Francesca Martinetto May, 28th
ABSCT SIBBM 2015
New insights into
FOXP2
alternative splicing
F. Martinetto1, B. Pardini2, R. Galavotti1, A. Naccarati2, D. De Pietri Tonelli3, M.G.
Romanelli1, P. M.-J. Lievens1
1Department and Life Reproduction Sciences, Section of Biology and Genetics,
University of Verona Medical School, Verona, Italy
2Human Genetics Foundation (HuGeF) Torino, Italy
3Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia,
Genova, Italy
FOXP2 is a forkhead transcription factor regulating the expression of several genes, among which key regulators of neural development. Previous studies have shown the existence of FOXP2 splice variants mainly represented by long isoforms (FOXP2-L) containing 17 exons and short transcripts truncated at exon 10 (FOXP2-10+). Translation of FOXP2-10+ predicts peptides lacking FOX domain whose function is undefined. The aim of this study is to identify the ribonucleoprotein complexes that may antagonize or favor splice site selection in different tissues, highlighting the mechanisms responsible for FOXP2 alternative splicing. We started by checking the presence of FOXP2 transcripts in mRNAs from several human cell lines and found that HeLa, Hek293 and KMS11 cells express FOXP2-L and FOXP2-10+ isoforms. Given the possible alternative splice variants, we designed RT-PCR experiments to amplify transcripts containing the expected 3b or 4a regulated exons. Both HeLa and Hek293 cells express FOXP2 transcripts with 3b exon. By sequencing the amplified FOXP2 cDNAs, we found FOXP2-10+ transcripts including exon 4a, not previously described. To investigate the ribonucleoproteins involved in FOXP2 alternative spicing, we performed bioinformatics analyses. We found putative consensus sites for PTB (Polypyrimidine Tract Binding protein), a repressor of alternatively spliced exons with tissue-specificity, upstream and downstream to exon 3b of FOXP2. Ongoing experiments aim to assay for changes in FOXP2 transcripts upon manipulation of PTB. Since exons 3b and 4a encode for amino acids close to FOXP2 ZnF (Zinc Finger) and Polyglutamine domains involved in protein-protein interactions, their alternative inclusion may determinate modifications of protein conformation, playing a role in homo- and heterodimerization of FOXP2 and therefore influencing its function. PTB can repress exon inclusion by preventing the binding of spliceosomal components via PTB expression-dependent levels.
