EXPRESSION OF MYELIN-SPECIFIC PROTEINS DURING DEVELOPMENT OF NORMAL AND HYPOMYELINATED PARALYTIC TREMOR MUTANT RABBITS .1. STUDIES ON THE BRAIN HOMOGENATES

The paralytic tremor (pt) rabbit is an X-linked recessive mutant chara cterized by hypomyelination of the CNS. The onset of myelin mutants' n eurological symptoms typically occurs about the tenth postnatal day. A partial recovery is often observed; thus, the life-span of affected a nimals is almost normal and they can breed successfully. Mutants prese nting this phenotype were chosen for our study. Because proteins can s erve as excellent markers for the myelin formation process, we examine d the developmental expression of several important myelin proteins (P LP/DM-20, MBP, CNP, MAG, and MOG) in both pt mutant and control rabbit brain homogenates. Expression of the investigated proteins occurs in rabbits as follows: CNP and MAG are already present at the early postn atal stage; PLP/DM-20 and MBP appear about the 10th postnatal day; MOG , expressed last, has been detected on the 28th postnatal day. Whereas the MBP, CNP, MAG, and MOG content is only slightly reduced in mature pt mutant brain homogenates (80-90% of control values), the amount of PLP corresponds to approximately 30-40% of that present in controls. Expression of all of the examined proteins is substantially retarded i n maturing brains, which leads to the conclusion that besides severe P LP deficiency, retardation of oligodendrocyte maturation is another pr obable feature of pt mutation.