dictyNews
Electronic Edition
Volume 49, number 26
October 20, 2023
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Abstracts
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Dynamics of actomyosin filaments in the contractile ring revealed
by ultrastructural analysis
Takeru Arima, Keisuke Okita, Shigehiko Yumura
published in Genes to Cells
https://onlinelibrary.wiley.com/doi/10.1111/gtc.13073
Cytokinesis, the final process of cell division, involves the
accumulation of actin and myosin II filaments at the cell's equator,
forming a contractile ring that facilitates the division into two
daughter cells. While light microscopy has provided valuable insights
into the molecular mechanism of this process, it has limitations in
examining individual filaments in vivo. In this study, we utilized
transmission electron microscopy to observe actin and myosin II
filaments in the contractile rings of dividing Dictyostelium cells. To
synchronize cytokinesis, we developed a novel method that allowed
us to visualize dividing cells undergoing cytokinesis with a frequency
as high as 18%. This improvement enabled us to examine the
lengths and alignments of individual filaments within the contractile
rings. As the furrow constricted, the length of actin filaments gradually
decreased. Moreover, both actin and myosin II filaments reoriented
perpendicularly to the long axis during furrow constriction. Through
experiments involving myosin II null cells, we discovered that
myosin II plays a role in regulating both the lengths and alignments
of actin filaments. Additionally, dynamin-like protein A was found to
contribute to regulating the length of actin filaments, while
cortexillins were involved in regulating their alignment.
Submitted by Shigehiko Yumura [[log in to unmask]]
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Collective signalling drives rapid jumping between cell states
Elizabeth R. Westbrook, Tchern Lenn, Jonathan R. Chubb and
Vlatka Antolović
UCL Laboratory for Molecular Cell Biology, University College London
Gower Street, WC1E 6BT, United Kingdom
Development (accepted)
Development can proceed in “fits and starts”, with rapid transitions
between cell states involving concerted transcriptome-wide changes
in gene expression. However, it is not clear how these transitions are
regulated in complex cell populations, in which cells receive multiple
inputs. We address this issue using Dictyostelium cells undergoing
development in their physiological niche. A continuous single cell
transcriptomics time series identifies a sharp “jump” in global gene
expression marking functionally different cell states. By simultaneously
imaging the physiological dynamics of transcription and signalling, we
show the jump coincides with the onset of collective oscillations of
cAMP. Optogenetic control of cAMP pulses shows that different jump
genes respond to distinct dynamic features of signalling. Late jump
gene expression changes are almost completely dependent on cAMP,
while transcript changes at the onset of the jump require additional
input. The coupling of collective signalling with gene expression is a
potentially powerful strategy to drive robust cell state transitions in
heterogeneous signalling environments. Based on the context of the
jump, we also conclude that sharp gene expression transitions may
not be sufficient for commitment.
Submitted by: Jonathan Chubb [[log in to unmask]]
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[End dictyNews, volume 49, number 26]
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