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B. Janke, B. Lorenz, M. Preising; Functional Analysis of AIPL1 Mutations and Splice Variants. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4667.
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© ARVO (1962-2015); The Authors (2016-present)
AIPL1 is the fourth gene involved in Leber Congenital Amaurosis (LCA), with mutations underlying a severe form of retinal degeneration (LCA4) leading to a rapid loss of vision in early childhood. Purpose of this study is to further clarify the gene’s function and the pathological effect of its mutations.
Full length transcripts of AIPL1 were amplified by RT-PCR from neuroretinal RNA of human donors, cloned and sequenced to identify unique splice variants, whose frequencies were estimated by quantitative RT-PCR (qRT-PCR). The yeast two-hybrid system was employed to identify interaction partners by screening retinal cDNA libraries with AIPL1 isoforms as baits. PCR-based mutagenesis of the baits and subsequent subjection to library screening shall determine the impact of LCA-causing mutations on the before detected protein interactions.
Six different human transcripts of AIPL1 were identified at various amounts differing in presence or absence of variable regions of exons 2, 3 and 5 which in part are conserved within mammals as we could previously show. QRT-PCR confirmed the full-length variant as the major one at 80-90% frequency, whereas the minor variants were present in 1-10 % of the gene’s transcripts each. Protein interaction assays revealed new potential functional partners of AIPL1, some of them involved in protein recycling and respiratory metabolism.
The observed alternative splicing events substantially modify the peptidyl-prolyl-isomerase domain and the binding site of cell cycle regulator NUB1 of the AIPL1 protein and might give rise to different minor isoforms fulfilling individual functions independent from the major isoform.The detected yeast two-hybrid interactions seem to confirm a chaperonesque role of the major AIPL1 isoform and further suggest an involvement in the proteasomic pathway. To assess whether this also applies to the minor isoforms further interaction assays are performed. The alternative exons 2 and 3 harbour mutations possibly underlying LCA. To evaluate the impact of these mutations on the functional capability of the protein, results of the confrontation of identified interaction partners with mutant AIPL1 will be presented.
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