THE EXPRESSION OF TENASCIN-C ALONG THE LAMPREY OLFACTORY PATHWAY DURING EMBRYONIC-DEVELOPMENT AND FOLLOWING AXOTOMY-INDUCED REPLACEMENT OF THE OLFACTORY RECEPTOR NEURONS
Au. Zaidi et al., THE EXPRESSION OF TENASCIN-C ALONG THE LAMPREY OLFACTORY PATHWAY DURING EMBRYONIC-DEVELOPMENT AND FOLLOWING AXOTOMY-INDUCED REPLACEMENT OF THE OLFACTORY RECEPTOR NEURONS, Developmental brain research, 109(2), 1998, pp. 157-168
Extracellular guidance molecules affect the pathway of growing axons b
y both attractive and repulsive interactions. Tenascin-C, a glycoprote
in of the extracellular matrix, is localized along developing axonal p
athways where it may function by repulsion, restricting axons within s
pecific boundaries. The lamprey olfactory pathway offers an advantageo
us model for studying the role of extracellular matrix proteins in axo
n guidance because the entire pathway is readily seen in horizontal se
ctions and because lesioning the olfactory nerve will induce the syste
m into a new phase of coordinated neurogenesis and axon outgrowth. Alt
hough tenascin-C expression was absent during embryonic development, o
lfactory nerve fascicles contained tenascin-C-immunoreactivity (IR) du
ring the larval stage. During retrograde degeneration, the fascicles l
ost tenascin-C-IR. Diffuse unfasciculated axonal processes extending f
rom the olfactory epithelium did not express tenascin-C-IR; however, a
cetylated tubulin and GAP-43-IR was present, indicating axonal outgrow
th. When the newly extended axons of olfactory receptor neurons conver
ged to form fascicles, tenascin-C-IR was evident within the fascicular
boundaries. The absence of tenascin-C expression when axonal process
were short and diffuse, and its return when axons coalesced within fas
cicles, supports the view that tenascin-C functions as a boundary mole
cule in the olfactory pathway. (C) 1998 Elsevier Science B.V. All righ
ts reserved.