Spir-2 is a 714 amino acid protein belonging to the spire family. Spir-2 is a cytoplasmic protein that contains one KIND domain and three WH2 domains. Spir-2 binds to actin via the WH2 domains and acts as an actin nucleation factor. Spir-2 is involved in vesicle transport and acts as a link between actin organization and intracellular transport. Spir-2 is expressed as four isoforms that are produced by alternative splicing events. The gene that encodes Spir-2 maps to human chromosome 16, which encodes over 900 genes and approximately 90 million base pairs, making up nearly 3% of human cellular DNA. The GAN gene is located on chromosome 16 and, with mutation, may lead to giant axonal neuropathy, a nervous system disorder characterized by increasing malfunction with growth. The rare disorder Rubinstein-Taybi syndrome is also associated with chromosome 16, though through the CREBBP gene which encodes a critical CREB binding protein. Signs of Rubinstein-Taybi include mental retardation and predisposition to tumor growth and white blood cell neoplasias. Crohn's disease is a gastrointestinal inflammatory condition associated with chromosome 16 through the NOD2 gene.