Abstract
Mutations in retinitis pigmentosa GTPase regulator (RPGR) account for over 70% of X-linked retinitis pigmentosa (XlRP), characterized by retinal degeneration and eventual blindness. RPGR mutations demonstrate extreme phenotypic heterogeneity, even within the same family, suggesting a role for genetic modifiers in disease expression. This study aimed to categorize the clinical diversity in a cohort of 98 affected males from 56 families with RPGR mutations, and to test candidate modifier genes for association with disease severity. Ninety-eight affected males from 56 families were enrolled. Patients were categorized as mild, moderate, or severe according to specific clinical criteria. Patient DNA was genotyped for common coding SNPs in four candidate modifier genes known to interact with RPGR: RPGRIP1, RPGRIP1L, CEP290, and NPHP5. Family-based association testing was performed using PLINK (pngu.mgh.harvard.edu/purcell/plink/). A wide range of severity was observed between and within families. Two SNPs showed association with severe disease: the minor allele (N) of I393N in IQCB1 (p = 0.044) and the common allele (R) of R744Q in RPGRIP1L (p = 0.049).
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Similar content being viewed by others
References
Adzhubei IA, Schmidt S, Peshkin L et al (2010) A method and server for predicting damaging missense mutations. Nat Methods 7:248–249
Arts HH, Doherty D, van Beersum SE et al (2007) Mutations in the gene encoding the basal body protein RPGRIP1L, a nephrocystin-4 interactor, cause Joubert syndrome. Nat Genet 39:882–888
Ayyagari R, Demirci FY, Liu J et al (2002) X-linked recessive atrophic macular degeneration from RPGR mutation. Genomics 80:166–171
Baala L, Audollent S, Martinovic J et al (2007) Pleiotropic effects of CEP290 (NPHP6) mutations extend to Meckel syndrome. Am J Hum Genet 81:170–179
Berson EL (2007) Long-term visual prognoses in patients with retinitis pigmentosa: the Ludwig von Sallmann lecture. Exp Eye Res 85:7–14
Berson EL, Sandberg MA, Rosner B et al (1985) Natural course of retinitis pigmentosa over a three-year interval. Am J Ophthalmol 99:240–251
Birch DG, Anderson JL, Fish GE (1999) Yearly rates of rod and cone functional loss in retinitis pigmentosa and cone-rod dystrophy. Ophthalmology 106:258–268
Boylan JP, Wright AF (2000) Identification of a novel protein interacting with RPGR. Hum Mol Genet 9:2085–2093
Chen TY, Illing M, Molday LL et al (1994) Subunit 2 (or beta) of retinal rod cGMP-gated cation channel is a component of the 240-kDa channel-associated protein and mediates Ca(2+)-calmodulin modulation. Proc Natl Acad Sci USA 91:11757–11761
Delous M, Baala L, Salomon R et al (2007) The ciliary gene RPGRIP1L is mutated in cerebello-oculo-renal syndrome (Joubert syndrome type B) and Meckel syndrome. Nat Genet 39:875–881
Demirci FY, Rigatti BW, Wen G et al (2002) X-linked cone-rod dystrophy (locus COD1): identification of mutations in RPGR exon ORF15. Am J Hum Genet 70:1049–1053
den Hollander AI, Koenekoop RK, Yzer S et al (2006) Mutations in the CEP290 (NPHP6) gene are a frequent cause of Leber congenital amaurosis. Am J Hum Genet 79:556–561
Dryja TP, Adams SM, Grimsby JL et al (2001) Null RPGRIP1 alleles in patients with Leber congenital amaurosis. Am J Hum Genet 68:1295–1298
Grover S, Fishman GA, Anderson RJ et al (2000) A longitudinal study of visual function in carriers of X-linked recessive retinitis pigmentosa. Ophthalmology 107:386-396
Guo DC, Milewicz DM (2003) Methodology for using a universal primer to label amplified DNA segments for molecular analysis. Biotechnol Lett 25:2079–2083
