Upregulation and redistribution of cadherins reveal specific glial and muscle cell phenotypes during Wallerian degeneration and muscle denervation inthe mouse

In the present work, we investigated the expression of cadherin mRNAs in th e adult neuromuscular system either under normal conditions or following ex perimental neurotomy. Cadherin-6, a marker of Schwann cell precursors, was not expressed in the adult peripheral nerve, while M-cadherin, cadherin-11, and N-cadherin were expressed both by glial and conjunctive cells. Moreove r, the three transcripts were transiently upregulated in the distal stump o f neurotomized sciatic nerve during Wallerian degeneration: N-cadherin was abundant in myelinating Schwann cells during myelin degradation, while M-ca dherin in and cadherin-11 may be upregulated in proliferating Schwann cells . M-cadherin, cadherin-11, and N-cadherin were also detected in myofibres a nd endomysium of adult gastrocnemius muscle. Following neurotomy, cadherin- 11 was only transiently increased in denervated myofibres, while N-cadherin was increased and sustained for at least 21 days postoperation. In contras t, N-cadherin was not upregulated in denervated myofibres. Thus, we defined here a combination of cadherins expressed in the adult nerve and muscle, a nd modulated during Wallerian degeneration and muscle denervation. The comp arison of the expression pattern of this combination of cadherins to the on e previously described during embryonic development shows that chronically denervated Schwann and muscle cells do not reverse to embryonic state (reca pitulative hypothesis), but present specific phenotypic features. (C) 1999 Wiley-Liss, Inc.