Dataset Information

Cytoplasmic streaming drifts the polarity cue and enables posteriorization of the Caenorhabditis elegans zygote at the side opposite of sperm entry.

ABSTRACT: Cell polarization is required to define body axes during development. The position of spatial cues for polarization is critical to direct the body axes. In Caenorhabditis elegans zygotes, the sperm-derived pronucleus/centrosome complex (SPCC) serves as the spatial cue to specify the anterior-posterior axis. Approximately 30 min after fertilization, the contractility of the cell cortex is relaxed near the SPCC, which is the earliest sign of polarization and called symmetry breaking (SB). It is unclear how the position of SPCC at SB is determined after fertilization. Here, we show that SPCC drifts dynamically through the cell-wide flow of the cytoplasm, called meiotic cytoplasmic streaming. This flow occasionally brings SPCC to the opposite side of the sperm entry site before SB. Our results demonstrate that cytoplasmic flow determines stochastically the position of the spatial cue of the body axis, even in an organism like C. elegans for which development is stereotyped.

SUBMITTER: Kimura K

PROVIDER: S-EPMC7521852 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Cytoplasmic streaming drifts the polarity cue and enables posteriorization of the <i>Caenorhabditis elegans</i> zygote at the side opposite of sperm entry.

Kimura Kenji K Kimura Akatsuki A

Molecular biology of the cell 20200527 16

Cell polarization is required to define body axes during development. The position of spatial cues for polarization is critical to direct the body axes. In <i>Caenorhabditis elegans</i> zygotes, the sperm-derived pronucleus/centrosome complex (SPCC) serves as the spatial cue to specify the anterior-posterior axis. Approximately 30 min after fertilization, the contractility of the cell cortex is relaxed near the SPCC, which is the earliest sign of polarization and called symmetry breaking (SB). I ...[more]

PMID: 32459552

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Project description:BackgroundThe anti-saccade task, when people must respond in the direction opposite to a visual stimulus, has been used as a marker of operation of the frontal cortical oculomotor area. However, early development of oculomotor control has been little studied with the infant anti-saccade paradigm, and a few studies did not recognize anti-saccades in infants in light of the results of adult anti-saccade. Since the characteristics of infant eye movements are little known, applying the criteria used in adult study is by no means the best way to study infant anti-saccade. As it is indicated that coordinated eye and head movements often enable infants to control the direction of their gaze, head movements should be examined as an infant orienting response. The aim of this study was to address how infants used eye and head movements during the anti-saccade paradigm. To distinguish infants' responses, we also investigated eye and head movements during a task for an inhibition of return. Inhibition of return, in which delayed responses occur in the direction to which attention had previously been oriented, has been thought to mark activity of the superior colliculus. Since the superior colliculus is thought to develop much earlier in life than the frontal lobes, we thought it useful to compare these task performances during infancy.MethodsInfants were divided into three groups according to age. Anti-saccade and inhibition-of-return tasks were given. Their eye and head movements during tasks were independently recorded by the corneal reflection method in the head-free condition.ResultsYounger infants tended to initiate eye movement less than older ones in both tasks. In the anti-saccade task, responses opposite to the cue tended to show longer latency than responses to the cue. Infants made faster responses toward the side opposite the cue when it was to the right than when it was left of fixation. Regarding the comparison of responses toward the side opposite the cue between two tasks, the leftward eye movement was faster than the leftward head movements in the inhibition-of-return task, while no difference of latency was observed between eye and head movements in the anti-saccade task. A qualitative analysis of the trajectory of these responses revealed that head movement trajectories were steeper in the anti-saccade than in the inhibition-of-return task.ConclusionYounger infants move head and eyes together, with head movements frequently starting first. On the other hand, both the leftward latency difference between eye and head and gentle trajectories of head in inhibition of return indicate that eye movements are more predominant over head movements in the inhibition-of-return task than in the anti-saccade task. This would suggest an earlier developing inhibition-of-return mechanism.

Dataset Information

Cytoplasmic streaming drifts the polarity cue and enables posteriorization of the Caenorhabditis elegans zygote at the side opposite of sperm entry.

Publications

Cytoplasmic streaming drifts the polarity cue and enables posteriorization of the <i>Caenorhabditis elegans</i> zygote at the side opposite of sperm entry.

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