Related Experiment Video
Updated: Jan 3, 2026
Ex Vivo Oculomotor Slice Culture from Embryonic GFP-Expressing Mice for Time-Lapse Imaging of Oculomotor Nerve Outgrowth
Published on: July 16, 2019
Expression of Developmentally Important Axon Guidance Cues in the Adult Optic Chiasm
Raquel Conceição1, Rachel S Evans1, Craig S Pearson1,2
1John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, United Kingdom.
Purpose:
Regeneration of optic nerve axons after injury can be facilitated by several approaches, but misguidance at the optic chiasm is often observed. We characterized guidance cues in the embryonic visual system and adult optic chiasm before and after optic nerve crush (ONC) injury to better understand barriers to optic nerve regeneration in adults.
Methods:
Radial glial (RC2/BLBP/Slit1), developmental (Pax2) and extracellular markers (CSPG: H2B/CS-56) were assessed in C57BL/6J mice by immunohistochemistry. RC2, BLBP, Slit1, and CSPG are known inhibitory guidance cues while Pax2 is a permissive guidance cue.
Results:
At embryonic day 15.5 (E.15.5), RC2 and BLBP were identified superior to, and extending through, the optic chiasm. The optic chiasm was BLBP-ve in adult uninjured mice but BLBP+ve in adult mice 10 days after ONC injury. The reverse was true for RC2. Both BLBP and RC2 were absent in adult mice 6 weeks post-ONC. Slit1 was present in the optic chiasm midline and optic tracts in embryonic samples but was absent in uninjured adult tissue. Slit1 was observed superior to and at the midline of the optic chiasm 10 days post-ONC but absent 6 weeks after injury. Pax2 was expressed at the junction between the optic nerve and optic chiasm in embryonic brain tissue. In embryonic sections, CS-56 was observed at the junction between the optic chiasm and optic tract, and immediately superior to the optic chiasm. Both 2H6 and CS-56 staining was absent in uninjured and ONC-injured adult brains.
Conclusion:
Differences in guidance cue expression during development, in adulthood and after injury may contribute to misguidance of regenerating RGC axons in the adult optic chiasm.
Insights
Guidance cues in the optic chiasm change after injury, potentially misdirecting regenerating axons. Understanding these shifts is key to improving optic nerve repair in adults.
Area of Science:
- Neuroscience
- Developmental Biology
- Regenerative Medicine
Background:
- Optic nerve regeneration is hindered by misguidance at the optic chiasm.
- Guidance cues play a critical role in directing axonal growth during development and regeneration.
Purpose of the Study:
- To characterize guidance cues in the embryonic and adult optic chiasm.
- To investigate changes in guidance cues after optic nerve crush (ONC) injury.
- To understand barriers to optic nerve regeneration in adults.
Main Methods:
- Immunohistochemistry was used to assess radial glial (RC2/BLBP/Slit1), developmental (Pax2), and extracellular matrix (CSPG: H2B/CS-56) markers.
- C57BL/6J mice were used, examining embryonic and adult stages, including post-ONC injury.
Main Results:
- Radial glial markers (RC2, BLBP) and Slit1 showed dynamic expression changes in the adult optic chiasm post-ONC.
- Developmental marker Pax2 was present at the embryonic optic nerve-chiasm junction.
- Chondroitin sulfate proteoglycans (CSPGs) were absent in adult brains, both uninjured and injured.
Conclusions:
- Dynamic expression of guidance cues like BLBP, RC2, and Slit1 in the adult optic chiasm after injury may contribute to axon misguidance.
- Differences in guidance cue expression between development, adulthood, and post-injury states present challenges for optic nerve regeneration.
