Developmental accumulation and heterogeneity of myelin basic protein transcripts in the chick visual system.

By selective cloning of gene products newly expressed in the developing chick optic tectum, we have isolated cDNA clones encoding myelin basic protein (MBP). Three different transcripts of the corresponding single copy gene of 2.7 kb, 2.0 kb, and 1.1 kb were observed on Northern blots. In the developing optic lobe, the most abundant RNA (2.7 kb) was detected first at the 14th day in ovo. Nuclease S1 protection experiments revealed further heterogeneity of MBP transcripts, which result from alternative splicing of segments corresponding to the fifth and sixth exon of the homologous murine MBP gene. From these data, at least three different forms of MBP are predicted to exist in the chicken central nervous system.