THE EXPRESSION OF RECEPTOR TYROSINE PHOSPHATASES IS RESPONSIVE TO SCIATIC-NERVE CRUSH

Given the importance of phosphotyrosine signaling in growth cone dynam ics, we have examined the embryonic and adult expression of receptor-l ike protein tyrosine phosphatases in sensory neurons and studied their responsiveness to nerve lesions in young adult animals. The phosphata ses LAR, PTP sigma, and PTP alpha are expressed in most neurons of E14 and E18 rat embryo dorsal root ganglia, while BEM-1 is expressed in a more restricted subset of these neurons. These phosphatases continue to be expressed in young adult animals, suggesting that they have role s in mature as well as in developing dorsal root ganglia neurons. Afte r an experimental sciatic nerve crush, the expression of the phosphata se genes was significantly and differentially altered in these neurons . PTP sigma mRNA was increased by 50% after 3 days, while LAR and PTP alpha expression dropped by 50 and 20%, respectively. BEM-1 mRNA level s were unaltered. These data show that mRNA levels of specific tyrosin e phosphatase genes are highly responsive to nerve damage and may be r eset to a new and potentially optimal pattern of expression more condu cive for nerve regeneration. We propose that tyrosine phosphatases are not only involved in primary axonogenesis but can also now be implica ted in the molecular control of adult nerve repair.