Characterization of mouse myelin basic protein messenger RNAs with a myelin basic protein cDNA clone

Using a family of synthetic tetradecamer oligonucleotides as a primer for cDNA synthesis and a second family of tetradecamers as a hybridization probe, we have prepared and isolated a cDNA clone of mouse myelin basic protein (MBP). The clone, pNZ111, corresponds to the region of the mRNA that codes for an amino acid sequence present in all four major forms of MBP. The relative abundance of MBP mRNA, estimated by dot blot hybridization, increased with the age of the mouse to a maximum at 18 days, then decreased to about one-fourth of that amount at later ages. Mouse MBP mRNAs, selected by their ability to hybridize to the clone, translate into the four forms of myelin basic protein. In RNA blot analyses, pNZ111 hybridized to multiple species of mouse mRNA. The predominant hybridization is to a broad band of RNAs ranging in length from 2,350 to 2,100 bases. These mRNA species are extremely long, considering that the largest MBP could be encoded by approximately 600 bases. In addition to these, there are also minor bands that hybridize with pNZ111, including a band of 4,100 bases and smaller ones of 1,900, 1,500, and 1,200 bases.