title: RPGR isoforms in photoreceptor connecting cilia and the transitional zone of motile cilia.
abstract: OBJECTIVE
  The retinitis pigmentosa guanosine triphosphatase (GTPase) regulator (RPGR) is essential for photoreceptor survival. There is as yet no consensus concerning the subcellular localization of RPGR. This study was undertaken as a comprehensive effort to resolve current controversies.
  
  
  METHODS
  RPGR in mice and other mammalian species was examined by immunofluorescence. RPGR variants were distinguished by using isoform-specific antibodies. Different tissue processing procedures were evaluated. Immunoblot analysis of serial cross-sections of photoreceptors was performed as a complementary approach to subcellular localization.
  
  
  RESULTS
  RPGR was found in the connecting cilia of rods and cones with no evidence for species-dependent variation. RPGR ORF15 was the predominant variant in photoreceptor connecting cilia whereas constitutive RPGR (default) was the sole variant in the transitional zone of motile cilia in airway epithelia. Removal of soluble materials in the interphotoreceptor matrix facilitated detection of RPGR in the connecting cilia in photoreceptors.
  
  
  CONCLUSIONS
  RPGR localizes in photoreceptor connecting cilia and in a homologous structure, the transitional zone of motile cilia. These data are important for understanding the multitude of clinical manifestations associated with mutations in RPGR. Interphotoreceptor matrix surrounding the connecting cilia is a key variable for in situ detection of a protein in the connecting cilia.
authors.affiliation: Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Hong
authors.forename: Basil
authors.initials: B
authors.lastname: Pawlyk
authors.forename: Maxim
authors.initials: M
authors.lastname: Sokolov
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Strissel
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Brian
authors.initials: B
authors.lastname: Tulloch
authors.forename: Alan F
authors.initials: AF
authors.lastname: Wright
authors.forename: Vadim Y
authors.initials: VY
authors.lastname: Arshavsky
authors.forename: Tiansen
authors.initials: T
authors.lastname: Li
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D002923:Cilia / Q000378:metabolism; D005136:Eye Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015151:Immunoblotting; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D020033:Protein Isoforms; D013552:Swine
chemical_list: D002352:Carrier Proteins; D005136:Eye Proteins; D020033:Protein Isoforms; C099929:RPGR protein, human