title: Cell cycle regulation in retinal progenitors by glia-derived neurotrophic factor and docosahexaenoic acid.
abstract: OBJECTIVE
  A recent study has shown that glia-derived neurotrophic factor (GDNF) and docosahexaenoic acid (DHA) promote the survival and differentiation of retina photoreceptors. The current study was undertaken to investigate whether these molecules participate in cell cycle regulation in retinal progenitors in vitro.
  
  
  METHODS
  Developmental changes in the expression of the stem cell marker nestin and of cell cycle and differentiated neuron markers were analyzed in neuroblasts obtained from 1-day-old rat retinas. The effects of GDNF and DHA on those changes were then determined.
  
  
  RESULTS
  Expression of nestin, found in more than one third of neuroblasts at day 1, rapidly decreased during development, with most neuroblasts acquiring the photoreceptor phenotype. GDNF increased the percentage of photoreceptor progenitors expressing nestin, whereas DHA reduced it, simultaneously enhancing photoreceptor differentiation. Several markers of cell cycle progression indicated that photoreceptor progenitors maintained an active cell cycle during the first 2 days in vitro. GDNF stimulated the cell cycle, increasing the number of dividing cells and generating more photoreceptor progenitors, whereas DHA induced cell cycle exit and photoreceptor differentiation. Analysis of the expression of the cyclin-Cdk inhibitor p27(Kip1) confirmed these results.
  
  
  CONCLUSIONS
  GDNF and DHA acted as molecular cues, counterbalancing the decision of photoreceptors to remain in or exit the cell cycle. The results strongly suggest that both factors participate in determining the number of photoreceptors in vitro, regulating the cell cycle and survival at early and late stages of development, respectively. Hence, GDNF and DHA may coordinately control the histogenesis of photoreceptors in the retina by modulating both neurogenesis and apoptosis.
authors.affiliation: Institute of Biochemical Research (INIBIBB) and Universidad Nacional del Sur, Bahia Blanca, Buenos Aires, Argentina.
authors.forename: M Fernanda
authors.initials: MF
authors.lastname: Insua
authors.forename: Andrés
authors.initials: A
authors.lastname: Garelli
authors.forename: Nora P
authors.initials: NP
authors.lastname: Rotstein
authors.forename: O Lorena
authors.initials: OL
authors.lastname: German
authors.forename: Andrés
authors.initials: A
authors.lastname: Arias
authors.forename: Luis E
authors.initials: LE
authors.lastname: Politi
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015536:Down-Regulation; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000378:metabolism; D051100:Glial Cell Line-Derived Neurotrophic Factor; D007211:Indoles / Q000378:metabolism; D007381:Intermediate Filament Proteins / Q000378:metabolism; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009419:Nerve Tissue Proteins; D064231:Nestin; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000166:cytology* / Q000378:metabolism; D017299:Rod Opsins / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D005456:Fluorescent Dyes; C495041:Gdnf protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D007211:Indoles; D007381:Intermediate Filament Proteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; C577486:Nes protein, rat; D064231:Nestin; D017299:Rod Opsins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004281:Docosahexaenoic Acids; C007293:DAPI