June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Author Affiliations & Notes
  • Caroline Van Cauwenbergh
    Center for Medical Genetics, Ghent University, Ghent, Belgium
  • Kris Vleminckx
    Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
  • Frauke Coppieters
    Center for Medical Genetics, Ghent University, Ghent, Belgium
  • Marcus Karlstetter
    Department of Ophthalmology, University of Cologne, Cologne, Germany
  • Thomas Langmann
    Department of Ophthalmology, University of Cologne, Cologne, Germany
  • Gael Manes
    INM - Institut des Neurosciences de Montpellier Hôpital Saint-Eloi, INSERM U1051, Montpellier, France
  • Christian P Hamel
    INM - Institut des Neurosciences de Montpellier Hôpital Saint-Eloi, INSERM U1051, Montpellier, France
  • Bart Peter Leroy
    Dept of Ophthalmology, Ghent University Hospital, Ghent, Belgium
    Center for Medical Genetics, Ghent University, Ghent, Belgium
  • Elfride De Baere
    Center for Medical Genetics, Ghent University, Ghent, Belgium
  • Footnotes
    Commercial Relationships Caroline Van Cauwenbergh, None; Kris Vleminckx, None; Frauke Coppieters, None; Marcus Karlstetter, None; Thomas Langmann, None; Gael Manes, None; Christian Hamel, None; Bart Leroy, None; Elfride De Baere, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 2873. doi:https://doi.org/
Abstract

Purpose: Identification and functional characterisation of a novel candidate gene for autosomal dominant retinitis pigmentosa (adRP).

Methods: Five affected and five unaffected individuals of a Belgian adRP family in which known adRP loci were excluded, were enrolled. They underwent genome-wide (GW) linkage analysis (BeadChip, Illumina). Whole exome sequencing was carried out in two affected individuals (HiSeq, Illumina; CLC bio). Segregation analysis of variants was done using Sanger sequencing and testing of 300 controls by HRM (LightScanner). Targeted resequencing of SF3B2 was performed (Miseq, Illumina) in 472 unrelated adRP patients. SF3B2 expression was tested using a commercial cDNA panel. Localization studies were carried out in 661W mouse cells using commercial anti-SF3B2 antibodies. Sf3b2 knockdown in Xenopus was done using targeted injection of a splicing blocking morpholino (MO) (GeneTools).

Results: GW linkage analysis revealed two novel candidate loci with a maximum LOD score of 1.7. In the 11q13 region, a missense variant c.2417A>G p.(Tyr806Cys) was found in the SF3B2 gene encoding the splicing factor 3b, subunit 2. The Tyr residue is highly conserved, the Grantham distance between Tyr and Cys is 194, predictions suggest an effect on protein function. The change is predicted to disrupt a phosphorylation site. The variant co-segregates with adRP and is absent in 300 controls. No additional SF3B2 mutations were found in a large adRP cohort.<br /> Ubiquitous expression of SF3B2 was demonstrated in human tissues, including retina and RPE, and localization in perinuclear and nuclear areas was shown in 661W mouse cells. Targeted MO knockdown in Xenopus showed gross developmental anomalies affecting the retina. Rescue experiments are ongoing.

Conclusions: SF3B2 was identified as a novel candidate gene for adRP. SF3B2 is required for binding of the U2 small nuclear ribonucleoprotein (snRNP) to the branchpoint and is involved in early spliceosome assembly. Interestingly, protein-protein interactions have been identified between SF3B2, SNRNP200 and PRPF8, the latter being two proteins implicated in adRP. So far, of the seven known adRP genes involved in splicing, six encode components of the U4/U6-U5 triple small nuclear ribonucleoprotein (tri-snRNP) complex. Our study potentially involves other components of the spliceosome apart from the tri-snRNP complex in adRP.

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