title: Evidence that "brain-specific" FOX-1, FOX-2, and nPTB alternatively spliced isoforms are produced in the lens.
abstract: OBJECTIVE
  Alternative RNA splicing is essential in development and more rapid physiological processes that include disease mechanisms. Studies over the last 20 years demonstrated that RNA binding protein families, which mediate the alternative splicing of a large percentage of genes in mammals, contain isoforms with mutually exclusive expression in non-neural and neural progenitor cells vs. post-mitotic neurons, and regulate the comprehensive reprogramming of alternative splicing during neurogenesis. Polypyrimidine tract binding (PTB) proteins and Fox-1 proteins also undergo mutually exclusive alternative splicing in neural and non-neural cells that regulates their tissue-specific expression and splicing activities. Over the past 50 years, striking morphological similarities noted between lens fiber cells and neurons suggested that cell biology processes and gene expression profiles may be shared as well. Here, we examined mouse and rat lenses to determine if alternative splicing of neuronal nPTB and Fox-1/Fox-2 isoforms also occurs in lenses.
  
  
  METHODS
  Immunoblot, immunofluorescence, and RT-PCR were used to examine expression and alternative splicing of transcripts in lens and brain.
  
  
  RESULTS
  We demonstrated that exon 10 is predominantly included in nPTB transcripts consistent with nPTB protein in lenses, and that alternatively spliced Fox-1/-2 lens transcripts contain exons that have been considered neuron-specific. We identified a 3' alternative Fox-1 exon in lenses that encodes a nuclear localization signal consistent with its protein distribution detected in fiber cells. Neuronal alternative splicing of kinesin KIF1Bβ2 has been associated with PTB/nPTB and Fox-2, and we found that two 'neuron-specific' exons are also included in lenses.
  
  
  CONCLUSIONS
  The present study provides evidence that alternative neuronal nPTB and Fox-1/Fox-2 isoforms are also produced in lenses. These findings raise questions regarding the extent these factors contribute to a similar reprogramming of alternative splicing during lens differentiation, and the degree that alternative gene transcripts produced during neurogenesis are also expressed in the lens.
authors.affiliation: Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Claudine L
authors.initials: CL
authors.lastname: Bitel
authors.forename: Rachel
authors.initials: R
authors.lastname: Nathan
authors.forename: Patrick
authors.initials: P
authors.lastname: Wong
authors.forename: Sunil
authors.initials: S
authors.lastname: Kuppasani
authors.forename: Masafumi
authors.initials: M
authors.lastname: Matsushita
authors.forename: Hrioshi
authors.initials: H
authors.lastname: Kanazawa
authors.forename: Peter H
authors.initials: PH
authors.lastname: Frederikse
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D005091:Exons / Q000235:genetics; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D015151:Immunoblotting; D016547:Kinesins / Q000235:genetics; D007908:Lens, Crystalline / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C490398:Kif1b protein, mouse; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; C429773:Ptbp2 protein, mouse; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; C465036:Rbfox1 protein, mouse; C558929:Rbfox2 protein, mouse; D038941:Polypyrimidine Tract-Binding Protein; D016547:Kinesins