Fig. 4.

A novel isoform of MBP was detected in the CNS and PNS of the les rat in addition to the low levels of properly spliced MBP transcripts. A, Schematic of the rodent Mbp gene and the predominant CNS isoforms generated from alternative splicing. Half arrows in exons 1 and 7 indicate the approximate positions of primers used in RT-PCR analysis. Numbers to the leftindicate the mass (kDa) of the MBP isoform generated from each transcript. B, EtBr-stained gel of RT-PCR analysis of RNA extracted from 4-week-old brains, spinal cord, and optic nerves using primers detecting all four major adult MBP isoforms. Thearrow to the right of thegel indicates the novel isoform generated inles. Sequence analysis of this PCR product revealed that it was similar to that encoding the 14 kDa isoform except it was missing exon 3. C, Control.