PGP9.5, a ubiquitin C-terminal hydrolase; pattern of mRNA and protein expression during neural development in the mouse.

PGP9.5 is a neurone and neuro-endocrine specific ubiquitin carboxyl terminal hydrolase estimated to form 1-2% of total brain protein. We have examined the temporal and spatial distribution of PGP9.5 mRNA and protein in the developing mouse embryo. These studies show that PGP9.5 is present at high levels in all differentiated neurones throughout the central and peripheral nervous systems at all stages of development. The mRNA is detected in the neural tube 1 day prior to the protein and before neuronal differentiation is underway. Both mRNA and protein are present during the initial appearance of motor and sensory neurones, prior to their peak production. PGP9.5 immunoreactivity was detected using microwave pretreatment of sections in order to unmask epitopes. In general unmasking led to an overall enhancement of immunoreactivity although in some sites, for example the dorsal root and cranial nerve ganglia and the bundle of His, there was evidence for anatomical variation in the distribution of masked versus unmasked protein. The very early expression of PGP9.5 suggests that there is a role for ubiquitin hydrolases in the differentiation of neurone precursors as well as in the differentiated neurone.