TRA2B and portal hypertension: Additionally, the expression of LZ+ MYPT1 isoforms as well as Tra-2β, an atypical member of RNA binding proteins, are higher in fast (phasic) compared with slow (tonic) smooth muscle, and in an animal model of portal hypertension, Tra-2β is downregulated coincident with the decrease in LZ+ MYPT1 expression (E23 exon exclusion) and the shift to the expression of LZ− MYPT1 isoforms (Shukla and Fisher, 2008).