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GAP-43 is critical for normal targeting of thalamocortical and corticothalamic, but not trigeminothalamic axons in the whisker barrel system.
- Source :
-
Somatosensory & motor research [Somatosens Mot Res] 2008 Mar; Vol. 25 (1), pp. 33-47. - Publication Year :
- 2008
-
Abstract
- Mice lacking the growth-associated protein GAP-43 (KO) show disrupted cortical topography and no barrels. Whisker-related patterns of cells are normal in the KO brainstem trigeminal complex (BSTC), while the pattern in KO ventrobasal thalamus (VB) is somewhat compromised. To better understand the basis for VB and cortical abnormalities, we used small placements of DiI to trace axonal projections between BSTC, VB, and barrel cortex in wildtype (WT) and GAP-43 KO mice. The trigeminothalamic (TT) pathway consists of axons from cells in the Nucleus Prinicipalis that project to the contralateral VB thalamus. DiI-labeled KO TT axons crossed the midline from BSTC and projected to contralateral VB normally, consistent with normal BSTC cytoarchitecture. By contrast, the KO thalamocortical axons (TCA) projection was highly abnormal. KO TCAs showed delays of 1-2 days in initial ingrowth to cortex. Postnatally, KO TCAs showed multiple pathfinding errors near intermediate targets, and were abnormally fasciculated within the internal capsule (IC). Interestingly, most individually labeled KO TCAs terminated in deep layers instead of in layer IV as in WT. This misprojection is consistent with birthdating analysis in KO mice, which revealed that neurons normally destined for layer IV remain in deep cortical layers. Early outgrowth of KO corticofugal (CF) axons was similar for both genotypes. However, at P7 KO CF fibers remained bundled as they entered the IC, and exhibited few terminal branches in VB. Thus, the establishment of axonal projections between thalamus and cortex are disrupted in GAP-43 KO mice.
- Subjects :
- Afferent Pathways anatomy & histology
Animals
Dominance, Cerebral physiology
Female
GAP-43 Protein genetics
Gestational Age
Mice
Mice, Inbred C57BL
Mice, Knockout
Microscopy, Confocal
Neurons diagnostic imaging
Pregnancy
Presynaptic Terminals diagnostic imaging
Ultrasonography
Axons diagnostic imaging
GAP-43 Protein physiology
Mechanoreceptors anatomy & histology
Signal Transduction physiology
Somatosensory Cortex anatomy & histology
Trigeminal Nuclei anatomy & histology
Ventral Thalamic Nuclei anatomy & histology
Vibrissae innervation
Subjects
Details
- Language :
- English
- ISSN :
- 1369-1651
- Volume :
- 25
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Somatosensory & motor research
- Publication Type :
- Academic Journal
- Accession number :
- 18344146
- Full Text :
- https://doi.org/10.1080/08990220701830696