By analyzing ESTs for cardiac muscle-specific transcripts, followed by screening heart cDNA libraries and 5-prime RACE, Soejima et al. (2001) cloned 4 splice variants of PDE4DIP
, which they called MMGL. The variant-1 transcript has a long 3-prime untranslated region containing 9 possible polyadenylation signals, and it encodes a deduced 174-amino acid protein. Variants 2, 3, and 4 encode proteins of 174, 173, and 240 amino acids, respectively. Northern blot analysis detected high expression of a 1.0- to 1.3-kb band and lower expression of 4.4- and 8.5-kb bands in adult and fetal heart, skeletal muscle, and all specific heart regions examined. Only the 4.4-kb transcript was detected in aorta. Fluorescence-tagged variants 1 and 4 were expressed in both the cytoplasm and nucleus of transfected mouse myocytes.