Messenger ribonucleic acid (mRNA) from developing rat cerebellum directs in vitro synthesis of plasma proteins

Poly(A)-containing messenger RNA from different ages of postnatal rat cerebellum was translated in the reticulocyte lysate system, using [³⁵S]methionine to label newly synthesized polypeptides. Translation products were identified using crossed immunoelectrophoresis and antisera against whole rat plasma and/or specific plasma proteins, followed by autoradiography. It was found that postnatal cerebellar mRNA directs the synthesis of low density lipoprotein (LDL), fibrinogen, transferrin, α₁-macroglobulin, α₂-macroglobulin and probably also α-fetoprotein, albumin and α₁-lipoprotein. mRNAs for several other yet undefined plasma proteins were also detected. In general, the synthesis of plasma proteins appeared to decline with cerebellar maturation. X-irradiation or hypothyroidism resulted in selective changes in the levels of mRNA-directed plasma proteins. In the X-irradiated cerebellum these included an increase in the level of mRNA for α-fetoprotein and a decrease in the level of mRNA for fibrinogen. In contrast, hypothyroidism decreased cerebellar plasma protein synthesis in general. These observations indicate that plasma proteins are actively produced within the developing rat cerebellum, and that the rate of their sysnthesis depends on the developmental stage and is influenced by the types of cells present.