ETR-3 represses Tau exons 2/3 inclusion, a splicing event abnormally enhanced in myotonic dystrophy type I

Altered splicing of transcripts, including the insulin receptor (IR) and the cardiac troponin (cTNT), is a key feature of myotonic dystrophy type I (DM1). CELF and MBNL splicing factor members regulate the splicing of those transcripts. We have previously described an alteration of Tau exon 2 splicing in DM1 brain, resulting in the favored exclusion of exon 2. However, the factors required for alternative splicing of Tau exon 2 remain undetermined. Here we report a decreased expression of CELF family member and MBNL transcripts in DM1 brains as assessed by RT-PCR. By using cellular models with a control- or DM1-like splicing pattern of Tau transcripts, we demonstrate that ETR-3 promotes selectively the exclusion of Tau exon 2. These results together with the analysis of Tau exon 6 and IR exon 11 splicing in brain, muscle, and cell models suggest that DM1 splicing alteration of several transcripts involves various factors.