Growth
A newborn cell grows without immediately dividing.
ICHTHYOSPOREA / MAIN EXPERIMENTAL SYSTEM
Sphaeroforma
arctica
One cell. Many nuclei.
A coordinated programme of cellularisation.
Scanning electron microscopy · Multicellgenome Lab
A DEVELOPMENTAL PARADOX
Many nuclei.
Still one cell.
Sphaeroforma arctica grows as a coenocyte: it repeatedly duplicates its nuclei while keeping them inside a shared cytoplasm. Then, with remarkable precision, it builds a new cell around each nucleus.
THE TRANSITION
One cytoplasm
becomes many cells.
THE DEVELOPMENTAL PROGRAMME
A life cycle
written in time.
Nuclear multiplication
Regular rounds of nuclear division create a coenocyte: many nuclei sharing one cytoplasm.
Cellularisation
An actomyosin network guides coordinated membrane invaginations around the nuclei.
Release
A transient layer of polarized cells reorganizes and releases a new generation.
WHY IT MATTERS
A unicellular system
with animal-like cell behaviours.
Sphaeroforma does not make an animal embryo. But its coordinated membrane invagination, actomyosin dynamics, cell polarity and control of developmental timing reveal that important ingredients of animal development existed before animals.
DECODING CELLULARISATION
How does one cell
organize many?
A developmental clock
Nuclear divisions follow a regular rhythm before cellularisation begins.
Nuclear-to-cytoplasmic ratio
The balance between nuclear content and cell volume helps determine when cellularisation starts.
Actomyosin
A spatially organized actomyosin network drives inward membrane growth.
Transient polarity
New cells briefly form a polarized, epithelium-like layer before release.
FOUNDATIONAL WORK
From genome
to mechanism.
2012
Placing Sphaeroforma on the tree
A phylogenomic framework resolved the major opisthokont lineages and established ichthyosporeans as key organisms for reconstructing animal origins.
↗2017Dynamics of genomic innovation
Comparative genomes, including Sphaeroforma, reconstructed the changing molecular toolkit along the animal stem lineage.
↗2019Actomyosin-dependent cellularisation
Imaging and transcriptomics revealed coordinated membrane invagination and a transient polarized cell layer.
↗2022Evolving multicellularity in the laboratory
Selection for faster sedimentation repeatedly produced clonal multicellular variants through incomplete separation of newborn cells.
↗GENOME & RESOURCES
Study the programme.
CONTINUE EXPLORING
