Tissue-specific Expression of Rat Aldolase A mRNAs

Three species of aldolase A mRNA (mRNAs I, 11, and 111) only differing in the structure of the 5’-terminal noncoding region were detected in rat tissues. The cDNA clones for mRNAs 11 and I11 were prepared from ascites hepatoma AHGOC and sequenced. The mRNA I1 is 1393 nucleotides long excluding poly(A) tail, while the mRNA 111 is 1440 nucleotides long, some 50 nucleotides longer than the mRNA 11. The mRNAs 11 and 111 differ in the sequence between -25 and the 5’ termini from the previously reported skeletal muscle aldolase A mRNA (mRNA I, 1343 nucleotides long). By contrast, the residual 5’ noncoding sequence (-24 to -1) and the coding and 3’ noncoding sequences are common to all the mRNAs. By dot spot hybridization and S1 mapping the distribution of these mRNAs in the various tissues was determined. The mRNA I appears exclusively in a skeletal muscle and some in heart and hepatoma AHGOC, whereas the mRNAs I1 and I11 appear more or less in all the tissues examined, implying that their appearances are under tissue-specific control. Furthermore, partial nucleotide sequence analysis of the fetal liver aldolase A mRNA supports that aldolase A mRNA that reappeared in hepatoma is really a resurgence of the gene product expressed in the fetus.