Hong DH, Pawlyk B, Sokolov M et al (2003) RPGR isoforms in photoreceptor connecting cilia and the transitional zone of motile cilia. Invest Ophthalmol Vis Sci 44:2413–2421
Keith CG, Denton MJ, Chen JD (1991) Clinical variability in a family with X-linked retinal dystrophy and the locus at the RP3 site. Ophthalmic Paediatr Genet 12:91–98
Khanna H, Hurd TW, Lillo C et al (2005) RPGR-ORF15, which is mutated in retinitis pigmentosa, associates with SMC1, SMC3, and microtubule transport proteins. J Biol Chem 280:33580–33587
Khanna H, Davis EE, Murga-Zamalloa CA et al (2009) A common allele in RPGRIP1L is a modifier of retinal degeneration in ciliopathies. Nat Genet 41:739–745
Louie CM, Caridi G, Lopes VS et al (2010) AHI1 is required for photoreceptor outer segment development and is a modifier for retinal degeneration in nephronophthisis. Nat Genet 42:175–180
Murga-Zamalloa CA, Atkins SJ, Peranen J et al (2010) Interaction of retinitis pigmentosa GTPase regulator (RPGR) with RAB8A GTPase: implications for cilia dysfunction and photoreceptor degeneration. Hum Mol Genet 19:3591–3598
Otto EA, Loeys B, Khanna H et al (2005) Nephrocystin-5, a ciliary IQ domain protein, is mutated in Senior-Loken syndrome and interacts with RPGR and calmodulin. Nat Genet 37:282-288
Purcell S, Neale B, Todd-Brown K et al (2007) PLINK: a tool set for whole-genome association and population-based linkage analyses. Am J Hum Genet 81:559–575
Roepman R, Bernoud-Hubac N, Schick DE et al (2000) The retinitis pigmentosa GTPase regulator (RPGR) interacts with novel transport-like proteins in the outer segments of rod photoreceptors. Hum Mol Genet 9:2095–2105
Sayer JA, Otto EA, O’Toole JF et al (2006) The centrosomal protein nephrocystin-6 is mutated in Joubert syndrome and activates transcription factor ATF4. Nat Genet 38:674–681
Souied E, Segues B, Ghazi I et al (1997) Severe manifestations in carrier females in X linked retinitis pigmentosa. J Med Genet 34:793–797
Tory K, Lacoste T, Burglen L et al (2007) High NPHP1 and NPHP6 mutation rate in patients with Joubert syndrome and nephronophthisis: potential epistatic effect of NPHP6 and AHI1 mutations in patients with NPHP1 mutations. J Am Soc Nephrol 18:1566–1575
Walia S, Fishman GA, Swaroop A et al (2008) Discordant phenotypes in fraternal twins having an identical mutation in exon ORF15 of the RPGR gene. Arch Ophthalmol 126:379–384
Yang Z, Peachey NS, Moshfeghi DM et al (2002) Mutations in the RPGR gene cause X-linked cone dystrophy. Hum Mol Genet 11:605–611
Acknowledgments
We thank James Hixson for the monsomic cell line DNA, Hemaxi Patel for assistance in visual function testing, and Martin Klein for assistance in creating Fig. 41.1. This work was funded by the Foundation Fighting Blindness and NEI/NIH grant EY007142 to SPD.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2012 Springer Science+Business Media, LLC
About this paper
Cite this paper
Fahim, A.T. et al. (2012). Polymorphic Variation of RPGRIP1L and IQCB1 as Modifiers of X-Linked Retinitis Pigmentosa Caused by Mutations in RPGR. In: LaVail, M., Ash, J., Anderson, R., Hollyfield, J., Grimm, C. (eds) Retinal Degenerative Diseases. Advances in Experimental Medicine and Biology, vol 723. Springer, Boston, MA. https://doi.org/10.1007/978-1-4614-0631-0_41
Download citation
DOI: https://doi.org/10.1007/978-1-4614-0631-0_41
Published:
Publisher Name: Springer, Boston, MA
Print ISBN: 978-1-4614-0630-3
Online ISBN: 978-1-4614-0631-0
eBook Packages: Biomedical and Life SciencesBiomedical and Life Sciences (R0)