Fig. 4. GDNF and NRTN are present in the eye during and after target innervation. (A) Western blot analysis for GDNF and NRTN in eye lysates collected from different embryonic ages. The GDNF-immunoreactive band at a similar molecular mass to recombinant human GDNF (rhGDNF) is present in E6 and E9 eye lysates, but is absent in E12 and E16 eye lysates. The anti-GDNF antibody used in this study does not cross react with recombinant human NRTN (rhNRTN) or ARTN (rhARTN). Each recombinant protein (rhGDNF, rhNRTN or rhARTN) was loaded at 1 ng/lane. In contrast to the temporal changes in GDNF, a constant level of NRTN is detected in eye lysates at all developmental stages tested. This anti-NRTN antibody does not cross react with rhGDNF or rhARTN. (B,C) Immunohistochemical localization of GDNF in E7 eye tissues. Strong immunoreactivity was observed in ciliary muscle (B) as well as lateral and medial rectus muscle located along the lateral sides of the eye (C). (Inset in C) A higher magnification photograph of immunoreactive rectus muscle. Scale bars, 200 µm (B), 500 µm (C).