Exhibits F-actin depolymerizing activity and regulates actin cytoskeleton dynamics (PubMed:21205790). Required for cytokinesis in both mitotic and meiotic cells and for aster migration and separation (PubMed:8522587). Promotes cell motility during ovary development and oogenesis (PubMed:11175754). During larval development, required for the cell rearrangement needed for formation of terminal filaments which are stacks of somatic cells that are important for the initiation of ovarioles (PubMed:11175754). Also required for border cell migration during oogenesis (PubMed:11175754). During border cell migration, required for actin turnover and lamellipodial protrusion (PubMed:21205790). Required for the establishment of planar cell polarity (PCP) where cells adopt a uniform orientation within the plane of an epithelium (PubMed:16571634). During establishment of PCP, required for the redistribution of the PCP core proteins fz and stan/fmi to the proximodistal cell boundary (PubMed:16571634). During pupal development, required for elongation of the retinal cell body and for rhabdomere morphogenesis (PubMed:18423434). Required for mushroom body neuroblast proliferation and axon growth (PubMed:15572110). Plays a role in the positive regulation of protein secretion (PubMed:20026655). Plays a role in the regulation of nuclear localization of actin (PubMed:22323606). Required for the maintenance of epithelial integrity by controlling cell junctions and is also necessary for cell survival and tissue growth through regulation of JNK and yki signaling (PubMed:27041568). Expressed during all stages of development and peaks in late larval and pupal stages. Expressed in both male and female adults. Phosphorylated in vitro by protein kinase LIMK1 (PubMed:20026655). Phosphorylation is required for inactivation of tsr and for cell proliferation and axon growth (PubMed:15572110). Phosphorylation is negatively regulated by the panthothenate kinase fbl which catalyzes the first step in the conversion of panthothenic acid to coenzyme A (PubMed:22912811). Dephosphorylated by protein phosphatase ssh which activates tsr. Late larval or pupal lethality with mutants showing defects in cytokinesis in both mitotic and meiotic cells, abnormal accumulation of F-actin in mature primary spermatocytes, and defective aster migration where the asters remain in close proximity to each other rather than separating from each other and migrating around the periphery of the nuclear envelope as in the wild type (PubMed:8522587). Failure of terminal filament formation in the ovary at the third larval instar at 25 degrees Celsius but formation occurs at 18 degrees Celsius (PubMed:11175754). Significantly thinner retina than controls, significantly increased F-actin levels in pupal eye disks and defective rhabdomere morphogenesis (PubMed:18423434). Defective mushroom body neuroblast proliferation with newly hatched larvae containing significantly fewer neurons than controls and severe axon growth defects with mutants failing to extend axons beyond the peduncle (PubMed:15572110). RNAi-mediated knockdown in the wing results in increased F-actin levels, altered subcellular location of the transcriptional coactivator yki, strong expression of the yki target genes wg and ex, cell extrusion from the basement membrane, reduced levels of the junction proteins dlg1, arm and shg, up-regulation of Rho1, apoptosis and JNK signaling (PubMed:27041568). The name 'twinstar' derives from the characteristic aberrant arrangement of asters seen in mutants. Belongs to the actin-binding proteins ADF family.