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. 2006 Jun 28;26(26):6911–6923. doi: 10.1523/JNEUROSCI.0505-06.2006

Figure 4.

Figure 4.

The Hs6st1−/− chiasm has a normal shape but unusually large numbers of RGC axons innervate the opposite eye. All panels are horizontal sections through the chiasm (A–C, F–H) or the retina (D, E, I, J) after unilateral DiI injection into the retina. In C–E and H–J, DiA has been injected into the optic tract on the same side as the DiI-injected eye. A–E, In the wild type, relatively few RGC axons enter the contralateral optic nerve at E14.5 (A), E15.5 (C), and E17.5 (B). D, E, At E15.5, very few RGCs in the contralateral eye are retrogradely labeled with DiI. The boxed area in D is magnified in E. F–J, In the mutant, the overall shape of the chiasm closely resembles that of the wild type at E14.5 (F), E15.5 (H), and E17.5 (G). However, many more axons enter the contralateral optic nerve (con) than in the wild type at these ages. I, J, In contrast to the wild type, many RGC bodies in the contralateral retina are retrogradely labeled with DiI. The boxed area in I is magnified in J. Note that RGCs labeled with DiI from the contralateral eye are not colabeled with DiA, indicating that they do not project to the DiA injection site in the thalamus. All sections are horizontal with posterior at the top. DiI and DiA injections summarized in diagram at the bottom and indicated by red or green asterisks, respectively, in the panels. K, Histogram showing numbers of RGCs retrogradely labeled in the contralateral retina after unilateral retinal DiI injection. Significantly more retrogradely labeled RGCs were counted in the Hs6st1−/− retina then in the wild type (p = 0.006, Student's t test). Note that Hs2st−/− did not exhibit increased innervation of the opposite eye; in fact, there was a significant decrease compared with wild type (p = 0.04, Student's t test). The total numbers of DiI-labeled RGCs were counted in serial sections. All bars are means ± SEM. Student's t test for comparison with wild type, ∗p < 0.05. L, Diagram summarizing aberrant growth of RGC axons into the contralateral optic nerve of the Hs6st1−/− mutant. r, Retina; l, lens; on, optic nerve; con, optic nerve contralateral to injected retina; oc, optic chiasm; ot, optic tract; P, posterior; A, anterior; Di, distal; Pr, proximal; M, ventral midline. Scale bars: A–C, F–H, 200 μm; D, I, 100 μm; E, J, 50 μm.