Myosin IX belongs to the family of unconventional myosins, distinct from the classical myosins I and myosins II. Myosin IX, thought to be involved in signal transduction and leukocyte differentiation, includes several isoforms. The rat isoforms are myosin IX/Myr5 (230 kDa) and Myr7 (300 kDa), and the human isoforms are myosin IXa (MYO9A) and myosin IXb (MYO9B). The isoforms of myosin IX have similar overall domain structure and are expressed in many tissues and cell types, although they have distinct tissue expression patterns. The subcellular localization of class IX myosins appears to be partly cytoplasmic, and partly associated with membranes and the actin cytoskeleton. The expression level of myosins IX may vary during development and differentiation.
Cytoplasm; cell cortex. Cytoplasm; perinuclear region. Note=In undifferentiated cells colocalizes with F-actin in the cell periphery while in differentiated cells its localization is cytoplasmic with the highest levels in the perinuclear region.