CELF1 and myotonic dystrophy type 1: This confirms the basis of the altered balance between MBNL and CELF in DM1 patients: on the one hand MBNL loss-of-function is mainly caused by the differential splicing of MBNL1/2 and/or the entrapment of MBNL1/2 proteins in foci which is insufficiently compensated by an increase in MBNL1/2 transcription levels, and on the other hand the increased activity of CELF1/-2 is due to increased protein levels and/or their phosphorylation level (10,83).