Expression of a myelin proteolipid protein (Plp)-lacZ transgene is reduced in both the CNS and PNS of Plp(jp) mice.

Jimpy (Plp(jp)) is an X-linked recessive mutation in mice that causes CNS dysmyelination and early death in affected males. It results from a point mutation in the acceptor splice site of myelin proteolipid protein (Plp) exon 5, producing transcripts that are missing exon 5, with a concomitant shift in the downstream reading frame. Expression of the mutant PLP product in Plp(jp) males leads to hypomyelination and oligodendrocyte death. Expression of our Plp-lacZ fusion gene, PLP(+)Z, in transgenic mice is an excellent readout for endogenous Plp transcriptional activity. The current studies assess expression of the PLP(+)Z transgene in the Plp(jp) background. These studies demonstrate that expression of the transgene is decreased in both the central and peripheral nervous systems of affected Plp(jp) males. Thus, expression of mutated PLP protein downregulates Plp gene activity both in oligodendrocytes, which eventually die, and in Schwann cells, which are apparently unaffected in Plp(jp) mice.