacques
authors.initials: J
authors.lastname: Haiech
authors.forename: Pierre
authors.initials: P
authors.lastname: Rustin
authors.forename: Michel
authors.initials: M
authors.lastname: Koenig
authors.forename: Hélène
authors.initials: H
authors.lastname: Puccio
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line / Q000166:cytology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D005621:Friedreich Ataxia / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D033862:Iron-Binding Proteins / Q000235:genetics*; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000096923:Frataxin
chemical_list: D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D000096923:Frataxin
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