Myelin Proteolipid Protein Gene Expression in Jimpy and Jimpymsd Mice

Abstract

Proteolipid protein (PLP) gene expression was studied in the dysmyelinating mouse mutant jimpy^msd (jp^msd; myelin synthesis deficient) and compared with that in wild-type mice and the allelic mutant, jimpy (jp). Southern analyses of genomic DNA from jp^msd mice revealed no major rearrangements of the PLP gene relative to the wild-type mouse PLP gene. PLP-specific mRNA levels were significantly reduced in these mutant mice, although both the 3.2- and 2.4-kilobase PLP-specific mRNAs were seen. Also, no size differences in either PLP or DM20 mRNAs were found by S1 nuclease assays of brain RNA from either jp^msd or wild-type mice. Both PLP and DM20 protein were detectable at low levels in jp^msd brain homoge-nates, and these proteins comigrated with PLP and DM20 protein from normal mice. Western analyses showed an altered PLP:DM20 ratio in jp^msd mice relative to wild-type mice; DM20 levels exceeded PLP levels. It is surprising that a similar pattern of expression was seen in normal mice at jp^msd mice are capable of synthesizing normal PLP and DM20 protein; however, the PLP gene defect has affected the normal developmental pattern of expression for these two proteins.