Multiple roles of neurotrypsin in tissue morphogenesis and nervous system development suggested by the mRNA expression pattern

We have mapped the spatio-temporal expression of the multidomain serine pro tease neurotrypsin in the developing mouse by In situ hybridization. On emb ryonic day (E) 8, mRNA is detected in giant trophoblast cells, later in emb ryonic mesenchymal tissues. On Ell, expression begins in Schwann cell precu rsors, olfactory epithelium, trigeminal ganglion, and midbrain. The floor p late shows strong expression on E12. Further prenatal development is charac terized by rising neurotrypsin mRNA in sensory ganglia and motor neurons. S taining in cerebral cortex emerges around birth and culminates toward the e nd of the first week with a complex laminar and areal pattern. Expression i n peripheral nerves and nonneural tissues vanishes soon after birth and the adult neuronal distribution is gradually established until weaning age. Th is developmental expression pattern suggests roles of neurotrypsin in morph ogenesis of nonneural tissues, as well as in neural development, in particu lar in axonal target invasion, synaptogenesis, and Schwann cell differentia tion.