BOTTLENECK ACTS AS A REGULATOR OF THE MICROFILAMENT NETWORK GOVERNINGCELLULARIZATION OF THE DROSOPHILA EMBRYO

A dynamic network of cortical microfilaments is associated with the cl eavage furrow membranes during cellularization of the Drosophila embry o. A specific set of structural rearrangements in this network is requ ired for orchestration and execution of its mechanistic roles. We desc ribe the characterization of the gene bottleneck (bnk), mutations in w hich disturb the proper sequence of rearrangements of the microfilamen t network, leading to a variety of morphological defects during cellul arization. bnk, whose expression is restricted to the blastoderm stage s of Drosophila embryogenesis, encodes a novel, exceptionally basic pr otein that specifically colocalizes with the microfilament network. Th e expression pattern and mutant phenotype of bnk suggest a direct role for this element in regulation of the dynamic restructuring of the ac tin-based cytoskeleton of cellularizing Drosophila embryos.