Functional gene expression analysis of tissue-specific isoforms of Mef2c.

Mef2c contains three alternative exons and generates six Mef2c isoforms in mice. Mef2c α1ß isoforms are expressed in neuronal tissues, α2 isoforms are expressed in muscle, and α1 isoforms are expressed in many other tissues. The γ region inclusion and skipped isoforms are present in equal amounts in many tissues. In this study, differences in the transcriptional activities of each tissue-specific isoform of Mef2c in neuronal cells were examined. Using an MEF2-responsive reporter, exon ß-dependent transactivation was found in neuronal cells, as well as in other cell lines previously described. Microarray analysis was used to examine the transcriptional activities of each Mef2c isoform and to assess differences in endogenous gene expression induced by the different isoforms. The results showed significant gene expression changes due to overexpression of Mef2c isoforms in both an isoforms-dependent and -independent manner.

Alternative splicing produces structural and functional changes in CUGBP2.

BACKGROUND: CELF/Bruno-like proteins play multiple roles, including the regulation of alternative splicing and translation. These RNA-binding proteins contain two RNA recognition motif (RRM) domains at the N-terminus and another RRM at the C-terminus. CUGBP2 is a member of this family of proteins that possesses several alternatively spliced exons. RESULTS: The present study investigated the expression of exon 14, which is an alternatively spliced exon and encodes the first half of the third RRM of CUGBP2. The ratio of exon 14 skipping product (R3δ) to its inclusion was reduced in neuronal cells induced from P19 cells and in the brain. Although full length CUGBP2 and the CUGBP2 R3δ isoforms showed a similar effect on the inclusion of the smooth muscle (SM) exon of the ACTN1 gene, these isoforms showed an opposite effect on the skipping of exon 11 in the insulin receptor gene. In addition, examination of structural changes in these isoforms by molecular dynamics simulation and NMR spectrometry suggested that the third RRM of R3δ isoform was flexible and did not form an RRM structure. CONCLUSION: Our results suggest that CUGBP2 regulates the splicing of ACTN1 and insulin receptor by different mechanisms. Alternative splicing of CUGBP2 exon 14 contributes to the regulation of the splicing of the insulin receptor. The present findings specifically show how alternative splicing events that result in three-dimensional structural changes in CUGBP2 can lead to changes in its biological activity.