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Abnormal corticospinal function but normal axonal guidance in human L1CAM mutations.
C B Dobson1, F Villagra, G J Clowry
1Developmental Neuroscience, Department of Child Health, University of Newcastle upon Tyne, UK.
Brain : a Journal of Neurology
|November 10, 2001
Summary
Mutations in the L1 cell adhesion molecule (L1CAM) gene impact corticospinal tract development in males and carrier females. This study found abnormalities in corticospinal projections, but not axonal guidance, in individuals with L1CAM mutations.
Area of Science:
- Neuroscience
- Genetics
- Developmental Biology
Background:
- L1 cell adhesion molecule (L1CAM) gene mutations cause X-linked neurological disorders with leg spasticity.
- L1CAM knockout mice exhibit corticospinal tract hypoplasia and failed axonal decussation.
Purpose of the Study:
- To investigate if similar neuropathology underlies spastic diplegia in males with L1CAM mutations.
- To assess the role of L1CAM in corticospinal tract development and axonal guidance.
Main Methods:
- Transcranial magnetic stimulation (TMS) was used to assess corticospinal tract excitability and responses in limb muscles.
- Stretch reflex conditioning was employed to evaluate projections to inhibitory interneurons.
- Histological examination of post-mortem tissue from an affected infant was performed.
Main Results:
- Hemizygous males and carrier females showed abnormal corticospinal tract responses, including high thresholds and delayed onsets.
- Reduced projections to inhibitory interneurons were suggested by abnormal stretch reflex conditioning.
- Histology revealed normal corticospinal decussation and projections in an infant with an L1CAM mutation.
Conclusions:
- L1CAM plays a role in corticospinal tract development in hemizygous males and carrier females.
- The findings do not support a critical role for L1CAM in corticospinal axonal guidance.
- Further research is needed to fully elucidate the function of L1CAM in neurological development.