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Iterative and Complex Asymmetric Divisions Control Cell Volume Differences in Ciona Notochord Tapering
Konner Winkley1, Spencer Ward1, Wendy Reeves1
1Division of Biology, Kansas State University, 1717 Claflin Road, Manhattan, KS 66506, USA.
Current Biology : CB
|October 15, 2019
Summary
Subtle, iterative asymmetric cell divisions in the Ciona notochord precisely control organ shape. These divisions, not cell fate, dictate the tapered rod structure, revealing a new role for cell division in development.
Area of Science:
- Developmental Biology
- Cell Biology
- Chordate Embryology
Background:
- The notochord, a key developmental structure in chordates, forms a tapered rod in Ciona.
- This shape is characterized by anterior-posterior differences in notochord cell volume.
- Understanding the cellular mechanisms generating this shape is crucial for developmental biology.
Purpose of the Study:
- To quantify sibling cell volume asymmetry during notochord development in Ciona.
- To determine if unequal cell divisions explain the anterior-posterior variation in notochord cell volume.
- To identify the cellular mechanisms driving these asymmetric divisions.
Main Methods:
- Quantitative 3D analysis of cell shape and spindle positioning.
- Analysis of sibling cell volume asymmetry in primary and secondary notochord founder cells.
- Development of a quantitative model to assess the sufficiency of unequal divisions in shaping the notochord.
Main Results:
- Distinct patterns of unequal cell cleavage were observed in all bilateral pairs of A-line and B-line notochord founder cells.
- A quantitative model confirmed that these asymmetric divisions are sufficient to explain the anterior-posterior variation in notochord cell volume.
- Multiple cellular mechanisms, including spindle positioning, cell shape, and cortical contractility, were inferred to drive unequal cleavages.
Conclusions:
- Asymmetric cell division plays a direct role in shaping the Ciona notochord organ.
- Iterative and patterned asymmetric divisions, rather than fate determination, are key to generating organ shape.
- Differential utilization of cellular mechanisms underlies the observed asymmetric divisions across different cells and division rounds.
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