5.27.24
Nikolaos Papageorgiou
Sphaeroforma arctica undergoing closed mitosis. Sample stained and imaged using Expansion Microscopy (U-ExM) with nuclei in pink and Microtubules in green. Credit: Omaya Dudin (EPFL)
EPFL scientists, in collaboration with researchers at EMBL Heidelberg, have discovered that a group of marine protists (eukaryotic organisms) closely related to animals use open or closed mitosis based on their life cycle stages, suggesting that the way animal cells perform cell division evolved long before animals themselves.
Cell division is fundamental to life, enabling growth, reproduction, and survival across all organisms, from single-celled bacteria to complex multicellular animals. While animals and fungi share a common eukaryotic ancestry, their mechanisms of cell division, particularly mitosis, have diverged significantly, raising intriguing evolutionary questions.
Animals typically undergo open mitosis, where the nuclear envelope disassembles during cell division, while fungi exhibit closed mitosis, maintaining an intact nuclear envelope. The evolutionary reasons behind these divergent strategies remain largely unexplored, making it a compelling area of research for scientists seeking to understand the underlying biological principles.
In a new study, Omaya Dudin’s group at EPFL, Gautam Dey and Yannick Schwab’s team at EMBL Heidelberg investigated this phenomenon in the Ichthyosporea, a group of marine protists that are closely related to both animals and fungi (a protist is a eukaryotic organism that is not an animal, land plant, or fungus). Dudin is an expert in Ichthyosporean life cycles, while Dey’s research focuses on the evolutionary origins of nuclear organization and cell division.
The scientists focused on two species of Ichthyosporea: Sphaeroforma arctica and Chromosphaera perkinsii. The research combined comparative genomics and advanced imaging techniques, such as Expansion Microscopy and Volume Electron Microscopy, to examine how these species’ life cycles influenced their modes of cell division. S. arctica was observed to undergo closed mitosis, similar to fungi, while C. perkinsii performed open mitosis, akin to animal cells.
“By studying diversity across organisms and reconstructing how things evolved, we can begin to ask if there are universal rules that underlie how such fundamental biological processes work,” says Dey.
The study found a clear link between the life cycle stages of Ichthyosporea and their mitotic strategies. Species with multinucleate stages, where cells contain multiple nuclei, tended to undergo closed mitosis. Conversely, species with predominantly mononucleate stages – single nuclei per cell – used open mitosis. This correlation suggests that the evolutionary path of cell division in animals and fungi may have been shaped by their respective life cycle needs.
“Ichthyosporean development displays remarkable diversity,” says Dudin. “On one hand, several species exhibit developmental patterns similar to those of early insect embryos, featuring multinucleated stages and synchronized cellularization. On the other hand, C. perkinsii undergoes cleavage division, symmetry breaking, and forms multicellular colonies with distinct cell types, similar to the ‘canonical view’ of early animal embryos. This diversity not only helps in understanding the path to animals but also offers a fascinating opportunity for comparative embryology outside of animals, which is, in itself, very exciting.”
The findings suggest that the way animal cells divide might have evolved long before the emergence of animals themselves. Meanwhile, the mode of mitosis appears to be intricately connected to the organism’s life cycle, which opens up new perspectives on the evolution of cell division mechanisms in eukaryotes.
Other contributors
EMBL Electron Microscopy Core Facility
Ruđer Bošković Institute (RBI)
University of Groningen
Science paper:
Nature
Fig. 1: Divergence of mitotic machinery in the Ichthyosporea with different life cycles.
a, Differences in life cycles and the uninucleated and multinucleated states of dermocystid C. perkinsii (Cper), ichthyophonids A. appalachense (Aapp), S. arctica (Sarc), C. fragrantissima (Cfra) and corallochytrean C. limacisporum (Clim), respectively. Ihof, Ichthyophonus hofleri. Representative image single-slice images through cells labelled for cell membranes with FM4-64 (magenta) and DNA (grey). b, Cladogram of opisthokonts, highlighting the position of Ichthyosporea between well-studied animal, fungal and amoebozoan model systems. Phylogenetic profiles of selected proteins involved in mitosis (complete profiles in Extended Data Fig. 1). Filled and empty circles or pie charts indicate the presence and absence of proteins, respectively (Methods). In addition to Ichthyosporea (Sarc and Cper) and Corallochytrea (Clim), profiles of key species are represented, including Homo sapiens (Hsap), Drosophila melanogaster (Dmel), S. pombe (Spom), the choanoflagellate Salpingoeca rosetta (Sros), the early-branching chytrid fungus Spizellomyces punctatus (Spun) and amoebozoa Dictyostelium discoideum (Ddis) and P. polycephalum (Ppol). The mitotic strategies, open (white), intermediate (grey squares) or closed (dark grey squares), of the represented opisthokont and amoebozoan species are indicated at the end of each profile, KT (kinetochore). c, C. perkinsii has a centriolar MTOC. Single slices from TEM tomography of C. perkinsii cells showing top and side views through centrioles. d, S. arctica has an acentriolar MTOC. Single slice from TEM tomography of S. arctica interphase nucleus. Side and top views of segmentation of S. arctica MTOC from an interphase nucleus. Scale bars, 2 μm (a), 200 nm (c), 500 nm (d).
