Developmental regulation of mRNA in mouse heart.

Abstract
The myocardium contains abundant translatable mRNA that change during development. Maximal cell-free synthesis of [3H]leucine, [35S]methionine- and [35S]cysteine-labeled translation products directed by poly(A)-containing mRNA from 12-, 14- and 17-day fetal; 5-day-old neonatal and 30-day-old adult mouse heart was determined by using 1- and 2-dimensional polyacrylamide gels. Three general developmental patterns of heart-specific mRNA translation products were observed: 2 translatable mRNA were most abundant in 12-day fetal heart; 5 mRNA were most abundant in 14- and 17-day fetal heart and occurred only at low concentrations in 12-day fetal and adult heart; 4 mRNA, including mRNA coding for actin, tropomyosin and myosin L chains 1 and 2, were most abundant in the adult heart. Differentiating cardiac muscle is characterized by a complex pattern of mRNA regulation.