Talk abstracts

Talk on Saturday 09:40-10:00am submitted by Victoria Barron

Regulation of NF1 Alternative Splicing By CELF Proteins

Victoria A. Barron (Department of Genetics, Case Western Reserve University), Hui Zhu (Department of Genetics, Case Western Reserve University), Andrea N. Ladd (Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, The Center for RNA Molecular Biology, Case Western Reserve University), Hua Lou (Department of Genetics, Case Western Reserve University, The Center for RNA Molecular Biology, Case Western Reserve University, Case Comprehensive Cancer Center)

Abstract:
Previous work in our laboratory has shown that regulation of alternative splicing of Neurofibromatosis type I exon 23a is carried out by two groups of proteins: Hu proteins and TIA-1/TIAR proteins. Preliminary studies using different lengths of sequences upstream of NF1 exon 23a suggest that additional factors are involved in promoting skipping or inclusion of exon 23a. A series of GU-rich elements were identified in the sequence upstream of exon 23a, which led us to hypothesize that the CELF (CUGBP and ETR-3-like factors) family of RNA-binding proteins might regulate exon 23a alternative splicing.
We have investigated the role of CELF proteins in regulation of exon 23a inclusion using both cell model systems and transgenic mouse models. HeLa cells and CA77 cells, a rat neuron-like cell line, are excellent models because the endogenously expressed NF1 pre-mRNA is processed to predominantly include or skip exon 23a respectively in these cell lines. The expression level of CELF proteins correlates well with the splicing phenotype with HeLa cells expressing only one of the CELF proteins members while CA77 cells expressing all six members. Over-expression of CELF proteins in HeLa cells promoted skipping of exon 23a from a NF1 splicing reporter transcript. Additionally, siRNA knockdowns of endogenous CUG-BP and ETR-3, promote exon 23a inclusion in CA77 cells. Importantly, alternative splicing of NF1 exon 23a is also affected in mouse models that over-express CUG-BP1 in cardiac and skeletal muscles, indicating that the CELF functions observed in cell models are physiologically relevant. These results demonstrate that CELF proteins regulate tissue-specific skipping of the NF1 exon 23a. Future work will involve dissecting the mechanism by which CELF proteins regulate alternative splicing of NF1 exon 23a.

Keywords: CELF proteins, Neurofibromatosis Type I, Alternative Splicing