repertoire of cellular interactions and molecular
signaling pathways that control this key dividing
line in the nervous system. These future studies
will likely also provide additional insights into
the roles of transition zones in response to ner-
vous system injury and regeneration. Finally,
some of the cell types and molecules control-
ling axon guidance at theDrosophilaCNS-PNS
boundary have been uncovered ( 93 – 97 ), and
continued study of this interface in multiple
model organisms, including invertebrates, will
contribute to our understanding of the evolu-
tion of CNS-PNS segregation and connectivity.
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