Brain-specific BNIP-2-homology protein Caytaxin relocalises glutaminase to neurite terminals and reduces glutamate levels

Clinical features and molecular genetics of autosomal recessive cerebellar ataxias

Among the hereditary ataxias, autosomal recessive spinocerebellar ataxias comprise a diverse group of neurodegenerative disorders. Clinical phenotypes vary from predominantly cerebellar syndromes to sensorimotor neuropathy, ophthalmological disturbances, involuntary movements, seizures, cognitive dysfunction, skeletal anomalies, and cutaneous disorders, among others. Molecular pathogenesis also ranges from disorders of mitochondrial or cellular metabolism to impairments of DNA repair or RNA processing functions. Diagnosis can be improved by a systematic approach to the categorisation of these disorders, which is used to direct further, more specific, biochemical and genetic investigations. In this Review, we discuss the clinical characteristics and molecular genetics of the more common autosomal recessive ataxias and provide a framework for assessment and differential diagnosis of patients with these disorders.

Expression and localization of Cayman ataxia-related protein, Caytaxin, is regulated in a developmental- and spatial-dependent manner

Mutation of the gene encoding Caytaxin causes human Cayman ataxia by interfering with normal splicing and, in mutant rodents, by reducing normal transcription, which leads to ataxia, dystonia, and mental retardation: These observations suggest that Caytaxin may be crucial for higher brain functions such as motor learning. We generated antibodies against mouse Caytaxin. Interestingly, we found that the expression of Caytaxin is regulated during brain development while quantitative real time RT-PCR indicated that the mRNA level did not change between postnatal days 7 (P7) and P14 in the cerebellum and hippocampus, implying that the expression of Caytaxin may be controlled by a post-transcriptional mechanism. Immunostaining analyses demonstrated that Caytaxin was localized in many brain areas including the cerebellum and hippocampus. Furthermore, Caytaxin was localized to the presynaptic cytosol by the subcellular fractionation of mouse brain and an observation that was confirmed by co-localization studies with synapsin I and VGLUT1. The above data, disease phenotypes, and mutant animals suggest that Caytaxin may be essential for synaptic function. Thus, identifying the role of Caytaxin in synapse maturation may lead to the development of therapeutic interventions for cerebellar ataxia as well as mental disorders.