Purchase this article with an account.
Giulia Venturini, Shomi S. Bhattacharya, Carlo Rivolta; Polymorphic Variation In The Expression Of CNOT3 Determines The Penetrance Of PRPF31 Mutations In Autosomal Dominant Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1734.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Within the same family, mutations in the PRPF31 gene can cause typical autosomal dominant retinitis pigmentosa (adRP) or otherwise produce no symptoms at all. We have previously shown that this incomplete penetrance is determined by at least one modifier gene, which has the power of increasing PRPF31 mRNA expression and therefore protect some individuals from developing the disease. Our aim is to identify the molecular nature of the most effective of these modifiers, found by linkage analysis to lie on chromosome 19q13.4, and understand its mode of action.
We studied 15 members of a large family with adRP (AD5), which segregates an 11-bp deletion in exon 11 of PRPF31. Gene expression analysis was performed by qPCR. Silencing experiments were performed in HeLa and ARPE-19 cells by the use of synthetic siRNA. Chromatin immunoprecipitation was performed on lymphoblastoid cell lines. Direct DNA sequencing was performed by Next-Generation Sequencing.
Gene expression analyses in all LCLs from controls, asymptomatic and symptomatic carriers of PRPF31 mutations was performed for ten candidate genes lying within the 19q13.4 interval. Statistical tests revealed that expression of only one of them, CNOT3, encoding a subunit of the Ccr4-not transcription complex, significantly (p=0.005) and inversely correlated with that of PRPF31. Silencing of CNOT3 in two different laboratory cell lines showed an increase of PRPF31 transcription, confirming the repressive nature of the CNOT3 protein on PRPF31. Chromatin immunoprecipitation analysis showed that CNOT3 could directly bind to the PRPF31 promoter. We are currently sequencing the full CNOT3 gene in symptomatic and asymptomatic carriers of mutations to identify the polymorphic DNA element that would directly determine its variable expression.
We ascertained that in asymptomatic carriers of PRPF31 mutations CNOT3 is expressed at low levels, allowing higher amounts of wild-type PRPF31 transcripts to be produced and preventing retinal degeneration to manifest in these individuals. Through this simple and direct mechanism, which likely depends on the presence of polymorphic DNA variants in its own sequence, CNOT3 could therefore represent the main regulator for penetrance of PRPF31 mutations.
This PDF is available to Subscribers Only