These findings suggest that bulk cytoplasm material properties may constitute important control elements for the regulation of division positioning and cellular organization.Ĭells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Spindle motion shears and fluidizes the cytoplasm, dissipating elastic energy and limiting spindle recoils with functional implications for asymmetric and oriented divisions. These forces are independent of cytoskeletal force generators yet reach hundreds of piconewtons and scale with cytoplasm crowding. Here, using magnetic tweezers to displace and rotate mitotic spindles in living embryos, we uncovered that the cytoplasm can impart viscoelastic reactive forces that move spindles, or passive objects with similar size, back to their original positions.
Although the role of these parameters in molecular diffusion, reaction kinetics, and cellular biochemistry is being increasingly recognized, their contributions to the motion and positioning of larger organelles, such as mitotic spindles for cell division, remain unknown. We identify the texture of the zona pellucida and the cytoplasmic particles size as features to assess mouse oocyte maturation potential and tested whether these features were applicable to human oocyte's developmental potential.Ĭells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Its second application is to predict and characterize the maturation potential of oocytes. We first demonstrate its potential to screen oocyte from different strains and automatically identify their morphological characteristics. We present a feature based machine learning pipeline to recognize oocyte populations and determine their morphological differences. These steps are implemented in an open-source Fiji plugin. We defined a comprehensive set of morphological features to describe an oocyte. We trained neural networks to segment the contour of oocytes and their zona pellucida using oocytes from diverse species. Here, we develop a computational framework to phenotype oocytes based on images acquired in transmitted light. Few computational tools based on non-invasive measurements are however available to characterize oocyte meiotic maturation.
Elucidating this process is important both for fundamental research and assisted reproductive technology. Meiotic maturation is a crucial step of oocyte formation allowing its potential fertilization and embryo development. The nucleus is in light blue, the nucleolus in dark blue, and the oil droplet in light brown microfilaments appear in red. (E) Scheme summarizing the fact that the bias toward the center is detected only in the presence of F-actin. The standard deviations of the MSD curves are presented in gray and light blue quadrants three independent experiments. Mean MSD curves are in bold (dark black curve for controls dark blue curve for Cyto D–treated oocytes). n = 29 oocytes in prophase I, and n = 14 oocytes in prophase I + Cyto D. (D) MSD in micrometers squared of the droplet centroid as a function of the delay (in seconds) for droplets injected in prophase I and observed at high temporal resolution (Δt = 500 ms). n = 22 oocytes three independent experiments. The black line represents the distance to the oocyte center as a function of time (in minutes) averaged from the whole dataset of droplet centroid trajectories.
(C) Distance of the droplet centroid to the oocyte center presented as a function of time (in minutes) for each individual droplet (gray curves).
Time (in minutes) is encoded in color on the droplet centroid trajectories (colored bar on the right side of the picture). The coordinates of the droplet centroid (X,Y) are given in the oocyte referential where (0,0) is the oocyte center.
Prophase picture movie#
The highly refringent object observed by transmitted light on the first frame of the movie corresponds to the nucleolus inside the nucleus. The yellow arrow points at the oil droplet. Frame interval displayed here is every 100 min. (A) Transmitted light images of an oil droplet moving toward the center in a prophase I oocyte (observation at low temporal resolution, Δt = 20 min). Peripherally injected oil droplets are centered in oocytes in prophase I.
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