In the mouse. development of the lateral semicircular canal of the inner ear is sensitive to Bmp4 heterozygosity In the C57BL6 background 30% of the heterozygotes display circling behavior, 66% have a specific defect in the vestibular part of the inner ear, namely the constriction, interruption or absence of the lateral semicircular canal Only mice having both ears affected display circling behavior. In the (C57BL6xCBA)N1 background, the penetrance of the canal phenotype is greatly reduced, and bilateral lateral canal defect is not sufficient to induce circling We found association of the canal phenotype with the genotype of markers on chromosome 14 and 4. co-localizing with Ecs and Eclb identified in the Eel mouse with similar lateral canal defects Candidate genes to contain the causal mutation are Bmp4 on chromosome 14, and Rere on chromosome 4 (C) 2010 Elsevier Inc All rights reserved