Human ataxin-2 contains a polyglutamine repeat that is expanded in patients with spinocerebellar ataxia type 2 (SCA2). Ataxin-2 is highly conserved in evolution with orthologs in mouse, Caenorhabditis elegans, and Drosophila melanogaster. It interacts at its C-terminus with ataxin-2 binding protein 1, A2BP1. This study presents a highly conserved mouse ortholog of A2BP1, designated A2bp1. The amino acid sequence of the human and mouse protein is 97.6% identical. This remarkable degree of conservation supports the fact that these proteins have an important basic function in development and differentiation. Sequence analysis reveals the existence of RNA binding motifs. The A2bp1 transcript was found in various regions of the CNS including cerebellum, cerebral cortex, brain stem, and thalamus/hypothalamus. The A2bp1 protein was detected by immunocytochemistry in the CNS and connective tissue of the mouse embryo starting at stage E11, as well as in the heart at all stages. Mouse embryos showed varying expression of A2bp1 at all stages. Previous studies in other model systems had implicated the orthologs of ataxin-2 and A2BP1 in development. This study suggests a role for A2bp1 in embryogenesis as well as in the adult nervous system, possibly mediated by a function in RNA distribution or processing.
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