IN-SITU EXPRESSION OF PLP DM-20, MBP, AND CNP DURING EMBRYONIC AND POSTNATAL-DEVELOPMENT OF THE JIMPY MUTANT AND OF TRANSGENIC MICE OVEREXPRESSING PLP/

We analyzed by in situ hybridization the spatiotemporal expression of dm-20, myelin basic protein (MBP) and 2'-3' cyclic nucleotide phosphod iesterase (CNP) during embryonic and postnatal development of the norm al mouse and two plp/dm-20 mutants: the jimpy mouse and a transgenic m ouse overexpressing the plp gene. In the central nervous system (CNS) of the normal mouse, am-20 mRNA was detected at embryonic day (E)9.5 i n the laterobasal plate of the diencephalon. The pattern of expression of CNP transcript was superimposable on that of dm-20, but appeared s lightly later, at E12.5. MBP mRNA was detected even later (E14.5), and , in addition, only in the caudal (rhombencephalon and spinal cord) te rritories of expression of dm-20 and CNP. These observations support o ur previous proposals: (1) dm-20-expressing cells in the germinative n euroepithelium are precursors of oligodendrocytes, and (2) oligodendro cytes emerge from distinct pools of precursors along the neural tube ( Timsit et al., 1995), In the jimpy mutant, despite the mutation in the plp gene, cells of the oligodendrocyte lineage developed normally, It is only at the time of myelin deposition that oligodendrocytes die. D uring embryonic development of the transgenic mutant overexpressing pl p, there were no alterations in the spatiotemporal pattern or the leve l of expression of dm-20 in the CNS, in contrast to the higher levels of dm-20 observed in the peripheral nervous system (PNS). (C) 1997 Wil ey-Liss, Inc.