Characterization of multiprotein complexes involved in actin remodeling and cytoskeleton reorganization is essential to understand the basic mechanisms of cell motility and migration. To identify proteins implicated in these processes, we have isolated the mouse Wave1/Scar gene, a member of the Wiskott-Aldrich syndrome protein (WASP) family. The mouse Wave1 gene was physically localized on chromosome 10 and spans over 12 Kb comprising eight exons and seven introns. The mouse Wave1 complementary DNA encodes a predicted 559 amino acid protein, with a SCAR homology domain, a basic domain, a proline-rich region, a WASP homology domain and an acidic domain conserved in the orthologous proteins. The Wave1 transcription initiation site was mapped 210 base pairs upstream of the ATG translational start site. The presumptive proximal promoter contains putative consensus binding sites for E2 basic helix-loop-helix transcription factors, hepatocyte nuclear factor-3beta, S8 homeodomain protein, zinc finger transcription factor MZF-1, and an interferon-stimulated response element. Northern analysis demonstrated a strong expression of a unique approximately 2.6 Kb Wave1 transcript in brain tissue, and in situ hybridization showed restricted expression to Purkinje cells from the cerebellum and pyramidal cells from the hippocampus. Characterization and expression analyses of the murine Wave1 gene provide the basis toward functional studies in mouse models of the role of Wave1 in neuronal cytoskeleton organization.