Biology subjects

Januschke, J.

Publications and source records attributed to Januschke, J..

4 recordsLinked to original sources

bioRxiv2018

Identification of endogenous Adenomatous polyposis coli interaction partners and β-catenin-independent targets by proteomics

Adenomatous polyposis coli (APC) is the most frequently mutated gene in colorectal cancer. APC negatively regulates the pro-proliferative Wnt signaling pathway by promoting the degradation of {beta}-catenin, but the extent to which APC exerts Wnt/{beta}-catenin-independent tumor suppressive activity is unclear. To identify interaction partners and {beta}-catenin-independent targets of endogenous, full-length APC, we applied label-free and multiplexed TMT mass spectrometry. Affinity enrichment-mass spectrometry revealed over 150 previously unidentified APC interaction partners. Moreover, our global proteomic analysis revealed that roughly half of the protein expression changes that occur in response to APC loss are independent of {beta}-catenin. By combining these two analyses, we identified Misshapen-like kinase 1 (MINK1) as a putative substrate of an alternative APC-containing destruction complex and provide evidence for the potential contribution of MINK1 to APC mutant phenotypes. Collectively, our results highlight the extent and importance of Wnt-independent APC functions in epithelial biology and disease.

cancer biology↗

bioRxiv2017

Requirement of the Dynein-adaptor Spindly for mitotic and post-mitotic functions in Drosophila

Spindly is a mitotic checkpoint protein originally identified as a specific regulator of Dynein activity at the kinetochore. In metaphase, Spindly recruits the Dynein/Dynactin complex, promoting the establishment of stable kinetochore-microtubule interactions and progression into anaphase. While details of Spindly function in mitosis have been worked out in cultured human cells and in the C. elegans zygote, the function of Spindly within the context of an organism has not yet been addressed. Here we present loss- and gain-of-function studies of Spindly in Drosophila. We investigated the requirements of distinct protein domains for the localisation and function of Spindly. We find that knock-down of Spindly results in a range of mitotic defects in the female germ line and during cleavage divisions in embryogenesis. Overexpression of Spindly in the female germ line is embryonic lethal and results in altered egg morphology. To determine whether Spindly plays a role in post-mitotic cells we altered Spindly protein levels in migrating cells and found that ovarian border cell migration is sensitive to the levels of Spindly protein. Our study uncovers novel functions of the mitotic checkpoint protein Spindly in Drosophila.

cell biology↗

bioRxiv2017

Drosophila neural stem cells are polarized by their daughter cells

Controlling the orientation of cell division is important in the context of cell fate choices and tissue morphogenesis. However, the mechanisms providing the required positional information remain incompletely understood. Here we use stem cells of the Drosophila larval brain that stably maintain their axis of polarity and division between cell cycles to identify cues that orient cell division. Using live cell imaging of cultured brains, laser ablation and genetics we reveal that these cells use the position of their last-born daughter cell as a polarizing cue. Remarkably, this daughter cell derived signal received at one pole of the stem cell has an effect on the opposite pole influencing where apical will be in the next mitosis, thereby directing the orientation of division. Therefore, in addition to known intrinsic cues, stem cells in the developing fly brain are polarized by an extrinsic signal that acts upstream of apico-basal polarity establishment.

cell biology↗

bioRxiv2017

aPKC-mediated displacement and actomyosin-mediated retention polarize Miranda in Drosophila neuroblasts

Cell fate generation can rely on the unequal distribution of molecules during progenitor cell division in the nervous system of vertebrates and invertebrates. Here we address asymmetric fate determinant localization in the developing Drosophila nervous system, focussing on the control of asymmetric Miranda distribution in larval neuroblasts. We used live imaging of neuroblast polarity reporters at endogenous levels of expression to address Miranda localization during the cell cycle. We reveal that the regulation and dynamics of cortical association of Miranda in interphase and mitosis are different. In interphase Miranda binds directly to the plasma membrane. At the onset of mitosis, Miranda is phosphorylated by aPKC and displaced from the PM. After nuclear envelope breakdown asymmetric localization of Miranda requires actomyosin activity. Therefore, Miranda phosphorylation by aPKC and differential binding to the actomyosin network are required at distinct phases of the cell cycle to polarize fate determinant localization.

cell biology↗