Actin-myosin network stability during cellularization. Might be involved in increasing actin-actin interactions or membrane-to-cytoskeleton attachments. nullo together with Sry-a and bnk may provide auxiliary functions, by acting both to stabilize a large and dynamic microfilament structure and regulate its functions. Blastoderm. Throughout the entire cortex of the embryo although the distribution is not uniform. Appears first at nuclear cell cycle 11 and disappears rapidly as cellularization begins. During cycle 14, nullo protein levels are coupled to the nucleocytoplasmic ratio.