Migratory defect of mesencephalic dopaminergic neurons in developing reeler mice / 대한해부학회지

Reelin, an extracellular glycoprotein has an important role in the proper migration and positioning of neurons during brain development. Lack of reelin causes not only disorganized lamination of the cerebral and cerebellar cortex but also malpositioning of mesencephalic dopaminergic (mDA) neurons. However, the accurate role of reelin in the migration and positioning of mDA neurons is not fully elucidated. In this study, reelin-deficient reeler mice exhibited a significant loss of mDA neurons in the substantia nigra pars compacta (SNc) and a severe alteration of cell distribution in the retrorubal field (RRF). This abnormality was also found in Dab1-deficinet, yotari mice. Stereological analysis revealed that total number of mDA neurons was not changed compared to wild type, suggesting that the loss of mDA neurons in reeler may not be due to the neurogenesis of mDA neurons. We also found that formation of PSA-NCAM-positive tangential nerve fibers rather than radial glial fibers was greatly reduced in the early developmental stage (E14.5) of reeler. These findings provide direct evidence that the alteration in distribution pattern of mDA neurons in the reeler mesencephalon mainly results from the defect of the lateral migration using tangential fibers as a scaffold.

Genetic, biochemical, and characterization of neurological mutant 3, a new mouse model for Parkinson's disease

We have identified a new mutant mouse that we have named new mouse neurological mutant 3 (NM3); it may be a useful model to understand the underlying molecular and genetic basis of Parkinson's disease (PD). A mouse carrying the NM3 mutation arose spontaneously in an RIIIS/J breeding colony and was identified as having a movement disorder. Upon neurological examination of these mice, their movement was found to be slow and abnormal, with characteristic choreaform and bradykinetic-type movements, typical of PD. The importance of the gene mutation in NM3 in the molecular pathway involved in this pathology is underscored by the fact that these mice do not survive past weaning age if they are homozygous for the genetic mutation. We localized the gene mutation by positional cloning and genetic mapping to mouse chromosome 2 in an area that corresponds to human chromosome 2q24-31, which does not contain any known genes associated with PD. However, there was a significant decrease of 15-20 in the levels of dopamine, and its principal metabolite, 3,4-dihydroxyphenylacetic acid, in the midbrain of affected mice. Low concentrations of these substances are associated with PD in human patients, making these mutant mice candidates for studies of this disease

Plasticity of synapses between Purkinje cell dendritic spines and parallel fiber varicosity in tottering/leaner mice cerebellum / 대한해부학회지

The tottering (tg/tg) is neurologic mutant mouse exhibiting three neurological disorders: ataxia, petit mal-like absence seizures and myoclonic intermittent movement disorder. The tottering mouse carries an autosomal recessive single gene mutation on chromosome 8. The leaner (tgla) and Nagoya rolling (tgrol) are another two alleles of the tottering (tg). The combination of two mutant (tottering and leaner) produces compound heterozygous, tottering/leaner (tg/tgla) mouse. The genetic etilogy of the tottering and leaner was identified to be a mutation in voltage-dependent calcium channel a1A subunit. It made us link these animal model to human neurologic disease such as autosomal dominant cerebellar ataxia (SCA6), familial hemiplegic migraine and episodic ataxia type-2. The different onset and severity of neurological symptom of these three mutants (tg/tg, tg/tgla, tgla/tgla) offer good scale to analysis of pathophysiolgy of the neurologic disorder. Altered synapase between parallel fiber varicosity and dendritic spines of Purkinje cell was observed in adult tottering and leaner mice. Through the electron microscopic observation and anticalbindin-28 kd immunohistochemistry, we anaylzed not only the relationship between neurologic symptoms and synaptic plasticity around the ataxic onset of tottering, leaner and tottering leaner double mutation but also Purkinje cell morphology affected by voltage-sensitive calcium channel a1A subunit mutation in totterring mouse. Purkinje cell dendritic spines from proximal dendrites and axonal swellings of Purkine cell were observed frequently in wild type mice. The first apperance point of altered synapse based on semi-quantitative analysis was postnatal 15 days in leaner, postnatal 18 days in totering/leaner double mutation, and 30 days in tottering. These data suggest that altered synapse is associated with ataxia in tottering and leaner mice. Further study is needed to determine whether altered synapse is primary cause of ataxia.