Myosin F controls actin organization and dynamics in Toxoplasma gondii

Video microscopy: an old story with a bright biological future

Single-cell analysis is increasingly popular in the field of biology, enabling more precise analyses of heterogeneous phenomena, particularly in the fields of embryology and the study of different diseases. At the heart of this evolution is video microscopy, an ancient but revolutionary technique. From its first use on embryos, through the study of C. Elegans, with the development of algorithms for its automation, the history of video microscopy has been fascinating. Unfortunately, many unresolved issues remain, such as the sheer volume of data produced and the quality of the images taken. The aim of this review is to explore the past, present and future of this technique, which could become indispensable in recent decades, to understand cell fate and how diseases affect their destiny.

Myosin A and F-Actin play a critical role in mitochondrial dynamics and inheritance in Toxoplasma gondii

The single mitochondrion of the obligate intracellular parasite Toxoplasma gondii is highly dynamic. Toxoplasma's mitochondrion changes morphology as the parasite moves from the intracellular to the extracellular environment and during division. Toxoplasma's mitochondrial dynamic is dependent on an outer mitochondrion membrane-associated protein LMF1 and its interaction with IMC10, a protein localized at the inner membrane complex (IMC). In the absence of either LMF1 or IMC10, parasites have defective mitochondrial morphology and inheritance defects. As little is known about mitochondrial inheritance in Toxoplasma, we have used the LMF1/IMC10 tethering complex as an entry point to dissect the machinery behind this process. Using a yeast two-hybrid screen, we previously identified Myosin A (MyoA) as a putative interactor of LMF1. Although MyoA is known to be located at the parasite's pellicle, we now show through ultrastructure expansion microscopy (U-ExM) that this protein accumulates around the mitochondrion in the late stages of parasite division. Parasites lacking MyoA show defective mitochondrial morphology and a delay in mitochondrion delivery to the daughter parasite buds during division, indicating that this protein is involved in organellar inheritance. Disruption of the parasite's actin network also affects mitochondrion morphology. We also show that parasite-extracted mitochondrion vesicles interact with actin filaments. Interestingly, mitochondrion vesicles extracted out of parasites lacking LMF1 pulled down less actin, showing that LMF1 might be important for mitochondrion and actin interaction. Accordingly, we are showing for the first time that actin and Myosin A are important for Toxoplasma mitochondrial morphology and inheritance.