PURPOSE: Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene are a frequent cause of X-linked retinitis pigmentosa. The RPGR transcript undergoes complex alternative splicing to express both constitutive (Rpgr(ex1-19)) and Rpgr(ORF15) variants. Both variants localize to photoreceptor connecting cilia and are believed to play roles in ciliary function. This study examined variability in isoform expression and tested whether the constitutive variant could substitute for Rpgr function in photoreceptors. METHODS: Rpgr(ex1-19) and Rpgr(ORF15) expression during retinal development were compared using immunoblot analysis and immunohistochemistry, and ciliary affinity in adult photoreceptors was assessed by protein fractionation. Transgenic mice expressing either the full-length Rpgr(ex1-19) or Rpgr(ORF15) variant were studied using light and electron microscopy and immunofluorescence imaging. The results were compared with those of wild-type and Rpgr(-/-) mice. RESULTS: Rpgr expression undergoes dynamic temporal regulation during retinal development, and variants exhibit variability for ciliary localization in adult photoreceptors. Transgenic expression of both variants grossly exceeded endogenous Rpgr expression in photoreceptors. Although both variants exhibited normal ciliary localization, overexpression of the Rpgr(ex1-19) variant resulted in atypical accumulation of Rpgr in photoreceptor outer segments, abnormal photoreceptor morphology, and severe retinal degeneration. CONCLUSIONS: The Rpgr isoform ratio in the adult retina is critical to photoreceptor integrity. The utilization of distinct Rpgr variants at different stages of photoreceptor maturation suggests independent roles in photoreceptor function. Finally, misexpression of Rpgr(ex1-19) causes retinal degeneration that is considerably more severe than that caused by Rpgr knockout but photoreceptors tolerate overexpression of Rpgr(ORF15) without evidence of degeneration.
PURPOSE: Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene are a frequent cause of X-linked retinitis pigmentosa. The RPGR transcript undergoes complex alternative splicing to express both constitutive (Rpgr(ex1-19)) and Rpgr(ORF15) variants. Both variants localize to photoreceptor connecting cilia and are believed to play roles in ciliary function. This study examined variability in isoform expression and tested whether the constitutive variant could substitute for Rpgr function in photoreceptors. METHODS: Rpgr(ex1-19) and Rpgr(ORF15) expression during retinal development were compared using immunoblot analysis and immunohistochemistry, and ciliary affinity in adult photoreceptors was assessed by protein fractionation. Transgenic mice expressing either the full-length Rpgr(ex1-19) or Rpgr(ORF15) variant were studied using light and electron microscopy and immunofluorescence imaging. The results were compared with those of wild-type and Rpgr(-/-) mice. RESULTS: Rpgr expression undergoes dynamic temporal regulation during retinal development, and variants exhibit variability for ciliary localization in adult photoreceptors. Transgenic expression of both variants grossly exceeded endogenous Rpgr expression in photoreceptors. Although both variants exhibited normal ciliary localization, overexpression of the Rpgr(ex1-19) variant resulted in atypical accumulation of Rpgr in photoreceptor outer segments, abnormal photoreceptor morphology, and severe retinal degeneration. CONCLUSIONS: The Rpgr isoform ratio in the adult retina is critical to photoreceptor integrity. The utilization of distinct Rpgr variants at different stages of photoreceptor maturation suggests independent roles in photoreceptor function. Finally, misexpression of Rpgr(ex1-19) causes retinal degeneration that is considerably more severe than that caused by Rpgr knockout but photoreceptors tolerate overexpression of Rpgr(ORF15) without evidence of degeneration.
Authors: R Roepman; N Bernoud-Hubac; D E Schick; A Maugeri; W Berger; H H Ropers; F P Cremers; P A Ferreira Journal: Hum Mol Genet Date: 2000-09-01 Impact factor: 6.150
Authors: Qi Zhang; Gregory M Acland; Wen X Wu; Jennifer L Johnson; Sue Pearce-Kelling; Brian Tulloch; Raf Vervoort; Alan F Wright; Gustavo D Aguirre Journal: Hum Mol Genet Date: 2002-05-01 Impact factor: 6.150
Authors: Xinhua Shu; Zhiqiang Zeng; Philippe Gautier; Alan Lennon; Milica Gakovic; E Elizabeth Patton; Alan F Wright Journal: Hum Mol Genet Date: 2009-12-01 Impact factor: 6.150
Authors: Yun Zhao; Dong-Hyun Hong; Basil Pawlyk; Guohua Yue; Michael Adamian; Marcin Grynberg; Adam Godzik; Tiansen Li Journal: Proc Natl Acad Sci U S A Date: 2003-03-21 Impact factor: 11.205
Authors: Zhijian Wu; Suja Hiriyanna; Haohua Qian; Suddhasil Mookherjee; Maria M Campos; Chun Gao; Robert Fariss; Paul A Sieving; Tiansen Li; Peter Colosi; Anand Swaroop Journal: Hum Mol Genet Date: 2015-04-15 Impact factor: 6.150
Authors: Qihong Zhang; Joseph C Giacalone; Charles Searby; Edwin M Stone; Budd A Tucker; Val C Sheffield Journal: Proc Natl Acad Sci U S A Date: 2019-01-08 Impact factor: 11.205
Authors: Wei Chieh Huang; Alan F Wright; Alejandro J Roman; Artur V Cideciyan; Forbes D Manson; Dina Y Gewaily; Sharon B Schwartz; Sam Sadigh; Maria P Limberis; Peter Bell; James M Wilson; Anand Swaroop; Samuel G Jacobson Journal: Invest Ophthalmol Vis Sci Date: 2012-08-15 Impact factor: 4.799
Authors: William A Beltran; Artur V Cideciyan; Alfred S Lewin; William W Hauswirth; Samuel G Jacobson; Gustavo D Aguirre Journal: Cold Spring Harb Perspect Med Date: 2014-10-09 Impact factor: 6.915
Authors: Valérie L Dufour; Artur V Cideciyan; Guo-Jie Ye; Chunjuan Song; Adrian Timmers; Perry L Habecker; Wei Pan; Nicole M Weinstein; Malgorzata Swider; Amy C Durham; Gui-Shuang Ying; Paulette M Robinson; Samuel G Jacobson; David R Knop; Jeffrey D Chulay; Mark S Shearman; Gustavo D Aguirre; William A Beltran Journal: Hum Gene Ther Date: 2020-02-06 Impact factor: 5.695