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Diffusible signals and fasciculated growth in reticulospinal axon pathfinding in the hindbrain
journal contribution
posted on 2023-06-09, 07:09 authored by Hebert L Hernández-Montiel, Esperanza Meléndez-Herrera, Ana C Cepeda-Nieto, Carmen Mejía-Viggiano, Jorge Larriva-Sahd, Sarah GuthrieSarah Guthrie, Alfredo Varela-EchavarríaWe have addressed the control of longitudinal axon pathfinding in the developing hindbrain, including the caudal projections of reticular and raphe neurons. To test potential sources of guidance signals, we assessed axon outgrowth from embryonic rat hindbrain explants cultured in collagen gels at a distance from explants of midbrain–hindbrain boundary (isthmus), caudal hindbrain, or cervical spinal cord. Our results showed that the isthmus inhibited caudally directed axon outgrowth by 80% relative to controls, whereas rostrally directed axon outgrowth was unaffected. Moreover, caudal hindbrain or cervical spinal cord explants did not inhibit caudal axons. Immunohistochemistry for reticular and raphe neuronal markers indicated that the caudal, but not the rostral projections of these neuronal subpopulations were inhibited by isthmic explants. Companion studies in chick embryos showed that, when the hindbrain was surgically separated from the isthmus, caudal reticulospinal axon projections failed to form and that descending pioneer axons of the medial longitudinal fasciculus (MLF) play an important role in the caudal reticulospinal projection. Taken together, these results suggest that diffusible chemorepellent or nonpermissive signals from the isthmus and substrate-anchored signals on the pioneer MLF axons are involved in the caudal direction of reticulospinal projections and might influence other longitudinal axon projections in the brainstem.
History
Publication status
- Published
Journal
Developmental BiologyISSN
0012-1606Publisher
ElsevierExternal DOI
Issue
1Volume
255Page range
99-112Department affiliated with
- Neuroscience Publications
Full text available
- No
Peer reviewed?
- Yes
Legacy Posted Date
2017-07-12Usage metrics
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