Cellularisation is a specialised form of cytokinesis in Drosophila melanogaster. Cellularisation occurs after the first 13 syncytial cell cycles of the embryo and involves targeted insertion of membrane to form the blastoderm, which represents a polarised epithelium made out of about 6000 cells. The molecular machinery driving cellularisation is complex and not well understood. In this work a novel gene regulating this process is identified and characterised. The mutation drop out causes defects in intracellular transport, cell polarity and nuclear positioning. Previous work provided evidence that dop1 is an allele of the RNA silencing gene argonaute2 (ago2). However, results presented in this thesis showed that ago2 functions are unimpaired in dop mutant embryos using genetic and biochemical tools. Moreover genetic and molecular mapping revealed that dop mutants carry a mutation in a gene within close proximity to ago2.This work demonstrates that dop encodes the sole Drosophila homolog of the mammalian MAST (microtubule associated serine/threonine) kinase family. The molecular lesion in the dop1 allele of dop leads to an amino acid exchange in the kinase domain and results in a significant reduction of Dop protein levels. A detailed investigation of the mutant phenotype indicated that dop1 affects microtubule rigidity and Dynein-dependent microtubule associated transport. Search for possible Dop targets revealed reduced phosphorylation of the Dynein intermediate chain (DIC). DIC is a subunit of Dynein and has been shown to be involved in the binding of cargo to the Dynein complex. Therefore, a possible function for Dop might be the phosphorylation of DIC to regulate microtubule dependent transport by controlling Dynein-cargo interaction.
|Date of Award
|Hans-Arno Müller (Supervisor)