The molecular mechanisms involved in the regulation and function of the Myoc/Tigr gene were studied. Mouse Myoc/Tigr gene was isolated and characterized. It was shown that mouse and human Myoc/Tigr genes have the same exon-intron structure and the corresponding proteins are 82% identical in amino acid sequence. The mouse and human genes show a similar pattern of expression in adult ocular and non-ocular tissues. The mouse gene was mapped to chromosome 1 82.8 cM from the centromere. The promoter of the mouse Myoc/Tigr gene was identified and was capable of driving a reporter gene expression in transgenic animals. Intracellular distribution of the Myoc/Tigr protein was studied using green fluorescent protein as a tag. Tagged mouse and human Myoc/Tigr proteins were localized in the perinuclear cytoplasm, consistent with a recent report for the localization of the native protein. We showed that a myosin-like domain in the N- terminal part of both the human and mouse proteins is responsible for the perinuclear localization of Myoc/Tigr.