Mast syndrome (SPG21) is a childhood-onset, autosomal recessive, complicated form of hereditary spastic paraplegia (HSP) characterized by dementia, thin corpus callosum, white matter abnormalities, and cerebellar and extrapyramidal signs in addition to spastic paraparesis. A nucleotide insertion resulting in premature truncation of the SPG21 gene product maspardin underlies this disorder, likely leading to loss of protein function. In this study, we generated SPG21-/- knockout mice by homologous recombination as a possible animal model for SPG21. Though SPG21-/- mice appeared normal at birth, within several months they developed gradually progressive hind limb dysfunction. Cerebral cortical neurons cultured from SPG21-/- mice exhibited significantly more axonal branching than neurons from wild-type animals, while comprehensive neuropathological analysis of SPG21-/- mice did not reveal definitive abnormalities. Since alterations in axon branching have been seen in neurons derived from animal models of other forms of HSP as well as motor neuron diseases, this may represent a common cellular pathogenic theme.
Title: Interaction of the SPG21 protein ACP33/maspardin with the aldehyde dehydrogenase ALDH16A1 Hanna MC, Blackstone C Ref: Neurogenetics, 10:217, 2009 : PubMed
Mast syndrome (SPG21) is an autosomal-recessive complicated form of hereditary spastic paraplegia characterized by dementia, thin corpus callosum, white matter abnormalities, and cerebellar and extrapyramidal signs in addition to spastic paraparesis. A nucleotide insertion resulting in premature truncation of the SPG21 gene product acidic cluster protein 33 (ACP33)/maspardin underlies this disorder, likely causing loss of protein function. However, little is known about the function of maspardin. Here, we report that maspardin localizes prominently to cytoplasm as well as to membranes, possibly at trans-Golgi network/late endosomal compartments. Immunoprecipitation of maspardin with identification of coprecipitating proteins by mass spectrometry revealed the aldehyde dehydrogenase ALDH16A1 as an interacting protein. This interaction was confirmed using overexpressed proteins as well as by fusion protein pull down experiments, and these proteins colocalized in cells. Further studies of the function of ALDH16A1 and the role of the maspardin-ALDH16A1 interaction in neuronal cells may clarify the cellular pathogenesis of Mast syndrome.
An approach for genome analysis based on sequencing and assembly of unselected pieces of DNA from the whole chromosome has been applied to obtain the complete nucleotide sequence (1,830,137 base pairs) of the genome from the bacterium Haemophilus influenzae Rd. This approach eliminates the need for initial mapping efforts and is therefore applicable to the vast array of microbial species for which genome maps are unavailable. The H. influenzae Rd genome sequence (Genome Sequence DataBase accession number L42023) represents the only complete genome sequence from a free-living organism.
