Developmental expression of myelin basic protein mRNA in a hypermyelinating mouse

Polysomal poly (A)⁺ RNA and total cellular RNA were isolated from the brains of C57BL/6J (B6), DBA/2J (D2), and F₁ hybrid mice. Both types of RNA were isolated at 9, 12, 16, 21, and 30 days of age. By using a ³²P‐labelled cDNA probe for myelin basic protein (MBP; pMBP‐1) the amounts of RNA coding for MBP present in the three strains at each age were determined. For both the polysomal poly(A)⁺ and total cellular RNA the peak of MBP RNA accumulation was at about 16–18 days for all three strains. These results imply that the developmental pattern of MBP RNA synthesis for F₁ mice is not shifted with respect to the parental strains. For the polysomal poly(A)⁺ RNA, F₁ had the greatest amount of MBP mRNA, B6 the least, and D2 an intermediate amount. F₁ again had the greatest amount of MBP RNA from the total cellular pool at all ages. However, B6 had a greater amount of MBP RNA in the total cellular RNA pool than did D2. This demonstrates elevated transcription of the MBP gene in the F₁ or an increase in message stability in this strain. It also suggests some form of translational control for MBP RNA in the B6 strain. In addition a second species of MBP RNA was found in the total cellular RNA pool. This species is larger than the major polysomal RNA band and may be a nuclear precursor.