Abstract
Abstract: :
Purpose:Alternative splicing (AS) is a significant factor that expands the proteomic diversity and functional complexity. AS can generate functionally diverse isoforms or provide a regulatory mechanism by modifying the elements that control RNA stability, localization, or translation. AS is regulated in a tissue–specific and developmental stage–specific manner. The retina is among the top 3 tissues with the highest levels of tissue–specific AS and a number of human retinal disease genes are known to undergo AS. The objective of this study has been to explore the murine retinal RNA splicing of a set of genes that have been implicated in human retinal degenerations. Methods: Various human and mouse databases have been used to specify the known and/or predicted AS events concerning a set of retinal disease genes. Initially, five genes (UNC119, RGR, NR2E3, NRL, CRB1) were evaluated. Total RNA was isolated from retinal tissues of 10–12 week–old inbred mice. The brain and spleen total RNA samples were also obtained in order to determine the tissue–specificity of AS events for those genes that also show non–retinal expression. RT/PCR was performed to amplify the transcript fragments that are known or predicted to undergo AS. The PCR fragments were gel–purified and directly sequenced in an automated sequencer. Results: Our analyses have identified some previously unreported murine retinal AS and alternative termination events in the initial set of the transcripts that we have investigated. The observed AS events included exon skipping, alternative exon inclusion, different splice site usage, and intron retention. Some of the murine variants were found to be different than the currently known human variants, while the others were confirmatory for the corresponding human forms. Conclusions: AS appears to occur in the retinal transcriptome more frequently and in a wider spectrum than previously thought. According to recent genome–wide analyses, ∼75% of human and ∼60% of mouse multi–exon genes are predicted to be alternatively spliced. Identification and characterization of splice variants of retinal transcripts will guide further studies toward understanding the functional diversity created by these variants and/or their contribution to regulatory mechanisms, their effect on retinal disease, and factors regulating retinal alternative RNA processing.
Keywords: retina • gene/expression • genetics