Biology subjects

Muller, H.-A. J.

Publications and source records attributed to Muller, H.-A. J..

4 recordsLinked to original sources

bioRxiv2022

Src42A is required for E-cadherin dynamics at cell junctions during Drosophila axis elongation

Src kinases are important regulators of cell adhesion. Here we explored the function of Src42A in junction remodelling during Drosophila gastrulation. Src42A is required for tyrosine phosphorylation at bicellular and tricellular junctions in germband cells and localizes to hotspots of mechanical tension. The role of Src42A was investigated using maternal RNAi and by CRISPR-Cas9-induced germline mosaics. We find that during cell intercalations, Src42A is required for the contraction of junctions at anterior-posterior cell interfaces. The planar polarity of E-cadherin is compromised and E-cadherin accumulates at tricellular junctions after Src42A knock down. Furthermore, we provide evidence that Src42A acts in parallel to Abl, which has also been implicated in cell intercalations. Our data suggest that Src42A is involved in two related processes, one affecting tension generated by the planar polarity of MyoII and secondly, it can act as a signalling factor at tAJs in controlling E-cadherin residence time.

developmental biology↗

bioRxiv2020

Kinetochore protein Spindly controls microtubule polarity in Drosophila axons

Microtubule polarity in axons and dendrites defines the direction of intracellular transport in neurons. Axons contain arrays of uniformly polarized microtubules with plus-ends facing the tips of the processes (plus-end-out), while dendrites contain microtubules with minus-end-out orientation. It has been shown that cytoplasmic dynein, targeted to cortical actin, removes minus-end-out microtubules from axons. Here we have identified Spindly, a protein known for recruitment of dynein to kinetochores in mitosis, as a key factor required for dynein-dependent microtubule sorting in axons of Drosophila neurons. Depletion of Spindly affects polarity of axonal microtubules in vivo and in primary neuronal cultures. In addition to these defects, depletion of Spindly in neurons causes major collapse of axonal patterning in the third-instar larval brain as well as severe coordination impairment in adult flies. These defects can be fully rescued by full-length Spindly, but not by variants with mutations in its dynein-binding site. Biochemical analysis demonstrated that Spindly binds F-actin, suggesting that Spindly serves as a link between dynein and cortical actin in axons. Therefore, Spindly plays a critical role during neurodevelopment by mediating dynein-driven sorting of axonal microtubules. Significance StatementNeurons send and receive electrical signals through long microtubule-filled neurites called axons and dendrites. One of the main structural differences between axons and dendrites is how their microtubules are organized. Axons contains microtubules with their plus-ends out while microtubules in dendrites are organized with mixed or plus-end-in orientation. Dynein, the main minus-end microtubule motor, anchored to cortical actin filaments in the axons is responsible for the uniform microtubule polarity in axons. However, it is unknown how dynein is recruited to the actin cortex in axons. The major finding of this work is that Spindly, a protein involved in anchoring dynein to kinetochores during cell division, has a second important function in interphase cells recruiting dynein to the actin cortex in axons.

cell biology↗

bioRxiv2018

SSPIM: a beam shaping toolbox for structured selective plane illumination microscopy

An important aim of the development of selective plane illumination microscopy (SPIM) is to present a completely open and flexible microscope set-up for nonspecialist users. Here, we report Structured SPIM (SSPIM), which provides an open-source, user-friendly and compact toolbox for beam shaping that can generate digital patterns for a wide range of illumination beams. SSPIM represents a toolbox to produce static, spherical Gaussian, Bessel and Airy beams by simple control of a Spatial Light Modulator (SLM). In addition, it is able to produce patterns for incoherent and coherent (lattice beam) array beam formation and tiling for all types of beams supported. We demonstrate the workflow and experimental and simulation results using the SSPIM toolbox. In final, the capability of the SSPIM is investigated with 3D imaging of Drosophila embryo using three different illumination beams such as scanned/dithered Gaussian, Bessel and Lattice beam which engineered with SSPIM. SSPIM toolbox is easy to use and applicable for a wide range of applications to generate and optimize the desired beam pattern and thus can help developing adaptation of the Open SPIM system towards a wider range of biological samples.

bioinformatics↗

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↗