ALS2
Alsin (Amyotrophic lateral sclerosis 2 chromosomal region candidate gene 6 protein) (Amyotrophic lateral sclerosis 2 protein) [ALS2CR6] [KIAA1563]
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Recessive mutations in the amyotrophic lateral sclerosis 2 (ALS2) gene have been linked to juvenile-onset ALS2. Although one of the molecular functions of the ALS2 protein is clearly the activation of Rab5, the mechanisms underlying the selective dysfunction and degeneration of motor neurons in vivo remain to be fully understood. Here, we focused on the ALS2 homologue of Drosophila melanogaster, isolated two independent deletions, and systematically compared phenotypes of the mutants with those of animals in which Rab5 function in identified neurons was abrogated. In the dALS2 mutant flies, we found that the stereotypic axonal and dendritic morphologies of neurons shared some features with those in Rab5-deficient flies, but the dALS2 mutant phenotypes were much milder. We also found that the abrogation of Rab5 function in motor neurons strongly depressed the locomotion activity of adults, resembling the behavior of aged dALS2 mutants. Importantly, this age-dependent locomotion deficit of dALS2 mutants was restored to normal by expressing the dALS2 transgene in a wide range of tissues. This finding provided a platform where we could potentially identify particular cell types responsible for the phenotype by tissue-specific rescue experiments. We discuss our results and the future usage of the dALS2 mutant as a new ALS model.
MeSH Terms
- Aging
- Animals
- Cell Line
- Drosophila Proteins
- Drosophila melanogaster
- Guanine Nucleotide Exchange Factors
- Heparin Lyase
- Humans
- Locomotion
- Motor Neurons
- Mutation
- Oxidative Stress
- Phenotype
- rab5 GTP-Binding Proteins
Loss-of-function mutations in human ALS2 account for several juvenile recessive motor neuron diseases (MNDs). To understand the molecular basis underlying motor dysfunction in ALS2-linked MNDs, several lines of Als2(-/-) mice with a mixed genetic background were thus far generated, and their phenotypes were thoroughly characterized. However, several phenotypic discrepancies among different Als2-deficient lines became evident. To investigate whether genetic backgrounds are associated with such discrepancies, we here generated congenic lines of Als2(-/-) mice on two different genetic backgrounds; C57BL/6 (B6) and FVB/N (FVB), and investigated their gross phenotypes. Both B6 and FVB congenic lines were viable and fertile with no evidences for obvious abnormalities. There were no differences in growth curves between wild-type and Als2(-/-) mice on each genetic background. Remarkably, Als2(-/-) mice on a FVB, but not a B6, background exhibited a shorter life span than wild-type litters. Further, B6 female, but not male, Als2(-/-) mice showed a significantly lower spontaneous rearing activity than wild-type litters. These genetic background- and/or gender-specific findings suggest the presence of modifiers for life span and motor activities in Als2(-/-) mice. These congenic mice should provide a useful means to understand the molecular and genetic basis for variable expression of pathological phenotypes in MNDs.
MeSH Terms
- Amyotrophic Lateral Sclerosis
- Analysis of Variance
- Animals
- Body Weight
- Disease Models, Animal
- Female
- Guanine Nucleotide Exchange Factors
- Longevity
- Male
- Mice
- Mice, Congenic
- Mice, Knockout
- Motor Activity
- Phenotype
- Psychomotor Performance
- Sex Characteristics
- Survival Analysis