See the science paper for further instructive material with images.
See the full article here .
Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct.
five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.
The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH) is a research institute and university in Lausanne, Switzerland, that specializes in natural sciences and engineering. It is one of the two Swiss Federal Institutes of Technology, and it has three main missions: education, research and technology transfer.
The QS World University Rankings ranks EPFL(CH) very high, whereas Times Higher Education World University Rankings ranks EPFL(CH) as one of the world’s best schools for Engineering and Technology.
EPFL(CH) is located in the French-speaking part of Switzerland; the sister institution in the German-speaking part of Switzerland is The Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich] (CH). Associated with several specialized research institutes, the two universities form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles Polytechniques Fédérales] (CH) which is directly dependent on the Federal Department of Economic Affairs, Education and Research. In connection with research and teaching activities, EPFL(CH) operates a nuclear reactor CROCUS; a Tokamak Fusion reactor; a Blue Gene/Q Supercomputer; and P3 bio-hazard facilities.
ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École Polytechnique Fédérale de Lausanne](CH), and four associated research institutes form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.
The roots of modern-day EPFL(CH) can be traced back to the foundation of a private school under the name École Spéciale de Lausanne in 1853 at the initiative of Lois Rivier, a graduate of the École Centrale Paris (FR) and John Gay the then professor and rector of the Académie de Lausanne. At its inception it had only 11 students and the offices were located at Rue du Valentin in Lausanne. In 1869, it became the technical department of the public Académie de Lausanne. When the Académie was reorganized and acquired the status of a university in 1890, the technical faculty changed its name to École d’Ingénieurs de l’Université de Lausanne. In 1946, it was renamed the École polytechnique de l’Université de Lausanne (EPUL). In 1969, the EPUL was separated from the rest of the University of Lausanne and became a federal institute under its current name. EPFL(CH), like ETH Zürich (CH), and it is thus directly controlled by the Swiss federal government. In contrast, all other universities in Switzerland are controlled by their respective cantonal governments. EPFL(CH) has started to develop into the field of life sciences. It absorbed the Swiss Institute for Experimental Cancer Research (ISREC) in 2008.
In 1946, there were 360 students. In 1969, EPFL(CH) had 1,400 students and 55 professors. In the past two decades the university has grown rapidly and over 14,000 people study or work on campus, about 10,000 of these being Bachelor, Master or PhD students. The environment at modern day EPFL(CH) is highly international with the school attracting students and researchers from all over the world. More than 125 countries are represented on the campus and the university has two official languages, French and English.
Organization
EPFL is organized into eight schools, themselves formed of institutes that group research units (laboratories or chairs) around common themes:
School of Basic Sciences
Institute of Mathematics
Institute of Chemical Sciences and Engineering
Institute of Physics
European Centre of Atomic and Molecular Computations
Bernoulli Center
Biomedical Imaging Research Center
Interdisciplinary Center for Electron Microscopy
MPG-EPFL Centre for Molecular Nanosciences and Technology
Swiss Plasma Center
Laboratory of Astrophysics
School of Engineering
Institute of Electrical Engineering
Institute of Mechanical Engineering
Institute of Materials
Institute of Microengineering
Institute of Bioengineering
School of Architecture, Civil and Environmental Engineering
Institute of Architecture
Civil Engineering Institute
Institute of Urban and Regional Sciences
Environmental Engineering Institute
School of Computer and Communication Sciences
Algorithms & Theoretical Computer Science
Artificial Intelligence & Machine Learning
Computational Biology
Computer Architecture & Integrated Systems
Data Management & Information Retrieval
Graphics & Vision
Human-Computer Interaction
Information & Communication Theory
Networking
Programming Languages & Formal Methods
Security & Cryptography
Signal & Image Processing
Systems
School of Life Sciences
Bachelor-Master Teaching Section in Life Sciences and Technologies
Brain Mind Institute
Institute of Bioengineering
Swiss Institute for Experimental Cancer Research
Global Health Institute
Ten Technology Platforms & Core Facilities (PTECH)
Center for Phenogenomics
NCCR Synaptic Bases of Mental Diseases
College of Management of Technology
Swiss Finance Institute at EPFL
Section of Management of Technology and Entrepreneurship
Institute of Technology and Public Policy
Institute of Management of Technology and Entrepreneurship
Section of Financial Engineering
College of Humanities
Human and social sciences teaching program
EPFL Middle East
Section of Energy Management and Sustainability
In addition to the eight schools there are seven closely related institutions
Swiss Cancer Centre
Center for Biomedical Imaging (CIBM)
Centre for Advanced Modelling Science (CADMOS)
École Cantonale d’art de Lausanne (ECAL)
Campus Biotech
Wyss Center for Bio- and Neuro-engineering
Swiss National Supercomputing Centre